The cerebral vasculature, with its extensive network of arteries, veins, capillaries, and perivascular compartments, constitutes a substantial component of the brain and provides indispensable support to brain cells. In fact, the proper functioning of neurons and neuronal circuits is strongly dependent on continuous and sufficient oxygen and glucose supply from the blood, and in general, a healthy brain relies on healthy cerebral blood vessels. The cerebral vasculature also presents unique properties, especially the blood-brain barrier (BBB), that prevent solutes and cells in the blood from non-selectively crossing into the extracellular fluid and the parenchyma of the central nervous system where neurons and other brain cells reside. Moreover, recent preclinical data support a critical role of the paravascular and the intramural periarterial compartments as drainage systems of the brain, while clinical studies investigate MRI-visible perivascular spaces (PVS) in the context of neurodegeneration. These findings have significant implications for a better understanding of the pathogenesis and development of therapeutic approaches in several neurological disorders, especially neurodegenerative diseases.The purpose of this Research Topic was to increase knowledge of the role played by the cerebral vasculature in neurodegenerative diseases, such as cerebral small vessel disease, vascular cognitive impairment, Alzheimer's disease (AD), and dementia. In recent years, novel neuroimaging methods and technological advancements enabled improvements in the visualization and quantification of the cerebral vasculature and its multiple components, including PVS and BBB. From a clinical point of view, these advancements are important for optimizing current diagnostic frameworks, identifying early biomarkers, and developing novel therapeutic strategies for neurodegenerative disease utilizing the cerebral vasculature.Lynch et al. give an overview of the current knowledge and gaps in understanding the contribution of PVS to AD. In particular, after describing AD, established AD biomarkers, and the glymphatic system, they summarized results from studies investigating the potential use of MRI-visible PVS as a non-invasive imaging biomarker in AD as well as the relationship between MRI-visible PVS, amyloid-beta, and tau. The review highlighted the need for further studies investigating these relationships, both cross-sectionally and longitudinally, to improve our comprehension of the role of PVS in AD in humans.In their review article, Pham et al. summarized the recent developments in PVS segmentation and quantification on MRI. They described the current approaches for evaluating PVS in humans, including visual rating scales, segmentation, and machine learning techniques, and made comparisons between these techniques when feasible. This review also summarized the current challenges in PVS segmentation and proposed potential solutions.Another review article by Moses et al., the authors evaluated the utility of PVS burden assessed on MRI as a biomarker in patients with behavioral variant frontotemporal dementia. They used an automated technique to segment PVS on T1-weighted images. In their exploratory study with 12 patients, they found a trend toward an association between PVS burden and disease progression, as well as between the measures of tau and neurofilament light chain in the cerebrospinal fluid and PVS burden longitudinally. Their study suggests a potential involvement of PVS in neurodegenerative changes observed in these patients. Further studies are needed in order to understand the possible use of PVS as a biomarker for disease progression and/or as a therapeutic target in frontotemporal dementia.In the study by Wang et al. in rats with painful diabetic neuropathy manifesting mechanical allodynia and impairment in the glymphatic system showed that β-Hydroxybutyrate is able to restore AQP4 polarity in the spinal glymphatic system leading to enhanced glymphatic clearance and reduced mechanical allodynia compared with untreated animals. These encouraging results provide a promising therapeutic strategy for diabetic neuropathy.The glymphatic system clearance activity is based on aquaporin-4 (AQP4) water channels expressed on the end-feet of astrocytes lining on the parenchymal side of the perivascular compartment. The study by Yuan et al. focused on brain endothelial cells of the BBB, and their role in the pathophysiology of neurodegenerative disorders. In particular, the authors described the studies investigating how active signals released and received by brain endothelial cells may contribute to the pathogenesis of neurodegeneration, both facilitating the accumulation and deposition of pathological proteins and through pathways independent of pathological proteins, such as neuroinflammation. A better understanding of the molecular mechanisms underlying BBB and brain endothelial cell dysfunction will be critical for the development of therapeutic strategies targeting the blood vessels.The BBB is a vascular component mediating the interaction between the blood, PVS, and the brain. In their review, Hayes et al. described the role of vascular smooth muscle cells in the most common neurodegenerative disorders and what biological signaling pathways and physiological systems may contribute to their dysfunction. Moreover, they reviewed recent studies investigating cerebrovascular reactivity dysfunction and cerebral blood flow in patients with neurodegenerative and/or cerebrovascular pathologies and discussed potential therapeutic opportunities for these disorders specifically targeting vascular smooth muscle cell dysfunction.Another important component of the brain vasculature is represented by the vascular smooth muscle cells, which play a key role in cerebrovascular dynamics, enabling the appropriate provision of oxygen and nutrients to the brain. In their review, In summary, these papers have collectively improved our understanding of perivascular and vascular contributions in Alzheimer's disease and other neurodegenerative conditions. These outcomes establish a basis for future studies and new opportunities for developing imaging biomarkers and interventional strategies for neurodegenerative disorders.GB: Writing—original draft, Writing—review and editing. DB: Writing—review and editing. YM: Writing—review and editing.


The prevalence of metastatic spine disease is progressively increasing, affecting a growing group of heterogeneous and complex patients. A multidisciplinary, personalized approach, enriched by the expertise of each involved specialty , is pivotal and achieves superior results in terms of clinical outcomes. We reviewed the most recent data regarding the pathophysiology of metastatic spine disease, prognostic scores, and available treatment options and formulated a proposal for an updated algorithmic approach to the pathology according to the clinical scenario of each patient. A flowchart-based approach to patients offers an evidence-based management of metastatic spine disease, providing a valuable clinical decision tool in a context of high uncertainty and quick-acting need. Nevertheless, we underline that the goal of this type of approach is to assist in clinical decisions, not to replace a case-by-case reflection concerning the specificities of each patient.Metastatic spine disease (MSD) and metastatic spinal cord compression (MSCC) are major causes of permanent neurological damage and long-term disability for cancer patients. The development of MSD is pathophysiologically framed by a cooperative interaction between general mechanisms of bone growth and specific mechanisms of spinal metastases (SM) expansion. SM most commonly affects the thoracic spine, even though multiple segments may be affected concomitantly. The great majority of SM are extradural, while intradural-extramedullary and intramedullary metastases are less frequently seen. The management of patients with SM is particularly complex and challenging, with multiple factors—such as the spinal stability status, primary tumor radio and chemosensitivity, cancer biological burden, patient performance status and comorbidities, and patient’s oncological prognosis—influencing the clinical decision-making process. Different frameworks were developed in order to systematize and support this process. A multidisciplinary, personalized approach, enriched by the expertise of each involved specialty, is crucial. We reviewed the most recent evidence and proposed an updated algorithmic approach to patients with MSD according to the clinical scenario of each patient. A flowchart-based approach offers an evidence-based management of MSD, providing a valuable clinical decision tool in a context of high uncertainty and quick-acting need. Spinal cord compression is counted among the classical cancer-related emergencies ,2. When A recent systematic review estimated that the overall cumulative incidence of spinal metastases and metastatic epidural spinal cord compression is, respectively, 15.67% and 2.84% in patients with a solid malignancy [Detailed analyses and estimations of the direct impact of metastatic spinal cord compression on the overall survival of cancer patients are scarce.Telles da Silva et al. performed a cohort study including 1112 patients with non-small-cell lung cancer and reported that, among patients with non-small-cell lung cancer, the ones that presented with metastatic spinal cord compression were 1.43 times more likely to die than those with no history of metastatic spinal cord compression . BesidesHe et al. studied patients with metastatic spinal cord compression secondary to primary hepatocellular carcinoma and described a median progression-free survival of 7.0 months and a median overall survival of 9.7 months within this population [Other studies reported the deleterious effects of metastatic spinal cord compression on the survival of patients with prostate cancer, cancer of unknown primary, and multiple myeloma ,9,10.Rades et al. developed the first overall survival predictive score for patients with metastatic spinal cord compression , while NThe tumors with the highest prevalence of bone involvement are the solid tumors arising from the breast , prostate (85%), lung (40%), and kidney (40%), as well as multiple myeloma 95%) . Vertebr5% . VertMetastatic bone disease is not a simple mechanical process resulting from the embolization of tumor cells. The formation of bone metastases depends on reciprocal interactions between the cancer cells and the stromal and immune cells in the bone microenvironment. This unique microenvironment is highly susceptible to tumor seeding. The key players in the cancer-bone interactions are the osteocytes (embedded within the bone matrix), the local immune cells, the osteoblasts (responsible for bone matrix deposition), and the osteoclasts (responsible for bone matrix reabsorption). Circulating pro-inflammatory cytokines such as TGF-beta, interleukin-6, and interleukin-1, as well as endocrine hormones such as estradiol and paracrine signaling molecules such as osteoprotegerin, mediate interactions between osteoblasts and osteoclasts, thus regulating bone homeostasis. Some of these interactions are mediated by the RANK/RANK-ligand system, which can be inhibited in vivo with the monoclonal antibody denosumab, with clinically proven results in metastatic bone disease ,14.blastic metastases , in which bone matrix deposition is dominant. These kinds of metastases are radio-opaque due to the increase of bone matrix deposition. Fractures are less frequent with these metastases, but bone pain is frequent. On the opposite end of the spectrum, tumors can create lytic metastases , in which bone resorption is dominant. With few exceptions (such as kidney cancer and multiple myeloma), and despite the dominance of bone matrix resorption, lytic bone lesions display substantial osteoblast activity, which can be shown in vivo through nuclear radioisotope imaging. These metastases are radiolucent due to a lower density of bone matrix and have a higher risk of fracture with minimal trauma. Most solid tumor metastases lie somewhere on the blastic-lytic spectrum, have simultaneous bone destruction and bone formation, and