While innate immune responses are typically short-lived, resolving upon clearance of the inciting pathogen or damage-associated molecular pattern, unresolved innate immune responses in the central nervous system (CNS) promote toxic inflammatory conditions that mediate neurodegenerative diseases. Understanding the cellular mechanisms that mediate the transition from neuroprotective immune responses to toxic chronic inflammatory responses in the CNS is a major area of ongoing research. Furthermore, neuroinflammatory signaling in neurological disease is a self-propagating process, worsening the disease state over time as additional immune cells are recruited and polarized toward inflammatory phenotypes, blood-brain barrier (BBB) function is disrupted, and neurodegeneration progresses. This Research Topic includes 14 peer-reviewed articles published in different Frontiers journals. Five are comprehensive reviews on the role of inflammatory alterations in neurological and neuropsychiatric diseases. The remaining nine articles are original research on innate immune activation in spinal cord injury, ischemia, and other neurological and neuroinflammatory conditions. This editorial summarizes these published reports and how they may advance our knowledge of innate immune activation driven by self- and non-self-triggers . FurtherSánchez et al. in their study on the effects of the innate immune molecules apoptosis-associated speck-like protein containing a CARD (ASC) and matrix metalloprotease 10 (MMP10) on inducing an inflammatory microglial phenotype and further upregulating inflammatory cytokine signaling. This study, and many others in this Research Topic demonstrate how innate inflammatory signaling molecules in the CNS contribute to pathological feed-forward processes in neurodegenerative diseases and identify many nodes for future therapeutic targeting.To start with, the nature of innate immune responses and the production of inflammatory cytokines is to recruit a more robust immune response from additional cells. This is highlighted by Xue et al. demonstrate the role of innate immune processes in mechanical spinal cord injury for mediating allodynia, highlighting the role of the RIPK-NF-κB-NLRP3 pathway for triggering inflammatory signaling in response to cellular damage signals even at sites away from the primary site of mechanical tissue injury. Ramos et al. review the mechanism of ethanol toxicity-induced neurodegeneration, highlighting the role of ethanol reactive microglia (ERMs) and innate immune neuroinflammatory processes as a key mediators of ethanol-induced neurotoxicity with parallels to Alzheimer's disease (AD) and potential contributions to AD etiology. Wang et al. identify a novel cytokine, Tissue Non-specific Alkaline Phosphatase, that plays a substantial role in the NF-κB-mediated inflammatory processes in response to the hypoxic injury related to the development of Spastic Cerebral Palsy. Finally, Yang G. et al. provide a detailed review of the innate immune signaling mechanisms in microglia in response to intracerebral hemorrhage that confers protection, promote resolution and cleanup of toxic blood products, or drive neuroinflammation that worsens neurodegenerative processes after a hemorrhagic stroke.Tissue injury in the CNS, such as mechanical trauma, environmental toxins, hypoxic insult, or hemorrhage, is a major instigator of innate immune processes, including toxic neuroinflammation, that worsens neurodegeneration. The role of innate immunity in response to each of these modes of CNS injury is explored in this Research Topic. The BBB is the primary interface between the CNS and the peripheral immune system. The neurovascular unit, which forms the BBB, comprises several cell types, including a monolayer of tightly sealed vascular endothelial cells with a basement membrane, surrounding pericytes, and a covering layer of astrocyte end feet. This selectively permeable barrier protects the CNS from circulating toxins, pathogens, and damaging immune cells and inflammatory mediators and was believed to maintain the CNS as an immune-privileged site. More recently, researchers have appreciated the importance of a coordinated cross-talk between the peripheral immune system and the CNS in health and disease.Su et al. assert that markers of increased BBB permeability and peripheral immune cell recruitment are signatures of normal aging across brain regions coinciding with increased molecular signatures of neuroinflammatory signaling. Disruption of the BBB with increased inflammatory infiltrate is a common pathological phenomenon in numerous disease states related to neurodegeneration. Interestingly, BBB disruption in response to inflammatory signaling is highlighted in Multiple Sclerosis , alcohol use disorder (AUD), and AD . In each of these disease states, the inflammatory cytokine interleukin-1β (IL-1β) is a key culprit in BBB dysfunction along with interleukin-6 (IL-6) and tumor necrosis factor-α (TNFα). These three critical inflammatory cytokine mediators of BBB disruption are explored in detail by Yang J. et al., highlighting the known molecular signaling mechanisms by which BBB integrity is disrupted, peripheral immune cells are recruited to the CNS, and inflammatory signaling in microglia and peripheral immune cells are upregulated.In this Research Topic, Zhou et al. describe brain-derived small extracellular vesicles (sEVs) circulating in the plasma after acute cerebral ischemia containing brain-specific micro-ribonucleic acids (miRNAs). Temporal dynamics of these sEVs indicated that their presence in the peripheral circulation correlated with BBB disruption and could serve as a marker of disease staging and progression. Conversely, Ramos et al. describe the potential role of peripherally derived sEVs containing inflammatory cargo from liver in AUD that can modulate CNS neuroinflammatory processes. In many disease states, peripheral inflammation may accompany and contribute to neuroinflammation and vice versa. Increases in peripheral inflammatory molecules and immune cells in response to neuroinflammatory processes in the brain are discussed in the context of MS , AUD and AD , Spastic Cerebral Palsy , and intracerebral hemorrhage . Eggerstorfer et al. and Li et al. both assert that peripheral inflammation, such as a peripheral bacterial lipopolysaccharide endotoxin (LPS) exposure in mice or during illness in humans, contributes to neuroinflammatory processes in the CNS that contribute to neuronal dysfunction.Cross-talk between the peripheral immune system and the innate immune system of the CNS involving the transfer of inflammatory signaling molecules across the BBB is described throughout this Research Topic. Eggerstorfer et al.; Li et al.). In a meta-analysis of eight separate imaging studies, Eggerstorfer et al. demonstrate that Translocator protein (TSPO), a marker of neuroinflammation, is elevated in several brain regions associated with disease symptoms in human patients assessed using positron emission tomography (PET). Li et al. dive into the mechanism of hypoxia-inducible factor 1 (HIF-1) and phosphoinositide 3 kinase (PI3K) signaling in response to LPS-induced peripheral inflammation for regulating depressive behaviors in rodent models. This study also demonstrated that repurposing of the FDA-approved HIF-1 stabilizing agent, FG-4592, could reduce depressive symptoms, neuroinflammation, and synaptic defects in rodents stimulated with LPS. These studies further support a new understanding of the role of neuroinflammation in mediating MDD, establishing a potential therapeutic target outside of monoamine neurotransmitter modulation that may yield improvements for many patients with MDD that are refractory to current pharmaceutical therapies.Major Depressive Disorder (MDD) is the topic of two articles in this Research Topic (While this editorial is not aimed to cover all 14 articles in this Research Topic, with some articles slightly outside the theme yet highly relevant to neuronal homeostasis, we express our gratitude to the many authors, reviewers, and editors around the world that contributed to this Research Topic to further our understanding of innate immunity in neurodegenerative diseases. We hope that readers will enjoy reading it.JH reviewed the articles published on this Research Topic, drafted the manuscript, and created the figure. AB, SP, and KB read through published articles and edited the manuscript and figures. All authors contributed to the article and approved the submitted version.