are aptly named mixed metastases. On the other hand, as mentioned above, kidney cancer metastases and myeloma bone disease usually give rise to exclusively lytic bone lesions. This is due to the suppression of osteoblast activity by the tumor. In the case of multiple myeloma, myeloma cells secrete soluble mediators such as Dickkopf-related protein 1 (DKK1), activin A, and soluble frizzled-related protein 3 (sFRP3), which directly suppress osteoblastic bone formation [Different cancer types have different impacts on this homeostatic balance. Tumors can create ormation .The central role of the osteoclast in bone metastases and myeloma bone disease has led to the use of bone-targeted agents in the setting of metastatic bone disease. Two main pharmacological classes are available, with clinically proven efficacy: the inhibitors RANK/RANKL , which inhibit osteoclast function through disruption of this signaling pathway, and the bisphosphonates , which are taken up by osteoclasts and directly inhibit bone resorption. Bisphosphonates can be further divided into nitrogen-containing bisphospohnates  and non-nitrogen-containing bisphosphonates , which act through different intracellular pathways. The common side-effects of these drugs result from inhibition of bone resorption: hypocalcemia and, more rarely, insufficiency fractures. Dosing must be adjusted for renal function. . DespiteWhen taken as a whole, the spine is the most frequent site of bone involvement, with around 87% of bone metastases localizing to the spine. Bone metastases are more common in the axial skeleton , as well as in the trabecular bone of the proximal humerus and femur. They are rare in the predominantly cortical bones of the appendicular skeleton (1% of bone metastases). The rich blood supply to the spine and the high amount of medullary bone, which acts as the main metastatic niche for tumor cells, probably explain the high prevalence of spinal metastases ,14. At tSpinal cord compression most frequently develops in a gradual and progressive way, as a consequence of the compressive effect of an enlarging vertebral mass on the spinal vasculature, thecal sac, and spinal cord . DestrucThe spinal cord compression process is not simply a physical phenomenon, but a temporal and pathophysiological continuum that may be conceptually divided in two phases: the primary and the secondary cord injury .Primary cord injury corresponds to the mechanical trauma from compression, developing immediately after the injury, leading to physiological, cellular, and biochemical changes that result in obliteration of the neural parenchyma, interruption of the axonal network, hemorrhage, and destruction of the glial membrane .Subsequently, the panoply of biological modifications within neural tissues elicited by the primary injury leads to an array of events that are related to the secondary injury and that perpetuate this loop of neuronal damage .The secondary injury is a product of the continued and persistent chemical and mechanical lesion of spinal tissues. This ultimately conducts to neuronal excitotoxicity, increased reactive oxygen concentrations and glutamate levels, and subsequent disassembly of underlying nucleic acids, proteins, and phospholipids .The secondary injury may thus be itself divided in three phases: acute, sub-acute, and chronic injury. The acute secondary injury phase is characterized by clinical features such as vascular damage , glutamate excitotoxicity, and ionic imbalance . In the Spinal metastases may affect all segments of the spine. They are most common in the thoracic spine, followed by the lumbosacral spine, and the cervical spine. Bone metastases commonly affect multiple segments . The topSpinal metastases may spread through diverse pathways, comprising venous hematogenous spread from Batson’s venous plexus, arterial spread, direct tumor extension, lymphatic dissemination, and by subarachnoid intracanalicular and leptomeningeal seeding of primary and secondary central nervous system malignancies .The seminal study of Batson, published in the 1940s , and latNowadays, it is believed that the center of the vertebral body is the primordial niche for the development of the complex interactions between the metastatic seeds and the vertebral bone soil, with subsequent posterior spatial dissemination, characterized by the involvement of the pedicles . A recenSpinal metastases may be anatomically classified as extradural, intradural-extramedullary, and intramedullary metastases, according to their location and extension . The vasThe burden of disease attributable to metastatic bone disease is high, and most of the decrease in quality of life can be traced to skeletal-related events, namely bone pain, fractures, and metastatic spinal cord compression . Among mPain related to metastatic spine disease is the most prevalent symptom and often precedes the development of neurological signs . RadiculSpinal cord compression or spinal root compression due to fracture or direct tumor invasion can be the inaugural manifestations of metastatic disease and even the first manifestation of cancer itself. A multidisciplinary approach is the hallmark of the current approach to cancer diagnosis and treatment, and spinal metastatic disease is no exception ,32.Before spinal cord compression, radiooncologists and medical oncologists cooperate to achieve control of the primary tumor and metastases  are essential;During In the post-acute phase, after an established neurological deficit, surgical decompression, and stabilization (if not performed before) may still play a role. Radiation therapy is almost universally recommended, and systemic treatment is often indicated. Because permanent neurological sequelae are expected, other professionals, such as palliative care physicians and formal or informal caregivers, will play a role in trying to avoid further loss of quality of life. Rehabilitation plays an important role, as function recovery after metastatic spinal cord compression is similar to the one observed in traumatic spinal injury [l injury .A multidisciplinary team plays essential roles at three distinct moments , the latter being the most weighting factor to consider, are variables of paramount importance for this decision process. Most decision tree proposals rely on the patients’ fitness degree for a surgical procedure or on the level of potential medium-to long- term benefit of any treatment . These dSome clinicians argue that previous data on randomized trials with surgery and/or radiotherapy and predictive factors are outdated, and new approaches should be explored with the introduction of new systemic treatments  that alter the overall survival and surgical and radiotherapy techniques  that can be used in oligometastatic patients. Therefore, some authors argue that neurologic symptom degree and onset are extremely relevant in a certain niche of patients with good performance status, who are almost naive to a wide variety of systemic treatments that could prolong survival. The neurological assessment based on both clinical   and imagExpected possible treatment complications must also be considered in the decision process. Regarding spinal surgery, complications can occur, namely durotomies resulting in pseudomeningoceles and/or cerebrospinal fluid leaks, intraoperative spinal cord hypoperfusion resulting in neurological deterioration, wound infections, postoperative hematomas resulting in spinal cord and/or nerve root compression, and also instrumentation failures such as screw pullout or pseudoarthrosis development ,50,51. IBone destruction and volumetric expansion of the tumoral lesion may lead to the collapse and compression of the of the neurological structures in and close to the spinal and nerve root canals . This deSpinal instability is itself a poorly defined concept, and the precise estimation of the degree of spinal instability is not easy to determine. An appropriate evaluation of the spinal instability degree is critical for the clinical decision-making process for patients with metastatic spinal lesions. Spinal instability may then be considered as the loss of spinal integrity under physiological loads, leading to pain, deformity, and/or neurological compromise under such physiological loads.The Spinal Instability Neoplastic Score (SINS), published in 2010, is a reliable and predictive tool for clinicians, guiding their decisions regarding the benefits of a surgical intervention in patients with primary or secondary neoplastic involvement of the spine .It assesses and scores six variables, namely the location of the lesion, characteristics of pain, type of bony lesion, radiographic spinal alignment, degree of vertebral body destruction, and involvement of posterolateral spinal elements . The scoPatients with SINS scores greater than six should be offered a surgical consultation, but the decision-making process is particularly challenging for the majority of patients, that display scores between 7 and 12, and, subsequently, have lesions labelled as “potentially unstable” . The proSINS also have limitations of different types, the biggest of which is the absence of modifiers for multiple spinal lesions  .Even though SINS has fragilities, it served as the basis for the development of the new location, mechanical instability, neurology, oncology, and patient’s features (LMNOP) approach (further explored in detail) and the Oswestry Spinal Risk Index .Machine learning algorithms and artificial intelligence-based survival predictive models have already shown promising predictive quality, in comparison with traditional risk scores, and may play a key role in the future .Each cancer type responds differently to non-surgical treatments, such as radiotherapy and/or systemic treatments, and ongoing predictive factors are known or under research. In terms of basic radiobiology concepts, cancer cells and healthy tissues have different intrinsic fractionation radiosensitivity, which is expressed with the term alpha-beta (α/β) ratio value, which is obtained through the Linear Quadratic (LQ) Model and describes the rate of clonogenic survival of certain types of cells to an amount of radiation dose per fractionation . AlthougIn clinical practice and relying on 3D radiotherapy techniques (3D-CRT) with the most frequent hypofractionation regimen published data , cancers are classically categorized in “radioresponsiveness” as described in This categorization should be revised in the future due to the emergence of new systemic treatments  and radiotherapy treatments , in which the data is not yet robust for spinal cord compression  and thern = 26), had poorer survival according to Rades et al. criteria (n = 10), were medically inoperable (n = 2), or had multiple myeloma (n = 2). Sixteen patients (40%) were not ambulatory prior to radiotherapy, and nine patients (22.5%) did not receive corticosteroids. The experimental prescription used was 25 Gy in five fractions and labelled as “precision radiation therapy” techniques  to explain the maximum dose constraint applied to the spinal cord (101.5% of the prescription dose). The experimental data outcomes were compared to a historical control group of patients treated with 20 Gy in 5 fractions in conventional RT techniques, and it was assumed that the control group would have inferior local progression-free survival. Improvement was observed in terms of the ambulatory recovery rate after radiation therapy  and in six-month survival rates (95% for LPFS and 42.6% for OS) with a low toxicity profile . When applying propensity score analysis for comparison with the historical control group (n = 664 patients), the 5 Gy in five fractions were significantly superior to the 4 Gy in five fractions with regard to LPFS (p = 0.026), but not motor function (p = 0.51) or OS (p = 0.82).The SABR-COMET phase II trial observed OS improvement with the employment of SBRT in patients in the oligometastatic setting compared to standard-of-care for each specific carcinoma. Unfortunately, this trial avoided including bone metastasis within 3 mm of the spinal cord . The PREn = 104), two distinct cohorts were observed: the laminectomy and postoperative radiotherapy cohort vs. the laminectomy plus vertebral stabilization followed by the postoperative cohort. Although Group III in each cohort had superior ambulatory rates compared to Group I in each cohort, laminectomy plus vertebral stabilization followed by postoperative RT conferred higher rates of ambulatory recovery in all prognostic groups when compared with laminectomy and postoperative radiotherapy.When patients are submitted to radiotherapy as a monotherapy treatment, the Rades criteria  can be aRecently, the same authors revisited the scoring system to assess if it was possible to select patients for upfront surgery based on data from 283 patients treated with radiotherapy alone in a prospective trial . MultiplThe anatomical, biomechanical, and neurological complexity of the spine makes the management of spinal metastases particularly challenging in comparison with the approach of bone metastases located in other skeletal topographies .There is a significant plethora of clinical criteria that should be taken into account and integrated in order to make a tailor-made and adapted decision.The patient’s performance status, a measurement of its ability to perform certain activities of daily living without the help of others and a reflection of its general condition and fitness to tolerate the treatment, is pivotal and may be classified either by the Eastern Cooperative Oncology Group (ECOG) or by the Karnofsky scales.The art of prognostication is difficult, and methodically establishing a 6-month expected survival is not simple. The Tomita and Tokuhashi modified scores, the SORG nomogram, and the New England Spinal Metastasis Score (NESMS) are useful and valuable tools to establish a prognosis, which is of paramount importance in order to decide what treatment option should be proposed.Intrinsic characteristics of cancer, such as cancer burden—conceptually estimated by the size and location of the primary tumor, the number, size, and location of metastases, the clinical effects directly attributable to the primary tumor and metastases in the neighbor or distant tissues and organs, and by markers of cellular turnover such as lactate dehydrogenase (LDH)—stage, biological behavior and histology, are also determinants of different treatments responsiveness and decisively shape the patient’s prognosis. In some cases—such as Hodgkin and non-Hodgkin lymphomas, germ-cell neoplasms, myelomas, neuroblastomas, prostate, and breast cancers—a high chemo and/or radiosensitivity is verified . For theThe clinical decision-making process is also constructed with the help of different frameworks such as the neurological, oncological, mechanical, and systemic (NOMS) framework, the already mentioned location, mechanical instability, neurology, oncology, and patient’s features (LMNOP) score, and also the Metastatic Spine Disease Multidisciplinary Working Group Algorithms (MSDA) .The golden principle that must guide the consideration of every single feature, its integration in the clinical decision process, and, overall, the management of patients with spinal metastases is multidisciplinarity.Although systemic therapy does not usually play a part in the acute management of spinal-related adverse events, the medical oncologist plays an important role in defining patient prognosis and planning systemic treatment after patient stabilization. Local treatments directed to spinal metastases and spinal cord compression are rarely curative, and systemic treatment is almost always required in the setting of metastatic disease. The long-term prognosis of the patient is thus dependent on the available options for systemic treatment, their efficacy, and tolerability.With recent advances in systemic treatment, many tumors that commonly metastasize to the spine have a good medium-term prognosis, even with metastatic disease, with overall survival measured in years. The role of the oncologist is thus essential when establishing a prognosis. For example, hormonal receptor-positive breast cancer has a median overall survival (OS) of 63.9 months with first-line hormone therapy and cyclin-dependent kinase inhibitors . HER2-poOn a slightly different note, although an uncommon source of bone metastases, germline testicular tumors deserve to be mentioned, as they are extremely chemosensitive to platinum agents and are potentially curable even with distant metastases . In thisPrognostication in lung cancer is complex because it depends on histological subtypes , the presence or absence of targetable mutations , and markers of response to immunotherapy (such PD-L1 expression) .The examples above help illustrate the complexity of prognostication and its possible impact on future decisions.The Tomita and Tokuhashi scores were originally considered the gold-standard tools for the prognostication of patients with spinal metastases, while the SORG nomogram represented a fresh and innovative strategy to tackle this issue, and, finally, NESMS took the spotlight as the score of choice. An individual, brief description is provided below.The NOMS, LMNOP, and MSDA frameworks are widely used algorithms to support and structure the clinical decision-making process. A more detailed explanation may also be read below.The Tomita score, introduced in 2001, is a prognostic and treatment-defining scoring system that categorizes cancers according to their grade, presence of visceral metastases, and number of bone metastases . An indiThe Tokuhashi score, firstly proposed in 1989 and later revised in 2005, takes a total of six variables into account, namely patient condition, number of extraspinal bone metastases, number of bone metastases in the vertebral bodies, resectability of metastases to major organs, site of primary cancer, and degree of subsequent paralysis ,87. In aDifferent series comparing the Tomita and the modified Tokuhashi scores accuracy in retrospectively determining prognosis for patients afflicted with spinal metastases have shown a higher prognostic power of both scores for patients with less than six months’ survival and a global better prognostic accuracy of the modified Tokuhashi score ,89.A nomogram offers advantages over traditional methods of constructing a survival algorithm. These traditional methods are based on rounding the effect estimates  of prognostic factors in order to weigh up the present factors and relate them to survival estimates . A nomogThe NESMS, originally published in 2015, was developed using 1-year mortality after metastatic spinal surgery as the sole outcome measure . This scNESMS has shown clinical accuracy for predicting short-term (30-day) major morbidity and mortality following metastatic spinal surgery .The most differential and striking feature of NESMS is its prospective validation as a clinical prediction score for survival in patients with spinal metastases, in a study including 180 patients . The stuDue to its accuracy and prospective validation, we have chosen this score for inclusion in our treatment algorithm.Despite their prognostic accuracy and clinical utility, one must always keep in mind that a common limitation in these scores is the fact that they are developed at a specific timepoint, framed by the treatment landscape of the moment of their development, not capturing the evolution of this treatment landscape and not taking into account new therapeutic options that are posteriorly developed—no scoring algorithm can be expected to remain relevant for long in the presence of systemic treatments developed after the algorithm’s publication.The NOMS framework development occurred in 2013. Its development process was an evidence-based medicine process, based on the available literature and expert consensus .This clinical decision framework takes four characteristics into account, namely the presence of myelopathy and degree of epidural extension (classified accordingly with the SOSG scoring system definition), tumor radiosensitivity, degree of spinal instability (defined by the SINS score), and general systemic status and conditions to tolerate a surgical procedure, providing a decision framework that considers sentinel decision points in the treatment of spinal metastatic patients ,99.The neurological assessment (N) combines specific characteristics of the clinical presentation and imaging findings, such as the presence and severity both of clinical myelopathy and radiculopathy, as well as imaging evidence of the epidural spine cord compression score (ESCC) .The oncologic (O) assessment evaluates the best method of achieving local tumor control, most often with radiation or systemic therapy .The neurological and oncological considerations together determine the need for radiotherapy and/or surgery ,98.Mechanical instability (M) is assessed separately, and its definition is based largely on the presence of mechanical pain correlated with radiographic criteria embedded in the SINS . As noteThe assessment of systemic disease (S) and comorbidities is paramount in this approach. A patient who is too frail may be unable to tolerate an intervention or to derive a benefit from it ,98.The LMNOP system evaluates a number of variables: (L) Location of the disease in the spine and the number of spinal levels involved, (M) mechanical instability, (N) neurological signs and symptoms, (O) oncology-related factors , and (P) patient-related factors such as patient fitness, prognosis, and response to prior therapy (P) .Although not an actual treatment algorithm, LMNOP works as a general framework to help decide the most appropriate treatment and is a useful mnemonic for the key factors that must be assessed in order to define the most appropriate treatment for an individual patient with metastatic spine disease .Location refers not only to the topographic levels of involvement (solitary vs. multilevel) but also the involvement of the anterior and/or posterior columns, and should be evaluated in detail . The assIn the LMNOP framework, patients with spinal cord compression may be offered open surgery depending on instability, prognosis, and patient fitness. Spinal instability without spinal cord compression may be treated with minimally invasive surgical procedures. For particularly radiosensitive tumors, external beam RT may be offered in monotherapy, even in the setting of spinal cord compression. In the case of radioresistant tumors, sterotactic radiosurgery is an attractive approach .This algorithm has been developed using evidence from the literature and expert consensus. While highlighting the need for a multidisciplinary approach and stressing the role of interdisciplinary referrals, it provides clear and direct recommendations regarding the use of available treatment options .Specific management algorithms are provided for five different clinical scenarios from the less severe asymptomatic spinal metastases or uncomplicated painful spinal metastases to the more severe stable pathologic vertebral compression fracture, unstable pathologic vertebral compression fracture, and metastatic epidural spinal cord compression . PatientMetastatic spine disease is comprised of a wide variety of clinical manifestations with variations according to the primary neoplastic disease involved, the topography of spinal involvement, the presence or absence of spinal cord compression, and spinal stability (which can be defined by the SINS) .As previously mentioned, there are some algorithms that guide decision-making in metastatic spine disease, namely the NOMS framework , LMNOP SHowever, it is crucial to note that the NOMS framework uses the SORG nomogram , the LMNOP system is a general framework and not an algorithm, and the MSDA is relatively complex and does not use a prospectively validated prognostication tool (such as NESMS). The override of prognostication tools by clinical judgement in cases of cancers for which the treatment is nowadays substantially better than it was at the time of the prognostication tool development is not foreseen in any of these clinical decision-making instruments. The quality and efficiency of the approach to metastatic spine disease patients tend to improve when a multidisciplinary vision and decision-making are adopted . A flowcWe propose an innovative updated flowchart that, in our view, is a simpler and more user-friendly tool than the previous mentioned frameworks/systems