Heated tobacco products (HTPs) are novel products that allow users to inhale nicotine by heating (350 °C) reconstituted tobacco rather than combustion (900 °C) as in conventional cigarettes. HTP sticks containing reconstituted tobacco come in various flavours such as menthol, citrus, etc., like electronic cigarette liquids. Thus, the composition of HTP aerosol will also vary according to the flavouring agents added. Overall, the content of toxic chemicals in HTP aerosol appears to be lower than in cigarette smoke. However, the concentrations of more than twenty harmful and potentially harmful constituents have been reported to be higher in HTP aerosol than in cigarette smoke. Further, several toxic compounds not detected in cigarette smoke are also reported in HTP aerosol. Thus, the risks of HTP use remain unknown. Most of the available data on the composition and health effects of mainstream HTP aerosol exposure are generated by the tobacco industry. Few independent studies have reported short-term pathophysiological effects of HTP use. Currently available HTP toxicity data are mainly on the pulmonary and cardiovascular systems. Moreover, there are no long-term toxicity data and, therefore, the claims of the tobacco industry regarding HTPs as a safer alternative to traditional combustible cigarettes are unsubstantiated. Furthermore, HTP aerosol contains the highly addictive substance nicotine, which is harmful to the adolescent brain, developing foetuses, pregnant women, and also adults. Hence, comprehensive studies addressing the safety profiling related to long-term HTP use are warranted. With this background, the following review summarizes the current state of knowledge on HTP toxicity on four broad lines: composition of mainstream HTP aerosol compared to traditional combustible cigarette smoke, biomarkers of HTP exposure, health effects of HTP exposure, and the harm reduction aspect. Heated tobacco products (HTPs) are a new category of tobacco products with limited toxicological data. HTPs heat reconstituted tobacco to about 350 °C to generate nicotine-containing aerosol. This contrasts the burning of traditional combustible cigarettes (TCCs), where temperatures up to 900 °C are reached ,2,3,4. IHeating versus combustion is the basic operational difference between HTPs and TCCs. The tobacco industry claims that due to this operational difference, HTP aerosol contains fewer toxic chemicals compared to TCC smoke and, hence, it is a safer alternative to conventional smoking. Based on the current state of independent toxicological data and lack of long-term toxicity data on HTP, we consider these claims to be unsubstantiated. In this review article, we summarize the current state of knowledge on the chemical composition of mainstream HTP emissions compared to those of mainstream conventional cigarettes. Harmful and potentially harmful chemicals present in higher amounts in HTP emissions compared to TCCs that may result in previously unknown toxicological effects among users are highlighted. Further, an assessment of the biomarkers of exposure to HTP use during randomized clinical trials by the tobacco industry to demonstrate harm reduction is also discussed. A wide range of potential adverse health outcomes ranging from the pulmonary, cardiovascular, and immune modulatory effects of HTP use are reviewed. Finally, we discuss the potential of the harm reduction aspect of HTPs based on the current knowledge from ECIG users. This article is therefore divided into the following four sections: (I) composition of mainstream HTP aerosol compared to TCC smoke, (II) biomarkers of HTP exposure, (III) health effects of HTP exposure, and (IV) the harm reduction aspect.This section compares the composition of mainstream HTP aerosol and mainstream cigarette smoke  with resThe nicotine content in the tobacco fillers (per cigarette) is higher in the TCCs than the HTP sticks . SimilarISO: puff volume: 35 mL; duration: 2 s; interval: 60 s; six puffs per HTP stick; six puffs per TCC.HCI: puff volume: 55 mL; duration: 2 s; interval: 30 s; 12 puffs per HTP stick; 8–12 puffs per TCC; ECIG: 24–55 puffs.CORESTA: puff volume: 75 mL; duration: 2.5 s; interval: 30 s; 7–12 puffs per HTP stick; 11 puffs per TCC; ECIG: 10 puffs.An overall description of the ISO, HCI, and CORESTA puffing regimens used in the different studies ,13,14,15Specific details of the puffing regimens with reference to each study and corresponding emissions are provided in the The current scientific literature on HTPs is dominated by tobacco-industry-sponsored research ,19, warrWhen comparing HTPs and TCCs, it should be kept in mind that HTP sticks are smaller  than TCCs, reflected as a lower nicotine content. The small size of the HTP sticks may lead to increased consumption, i.e., two sticks replacing one cigarette, to obtain a similar nicotine dose. The strive to reach a certain nicotine dose may explain why the widely popular IQOS device comes in two varieties, one where the battery discharges after approximately 6 min, allowing the use of one HTP stick in a smoking session, and one where the battery supports the use of two consecutive HTP sticks . Thus, tIn this context, it would plausibly be more appropriate to normalize the emissions from TCCs and HTPs with the mass of tobacco. However, most of the studies used for this review article lacked information on the mass of tobacco. Bekki et al.  reportedA systematic review and meta-analysis study by Drovandi et al.  evaluateThe current knowledge on the plausible adverse health outcomes of exposure to HTP aerosol is primarily focused on the pulmonary and cardiovascular systems. However, there is a paucity of long-term toxicity data on the use of HTP products.Independent analysis of publicly available tobacco industry data revealed a significant reduction in white blood cells among adult smokers (Japan-based study) when they switched to HTPs . However, no improvement in pulmonary function (forced expiratory volume in 1 s) or reduction in the systemic acute phase inflammatory marker C-reactive protein (CRP) were observed ,24. A thInhalation exposure of HTP aerosol in female rats for 90 days  resulted in significantly increased lung weight, bronchoalveolar lavage inflammatory cell recruitment, epithelial hyperplasia and metaplasia, and elevated levels of bronchoalveolar lavage inflammatory markers  in the airways compared to controls. However, the inflammatory response was significantly lower when compared to female rats exposed to TCC smoke . Short-tSeveral studies using human bronchial epithelial cells demonstrated that HTP exposure resulted in oxidative stress and pro-inflammatory response ,31. HighThe effects of exposure to mainstream HTP emissions are regarded as potentially harmful to cardiovascular health though less than that of TCC smoke . Acute eA study in rats indicated that acute exposure to HTP aerosol impairs arterial flow-mediated dilation. Other studies also demonstrated that HTP aerosol can rapidly and substantially impair endothelial function comparably to TCC smoke. The post-exposure serum nicotine levels were more than 4-fold higher in the HTP-aerosol-exposed rats compared to those exposed to TCC smoke . An indeData from the tobacco industry indicate immunomodulatory effects of HTP aerosol exposure. Rats (7–10 per group) exposed to HTP aerosol developed 270% and 75% higher systemic neutrophilia compared to sham- and TCC-smoke-exposed rats. In female rats, following a 6-week recovery period, the blood neutrophil counts remained elevated compared to both sham- and TCC-exposed-animals. HTP-exposed rats also exhibited higher levels of thymic atrophy (by gross organ weight and histology) than both the sham- and TCC-smoke-exposed groups . An indeOne of the main claims by the tobacco industry regarding HTP is harm reduction although such claims remain unsubstantiated . ECIG waThe role of ECIGs to help quit smoking or to reduce harm compared to TCCs remains unsubstantiated even though ECIGs were launched on the market much earlier than the modern HTPs. Most ECIG liquids with extremely attractive flavours previously contained nicotine. Due to recent amendments of tobacco directives globally, nicotine is sold separately, and both ECIG liquid and nicotine are sold only to adults (≥18 years). It is important to note here that individuals at 18 years old are still in their youth. Though such regulations can somewhat reduce children’s access to ECIGs, they cannot substantially inhibit it due to access through other channels in society. Similar risks remain with HTPs as well. Thus, HTPs, similar to ECIGs, can act as a gateway to conventional smoking and the use of other tobacco products like snus or waterpipes ,48. RiskECIGs, instead of helping as a tool for quitting smoking, have eventually led to increased dual use (ECIGs and TCCs). The Population Assessment of Tobacco and Health study reported that 37.4% of adults and 43% of youths used multiple nicotine products, the most common combination being TCCs and ECIGs . Other sFurthermore, it has also been reported that dual users had the highest urine cotinine concentration. Cotinine is the predominant metabolite of nicotine. Measuring cotinine is preferred to measuring nicotine because cotinine remains in the body longer and correlates well to the exposure to nicotine for both smokers and nonsmokers exposed to environmental tobacco smoke . A KoreaIn a cross-sectional study, Osei et al.  found thTo summarize, HTPs are novel products that allow the user to inhale nicotine by heating tobacco rather than combustion as in conventional cigarettes. However, the presence of CO and a number of other TCC smoke constituents in HTP aerosol may correspond to what would be expected from slight combustion. HTP sticks have a smaller size and lower amount of tobacco than TCCs. Therefore, the amount of nicotine delivered in the mainstream emission from an HTP stick is generally lower than that delivered in the mainstream smoke from a TCC. However, technological advancements of HTP devices, such as improvement in the battery capacity, may result in increased rather than reduced consumption, e.g., by shifting from one to two sticks per smoking session. Apart from nicotine and CO, several other chemicals are also present in HTP aerosol, including a number of so-called HPHCs. The levels of these HPHCs are influenced by several factors such as the puffing regime, the HTP device, and additives to the HTP stick. Several HPHCs have been detected in higher concentrations in HTP aerosol than in TCC smoke. Currently, there is not sufficient evidence from independent sources to draw conclusions on the health effects of long-term use of HTP sticks. Few independent studies have reported short-term pathophysiological effects of HTP use. Multiple tobacco-industry-sponsored studies on human bronchial epithelial cells, coronary arterial endothelial cells, 3D nasal culture models, gingival epithelial organotypic cultures, monocytic cells, and mouse models indicate lower toxicity of HTP aerosol compared to TCC smoke . In geneNevertheless, it must be noted that HTP aerosol does contain nicotine, allowing users to inhale nicotine. Nicotine is highly addictive, and exposure to nicotine is harmful to the adolescent brain (the brain develops until about 25 years of age), particularly in the regions controlling attention, learning, mood, and impulse control. The use of nicotine among adolescents may also act as a gateway for future use and addiction to other drugs. Nicotine is toxic to developing foetuses and harmful for pregnant women. The use of nicotine is also harmful for adults . TherefoIn conclusion, the health effects of short-term and, in particular, long-term use of HTP sticks are uncertain. Accordingly, the European Respiratory Society recommended against the use of any product, including HTP tobacco products, that can potentially damage the lungs and human health . It can