to guide decision-making, with a dichotomized approach to two distinct clinical scenarios as opposed to multiple scenarios, which render previous scores harder to use.This integrative approach conceptualization was primarily based on an extensive literature review and was enriched by the personal clinical experience of the experts at our center. Its development was gradual and resulted from the integration of the most updated data regarding the subject and different critical inputs and views of the experts at our center.Our objective is to define a set of guidelines to facilitate a multidisciplinary and systematic approach to patients with metastatic spine disease.As previously mentioned, owing to the inherent heterogeneity of metastatic spine disease, the definition of an algorithm-based diagnostic and therapeutic approach is a complex task.We aim to create a proposal for a multidisciplinary team-based approach to metastatic spine disease. In our center, we considered that the team should include oncologists, radiotherapists, neurosurgeons, orthopedic surgeons, hematologists, and neuroradiologists.The design of the proposed flowcharts intends to avoid the time-crystallization phenomenon that is inherent to many of the previously described algorithms and flowcharts. Otherwise, our aim is to draw an evolution-sensitive and flexible tool that has the potential to keep accuracy and rigor when used in an unknown future timepoint with radically different options for systemic treatment .The flowcharts in our proposal for decision-making regarding metastatic spine disease integrate multidisciplinary care, allowing for a quicker and more objective approach, which is paramount to achieving better clinical results.Our proposal does not aim to lessen the importance of a personalized case-by-case analysis of each patient’s clinical status. Consequently, our goal is not to make the approach to metastatic spine disease rigid and inflexible.Scenario 1 comprises patients with KPS ≤ 40% and/or expected 6-month survival < 50% and/or oncologic disease with multisystemic and progressive involvement and a lack of therapeutic options .Scenario 2 includes patients with KPS > 40% and expected 6-month survival ≥ 50% and oncologic disease with stable/limited involvement or multisystemic involvement with available therapeutic options .We propose the division of patients with MSD into two clinical scenarios involving the Karnofsky Performance Status (KPS), expected 6-month survival according to the NESMS, and the status of neoplastic disease:The clinical scenarios were defined to facilitate the dichotomization of patients into two distinct groups that differ according to their performance status, predicted survival at 6-months based on the NESMS score, and status of neoplastic disease (encompassing the stage of systemic disease and the presence or absence of therapeutic options).We chose to utilize the Karnofsky performance status as it is an ordinal scale which allows for a descriptive prediction of the clinical status of the patient and his capacity to perform ordinary tasks critical for daylife functionality. The 40% cutoff was defined as it signifies that the patient is bedridden for more than half of a day, translating into a clinical stage of oncologic disease in which the patient probably is not capable of tolerating more invasive or aggressive therapeutic modalities.The NESMS scoring system was our choice in terms of prognostication tools owing to the fact the prospectively validated this score’s statistical significance as a tool to calculate survival at 6-months and 1-year, regardless of the therapeutic strategy chosen.However, while prognostication using the NESMS score is advocated, the medical oncologist may override this score in the case of the existence of innovative treatments with good efficiency and tolerability which have appeared since the development and validation of the NESMS. The therapeutic approaches in oncologic patients are ever-evolving, and new efficient drugs are regularly being approved by regulating pharmaceutical associations.Regarding the status of neoplastic disease, progressive disease with a lack of oncological therapeutic options should tend to deter the clinician from proposing the patient undergo more invasive therapeutic modalities which the patient possibly is not able to tolerate.Our algorithm shares many similarities with the NOMS algorithm, upon which it was based. As in the NOMS algorithm, treatment is based on factors related to the tumor , to the patient (performance status and fitness for surgery), and to the degree of spinal cord compression and spinal instability. Similar to the NOMS algorithm and the LMNOP framework, it highlights the role of palliative surgery for pain control in spinal instability and refractory pain. Unlike the NOMS algorithm, we have chosen to use NESMS for prognostication instead of the SORG nomogram, as the former has been prospectively validated with excellent accuracy. Newly expected data regarding further validation of the SORG ML algorithm may also allow the possibility of using that specific tool for prognostication as part of these flowcharts.We note that we propose the use of these algorithms as an aid to the clinical decision, not as a replacement of clinical judgement. The clinical judgement of the patient’s oncologist should always be taken into account, and prognosis-prediction scores must be used with caution as it is not possible to guarantee that a specific patient’s clinical scenario is completely foreseeable by the NESMS scoring system or other prognostication tools. Therefore, although our support for having the medical oncologist override the NESMS may be criticized as a way of introducing subjectivity into what is meant to be an objective decision, we claim that the use of expert opinion is advisable in this case until the NESMS has been validated in a more modern setting, taking into account new developments in systemic treatment.Due to the improvement of medical and surgical management of oncologic patients, metastatic spinal disease is gradually becoming more prevalent in the current day . This coIn this multidisciplinary article, we present a review of the most recent data regarding the physiopathology of metastatic spinal disease, prognostic scores, treatment options, and we propose an updated algorithmic approach to the pathology according to the clinical scenario of each patient ,98,102.We propose a flowchart-based approach to patient management, which we believe will result in better results in an evidence-based management of metastatic spinal disease and spinal cord compression.Nevertheless, we underline that the goal of this type of approach is to assist in clinical decisions and not to replace a case-by-case reflection concerning the specificities of each patient.Metastatic spine disease management remains a palliative approach. Nonetheless, medical and surgical care are cardinal in ameliorating pain and improving quality of life in such patients .


The electroencephalogram (EEG), based on brain–computer interfacing (BCI) and medical images generated as secondary or tertiary byproducts within neural activities, is widely used in clinical diagnosis, patient monitoring, and biomedical research. Therefore, how to effectively detect, analyze, and study biomedical signals is of great significance for human beings to study life phenomena and medical science. Recently, machine learning technologies, especially deep learning, have significantly advanced biomedical signal analysis. Following this line, the articles contemplated in this Research Topic show that this field of knowledge is rapidly expanding, and considerable advances have been made in the last few years. There remain various unsolved problems with respect to the use of advanced deep learning methods and machine learning in biomedical signal analysis, e.g., weak generalization, inexplicability, limited datasets, and data silos. In this Research Topic, we have an example of using a multi-modal deep learning model for the EEG or medical images, but the feasibility of these multi-modal works relies on raw datasets. Furthermore, the potential of transfer learning frameworks and adversarial learning is being studied in EEG or medical image processing.Resting on their strong fitting ability for mass data, machine learning and deep learning models are popularly used to analyze biomedical signals such as the EEG and medical images, which have shown superiority in P300-BCI, motor imagery, and medical image processing, but their ability of generalization in small datasets is still limited. Research works devoted to studying proper machine learning and deep learning solutions of biomedical signals analysis, and the interpretability of models, are therefore of utmost importance. In this editorial, we summarize the main findings and viewpoints detailed within each of the seven contributing articles using deep learning in the EGG or medical image analysis.Hou et al.. They found that the multi-modal dual-level stimulation paradigm is a powerful tool for enhancing the performance of motor imagery classification, and the proposed method can precisely select a few key frequency sub-bands from the filter bank.The advantages of machine learning methods in decoding EGG signals have been discussed, and a sparse spatial decoding method based on the support vector machine has been proposed by Qiu et al. proposed a multi-modal fusion framework to achieve the complementary characteristics between the EGG and functional near-infrared spectroscopy (fNIRS) based on multi-level progressive learning with multi-domain features. The experimental results prove that the task-related brain electrical and hemodynamic information can be fully extracted through multi-domain features, and the redundant information can be eliminated through the ASO algorithm. The multi-domain features of the EEG and fNIRS can be effectively fused through multi-level progressive machine learning. Zhou et al. reported that the modality-specific features extracted by deep networks are also important in aggregating task-related and complementary information from different modalities. Moreover, the ablation study proved that the bilateral symmetry of head in MRI images may help to progress the performance .Multi-modal biomedical signals can provide complementary physiological activity information so as to provide a more comprehensive and accurate interpretation of the brain function. For improving the performance of classification in motor imagery and mental arithmetic tasks, Xuan et al. directly transferred natural image knowledge into a model of MRI image segmentation and achieved better accuracy than physicians. In this line, Chen and Chen proposed an adaptive selection-based dual-source domain feature matching network that can sift helpful knowledge into the target model from dual-source models. In addition to selecting beneficial knowledge from the source domain, mapping the source domain and target domain into a specific feature space with the same distribution is also a proper way. This mapping was performed by Liu and Cui. The utilization of the maximum mean discrepancy is also reported in this Research Topic. On the other hand, adversarial learning is a novel strategy to augment small datasets or improve the ability of generalization. Zhang et al. studied boundary and mask adversarial learning to aggregate helpful features of boundaries and assist the mask segmentation task.For the weak generalization and unsatisfying performance caused by the small amount of biomedical signal datasets, transfer learning is a popular and potential solution. The application of machine learning and deep learning is expanding in the field of biomedical signal analysis. The support vector machine-based, multi-modal, transfer, and adversarial learning works summarized here are practical and outstanding. These works are new, meaningful examples of the application of machine learning and deep learning in biomedical signal analysis, and more excellent works about this promising area will be reported in the future.All authors listed have made a substantial, direct, and intellectual contribution to the work and approved it for publication.


The human gut microbiota is believed to be responsible for multiple health-impacting host effects. The influence of gut microorganisms on the human host begins immediately after birth, having long-lasting health effects, while the gut microbiota itself continues to develop throughout the host’s entire life. The purported health-associated effects of the gut microbiota have fueled extensive and ongoing research efforts. Nonetheless, the precise mode of action of functionalities exerted by microbial colonizers of the infant intestine is still largely unknown. The current perspective intends to illustrate major future investigative directions concerning the human gut microbiota with a specific focus on infant-associated gut microbes. The gut microbiota develops and expands during the course of host infancy and adolescence to ultimately reach its relatively stable form during host adulthood-4. Increasing scientific and clinical data reveal that the early life gut microbiota elicits, within a critical window of time, long-lasting health effects on its human host-7. Remarkably, there are many scientific indications suggesting that specific microbial compositional profiles of the human large intestine are correlated with certain diseases. Nevertheless, current knowledge on the composition and associated functions of the intestinal microbiome is mostly derived from bioinformatic analyses, and at best, there are currently fragmented data concerning the biology of intestinal bacteria and the molecular mechanisms that allow microbe-microbe and microbe-host interactions. This thus represents a very serious limitation in defining predictor variables of human health that are based on microbiota composition and their associated functionalities. This knowledge gap is a major impediment preventing clinical advances, as it, for example, would allow us to discern if a microbiota shift observed in an individual represents a cause or a consequence of a disease. Documentation of the factors that drive the establishment and persistence of gut microbiota is still in its infancy. In this context, there is an extensive body of data pertaining to external factors such as mode of delivery, infant feeding mode, gestational age, environments, and prophylactic therapy during pregnancy, all of which have been shown to modulate the composition and function of the gut microbiota. Conversely, while the maternal inheritance of bacteria by vertical transmission has been well documented, this being consistent with the co-evolutionary scenario as supported by the holobiont concept,10, scientific knowledge on host factors driving such key biological phenomena remains scarce. The human gut is considered an organ, most of which is densely colonized by microbial communities, commonly referred to as the gut microbiotaAltogether, this underscores the important scientific challenges that remain to be overcome in terms of elucidating functional aspects exerted by the intestinal microbiome in infants and uncovering host factors responsible for the assembly of the neonatal enteric microbiome. However, despite an ever-increasing interest in the functional discovery of microbiota functionalities, progress in such research endeavors and associated molecular mechanisms is still very slow and patchy at best.The need to establish and expand our knowledge concerning the functionalities of human gut microbes, therefore, represents a major challenge and research frontier for the microbiologist. Such research efforts may best be initiated with a focus on the infant gut microbiota because it is simpler in terms of the number of bacterial taxa with respect to the adult microbiota, and, as outlined above, infant gut microbes are expected to play a pivotal role in the foundation of human health.in vitro conditions-16. This prompted the establishment of novel methodologies intended to cultivate these thus far unculturable bacteria [. Furthermore, the application of various cultivation parameters permitted the identification and subsequent characterization of many new microbial taxa representing elements of this human microbiota dark matter. The introduction of culturomics protocols in research projects aimed at exploring as yet unknown elements of the complex intestinal microbiota has provoked an approximately 23% increase in the current collection of cultivated gut microbes. MALDI-TOF mass spectrometry allows very reliable and low-cost identification of bacterial isolates in high-throughput culturomics workflows such as those that need to be applied for the precise mapping of the microbial biodiversity of the human gut-16. The establishment of cultivation-independent techniques, in particular 16S rRNA-based microbial profiling and shotgun metagenomics, facilitated the discovery of novel microbes residing in the human body. Most of these newly identified microbes had escaped detection because they were unculturable under the applied bacteria . These ain vitro and/or in vivo settings to assess their biological features. In addition, culturomics efforts may also produce new therapeutic agents in the form of microbial taxa to be exploited as bacteriotherapy approaches. However, the principal limitation of culturomics is denoted by the considerable requirements of biological material and the difficulty of acting as a high-throughput system . Nevertheless, recent technological developments offer the use of robotic systems which can transform culturomics approaches into high-throughput processing procedures. An additional important constraint of culturomics is represented by the fact that such approaches cannot detect bacteria that were identified by culture-independent attempts, such as 16S rRNA-based microbial profiling, but as yet have escaped isolation, commonly referred to as “still not culturable” bacteria. To overcome this limitation, a novel method, i.e., the “hybrid approach”, has recently been established, which is based on the combined use of culturomics trials and deep shotgun metagenomic sequencing. Thanks to metabolic modeling facilitated by shotgun metagenomics data, this hybrid approach provides insights into the nutritional requirements and metabolic features of those microbial species that have been recognized as new, thus guiding the design of culturomics approaches for their isolation. The key role of culturomics in the context of dissecting the functional roles played by the enteric microbiome is demonstrated by the fact that the use of this novel omics approach has uncovered the existence of microbial taxa that can be examined under The isolation and subsequent cultivation of those not yet cultivable microorganisms by culturomics approaches will also be important to establish exhaustive public repositories of bacterial strains. In fact, an important new perspective for the future development of gut microbiota-based science is to invest resources that will allow the isolation and subsequent genetic characterization of novel gut microbes representing the complete microbial genetic diversity of the human gut microbiota. In this context, it will also be crucial to archive these gut bacteria as pure culture in the form of viable stocks that can then be stored in international and open-source microbial culture repositories that are publicly available to every scientist interested in investigating the functional contribution of these microorganisms to the human gut. in vitro approaches to perform such experimental trials. In this context, human gut organoids, which have recently been realized as the “gut-on-a-chip” model and represent self-organizing three-dimensional epithelial structures originating from stem cells, are important developments that may be used to mimic the human host-21. More specifically, the “gut-on-a-chip” is a microfluidic device in which cells are cultivated with organ-relevant chemical gradients and dynamic mechanical signals, therefore reflecting structural tissue characteristics and functional intricacies of a living organ in an in vitro format. Furthermore, unlike other host models, such as human cell monolayers, this device is an active arrangement simulating gut peristalsis and containing peripheral blood mononuclear cells and endothelial cells, overall encompassing a highly relevant and valuable human intestinal model. As described above, the recent discovery and dissection of the intestinal microbiota in terms of composition and putative correlations with health conditions of the host have facilitated amazing insights, thereby creating therapeutic opportunities. Conversely, very little is known about the functional features of the human gut microbiome and, specifically, about the presumed crosstalk established between enteric bacteria and their human host, i.e., microbe-host communication, as well as with each other, i.e., microbe-microbe interactions . Importain vitro model system displays some limitations due to the difficulties associated with the settings of the appropriated environmental conditions  for the maintenance of complex microbial communities and the absence of several crucial functionalities of the host, such as the host endocrine system. Nevertheless, this . Nevertheless, murine models, similar to all other animal models , have important limitations, which prevent direct translation of animal model-based research results to humans. Instead, pig-based models display the potential to be a viable model for host-microbe interactions, particularly for the human infant and gut-brain axis research. A large part of current scientific literature concerning microbe-host interplays is based on conventional and/or axenic micein vitro approaches that mimic the human intestine and could be employed to evaluate microbe-microbe crosstalk-27. These synthetic microbiota assemblies were accomplished based on complex culturomics approaches, allowing the establishment of defined microbial communities which resemble the adult intestinal microbiome. These artificial gut microbiotas are generated to encompass “a core intestinal microbiota”, consistent with the classification of the enteric microbiome in enterotypes. The core gut microbiota includes bacterial species, whose biological roles are presumed to be essential for the functionality of the intestinal microbiome. Nevertheless, the concepts of enterotypes as well as a core intestinal microbiota are still not universally accepted by the scientific community, and there is still a large debate around them. Synthetic or defined microbial microcosms have recently been described for the purpose of in vitro models that can host such synthetic microbiotas. In this context, the use of bioreactor systems has been demonstrated to be an efficacious approach to achieving stable cultivation of keystone species of the intestinal microbiota,32. Nevertheless, most of these systems do not incorporate the mucosal component of the human gut and, except for some environmental parameters, reproducing those occurring in the human gut, lack the majority of host-produced molecules such as mucins. These limitations are likely to reduce the overall feasibility of these systems in terms of their relevance as models to reproduce microbe-host crosstalk; nonetheless, they may still be valuable to uncover and investigate microbe-microbe interplays. For the purpose of disclosing microbe-microbe crosstalk pathways and mechanisms, it will be crucial to employ . Similarly, the discovery of other microbiota-derived small molecules, including ribosomal synthetized posttranslational modified peptides, lantibiotics, bacteriocins, microcins, and other products of fatty acid, vitamin, carbohydrate, and/or amino acid metabolism, represent new frontiers of research regarding the functionality of gut microbes and their potential biological role in terms of immune-modulation and antibiosis. Such exploration will be fueled by in silico prediction of microbiome data, but it will require a detailed experimental metabolomic validation based on the cultivation of single bacterial strains or synthetic microbiota under in vitro settings using gut microbiota models.An important new avenue of research involving the gut microbiota is aimed at understanding the metabolic contribution of gut microbes in infants, with a specific focus on microbial-driven metabolites such as indole-3-lactic acid and its interaction with the host. In this context, it has been shown that tryptophan metabolism by Bifidobacteria leads to the production of indole-3-lactic acid, which in turn affects the host immune system, thus representing an intriguing example of microbe-host communicationin vitro reconstruction of the microbiota naturally residing in different human body sites has been achieved using bioreactor models. Such an in vitro system allows the cultivation and maintenance of a simplified microbiota, i.e., a synthetic microbiota, in an in vitro gut environment setting, and, thanks to functional genomics analyses such as metatranscriptomics and metabolomics experiments, it will be possible to identify the microbial genetic elements involved in microbe-microbe crosstalk.To better understand the biological functions of gut microbes, it will be crucial to evaluate how the co-occurrence of different gut microorganisms might influence the molecular dialog of each bacterial strain . Recentlin vitro conditions have delineated trophic interactions aimed at utilizing complex carbon sources  that are practically inaccessible to most bacterial strains when cultivated on their own. Such cross-feeding scenarios appear to represent a very common metabolic strategy of members of the human gut microbiota that will most likely target very different classes of molecules, including not only components of the diet or host-produced molecules but also drugs, with very important effects on host physiology and host health.Preliminary analyses involving simple microbial gut communities represented by two bacterial strains cultivated under . Nevertheless, relatively limited research efforts have focused on investigating microbiome interactions that occur between bacteria and the human host and evaluating how the microbiota composition and its linked metabolic features influence host health. There are fundamental and commercial interests directed at applying microbiome members and/or their metabolic products as accurate human health predictors and developing novel strategies to modify and shape the infant intestinal microbiome, especially in those babies delivered prematurely and/or by Caesarian section (CS) as they frequently possess a gut microbiota that is different from their full-term, vaginally delivered counterparts,7. Therefore, future preventive clinical procedures may be aimed at encouraging the establishment of CS/premature babies with an artificial microbiota encompassing bacteria known to be typically obtained from the mother during vaginal birth. Recently, very significant progress has been made in understanding the composition of the infant intestinal microbiome thanks to the use of novel culture-independent approaches such as metagenomics methodsHowever, these intervention strategies necessitate a profound knowledge of the composition of the infant intestinal microbiome and the microbiota components responsible for the support of human health. Another important potential application is to artificially influence the establishment of the initial human intestinal microbiome through the pregnant (future) mother. Handling the maternal intestinal microbiome throughout pregnancy is assumed to change the assembly of the gut microbiota during the very early stages of life. Nevertheless, many unanswered questions remain, for example, how and why specific bacterial taxa are acquired by infants as a result of vertical inheritance from their mothers. Furthermore, our knowledge concerning the persistence of certain bacteria in the large intestine of infants upon weaning, as well as their influence on host health conditions, remains relatively limited. Another question that remains open is about the contribution of host genetics in driving the transfer of microbes between generations and the understanding of the genetic contributions shaping intergenerational sharing of microbiomes.-What is the extent of the microbial biodiversity residing in the human gut? -What is the functional contribution of the gut microbes to the host’s wellness?-Are there bacterial strains that persist in the human gut for the entire life of a human being?-How should gut microbes be selected to constitute a synthetic microbiota?-What is the contribution of host genetics in modulating the vertical transmission of microbes from one human generation to the next?