Staphylococcus aureus (CA-MRSA) infection is a rare, yet highly fatal disease. This article presents the case of a 45-year-old homeless female with a medical history of bipolar disorder, seizure disorder, and substance use disorder who was admitted with altered mental status. Laboratory tests on admission revealed neutrophil-predominant leukocytosis, elevated inflammatory markers , and lactic acid. MRI brain demonstrated multiple cerebral abscesses with surrounding edema and sagittal vein thrombosis. The patient was initiated on broad-spectrum antibiotics and underwent a right-sided minimally invasive needle biopsy of the abscess and left frontal craniotomy for abscess evacuation, the culture of which confirmed the diagnosis of MRSA infection. As the patient did not have any hospitalization or procedure in the recent past, a diagnosis of CA-MRSA was made. The patient's clinical status improved following the procedure and antibiotic administration, but she left against medical advice before completing treatment. This case highlights the importance of early recognition and aggressive management of CA-MRSA infections, especially in vulnerable populations such as the homeless.Brain abscess secondary to community-acquired methicillin-resistant  Staphylococcus aureus (MRSA) infection is a major public health concern due to its high prevalence and resistance to multiple antibiotics [Staphylococcus aureus (CA-MRSA) infections are becoming increasingly common, with neurologic manifestations being a rare but serious complication [Methicillin-resistant ibiotics . Communilication . Brain alication . In thisThe diagnosis of cerebral abscesses can be challenging due to the broad range of clinical presentations and variable imaging findings. The nonspecific nature of symptoms and lack of systemic features often lead to a delay in diagnosis, which can have catastrophic consequences. Although MRSA is known to cause infections in immunocompromised and hospitalized patients, CA-MRSA infections are becoming increasingly prevalent in the general population, particularly in individuals with predisposing factors such as homelessness and substance use disorder ,2. This A 45-year-old homeless woman was admitted to the hospital for evaluation of altered mental status. She was brought to the emergency department by emergency medical services (EMS), who found her walking along the streets in a confused state. Her medical history was significant for bipolar disorder, seizure disorder, IV drug use, and substance use disorder. EMS administered Narcan due to suspicion of opiate overdose, but there was minimal response. Upon admission, she exhibited uncooperative and combative behavior. Significant vital signs included a blood pressure of 95/65 mm Hg. The physical examination was unremarkable, except for the neurological exam, which revealed the patient's unresponsiveness to verbal stimuli but the withdrawal of extremities in response to painful stimuli , without any focal neurological findings. She was noted to move independently in bed, and there was no evidence of soft tissue or skin infection. Escherichia coli and blood cultures grew MRSA. MRSA screen was negative. The urine toxicology screen was positive for amphetamines. Viral panel including HIV and hepatitis was unremarkable. Thrombophilia workup was negative.Initial laboratory workup showed the following results Table  and urinInitial head CT showed a focal region of hypodensity at the right frontal lobe with surrounding hyperdensity, suspicious for infarct vs mass Figure . MRI braMagnetic resonance angiography (MRA) of the head and neck was unremarkable. Transthoracic echocardiography (TTE) did not show any signs of valvular endocarditis. Additionally, the absence of focal neurological findings at the time of presentation indicated that a lumbar puncture was not necessary.The clinical presentation along with laboratory and imaging findings in the setting of homelessness, IV drug use, and no recent hospitalization or procedure led to a diagnosis of brain abscesses likely secondary to CA-MRSA. The patient was initially receiving IV vancomycin; however, she was intubated due to worsening mentation and metronidazole, cefepime, and dexamethasone were added to the treatment regimen. Repeat head CT and MRI brain showed the increased size of cerebral abscesses with mass effect. As a result, an emergent right-sided minimally invasive needle biopsy and left frontal craniotomy for abscess evacuation were performed. Cultures of the abscess aspirate grew MRSA, confirming the diagnosis of CA-MRSA brain abscesses. Following the procedure, the patient's clinical status improved, and she was eventually extubated. Additionally, the patient was started on Lovenox (60 mg BID) subcutaneously for sagittal vein thrombosis.The plan was to continue vancomycin for four weeks, as repeat CT head showed improving edema. However, the patient left against medical advice prior to treatment completion and was lost to follow-up.Staphylococcus aureus is a challenging pathogen in the management and treatment of central nervous system infections, with recent neurosurgical procedures and immunocompromised status as major risk factors, requiring anti-MRSA antibiotics and prompt source control [This case report highlights a rare presentation of CA-MRSA infection causing multiple cerebral abscesses and sagittal vein thrombosis in a homeless patient with a history of bipolar disorder, seizure disorder, and substance use disorder. Although MRSA infections are becoming increasingly prevalent in the community, cerebral abscesses caused by this pathogen remain rare . Staphyl control . Further control .The nonspecific clinical presentation of cerebral abscesses often leads to a delay in diagnosis, which can have catastrophic consequences. The initial presentation and laboratory evidence of the patient in this case report with altered mental status is similar to that seen in other infectious etiologies and non-infectious brain lesions, further complicating the diagnosis. The role of imaging studies, including CT head and MRI brain, in the diagnosis of cerebral abscesses cannot be overstated, as these studies can reveal important diagnostic clues such as the presence of rim-enhancing lesions and surrounding edema .The management of cerebral abscesses caused by MRSA requires a multidisciplinary approach, including the use of IV antibiotics and surgical intervention for abscess evacuation. The treatment of bacterial brain abscess typically involves cefotaxime and metronidazole with additional antibiotics for immunocompromised patients; however, more research is needed to improve understanding of the pharmacokinetic profiles of treatments and the efficacy and safety of drainage and anti-infective treatments in these patients . In thisThis case report highlights the importance of considering CA-MRSA as a potential causative agent in patients presenting with neurological symptoms, particularly in vulnerable populations such as the homeless. The rarity of cerebral abscesses caused by MRSA and the unique presentation of sagittal vein thrombosis in this case further emphasize the diagnostic and therapeutic challenges posed by these infections . This caThis case underscores the diagnostic and therapeutic challenges posed by MRSA infections. Early recognition and prompt treatment of MRSA infections are essential to prevent serious neurological complications such as cerebral abscesses and sagittal vein thrombosis. Multidisciplinary management, including broad-spectrum antibiotics and surgical intervention, is crucial for successful treatment of these infections. Further research is needed to identify the risk factors for MRSA, especially CA-MRSA infections in vulnerable populations, and to develop effective prevention and treatment strategies. Overall, this case report highlights the need for continued vigilance and prompt action in the diagnosis and management of MRSA infections in patients with neurological symptoms.


Continuous replenishment of the corneal epithelium is pivotal for maintaining optical transparency and achieving optimal visual perception. This dynamic process is driven by limbal epithelial stem cells (LESCs) located at the junction between the cornea and conjunctiva, which is otherwise known as the limbus. In patients afflicted with diabetes, hyperglycemia-induced impairments in corneal epithelial regeneration results in persistent epithelial and other defects on the ocular surface, termed diabetic keratopathy (DK), which progressively diminish vision and quality of life. Reports of delayed corneal wound healing and the reduced expression of putative stem cell markers in diabetic relative to healthy eyes suggest that the pathogenesis of DK may be associated with the abnormal activity of LESCs. However, the precise role of these cells in diabetic corneal disease is poorly understood and yet to be comprehensively explored. Herein, we review existing literature highlighting aberrant LESC activity in diabetes, focusing on factors that influence their form and function, and emerging therapies to correct these defects. The consequences of malfunctioning or depleted LESC stocks in DK and limbal stem cell deficiency (LSCD) are also discussed. These insights could be exploited to identify novel targets for improving the management of ocular surface complications that manifest in patients with diabetes.  Diabetes mellitus (commonly known as diabetes) is a metabolic disorder characterized by prolonged elevation of blood glucose or hyperglycemia. Its two main forms include type 1 diabetes (T1D) where chronic hyperglycemia results from the autoimmune destruction of pancreatic β-cells, and type 2 diabetes (T2D) which features defective insulin secretion or sensitivity . Diabetes increases the likelihood of visual impairment by approximately 3-fold and is the leading cause of preventable blindness in working-age adults . Ocular The current management of DK is complicated by the paucity of diagnostic markers and is largely reliant on symptom-specific treatments such as topical ointments and antibiotics, owing to its complex pathophysiology and the limited number of clinical studies ,17. As cLimbal epithelial stem cells (LESCs) are the quintessential hierarchical cellular source for the lifelong renewal and replenishment of the corneal epithelium . When thHerein, evidence demonstrating the loss or dysfunction of LESCs in the diabetic cornea is evaluated to determine the mechanisms by which they impinge on corneal health, become defective under hyperglycemic conditions, and therefore contribute to the pathogenesis of DK. Because LESCs play a beneficial role in corneal wound healing and epithelial regeneration, bridging the current knowledge gap concerning factors that trigger pathological processes leading to diabetic corneal disease will provide novel insights toward developing innovative clinical tools for early diagnosis and the effective management of ocular surface complications in patients with diabetes. The cornea is a transparent tissue which comprises the outermost layer of the eye and consists of non-keratinized stratified squamous epithelium on its anterior surface. It forms a protective barrier against noxious external agents and acts as a clear avascular window for projecting light onto the retina, thereby facilitating optimal visual perception. These structural and functional attributes are reliant on LESCs, which constitute a rare population of total ocular surface epithelia compartmentalized in the basal layer of a highly vascularized and innervated zone between the cornea and conjunctiva otherwise known as the limbus ,41,42. LUnder steady state, cellular attrition in the superficial layer of the central corneal epithelium prompts LESCs to replace lost cells by spawning progeny that can enter a differentiation program. Typically, asymmetric division prevails whereby a LESC divides to generate two daughter cells: a newly formed LESC and an early transient amplifying cell (TAC) . SymmetrLESC activity is also influenced by their immediate microenvironment. This comprises (but is not limited to) the underlying basement membrane, stroma and its supporting cells, and the neurovascular network, which are collectively referred to as the LESC niche . In humaAn inadequate number or depleted LESC stocks can result in the development of a vision-threatening disease known as limbal stem cell deficiency (LSCD). Under these conditions, the barrier function imposed by the limbus is breached and the corneal epithelium is unable to self-renew, thereby triggering a pathological wound-healing response which involves the invasion of an inflamed fibrovascular pannus of conjunctival cells into the cornea , resulting in a compromised ocular surface . SignifiBecause of their pivotal role in supporting the corneal epithelium, especially during wound resolution, it is postulated that functional abnormalities in LESCs account for persistent epithelial defects that manifest on the diabetic ocular surface. To date, there have been few independent reports on the effect of diabetes on LESC dynamics ,33,34,621 integrin, thereby hinting that these cells are either depleted or dysfunctional under disease-bearing conditions [A direct association between diabetes and LESC marker expression was first demonstrated in tissue sections from organ-cultured human corneas . Comparenditions . Notablynditions   in db/db mice [Changes in LESC marker expression have also been observed in animal models of diabetes. Compared to age-matched wild-type (WT) controls, histological sections of corneas from mice with T2D  exhibited markedly reduced immunoreactivity and number of cells positive for HES1 and K19 proteins in basal limbal epithelia . To over/db mice . Most re/db mice . Hence, Evidence for LESC loss or dysfunction in diabetes has been strengthened through observations that elucidated the impact of this supposition on corneal wound healing . To thisc-met, and upregulation of proteinase-encoding genes such as matrix metalloproteinase-10 (MMP-10) and cathepsin F (CF) in human diabetic corneas [c-met overexpression promoted epithelial repair, re-established a basement membrane and restored LESC marker expression in ex vivo organ-cultured diabetic human corneas [c-met overexpression and silencing of MMP-10 and CF genes significantly accelerated wound closure, which is concurrent with increased ABCG2, ∆Np63α, K14, K15, K17 and laminin γ3 expression  revealed unimpressive differences between diabetic and healthy murine corneas . Specifiithelium . In thisithelium . These rithelium ,34,62 isithelium , it is pWNT5A gene in cells isolated from diabetic compared to human cadaveric corneolimbal rims, suggesting its inactivation or downregulation [FZD6 gene (a putative WNT5A receptor) in distinct clusters of LECs isolated from diabetic compared to otherwise healthy human eyes [Alternative explanations exist, which pertain to epigenetic changes pertinent to differences between humans and animal models of diabetes. Genome-wide DNA methylation of LESC-containing primary LECs exhibited significant hypermethylation of the gulation . This wagulation . Importagulation , suggestgulation . Interesman eyes . Taken together, alterations in the limbal morphology, LESC biomarker expression and their strong associations with corneal epithelial defects in diabetes emphasize that the limbal compartment and its resident cells play an important role in the pathogenesis of DK. However, since many of the current, well-accepted markers for LESCs also detect cells in other regions of the ocular surface, such as the conjunctiva, and/or cannot accurately discriminate bona fide SCs from early TACs , alternaNerve axons that infiltrate the cornea have multiple functions, one of which is to influence LESC activity. The causal relationship between corneal innervation and LESC function is well established in healthy mice . In db/dRecently, a link between the sympathetic nervous system and LESC function was reported in corneas from the STZ-induced T1D mouse model . In thisSensory nerves also interact with resident immune cells such as dendritic cells and T cells which patrol the cornea as first-line responders to microbial insurance and trauma by initiating effective responses to acute and chronic stimuli . TherefoThe importance of corneal innervation in modifying LESC function in diabetic corneas is further highlighted by the concurrent restoration of nerve parameters, normalization of LESC marker expression and considerable improvements in epithelial regeneration, following treatment with various interventions , suggestMicroRNAs (miRNAs) are short non-coding RNA molecules consisting of 18–25 nucleotides that bind complementary mRNAs to negatively regulate the expression of protein-coding genes after transcription . AccumulBoth human and animal studies have identified miRNAs within the cornea which regulate a variety of homeostatic processes including cell differentiation , prolifeIn the diabetic cornea, variations in the expression of several wound healing-related miRNAs have been reported. qPCR-validated microarray analysis revealed that the expression of 29 miRNAs, previously linked to cell migration, inflammation, and proliferation, were indeed altered in diabetic compared to non-diabetic human cadaveric corneas . These omiR-146a is a key modulator of the innate immune response and is associated with the pathogenesis of numerous autoimmune diseases . Its higmiR-10b has been linked to SC migration, epithelial–mesenchymal transition, and cancer metastasis ,111,112.Exosomes are a subset of extracellular vesicles comprising cellular constituents released upon fusion with the plasma membrane. They mediate numerous biological functions, including homeostasis, signal transduction and intercellular communication . AlthougRecent studies demonstrated the benefits of administering healthy SC-derived exosomes in improving the corneal healing response in diabetes. The subconjunctival injection of healthy bone marrow mesenchymal SC-derived exosomes in diabetic mice, inflicted with a central corneal epithelial injury, displayed a significant reduction in corneal wound-healing rate . TreatmeSC therapies for treating diabetic corneal complications have also been considered, revealing promising results. The administration of hematopoietic and mesenchymal SCs promotes corneal epithelial regeneration in animal models of diabetes ,39. MoreDespite current evidence highlighting the loss and/or dysfunction of LESCs in diabetes, there is scant in vivo functional data implicating these insufficiencies as being responsible for DK . If it wIt is evident that LESCs are influenced by a myriad of complexities that prevail systemically and locally in the diabetic cornea, ultimately resulting in their depletion or loss of function. Although the precise programs and molecular circuits that lead to the development of corneal defects in diabetes have not been fully elucidated, evidence suggests that defects in cell movement and the proliferation of LESCs exist. These processes are likely influenced by modifications to components of the limbal niche which have been imposed by a chronic hyperglycemic state. Direct links are established between LESC marker expression and corneal wound healing, innervation as well as inflammation in patients with diabetes and in representative animal models of this disease. Overall, these studies reveal the contribution of discoordinated healing-related signaling pathways, differentially expressed miRNAs and impairments in exosomes that impinge on LESC form and function . HoweverSpecific gene-modifying strategies have further elucidated the importance of rescuing LESC function in treating diabetes-associated corneal defects. However, the clinical application of these techniques warrants further development to ensure side effects are minimized in the quest to restore LESC activity. Knowledge as to whether diabetes imposes major changes in the characteristic features displayed by LESCs, TACs or both populations and unravelling the detailed molecular pathways related to LESC dysfunction would be an invaluable undertaking to determine the efficacy of a therapeutic. Moreover, the pathological characteristics that distinguish the LESC phenotype in diabetes and LESC-associated diseases such as LSCD have not been explored. This would be imperative for developing advanced clinical management strategies and examining whether current diagnostic tools for LSCD can be exploited for diabetic corneal disease. With further confirmation of impaired LESC activity and knowledge on how treatment restores their density, a higher-order understanding of their role in diabetes would be gleaned. As biomarkers specific for DK are currently lacking, investigating clinical tools for the detection of changes in the limbal architecture and LESCs would be a key priority for improving the diagnosis of DK at early stages and advancing the future clinical management of ocular surface complications that arise in patients with diabetes.