The glymphatic system is a brain-wide perivascular pathway driven by aquaporin-4 on the endfeet of astrocytes, which can deliver nutrients and active substances to the brain parenchyma through periarterial cerebrospinal fluid (CSF) influx pathway and remove metabolic wastes through perivenous clearance routes. This paper summarizes the composition, overall fluid flow, solute transport, related diseases, affecting factors, and preclinical research methods of the glymphatic system. In doing so, we aim to provide direction and reference for more relevant researchers in the future. It is traditionally believed that the lymphatic system doesn’t exist in the central nervous system . Thus, cSince last decade, many researchers in the field of neurology, neurodegenerative diseases and physiology have aimed to study and develop the glymphatic system, providing a brand-new perspective for us to understand brain diseases: the overall fluid flow of the brain rather than a specific lesion or structure. Herein, we summarized the components of the glymphatic system, the fluid circulation mode within this system, how pathogenic solutes are transported in certain diseases, affecting factors of its function, and by what means we can study the glymphatic system. All above may provide direction and reference for brain diseases and medical researchers.The glymphatic system is a brain-wide perivascular pathway driven by AQP4 on astrocytic endfeet, which can deliver nutrients and neuroactive substances to the brain parenchyma through peri-arterial CSF influx pathway and remove metabolic wastes through peri-venous clearance routes . This syIn the 19th century, Rudolf Virchow and Charles Robin found annular tunnel spaces around penetrating arterioles in the brain parenchyma and named them Virchow-Robin spaces (VRS). Subsequently, researchers found that all arterioles, capillaries, and venules in the brain parenchyma were surrounded by this structure resembling a donut-shaped tunnel, and called it Perivascular spaces (PVS) . The innin vivo two-photon imaging and immunofluorescence techniques to track the CSF circulation through the brain interstitial space. Results from this study demonstrated that CSF entered brain parenchyma along the PVS and rapidly exchanged with ISF. Then the mixture of CSF and ISF was cleared along the perivenous drainage pathways , b-fibroblast growth factor (bFGF), interleukin-6 (IL-6) and angiopoietins, prostaglandin E2 (PGE2), epoxyeicosatrienoic acids (EETs), and 20-hydroxyeicosatetraenoic acid (20-HETE)  , leading20-HETE) , further20-HETE) .AQP4s are located in surfaces of the blood–brain barrier and CSF–brain barrier and are expressed in astrocyte endfeet processes surrounding capillaries. Astrocyte processes comprise the subpial and subependymal glial-limiting membranes and the perivascular astrocytic end-foot processes that circumscribe the entirety of the cerebrovasculature . The disMoreover, the glymphatic system is not only a specific tissue or structure but also a functional generalization of the flow and transportation of fluid in the brain. After CSF enters the brain parenchyma, it mixes with ISF, exchanges substances, and clears the metabolites of brain tissue through the perivenular outflow channel. A functional diagram of the glymphatic system is shown in There are four kinds of fluid in the brain: blood, CSF, ISF, and intracellular fluid. Blood in vessels and ISF in brain parenchyma are separated by the blood-brain barrier (BBB), while blood and CSF are separated by the blood-cerebrospinal fluid barrier (B-CSFB) . The comTraditionally, fluid circulation in the glymphatic system is thought to be driven by pressure difference, respiration, and arterial pulsation . CSF is The glymphatic system complements the problems that cannot be explained in the traditional CSF circulation theory. For example, in traditional theory, CSF is mainly produced by the choroid plexus . In thisThere are two categories of solutes transported in the glymphatic system: (1) Nutrients (such as glucose and lipids)  and neurAlzheimer’s disease (AD) is a neurodegenerative disease mainly characterized by memory impairment and decreases in brain volume . The patParkinson’s disease (PD) is a chronic neurodegenerative disease related to unbalanced production and clearance of α-syn . When meStroke is mainly divided into hemorrhagic and ischemic stroke, characterized by local nerve dysfunction due to cerebral blood circulation disorder . HemorrhBrain edema is a pathological phenomenon of brain tissue damage caused by increased brain volume and cranial pressure due to excessive intracellular or intercellular fluid. Brain edema is traditionally divided into two phases: early cytotoxic and later vasogenic phases . In cytoTraumatic brain injury (TBI) is caused by brain tissue trauma, which leads to brain dysfunction . FollowiMultiple sclerosis (MS) is a chronic immune dysfunction disease characterized by inflammation and demyelinating plaques . The chaAmyotrophic lateral sclerosis (ALS) is a progressive degenerative motor neuron disease characterized by the selective death of motor neurons . AlthougDiabetic patients often have cognitive and memory decline, and are at higher risk of vascular diseases and AD . MRI anaA migraine is a recurrent unilateral or bilateral fluctuating headache. Cortical spreading depression (CSD) is a potential signal that waveform can be characterized by an intense neuronal activity that slowly progresses over the cortex and a period of neuronal inactivity . Acute pThe discovery of the glymphatic system gives us a new understanding of the efficient fluid transport and metabolite clearance of the central nervous system, which can help us better understand the pathogenesis of diseases and find new ways to treat them. Notably, the abnormal accumulation of Aβ , tau proThe function of the glymphatic system is partly influenced by the sleep-wake cycle. In the sleep state, the function of the glymphatic system is significantly enhanced than in the awake. CSF inflow of mice in sleep and awake states were compared by in vivo two-photon imaging technology, and results showed that, within 30 minutes after CSF tracer injecting, the tracer inflow of the same mice in the awake state was 95% lower than that in the sleep state . MoreoveMany neurodegenerative diseases  often occur in middle and old age, and their pathogenesis is associated with the accumulation of Aβ and tau protein . Aβ and The function of the glymphatic system is closely related to the anesthetics selected in the experiment, and different anesthetics play a role in promoting or inhibiting. In the awake state, CSF tracers injected into mice cisterna magma hardly enters brain parenchyma . HoweverDifferent body positions can also affect the function of the glymphatic system during sleep or anesthesia. The transport efficiency of the glymphatic system in the lateral position of anesthetized rats was higher than that in the supine and prone positions by dynamic-contrast-enhanced MRI and kinetic modeling. The tracer in the brain of prone rats entered and cleared slowly in the glymphatic system . OpticalAlcohol influences the glymphatic system in two different ways. Glymphatic system function was significantly inhibited after mice were exposed to 1.5 g/kg (binge level) ethanol acutely and chronically . ChronicSports can improve cognitive ability, especially in patients with vascular degeneration and neurodegenerative diseases. The glymphatic system function of voluntary wheel running and sedentary mice were compared. CSF inflow continuously increased in voluntary exercise mice during the awake period, mainly concentrated in the hypothalamus and ventral parts of the cortex. However, it also occurred in the middle cerebral artery territory. Voluntary exercise increases CSF flux in a wide range of brain regions in mice, which may be related to the role of exercise in promoting cognition . AnotherIn short, these influencing factors affect the fluid inflow and outflow of the glymphatic system mainly by regulating the cardiovascular and respiratory systems. When arterial pulsation slows down, or respiration is inhibited, the flow of CSF is inhibited, affecting the clearance of macromolecular metabolic proteins in the brain. The accumulation of metabolic proteins in the brain parenchyma further affects the size of the brain interstitial space, thus increasing the resistance to CSF inflow. However, the specific mechanisms involved in this process still need further exploration. These influencing factors suggest that attention should be paid to the patient’s daily sleep, drinking, and exercise behaviors to prevent brain-related diseases. When designing experiments related to the glymphatic system, attention should be paid to the choice of anesthesia, the position, and the age of experimental animals.in vivo and ex vivo techniques. Imaging ex vivo is usually performed with light sheet fluorescence microscopy of an observed brain or spinal cord sections from the optically cleared brains of mice receiving CSF tracer injections while under anesthesia (in vivo is mainly utilized to observe the flow of CSF in the brain by injecting a CSF tracer into the cisterna magna and using two-photon fluorescence imaging (TPI)  , near-inng (TPI) , transcrng (TPI) , magneting (TPI)  and so ong (TPI) . Howeverng (TPI) . Compareng (TPI) . Howeverng (TPI) . MRI canng (TPI) . It can ar space . MRI  - loaded PLGA nanoparticles were injected near the regional lymph node in the neck of mice. The particles would first converge in the regional deep cervical lymph nodes, then be efficiently transported to the brain through meningeal lymphatic vessels, significantly inhibiting glioma growth in mice and prolonging the survival period of treatment. The uptake of drugs injected with this method in the brain is 44 times higher than that by intravenous injection . Drug deHowever, the theory of the glymphatic system is still controversial. Firstly, some researchers believe that the function of the glymphatic system is exaggerated. For instance, several studies have proved that CSF flows along the peripheral spaces of large vessels in convective flow or dispersion and then regulates CSF / ISF exchange in diffusion. This is inconsistent with the fact that CSF / ISF exchange is realized through bulk flow in the glymphatic system . SecondlMoreover, there are still some situations that the glymphatic system has not explained. In some diseases like AD or PD, it is not clear whether the malfunction of the glymphatic system occurs first or whether the relevant pathological changes like Aβ or tau-protein deposit happen in the first place. This is crucial to understanding the etiology of diseases. Besides the exchange between CSF/ISF, will the balance be influenced by diseases or altered in some scenarios?In a word, the proposal of the glymphatic system breaks the traditional understanding that there is no lymphatic system in the brain, complements the theory of fluid circulation and metabolic pathways of brain wastes, and draws a lot of attention to the critical role of fluid circulation in maintaining the homeostasis of the brain environment, which is of great significance. However, there are also many controversies and unsolved problems in the glymphatic system, which requires more researchers to engage in the field for further study, constantly innovate and improve the research paradigm and methods, and make better use of the results of the glymphatic system, to play a more significant role in treating related diseases.All authors listed have made a substantial, direct, and intellectual contribution to the work, and approved it for publication.


Oral submucosal fibrosis (OSF) is a chronic, progressive and potentially malignant oral disorder with a high regional incidence and malignant rate. With the development of the disease, the normal oral function and social life of patients are seriously affected. This review mainly introduces the various pathogenic factors and mechanisms of OSF, the mechanism of malignant transformation into oral squamous cell carcinoma (OSCC), and the existing treatment methods and new therapeutic targets and drugs. This paper summarizes the key molecules in the pathogenic and malignant mechanism of OSF, the miRNAs and lncRNAs with abnormal changes, and the natural compounds with therapeutic effects, which provides new molecular targets and further research directions for the prevention and treatment of OSF. OSF is a chronic and insidious oral disease involving multiple parts of the oral cavity and is generally considered to be a disease related to collagen metabolism disorder. Increased collagen formation and decreased collagen degradation lead to the deposition of collagen fibers in oral tissues, which in turn leads to the development of OSF. Patients often go to the doctor because of burning pain of the oral mucosa, accompanied by ulcers, blisters, a diminished sense of taste, a dry mouth, lip and tongue numbness and other symptoms, such as a serious mouth opening restriction, dysphagia and tongue movement disorder. The disease has a certain malignant potential, which belongs to oral potentially malignant disorders (OPMD). At the same time, OSF is closely related to the occurrence of OSCC .The data published by the World Health Organization (WHO) in 2022 reported that the global prevalence of OSF was 4.96%, with a 95% confidence interval of 2.28–8.62 . The disStimulating factors such as eating pepper, smoking and drinking can aggravate the progression of OSF . A studyIndividuals who are anemic and deficient in vitamins A, B, C and iron have an increased risk of OSF . StudiesThe interaction between trace elements in saliva and OSF has been confirmed by some studies; the copper level and copper/zinc ratio in the saliva of OSF patients are significantly increased . The levSome scholars believe that mucosal fibrosis may be related to allergic reactions caused by exogenous antigen stimulation . MoreoveStudies have found that the frequency of HLA-A10, HLA-B7, HLA-DR3, haplotypes A10/DR3, B3/DR3 and A10/B8 in OSF patients increases. The increased frequency of the HLA-B76 phenotype and the increased frequency of the HLA-B51/Cw7 and HLA-B62/Cw7 haplotypes were also associated with OSF susceptibility . Some inBetel quid (BQ) is chewed by over 0.6 billion people globally, especially in Asia, where the BQ chews are formulated in a variety of formulas, but usually include betel nuts, betel leaves and hydrated lime, and often contain tobacco . The IntThe crude fiber, areca alkaloids, slaked lime, ROS, copper and other components of BQ play different degrees of promoting role in the process of OSF. Long-term chewing of BQ is both a physical and chemical stimulus. Arecoline is a primary areca alkaloid, which itself induces ectopic changes in homologous chromosome alleles , and alsArecoline activated YAP by increasing the level of ROS and inducing the PERK pathway, leads to the start of the endothelial–mesenchymal transition (EMT) and then OSF . The ROSMore soluble copper can be detected in the oral environment of QB chewers and can be absorbed by buccal mucosa, which will promote the process of OSF . PlasminIn the past two decades, non-coding RNAs (ncRNAs), which do not encode proteins, have been found to play a key role in physiological and pathological processes by regulating gene transcription and translation through various mechanisms, such as microRNAs (miRNAs), long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), etc. .Yang et al. observed that the expression of miR-29c in fibrotic buccal mucosa fibroblasts (fBMFs) was downregulated and that transfection of miR-29c mimics reduced the fBMFs migration ability and collagen gel contractility whereas inhibition of miR-29c could induce a myofibroblast phenotype, and mir-29c also inhibited the activation of myofibroblasts by inhibiting tropomyosin-1 (TPM1) . From thIn the above papers, some scholars have verified the targets of miRNAs  and induced the transdifferentiation of myofibroblasts, causing an increase of ECM and fibrosis . TherefoAccording to the above, we proposed a multi-factor pathogenic model of OSF with BQ as the main cause . The aboOral cancer refers to malignant tumors of the mouth and lips, about 90% of which are diagnosed as OSCC . In the BQ and its additive tobacco consumed by OSF patients are both first-level carcinogens that have been clearly defined by the IARC, which can damage cell genes, cause radiation damage, impair immune function, and further induce OSCC ,58. The ROS are a group of short-lived, highly active, oxygen-containing molecules that can induce DNA damage and influence DNA damage response . NumerouSenescence is the common feature of wound healing, fibrosis and cancer . AlthougEMT is a cellular process that transforms epithelial cells into a mesenchymal phenotype and is critical for tumor migration, tumor stem cell properties, chemotherapy resistance and metastatic potential . During Several articles demonstrated that arecoline activates the TGF-β pathway , and theAnother factor in the malignant transformation of OSF is the HIF-1α. At this stage of OSF, collagen fiber accumulation, degeneration and vascular occlusion in the lamina propria and submucosa make oxygen supply to the diseased tissue more insufficient. HIF-1α, a tumor growth signal that is upregulated during hypoxia, is responsible for activating the vascular endothelial growth factor pro-angiogenic gene, which has an effect on tumor growth, glucose metabolism, invasion, chemoradiotherapy resistance and prognosis .Studies have also confirmed that hypoxia modulates the activity of three key transcription factors , leading to the continuous accumulation of ROS and the malignant transformation of cells . Ishida The inflammatory environment and degree of fibrosis also play a contributing role in the malignant transformation of OSF. Microtrauma in the process of OSF accelerates the diffusion of chemical components in the BQ into the submucosal tissues, and immune cells are locally recruited and secrete proinflammatory cytokines , resultiThe study by Reis et al. showed that the loss of PDCD4 expression was associated with tumorigenesis and invasion of OSCC, and the downregulation of PDCD4 by miR-21 was proved to increase the invasivity of oral cancer . As a taExisting evidence has long been clear that OSF can go through malignant transformation into OSCC, and OSCC of OSF origin is clinically more aggressive than OSCC of non-OSF origin, with a higher rate of metastasis and recurrence . OSF is Patients generally have a history of chewing BQ, and the clinical symptoms are white oral mucosa accompanied by leather-like texture changes. Patients will have severe burning in the oral cavity after eating spicy food . With thThe main pathological changes in OSF include epithelial atrophy, collagen fiber accumulation, degeneration, vascular occlusion and reduction in the lamina propria and submucosa of the mucosa, and some patients experience epithelial dysplasia . In patiTissue biopsy is the gold standard, but it is invasive. So, we need to find easier, less invasive, more accurate and less expensive screening and diagnosis methods. Some biochemical parameters are changed in the process of OSF, which suggests that these biomarkers can be used as tools for disease progression and detection of malignant transformation.Shaikh et al. used attenuated total reflection–Fourier transform infrared spectroscopy (ATR-FTIR) combined with salivary total protein measurement to distinguish between OSF patients and healthy controls . AnalysiOSF is an irreversible disease, even if the pathogenic factors are removed in the latter stage, so early treatment will have a better prognosis and prevent malignant transformation as much as possible.The incidence of OSF is closely related to chewing BQ. Health education should be strengthened to enhance people’s understanding of the potential harm from chewing BQ. Patients with clinical symptoms should be treated in stomatological hospitals as soon as possible.Quit the chewing BQ habit, quit smoking, quit alcohol and avoid spicy food stimulation.(1)Glucocorticoids: glucocorticoids can inhibit the production of inflammatory factors and promote the apoptosis of inflammatory cells, thereby playing the role of anti-inflammatory and inhibiting the process of fibrosis ,93;(2)Antifibrotic drugs and proteolytic enzymes: exogenous antifibrotic factors and proteolytic enzymes can reverse the process of OSF fibrosis . In clin(3)Peripheral vascular dilators: improve the microcirculation and hemorheology in the lesion area to improve clinical efficacy and relieve the symptoms of patients with OSF ,95. Clin(4)Antioxidants and nutritional elements: in the treatment of OSF, the use of antioxidants and nutritional elements can reduce the damage to macromolecules caused by reactive oxygen species, thereby slowing down the progression of OSF ,97.The therapeutic principles of OSF mainly include anti-inflammatory, anti-fibrosis, improvement of ischemic state and anti-oxidation. Commonly used OSF therapeutic drugs mainly include the following categories:With the help of oral physiotherapy exercise, tissue elasticity and mouth opening can be increased . There aThe first choice is surgical treatment for advanced patients, who have limited mouth opening movement due to heavy fibrous bands in the mucosa. The operation included excision of the fibrous band and insertion of different flaps, such as a palatal flap, tongue flap, nasolabial flap, platysma myocutaneous flap, etc. . PlatysmIn addition to the above conventional treatment methods, in recent years, some scholars have adopted new treatment methods for the clinical manifestations and pathogenesis of OSF, such as hyperbaric oxygen therapy , laser tHyperbaric oxygen can increase blood oxygen content, improve local ischemia and hypoxia, promote neovascularization and collateral circulation in the affected area . ExistinArctigenin is a lignan extracted from Arctium lappa, which has a lot of pharmacological effects, including antifibrotic effects . The resThe treatment methods and principles of OSF are listed in The above studies on the mechanism of OSF and malignant transformation into OSCC make the key molecules and abnormal RNAs clear, which are of great significance for the occurrence, development, detection, diagnosis, monitoring and prognosis of the disease. The important molecules and processes involved in OSF pathogenesis and malignant transformation to OSCC are shown in Therefore, targeted blocking of these key molecules is the trend and key for disease prevention and treatment in the future. The application of natural compounds has also shown its therapeutic potential, so it is necessary to conduct further research on natural compounds in the hope that they will become first-line drugs for OSF treatment in the future.