Neutrophils, the most prevalent innate immune cells in humans, have garnered significant attention in recent years due to their involvement in cancer progression. This comprehensive review aimed to elucidate the important roles and underlying mechanisms of neutrophils in cancer from the perspective of their whole life cycle, tracking them from development in the bone marrow to circulation and finally to the tumor microenvironment (TME). Based on an understanding of their heterogeneity, we described the relationship between abnormal neutrophils and clinical manifestations in cancer. Specifically, we explored the function, origin, and polarization of neutrophils within the TME. Furthermore, we also undertook an extensive analysis of the intricate relationship between neutrophils and clinical management, including neutrophil-based clinical treatment strategies. In conclusion, we firmly assert that directing future research endeavors towards comprehending the remarkable heterogeneity exhibited by neutrophils is of paramount importance. Neutrophils, the predominant common type of polymorphonuclear leukocytes , hold a Understanding the nature of immune cells in cancer is a gradual process, with earlier investigations primarily centered around adaptive immune cells. There is a generally accepted classification of T helper cell as the “Th1/Th2” paradigm, which subsequently directs the grouping of other immune cell populations . NeverthHowever, recent research suggests that the simplistic dichotomy of immune cells in cancer may not provide a comprehensive depiction of the entire landscape. Studies have unraveled the heterogeneity within T cells, revealing the existence of different subsets of less-differentiated T cells that possess extended lifespans and greater potential to overcome T cell inhibition , 16. FurNumerous studies have demonstrated that neutrophils in cancer exhibit the biological heterogeneity in their lifespan, prompting the need for a fresh investigation approach. Does heterogeneity present in neutrophil progenitors result in specific neutrophil progeny within circulation and contribute to tissue heterogeneity? Considering the different functions of neutrophil subsets in the TME, is targeting all TAN subsets a viable therapeutic strategy? While research has predominantly focused on targeting immunosuppressive or other pro-tumor TAN subsets, is it feasible to control and harness their anti-tumor functions? It is worth noting that the answers to these questions may vary depending on tumor types and stages of disease progression, further complicating the matter . TherefoThis comprehensive review delved into the entire developmental process of neutrophils in the context of cancer, aiming to interpret the complex phenomenon that correlates neutrophils with the occurrence and development of cancer by taking into account their heterogeneity. We provided an in-depth exploration of the past and present lives of TANs, including their sources, factors influencing chemotaxis and activation, as well as their phenotypes within the TME. Furthermore, we systematically outline the intimate relationship between neutrophils and prognosis, along with neutrophil-based therapeutic strategies. Overall, we firmly believe that directing research efforts towards unraveling the remarkable heterogeneity of neutrophils holds paramount significance, as it bears crucial implications for the development of neutrophil-related therapeutics.Bone marrow is the origin of all mature neutrophils. Neutrophil precursors continuously differentiate through different hematopoietic progenitor stem cells until they mature. Density gradients, followed by Giemsa staining, are widely accepted methods to isolate and identify granulocyte precursors. Morphological observation can be the second step to identify granulocytes based on their special characteristics, including cell size, nuclear condensation, and granule content . MultipoRecently, state-of-the-art technologies such as single-cell RNA sequencing and mass cytometry have garnered substantial attention in the field of scientific research, providing a comprehensive description of genomic states. Consequently, our understanding of the developmental and maturational process of neutrophils has witnessed significant advancements , 23, givRecent studies using single-cell RNA sequencing and mass cytometry have identified several subsets of proliferative neutrophil progenitors that can enter circulation in both humans and mice under cancerous conditions. However, despite these advancements, our current understanding of the intricate processes involved in the entry of abnormal and proliferative neutrophils into the circulation from the bone marrow remains incomplete. Moreover, the mechanisms governing their subsequent recruitment into the TME and their consequential role in in cancer immunity remain inadequately elucidated. The heterogeneity exhibited by neutrophils arising from different subsets of neutrophil progenitor cells, along with their commonalities in the TME, the dynamic interplay between progenitor cells and progeny, and the regulatory factors governing these processes collectively serve as pivotal focal points linking neutrophil developmental biology and tumor immunology.Under normal physiological conditions, mature neutrophils are released from the bone marrow and enter the bloodstream due to the stimulation of granulocyte colony-stimulating factor (G-CSF) . Notably+ T cell proliferation, thereby promoting tumor growth [The initial investigation into circulating neutrophils in cancer patients employed density centrifugation to separate neutrophils into three distinct subsets . Subsequr growth , 43. Givr growth . On the r growth . Notablyr growth , 26, arer growth  as well r growth .One classical approach in investigating the recruitment of neutrophils by tumors is to examine this phenomenon from an inflammatory perspective. Previous studies have confirmed the intricate association between inflammation and cancer . NotablyAs mentioned above, colony-stimulating factors (CSFs) play a pivotal role in stimulating the proliferation and differentiation of neutrophils in the bone marrow. Notably, this mechanism is also exploited by tumors to recruit neutrophils into the TME . NumerouThe exact proportion of these abnormal immature circulating neutrophils that infiltrate the TME and transform into TANs remains unclear. Additionally, the relationship between neutrophil subsets in the bone marrow and those present in the TME has not yet been definitively established. Previous studies have proposed that, in addition to the bone marrow-circulation-TME pathway, the spleen serves as another important source of TANs, where neutrophils may be reprogrammed and induced . NeverthAnother interesting question is whether the modality by which neutrophils infiltrate the TME and the different upstream subsets are related to the total amount of TANs, a metric closely related to prognosis , althougHowever, the inherent heterogeneity of neutrophils is evident in studies that aim to localize the upstream of CXCR2 and other pivotal determinants of neutrophil recruitment. Consequently, a fundamental question arises: do these genotypes solely correlate with specific neutrophil subsets or do they possess broader regulatory roles in the recruitment of TANs? Another noteworthy observation on neutrophil recruitment tend to combine T cell activation or response with immunotherapies. These findings lend support to the hypothesis that targeted modulation of pathways implicated in neutrophil recruitment to malignancies may hold promise for enhancing prognosis in cancer patients. Moreover, these studies underscore the significance of comprehensive consideration of remodeling the TME to counteract immune-suppression. Both innate immunity, represented by neutrophils, and adaptive immunity play pivotal roles in this regard.Studies investigating the functionality of circulating neutrophils have primarily focused on their involvement in the process of metastasis. Notably, one study proposes that neutrophils can facilitate metastatic progression through their interaction with circulating tumor cells (CTCs) in breast cancer . InteresThe direct interactions between neutrophils and tumor cells, including both anti-tumor and pro-tumor functions, have long been a focal point in neutrophil research, particularly regarding TANs with their diverse mechanisms. The initial focus was on confirming the anti-tumor function, which was believed to be achieved through various mechanisms, including direct killing via the production of reactive oxygen species (ROS) whose killing function is dependent on tumor cell expression of TRPM2, 73 and The relationship between neutrophils and tumor metastasis has been extensively studied for decades. Initial investigations thirty years ago involved injecting neutrophils in animal models to examine the contribution of neutrophils to metastasis . As reseRecently, a completely novel perspective has emerged, examining the link between neutrophils and tumor metastasis from the standpoint of energy metabolism. A study on lung metastasis in breast cancer suggests that TANs can act as a source of fuel to promote metastasis . This raTANs play a significant role in angiogenesis, a crucial process in the TME. Angiogenesis is mainly induced by cytokines secreted by various cells in the TME . NeutropWith the improvement of research technology, the analysis of the transcription and chromatin landscapes has become more feasible, which is instrumental in uncovering the key molecules and potential targets in angiogenesis-related therapy. Identifying their biomarkers can facilitate us gradually improve our insight into the phenotypes related to angiogenesis in different subsets .+ T cells to T-cell receptor triggering, thereby improving the OS in colorectal cancer. On the other hand, a previous study pointed out that neutrophils can inhibit the anti-tumor function of T cells and promote tumor metastasis [+ TANs can suppress T-cell cytotoxicity [Neutrophils also play a dual role in tumor immunity through crucial molecules and interactions with multiple cells, encompassing both innate and adaptive immune cells. These interactions have been extensively studied in the context of inflammation . In the tastasis . A recentoxicity . Due to + TANs recruit macrophages via chemokine secretion, albeit the phenotypic characteristics of these macrophages remain unknown [As the depth of research in this field expands, investigators are delving into the intricate interactions between TANs and other components of the innate cells . Most of unknown . The dyn unknown .−CD8− unconventional αβ T cells, showing anti-tumor function [A comparative study has scrutinized the phenotypes and immune functions of TANs in circulation and bone marrow, discerning a distinctive subset of TANs in sarcoma characterized by augmented expression of CD11b and CD54, and diminished expression of CD62L. Remarkably, these TANs exhibit an exceptional cytokine profile, encompassing the secretion of cytokines such as Cxcl10, Il23a, and Arg1, which potently bolster the polarization of a subset of CD4function .Furthermore, researchers have discovered TANs could also interact with infiltrating B cells in various types of cancer, leading to changes in the behavior of plasma cells accordingly . This inSpecifically, TANs play a role in mediating B-cell chemotaxis, through the secretion of TNF-α, in conjunction with the presence of CXCL13 or CXCL12 . As the NETs, composed of decondensed chromatin DNA filaments coated with granule proteins, can be induced by tumors through the secretion of various factors derived from tumors and infections. NETs are released by neutrophils and serve as an important mechanism for trapping pathogens with microbicidal activity by binding to these DNA structures . HoweverTumors can induce the formation of NETs through the secretion of various tumor- and infection-derived factors, such as the overexpression of G-CSF commonly observed in cancer. Cutting off this potential cascade reaction cycle to suppress tumor activities is an intriguing concept worth considering . Recent +CD62Llow), induced by tumor-derived Nicotinamide Phosphoribosyl transferase (NAMPT), are capable of forming two types of NETs: mitochondria-dependent vital NETs, where SIRT1 induces the opening of mitochondrial permeability transition pore channels to release mitochondrial DNA, and traditional Cit-Histone H3-dependent fatal-NETs [In tumor-associated aged neutrophils  to the time they are cleared from circulation (aged neutrophils). The aging process emphasizes the importance of time as a crucial parameter for neutrophil clearance . Neutroplo in immature neutrophils and CXCR4hi and CD62Llo in older neutrophils during human neutrophil senescence, which is thought to be the result of activation rather than a distinguishing marker in the growth program, it is important to conduct further explorations and establish a generally accepted classification of neutrophil subsets based on different ages [Although some phenotypes have been revealed, such as CD16ent ages .Meanwhile, questions are being raised regarding the lifespan of TANs compared to other neutrophils and how this difference is regulated in the TME . StudiesNumerous studies have elucidated the correlation between neutrophils and cancer prognosis, albeit with a predominant focus on peripheral blood neutrophils rather than TANs, primarily due to challenges in assessing the status (including number and subsets) of TAN infiltration . InitialIntriguing findings have emerged when investigating the infiltrating neutrophils within tumors. Higher TAN infiltration in the TME has been consistently associated with poorer outcomes in various cancers, such as renal cell carcinoma, head and neck cancers, and esophageal cancers . HoweverAs scientific research progresses, the underlying complexity of the controversial issue surrounding TANs has begun to unveil, highlighting their plasticity and heterogeneity. For instance, in pancreatic ductal adenocarcinoma (PDAC), higher TAN infiltration was initially believed to correlate with poorer OS , 159. HoIn addition, NETs have been identified as independent prognostic factors in cancer . In breaAn alternative perspective involves considering the correlation between neutrophils and prognosis in terms of metastasis. Within the circulation, neutrophils have been observed to transport metastatic cancer cells by forming cell clusters through interactions with endothelial cells . These nNeutrophils are closely linked to the clinical management of cancer and the benefits of several therapies, such as chemotherapy and radiotherapy. The numbers of circulating neutrophils and their infiltration status have been found to be associated with treatment outcomes.In the context of chemotherapy, neutropenia is a common concern as it can impact treatment , 169. ReThe pivotal involvement of neutrophils in the realm of immunotherapy has been initially elucidated through several retrospective cohort studies. These studies have consistently demonstrated a significant association between elevated NLRs and a compromised prognosis following immune checkpoint inhibitors (ICIs) therapy in multiple cancers . NotablyThe burgeoning correlation between neutrophils and prognosis, along with their potential role in chemotherapy, radiotherapy, and immunotherapy, has sparked significant interest in the notion of directly targeting neutrophils as a promising treatment strategy. This emerging topic has garnered widespread attention , 183.One potential therapeutic approach involves augmenting the number of circulating neutrophils and enhancing their biological function. Parenteral administration of recombinant human G-CSF has demonstrated efficacy in the treatment of severe neutropenia. G-CSF facilitates faster release of neutrophils from the bone marrow and amplifies their function . HoweverAnother feasible study to enhance the anti-tumor function of neutrophils is to directly enhance their functional responsiveness. Antagonizing various inhibitory receptors on neutrophils may facilitate the neutrophil-mediated anti-tumor function, thereby engendering a notion of neutrophil checkpoint blockade , 187. NeOn the other hand, certain studies explore the inhibition of neutrophil function due to their pro-tumor phenotype, focusing on reducing neutrophil numbers or blocking their activation. Therapeutic strategies encompass the utilization of selectin antagonists, anti-integrin antibodies, CXCR1 inhibitors, CXCR2 inhibitors, leukotriene B receptor 1 (BLT1) inhibitors, C5a receptor inhibitors, and NETs inhibitors, aiming to neutralize neutrophil-derived molecules, block receptor activation, and impede signal transduction –194. NotThe phenotype of TANs allows for their transition between anti-tumor and pro-tumor phenotypes, underscoring the need for therapeutic strategies aimed at restoring neutrophil function, rather than simply enhancing or inhibiting . This poNeutrophils, with their relatively short lifespan, continuously differentiate from the bone marrow into various subsets, each possessing distinct functions In the context of tumor-related pathology, these subsets exhibit multifaceted functions, including angiogenesis, extracellular matrix remodeling, metastasis, and immunosuppression, exerting both direct and indirect anti-tumor effects, possibly via a complicated cellular network involving neutrophils, ultimately contributing to immune suppression within the TME , 206. AsThe heterogeneity of neutrophil subsets in the context of cancer exerts a pivotal influence on prognosis. Future endeavors must intimately delve into the complete lifespan of these neutrophils. The accurate identification of distinct neutrophil subsets and the precise targeting of key pro-tumor/anti-tumor subsets hold immense promise as therapeutic approaches.