Meanwhile, the osmotic stimuli are relayed to the supraoptic nucleus (SON) and paraventricular nucleus of the hypothalamus (PVN) via direct neural projections or the median preoptic nucleus (MnPO) to promote the secretion of vasopressin which plays a vital role in the regulation of body fluid homeostasis. Importantly, the vital role of OVLT in sleep-arousal regulation is discussed, where vasopressin is proposed as the mediator in the regulation when OVLT senses osmotic stimuli.Thirst and water intake are regulated by the organum vasculosum of the lamina terminalis (OVLT) and subfornical organ (SFO), located around the anteroventral third ventricle, which plays a critical role in sensing dynamic changes in sodium and water balance in body fluids. Meanwhile, neural circuits involved in thirst regulation and intracellular mechanisms underlying the osmosensitive function of OVLT and SFO are reviewed. Having specific Na They areostasis . They areostasis . LackingThe OVLT was described as the supraoptic crest early. Brizzee and Wislocki performed earlier investigations into the cell structure of the supraoptic crest in cats and rats, respectively . Until 1x channels were found to be on the SFO, which is the structural basis for the SFO to monitor changes in cerebrospinal fluid osmolality  infusions of hypertonic saline altered the intensity and the distribution pattern of c-fos expression neurons in OVLT of rats . As revex channels of the SFO can sense the increase in sodium concentration in cerebrospinal fluid, thus activating GABAergic interneurons to inhibit the activity of neurons conveying osmotic stimuli to subsequent nuclei, while under conditions of sodium depletion, thirst-driving neurons are inhibited via a CCK-mediated pathway, thus increasing the concentration of Na+ in body fluids  of the OVLT and SFO functioned as sensors for Na+, and a high level of Na+ promoted the synthesis of epoxyeicosatrienoic acids (EETs) from arachidonic acid (AA), which acted on transient receptor potential vanilloid 4 (TRPV4) within the OVLT and then enhanced water intake  exists in the OVLT and SFO expressed in AT1a-positive neurons sensing extracellular [Na+]. Additionally, it can promote water intake by acting as a sodium (Na+)/hydrogen (H+) exchanger when the extracellular [Na+] increases and then induces the activation of acid-sensing channel 1a (ASIC1a)  . Howevern ASIC1a . Thus, t+ and Na+  activation utilizing a uniquely interweaved scaffold interacting with the C-terminus of TRPV1 and ultimately induce the depolarization of the osmosensory neurons . It has  and Na+ .+ concentrations and osmolarity to regulate fluid homeostasis, while how OVLT and SFO neurons sense hypovolaemic stimuli needs to be further elucidated. Moreover, water-channel aquaporin 4, which may contribute to cell deformation to trigger the activation of osmosensory neurons, is found within the OVLT except for the middle triangular area  as well as the suprachiasmatic nucleus (SCN) and magnocellular neurons of the paraventricular nucleus of the hypothalamus (PVN) secretes vasopressin, which could be stimulated when the OVLT and SFO sense the osmotic stimuli . Rather The regulation of SFO on osmotic pressure is also closely related to vasopressin, there is evidence that electrical stimulation of SFO can increase the release of vasopressin in the posterior pituitary . The injIn recent years, more advanced technology has brought insights into the correlation between OVLT and SFO and vasopressin secretion. An experiment in c-fos-mRFP1 transgenic rats shows that osmotic stimulation  induces the activation of the OVLT, SFO, and MnPO as well as raises vasopressin-enhanced green fluorescence in the SON and PVN, suggesting that the osmosensitive brain regions may innervate the SON and PVN . Fos-immHorseradish peroxidase iontophoresis into the PVN nucleus has labeled neurons within the OVLT and SFO projecting to the PVN . Indeed,As to the mediator participating in the process, intensive cholinergic fibers are located in the SFO, OVLT, and vasopressin-secretion nuclei (SON and PVN) . ICV injAs to the neural circuits , the MnPOne experiment marked thirst-triggering neurons in the SFO with the transcription factor ETV-1 and optogenetic activation of them trigger thirst. Moreover, the OVLT and MnPO are observed to receive projections from the ETV1 neuronal population. Furthermore, the neurons projecting to the SON and PVN are glutamatergic . The afo3 receptor in the magnocellular neurons of the PVN plays a critical role in vasopressin secretion in response to the osmotic challenge, in which hyperosmolarity induced by hypertonic saline can activate the Tachykinin NK3 receptor to enhance the secretion of vasopressin  plays a vital role in the body homeostasis, for example, cardiovascular regulation . Further+ has been considered a crucial pressor effector for decades. Kengo Nomura identified Nax channels that detect the increase in plasma [Na+] expressed in glial cells in the OVLT, and Nax-positive glial cells export H+ to activate OVLT neurons projecting to the PVN via ASIC1a, which is responsible for enhancing the SNA  can be involved in the development of neurogenic hypertension through the SFO-PVN-RVLM pathway . The aboSome studies have shown that central administration of angiotensin II can inhibit renin secretion in rats and renal sympathetic nerve activity in sheep, reflecting the role of forebrain structures in renal regulation . The revAt the same time, vasopressin can promote the release of renin from the renal collecting duct, causing the activation of the renin-angiotensin-aldosterone system (RAAS), which together with water retention causes an increase in blood pressure . There iDuring sleep, the body gradually becomes dehydrated as it breathes and sweat evaporates without replenishing water, mammals can alleviate this effect by improving the circadian rhythm of osmotic pressure regulation . Recent It has been revealed that the OVLT could relay hypertonic saline-induced hyperosmolality signals to VP neurons of the SCN to enhance the release of VP via excitatory projections from GABAergic neurons and phase-advanced the clock time of mice, demonstrating that the OVLT can drive clock neurons within the SCN to carry out unscheduled homeostatic responses  Figure . The aboIn rats, vasopressin-immunoreactive cells were observed in the locus coeruleus (LC), and VP induced excitatory effects on it . The LC 2 receptors and noradrenergic β- and α₁-receptors, respectively  . Recentlectively . Meanwhiectively .In summary, current evidence shows that the OVLT contributes to the phase-advanced clock time when sensing osmotic stimuli. Meanwhile, the LC plays a vital role in this shift of clock time via innervations to the vlPOA and vlPAG. However, further evidence supporting this idea is needed.x channels, hyperosmolality of the third ventricular or blood could be detected by the OVLT and SFO, and the osmotic signals orchestrated by the OVLT and SFO are relayed to the cingulate cortex and insular cortex to regulate thirst via the MnPO, paraventricular, rhomboid, and reuniens nuclei of the thalamus. Vasopressin plays an important role in the regulation of blood osmolality, and the OVLT and SFO could regulate renal excretion by regulating the secretion of VP and regulating RSNA via the PVN-RVLM pathway. Furthermore, after sensing the osmotic change, the OVLT could orchestrate the osmotic stimuli into the sleep–wake oscillation by regulating VP secretion from the SCN. Noradrenergic LC neurons serve as the integrating site, changing the osmotic stimuli to sleep–wake oscillation by relaying the signal to the vlPOA and vlPAG to phase-advance clock time. This review shows the critical role of the OVLT and SFO in the regulation of thirst and fluid homeostasis, emphasizing that the OVLT and SFO have emerged as the major sensor to regulate thirst and body fluid homeostasis.In summary, thirst regulation needs vital osmotic sensors, OVLT and SFO, and innervations among different nuclei. Meanwhile, the role of the OVLT in sleep-arousal regulation is emphasized and explored. With specific NaAll authors listed have made a substantial, direct, and intellectual contribution to the work and approved it for publication.This work was supported by the National Science Foundation of China. The project reference was 81871044.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.