Patients with atrial fibrillation who take a high bleeding risk and are not candidates for oral anticoagulation therapy are increasingly being referred for left atrial appendage closure (LAAC) as an alternative method of stroke prevention. However, certain manipulations performed during the LAAC procedure, such as transseptal puncture (TSP), may potentially result in vessel injury and lead to cardiac tamponade or even fatality. Clinical significance and management strategies associated with these complications remain controversial. A 74-year-old female patient with atrial fibrillation was referred for left atrial appendage occlusion. During the puncture of the atrial septum, the catheter sheath inadvertently exited through the roof of the right atrium and continued to advance, resulting in pulmonary artery perforation. The patient underwent immediate pericardiocentesis and drainage, followed by surgical exploration for suturing the tear in the pulmonary artery and ligation of the left atrial appendage. This represents the first reported case of a pulmonary artery perforation occurring during a transseptal puncture procedure for left atrial appendage closure. The case exemplifies the feasibility of emergency cardiac surgery as a therapeutic intervention. In recent years, advancements in electrophysiology and structural cardiac interventions have propelled the growing demand for transseptal procedures, primarily encompassing radiofrequency ablation, left atrial appendage closure, and mitral valve repair , 2. LeftA 74-year-old female, was diagnosed with paroxysmal atrial fibrillation. Past medical history included coronary atherosclerotic heart disease, thrombosis in the left upper limb artery, heart failure, hypertension, ischemic cerebrovascular disease, and surgically treated endometrial cancer. Following coronary stent implantation and left upper extremity artery thrombectomy procedures, the patient received regular treatment with standard-dose oral Aspirin, Clopidogrel sulfate, Pitavastine, Sacubitril-valsartan, Nifedipine, and Metoprolol. The patient presented with a CHA2DS2-VASC score of 7 and a HAS-BLED score of 3, clearly indicating the necessity for left atrial appendage closure. Considering the potential risks associated with long-term anticoagulation therapy, percutaneous LAAC is performed for secondary stroke prevention.9/L, and an international normalized ratio (INR) of 0.96.Preoperative left atrial CT angiography showed that the left atrial appendage was complex with a large branch, while no evident filling defect was observed in both the left atrial appendage and left atrium. No diverticulum or accessory atrial appendage was observed in the left atrium . LaboratThe procedure was performed under digital subtraction angiography (DSA) guidance, with puncture of the right femoral vein, placement of a 6F sheath, and transseptal puncture using a catheter in the conventional manner. Afterwards, we promptly advanced the transseptal sheath and encountered difficulty in accessing the left superior pulmonary vein with the guidewire, while contrast injection indicated visualization of the pulmonary artery .Patient experienced a sudden onset of hypotension and tachycardia, intraoperative echocardiography revealed the inadvertent insertion of the delivery tube sheath into the pulmonary artery, accompanied by a pericardial effusion measuring 17 mm. The ultrasound intervention department was promptly contacted for pericardiocentesis and drainage, while norepinephrine and dopamine were administered to augment blood pressure. Following active therapeutic interventions, hemodynamic stability was achieved in the patient.Cardiac surgery team was consulted to perform surgical exploration in order to identify and suture the tear. A median sternotomy was performed under general anesthesia, and the pericardium was opened to locate the source of bleeding, revealing a subepicardial hematoma in the right atrioventricular groove. Exploration was initiated subsequent to the establishment of cardiopulmonary bypass, revealing that the delivery tube sheath had entered through the superior aspect of the right atrium and traversed through the posterior wall of the right pulmonary artery into the main pulmonary artery . The lacPatient was transferred back to the intensive care unit for a day of close monitoring. On the second postoperative day, she returned to the cardiovascular surgery department and initiated anticoagulant therapy with low molecular weight heparin (LVMH). Two days later, she was transferred back to the cardiology department with a gradual reduction in pericardial and mediastinal drainage and discharged on postoperative day 25. Dual antiplatelet therapy with Indobufen and Clopidogrel bisulfate was regularly applied outside the hospital. After seven days, the patient returned to the outpatient clinic exhibiting no subjective symptoms and normalization of N-terminal pro-B-type natriuretic peptide levels .Left atrial appendage closure has proven to be an effective alternative treatment to long-term oral anticoagulation for stroke prevention in patients with nonvalvular atrial fibrillation , 4. The The operation of DSA-guided TSP is relatively straightforward and safe, but anatomical abnormalities may obscure the exact position of the needle or even mislead to the wrong puncture point. Therefore, it is crucial to evaluate the patient's left atrial appendage condition and anatomical morphology prior to surgery. Transesophageal echocardiography (TEE) enables clear determination of LAA thrombus presence, as well as measurement of basal diameter and depth, providing a foundation for the operator in selecting the appropriate occluder model. Cardiac CT angiography (CCTA)enables objective and accurate assessment of the left atrial appendage's shape, lobulation, and orifice parameters in the lateral aspect, providing a more comprehensive basis for determining the need for left atrial appendage occlusion. The utilization of these two methods enables the execution of multiplanar imaging and three-dimensional reconstruction, thereby establishing a solid foundation for medical professionals to formulate treatment plans and assess potential risks. Additionally, cardiac magnetic resonance imaging (CMR) can also offer high-quality multiplanar images. For patients with contraindications or intolerance to TEE, intracardiac echocardiography (ICE) can serve as an alternative method for obtaining high-quality multiplanar images .Previous cases have shown that pulmonary artery injury is the most common type of collateral vessel injury during left atrial appendage occlusion  which moSeveral cases have been reported in which a percutaneous occluder was utilized to block aortic or cardiac perforations , 7 durinCombined with previous literature recommendations, when we encountered complications of pulmonary artery perforation, emergency cardiac decompression was performed immediately, followed by surgical suturing of the ruptured artery and ligation of the left atrial appendage in order to avoid active bleeding. Postoperative follow-up showed that the patient recovered well, which confirmed that surgical repair was an effective treatment.Pulmonary artery perforation is a rare but critical complication associated with left atrial appendage closure, which may occur during transseptal puncture. Clinicians should maintain vigilance for uncommon complications and actively enhance preoperative assessment in order to decrease the occurrence of complications. In the event of such complications, emergency surgical exploration and ligation of the left atrial appendage represent a feasible treatment option.“Although a rare complication occurred and the left atrial appendage closure was not successfully completed, I was fortunate to undergo timely surgical intervention, ensuring my safety. I express my gratitude to the medical staff for their exceptional treatment. I hope that my experience can serve as a valuable reference for similar cases”.


Intraductal papillary mucinous neoplasms (IPMN) are benign pancreatic cysts found in the ducts of the pancreas that have the potential to become malignant. Identifying IPMNs that have high potential to become pancreatic cancer may help prevent unnecessary surgery which is the definitive treatment of IPMNs. Currently, the management of IPMNs are dependent on variable factors including characteristics of the cyst, size of the pancreatic duct, and the presence or absence of obstructive jaundice. Identifying potential biomarkers may help more accurately distinguish high risk IPMNs from low risk IPMNs that do not need surgical intervention. This review summarized the various changes within IPMNs that promotes their progression to pancreatic adenocarcinoma. In addition, this review highlighted potential biomarkers that can distinguish IPMNs that have a high risk of becoming cancerous.Intraductal papillary mucinous neoplasms (IPMN) have the potential to progress to pancreatic ductal adenocarcinoma (PDAC). As with any progression to malignancy, there are a variety of genetic and metabolic changes, as well as other disruptions to the cellular microenvironment including immune alterations and inflammation, that can contribute to tumorigenesis. Previous studies further characterized these alterations, revealing changes in lipid and glucose metabolism, and signaling pathways that mediate the progression of IPMN to PDAC. With the increased diagnosis of IPMNs and pancreatic cysts on imaging, the opportunity to attenuate risk with the removal of high-risk lesions is possible with the understanding of what factors accelerate malignant progression and how they can be clinically utilized to determine the level of dysplasia and stratify the risk of progression. Here, we reviewed the genetic, metabolic, inflammatory, and immunologic pathways regulating the progression of IPMN to PDAC. Pancreatic ductal adenocarcinoma (PDAC), currently the third leading cause of cancer-related mortality, is projected to be the second most common cause of death due to malignancies in the United States by 2030 . This poThese cysts are mucin-producing and arise from the main pancreatic or the branch duct. Main duct lesions (MD-IPMN) has a higher risk of malignancy compared to branch duct (BD-IPMN). There is a third type that shares features of MD-IPMN and BD-IPMN and is referred to as mixed type (MT-IPMN). MT-IPMN and MD-IPMN tend to be more symptomatic. Symptomatic patients tend to progress to malignancy more than those who are asymptomatic, regardless of subtype. While they all arise from cells which produce mucin, four histopathological IPMN types are distinguished by the specific mucin(s) they produce: gastric 49–63%), intestinal (18–36%), pacreaticobiliary (7–18%), and oncocytic (1–8%). Of these, gastric is the most common and rarely progresses to malignancy. While pancreaticobiliary is less common, it is commonly associated with aggressive PDAC [%, intestThe primary management of IPMN is the surgical resection of high-risk lesions that can progress to malignant disease . Risk stKRAS with 50–80% of IPMNs harboring a KRAS mutation [KRAS mutation is in codon 12, resulting in a G12D mutation. This KRAS mutation encodes a constitutively active GTP-binding protein that regulates various signaling cascades including cell growth and proliferation. Furthermore, KRAS mutations are found in >90% of PDACs and, hence, are thought to be essential and an early event for tumorigenesis [GNAS gene is another common alteration in IPMNs and was identified in 40–70% of lesions [GNAS encodes the stimulatory alpha subunit of the guanine nucleotide-binding protein which activates cyclic adenosine monophosphate (cAMP), leading to the activation of multiple effectors including protein kinase A and EPAC (Exchange Protein directly activated by cAMP). Although the relevance of these pathways in pancreatic cancer was not fully established, these pathways were implicated in other cancer types [GNAS mutation is predominantly located at codon 201, commonly leading to R201H or R201C alterations [GNAS. In contrast to KRAS, GNAS mutations are not commonly observed in non-IPMN PDACs but were found in 25–61% of IPMN- derived PDACs [Whole exome and targeted sequencing were utilized to better characterize the genetic alterations in IPMNs. The most commonly mutated gene in IPMNs is mutation ,7. The mer types ,11. The ed PDACs .KRAS and/or GNAS mutations are found in >90% of IPMNs, both in those with advanced neoplasia (high-grade dysplasia or adenocarcinoma) and low-grade dysplasia [GNAS and KRAS to generate cystic lesions that are histologically similar to human IPMNs [KRAS and GNAS alterations in IPMNs with and without advanced neoplasia, a difference in mutation frequency were observed when analyzing the histological subtypes [ysplasia . The prean IPMNs . Althougsubtypes .GNAS mutation in IPMN-associated colloid carcinoma and KRAS mutations in IPMN-associated tubular carcinoma [IPMNs can be divided into histological subtypes including gastric, intestinal, and pancreatobiliary. The oncocytic subtype is now considered a separate entity, i.e., “Intraductal Oncocytic Papillary Neoplasm”, by WHO’s classification of tumors, due to its different molecular and clinical features. These subtypes can give rise to different types of invasive carcinoma . In genearcinoma . This diRNF43 gene is another common genetic alteration found in IPMNs, occurring in 10–75% of cystic lesions [TP53, CDKN2A, and SMAD4. These genetic alterations occur at a lower rate in IPMNs with low-grade dysplasia compared to those with advanced neoplasia, suggesting that these genes may play a role in mediating progression to malignancy [Inactivating mutation in the  lesions ,17. OtheKRAS, GNAS, RNF43, CDKN2A, TP53, and SMAD4. In addition, the use of WES revealed novel mutations in IPMN tumorigenesis. Somatic mutations in the ATM gene were found in 17% of lesions. ATM encodes a serine/threonine kinase that is involved in DNA double-strand break repair as well as other cellular processes including metabolism and chromatin remodeling. Moreover, individuals with germline pathogenic ATM variants appear to have an increased lifetime risk of pancreatic cancer [GLI3 gene was also observed in 8% of samples. GLI3 gene encodes a transcription factor that is a member of the Hedgehog signaling pathway and is involved in normal cellular processes including tissue and immune cell development. Furthermore, studies implicated GLI3 in mediating pro-tumorigenesis pathways in various cancers, including pancreatic cancer [More recently, Noe et al. performed whole exome sequencing (WES) of IPMNs and MCNs and their associated invasive carcinomas to better understand the genetic alteration driving tumorigenesis in these cystic precursors . WES anac cancer ,20. In ac cancer . Somaticc cancer ,23,24.In addition to mutational changes, gene expression can be altered through DNA methylation. This form of epigenetic modification involves adding a methyl group to the fifth carbons of the cytosine ring of DNA. DNA is primarily methylated at CpG islands which are GC-enriched regions. When DNA methylation occurs on a gene promoter, it can inhibit transcriptional regulators from binding and initiating transcription. Alternatively, DNA methylation can lead to an alteration in chromatin structures, typically resulting in a repressive state. Methylation profiling of IPMNs revealed aberrant methylation of at least one CpG island in >80% of IPMNs . FurtherGenotypic changes can allow for measurable differences within the cells of IPMN. Techniques including nuclear magnetic resonance, liquid chromatography mass spectrometry, and gas chromatography mass spectrometry are all utilized to analyze what metabolites are present in cells, tissues, and, even more broadly, in blood or other body fluids. This is the basis of several biomarkers that are increased due to reprogrammed cellular metabolomics compared to an unaltered cells. For example, one of the most well-known biomarkers of pancreatic cancer, glycoprotein CA19-9, is thought to be increased secondary to perverse glycosylation and was used as a biomarker for pancreatic cancer as well as various other digestive tract cancers . CA19-9 As an IPMN potentially progresses through a presumed stepwise pathway of low-grade dysplasia to advanced neoplasia, potential metabolites can be measured to determine the grade of dysplasia . IdeallyIn malignancy, metabolic reprogramming occurs to support increased proliferation and to support survival of altered cells. The Warburg effect, an early proposed example of this, is rapid glycolysis in response to resulting hypoxia from high energy demand not met by aerobic respiration alone . IncreasHistologically, glucose transporter-1 expression (GLUT-1) was detected at higher levels in poorly differentiated PDACs compared to regular pancreatic tissue. When GLUT-1 expression in IPMNs was analyzed, it was not found in low-grade dysplasia, but detected in 60% of the IPMNs with high-grade dysplasia, suggesting increased transporter expression occurs late in dysplasia prior to invasive adenocarcinoma . ImmunohKRAS and GNAS are known to be mutated in IPMN tissue and such alterations were repeatedly connected to downstream activation of mTOR signaling, which, in turn, increases glucose uptake [Supporting the theory that increased glucose needs are linked to increased cell growth, phosphorylated S6 ribosomal protein (pS6) was also studied with relation to GLUT1 expression. The presence of pS6 indicates mechanistic Target or Rapamycin (mTORC1) activity, which is a key coordinator for cell growth and metabolism . mTOR ite uptake . Of the e uptake . Deprivae uptake ,37. In ae uptake . Increase uptake ,40. As KSince glucose is needed for the proliferation of cancer cells, in parallel, there is increased utilization of lipids for neoplastic growth. Lipids can be utilized for energy production in glycolysis via fatty acid oxidation, or beta-oxidation, to produce ATP and NADPH, both for energy storage. In addition, lipids are utilized for the production of cellular membranes, including special glycolipids responsible for recognition and signaling molecules. The reprogramming of lipid metabolism in tumorigenesis not only helps the rapid proliferation of the cell by supporting energy needs and supplying necessary building blocks, but also can alter communication with nearby cells, affect immune surveillance, and encourage inflammation of the tumor microenvironment. Altogether, changes in lipid metabolism support the changing cellular landscape to promote neoplastic growth and proliferation .When cyst fluid of resected IPMNs were analyzed, phospholipid biosynthesis, beta oxidation of very long chain fatty acids, fatty acid metabolism, oxidation of branched chain fatty acids, and other lipid pathways appeared to dwarf the activity of other metabolic pathways when compared to serous cystic neoplasms (SCN) . SCNs arAltered lipoprotein processing was also observed in regard to apolipoprotein A2 (apoA2) and deviant C terminal processing associated with IPMN progression to malignancy. ApoA2 is often part of the atherosclerosis conversation, as it is found within high-density lipoproteins (HDL), and alterations in its processing may likely lead to changes in lipid metabolism. This abnormal processing may reflect dysfunction of the exocrine process of the pancreas. However, the potential to use apoA2 as a biomarker exists regardless of the causative pathway. Hypo-processing of these lipoproteins is associated with increased dysplasia and malignant potential, likely to further alteration of lipid metabolism via its effect on HDL. When used as a biomarker to differentiate between low- and high-grade dysplasia, apoA2 performed better than CA19-9 .GNAS alteration likely plays a key role in IPMN progression through various signaling pathways that regulate different cellular processes, including alteration of lipid metabolism. Mutant GNAS signaling promoted fatty acid oxidation and increased TAG and acetyl CoA levels [GNAS mutations may very well be responsible for the overall increase in lipidomic pathways observed. However, further elucidations on the affected lipid pathways would help illuminate our understanding of the significance of the detected changes.As discussed above, A levels . Most ceOther metabolic alterations include hormonal signaling. Leptin, a hormone that increases glucose uptake and fatty acid oxidation is increased by adipocytes. Leptin may also be altered in the progression of IPMN to PDAC and was found to be actually decreased in higher grades of dysplasia and invasive cancer as compared to low-grade dysplasia. Lower leptin levels were associated with cancer cachexia  and thisAltered metabolites were proposed as key players in cellular signaling between cancerous and host cells. Metabolite cross feeding allows cancer cells to overcome limitations in nutrition and oxygen they may face within the tumor microenvironment. In PDAC, communication between fibroblasts and other cells in the microenvironment are thought to promote tumorigenesis . Both ca2). PGE2 is a lipid that plays a key role in inflammation pathways. Derived from arachidonic acid released from the cell membrane and produced by the COX enzyme, PGE2 functions to increase local inflammation [While the above changes in metabolites reflect the increased energy demand of increased cellular proliferation, changes in the expression of lipids and proteins can also enact change via their role in signaling. Another example of metabolite signaling is prostaglandin E2 , a marker of inflammation, is associated with worse outcomes in various malignancies, PDAC included. Neutrophilia and declining lymphocytes are thought to be indicative of increased inflammation and decreased immune surveillance. When elevated, patients had worse survival following resection . ElevateAnother proposed ratio indicative of systemic inflammation is the CRP to albumin ratio (CAR). It was investigated in patients with PDAC and found to be predictive of poor outcomes following resection, similar to NLR. When applied to IPMNs, low CAR predicted better survival. CAR also has potential utility as an independent predictor of advanced neoplasia in IPMN . The CARIf increased inflammation occurs with progression to cancer, biomarkers already associated with systemic inflammation may have utility in identifying high-risk IPMNs. Ferritin, a marker of acute and chronic inflammation, is also elevated in several malignancies. By modulating iron availability, ferritin may play a role in immunosuppressive modifications in myeloid and lymphocytes and contribute to overall immunosuppression in cancer patients . It is aWhere there is inflammation, alterations in the immunological landscape also occur. While the specificities of this are beyond the scope of this paper, some of these alterations result in useful biomarkers for grades of dysplastic progression. T cell frequency and localization dramatically change. Cytotoxic T cells, activated Th cells, and dendritic cells infiltrate low-grade dysplastic IPMNs. Eventually, they are replaced by new immune cells with immune suppressive phenotypes, allowing progressive dysplasia and malignant growth without immune detection. CD8+ lymphocytes, significant players in antitumor immunity, when present, are associated with survival of the cancer patient and are sequestered off in peritumoral compartments, while more passive Tregs infiltrate the neoplasm microenvironment. In addition to Tregs, macrophages also are thought to begin to infiltrate low-grade dysplasia and numbers of both increase with progression. Higher levels of Tregs and macrophages within the local site of malignancy are a negative prognostic factor, as it correlates with poor immune detection of the malignant cells. Detection and quantification of these cell types at the site of the IPMN may help guide where in the pathway to malignancy a given IPMN is. In addition, Th cell subsets populations at the tumor site also change during progression. For example, Th1-polarized CD4+ cells are fewer than Th2-polarized CD4+ T cells with more advanced dysplasia. Similar to the inflammatory ratios discussed above, the ratio of these two Th1 cells show association with the grade of dysplasia . When evCAF, in addition to its role with altered metabolism and nutritional support, also is a player in immune evasion. As mentioned previously, populations of CAF were observed when RNA of 5403 cells of IPMN were analyzed by Bernard et al. Within the CAF population, two known different subtypes of CAF emerged. Inflammatory CAF (iCAF), characterized by lack of alpha smooth muscle actin (SMA) expression and secretion of IL6 and other inflammatory mediators such as IL-11 . In contPrior to differentiating into CAF, PSC can become activated in comparison to their typical quiescent state in health. Activated PSC begin to express alpha smooth muscle actin, loose their lipid content, as discussed previously, and produce extracellular matrix proteins . IncludeThe majority of pancreatic cystic lesions are incidentally diagnosed initially on abdominal imaging. While definitive diagnosis is achieved via surgical resection or less invasive endoscopic ultrasound (EUS)-guided needle based laser confocal endomicroscopy (nCLE), cyst fluid molecular analysis by next-generation sequencing (NGS) analysis, or, in some instances, through-the-needle biopsy (TTNB), there is a need for further risk stratification of IPMNs ,82,83. MIn addition to obtainable biomarkers, imaging also remains important in initial diagnosis and monitoring of the progression in a non-invasive manner for patients who undergo surveillance of their lesions. Magnetic resonance imaging/magnetic resonance cholangiopancreatography (MRI/MRCP) and computed topography (CT) imaging both can offer non-invasive routes of surveillance. In a retrospective study comparing CT and MRI modalities of IPMN patients and their ability to identify the high risk features mentioned above according to the international consensus guidelines, CT and MRI performed similarly in their ability to identify malignant vs. non-malignant IPMN. However, MRI was able to identify enhancing mural nodules superiorly .KRAS and GNAS were detected in the cfDNA of IPMN samples but not in benign lesions such as SCN [Liquid biopsy is another non-invasive tool that may aid in the diagnosis of high-grade IPMNs. The analysis of circulating cell-free DNA (cfDNA) isolated from blood samples was able to distinguish IPMN patients from controls. In addition, driver mutations including h as SCN . This suh as SCN .In further efforts to limit unnecessary resections, advanced diagnostics via EUS procedures such as EUS-nCLE, NGS of cyst fluid, TTNB, and contrast enhanced harmonic endoscopic ultrasound (CH-EUS) were utilized. EUS-nCLE utilizes a laser scanning unit to also visualize the intracystic epithelium further and, in the case of IPMNs, reveal characteristic papillary projections. In a prospective study, EUS-nCLE was able to distinguish mucinous cyst vs. non-mucinous cyst with greater accuracy than measuring carcinoembryonic antigen (CEA) levels and cytology analysis . Using cIPMNs are often identified incidentally on imaging especially with advancing age. Accurate diagnosis and risk-stratification is critical to intervene prior to onset of invasive carcinoma and also to avoid unwarranted surgery. There is an ever increasing need to accurately grade the dysplasia and avoid surgical overtreatment of IPMNs; currently, nearly 50% of IPMNs resected have only low-grade dysplasia . RoutineKRAS and GNAS, play an important role in mediating IPMN progression to PDAC. In addition to activating various signaling pathways that promote cell growth and survival, KRAS and GNAS mutation also results in downstream metabolic effects including lipid metabolism and glucose metabolism. Changes in the metabolic needs and altered pathways are both necessary for cancerous growth and may be measurable along the way to malignancy in the case of IPMN. Metabolic changes resulting in lipidomic pathway enhancement, in particular, show the promise for both a serum and cyst fluid biomarker. Not only may the altered metabolism be a key player in the progression of malignancy and perhaps allow for risk stratification of patients via utilization of metabolites as biomarkers, cross feeding and cross talk between cancerous cells and noncancerous cells likely lead to activation of PSC and eventual differentiation into CAF. These are critical for the desmoplasia, inflammation, and immune modulation and evasion that PDAC displays. Alterations within the microenvironment of IPMNs leading to increased inflammation and immune modulation also may allow for measurable differences in cell populations and inflammatory signals. Those reviewed had varying utility alone and may have increased utility if used in conjunction with other risk stratification tools outlined in the international consensus guidelines. Changes in the immune population are becoming better understood and offer a place of possible intervention to restore or keep the immune surveillance of the patient active, resulting in inability of PDAC to thrive. Continued characterization of precursor cystic lesions and the mechanisms underlying progression to PDAC may help identify new biomarkers which along with high-risk imaging features may more accurately guide IPMN management and possibly mitigate the need for unnecessary surgical intervention.As discussed in this review, the molecular and metabolic profiles driving IPMN tumorigenesis provided insight into potential biomarkers as well as novel therapeutic strategies. Molecular analysis of cystic fluid and tissue identified high risk mutations and novel drivers of IPMN tumorigenesis. Genomic alterations, in particular