Tumor-derived exosomes play a multifaceted role in preparing the pre-metastatic niche, promoting cancer dissemination, and regulating cancer cell dormancy. A brief review of three types of cells implicated in metastasis and an overview of other types of extracellular vesicles related to metastasis are described. A central focus of this review is on how exosomes influence cancer progression throughout metastatic disease. Exosomes are crucial mediators of intercellular communication by transferring their cargo to recipient cells, modulating their behavior, and promoting tumor pro-gression. First, their functional role in cancer cell dissemination in the peripheral blood by facilitating the establishment of a pro-angiogenic and pro-inflammatory niche is described during organotro-pism and in lymphatic-mediated metastasis. Second, tumor-derived exosomes can transfer molecular signals that induce cell cycle arrest, dormancy, and survival pathways in disseminated cells, promoting a dormant state are reviewed. Third, several studies highlight exosome involvement in maintaining cellular dormancy in the bone marrow endosteum. Finally, the clinical implications of exosomes as biomarkers or diagnostic tools for cancer progression are also outlined. Understanding the complex interplay between tumor-derived exosomes and the pre-metastatic niche is crucial for developing novel therapeutic strategies to target metastasis and prevent cancer recurrence. To that end, several examples of how exosomes or other nanocarriers are used as a drug delivery system to inhibit cancer metastasis are discussed. Strategies are discussed to alter exosome cargo content for better loading capacity or direct cell targeting by integrins. Further, pre-clinical models or Phase I clinical trials implementing exosomes or other nanocarriers to attack metastatic cancer cells are highlighted. In the endosome compartment, exosome synthesis occurs when multivesicular bodies mature into intraluminal vesicles A. FusingKLF2 and KLF4 [By secreting exosomes into the circulation, tumor cells can communicate with noncancerous cells at distant sites in preparation for tumor dissemination in an autocrine-, paracrine-, or endocrine-like manner . In the and KLF4 . Anotherand KLF4 . Tumor-derived exosomes are a type of extracellular vesicle distinguished from apoptotic bodies, microvesicles, and oncosomes by their size, morphology, and protein markers ,22,23,24ARF6 regulates the sorting and shedding of microvesicles from tumor cells at specific regions of the plasma membrane. Microvesicles are directly transferred to the plasma membrane of the recipient cell, altering their function to promote cell growth [Furthermore, microvesicles have been isolated from the peripheral blood of cancer patients, suggesting that they can promote long-distance communication to influence metastatic spread or aid in preparing the recruitment of the pre-metastatic niche ,28. Accol growth . In contl growth . Numeroul growth . Large oncosomes (LO) are another type of extracellular vesicle worthy of attention for their involvement in tumor progression. They are larger (1–10 μm) compared to microvesicles or exosomes, are secreted by tumor cells, and transport proteins from the plasma membrane to recipient cells  Figure C. As a rOncosomes are secreted in large amounts by tumor cells, and the amount seems to correlate with aggressive tumors. Di Vizio et al. demonstrated that oncosomes are secreted in large amounts upon the silencing of a protein, Diaphanous-related formin-3 (DIAPH3), which is involved in cell motility . DependiALIX, and TSG101 are commonly shared proteins among TD-EVs, requiring additional markers to stratify the unique features associated with the different TD-EVs. An ideal approach would be quantifying the protein markers enriched in one type of TD-EV over another and the tumor markers associated with specific vesicles. Mincaicchi et al. studied used enrichment strategies in proteomics to isolate three different TD-EVs and compared the protein expressions among them in search of distinct proteins solely expressed in LOs , a tumor-suppressor gene [PTEN loss activated the PI3K signaling pathway, upregulating aerobic glycolysis over oxidative phosphorylation, creating an anabolic, pro-proliferative state characteristic of Warburg tumors. It remains unclear how astrocytes are initially reprogrammed to secrete these miR19a-containing exosomes by disseminated breast cancer cells or exosomes. Nonetheless, these two studies highlight the metabolic changes within the brain premetastatic niche, promoting Warburg tumor metabolism and facilitating breast cancer metastasis, suggesting that they may be particularly susceptible to Warburg-based therapeutic strategies such as:GLUT1, HKII, LDHA, and PKM2).Targeting glycolytic enzymes preferentially elevated in cancer cells , which leads to the recruitment of myeloid-derived suppressor cells and immunosuppressive macrophages, promoting an immunosuppressive, pre-metastatic niche that promoted 4T1 lung colonization. Specifically, miR-200b-3p was identified as the exosome cargo driving CCL2 expression through PTEN inhibition. In these studies, the recruitment of immunosuppressive cells by breast cancer exosomes was suggested as an alternative method of driving lung metastasis .Cells that migrate from the primary tumor to metastatic sites have received attention, because they promote distant metastases, are used as prognostic markers, and are chemoresistant. Perhaps migratory cells should be considered a part of the tumor’s secretome, since they can efficiently communicate with the circulatory system and tumor microenvironment. Three subtypes of migratory cells are involved in fostering metastasis and relapse and are briefly described below. (A) Cancer stem cells (CSCs) have been isolated from the peripheral blood of cancer patients and are involved in promoting metastases, chemoresistance, and cellular dormancy ,55. FurtThe lymphatic system plays a critical role in immune cell tolerance. Given that secreted factors drain into the lymph before dilution into the blood, lymph fluid is thought to be enriched in cancer biomarkers. It is also postulated that cancer-derived exosomes can promote immune cell tolerance by reprogramming T cells in the lymph fluid . Several groups, including Broggi et al., identified and characterized exosomes in the lymphatic system of melanoma patients. They demonstrated that melanoma cells could reprogram resident immune cells in the lymph to protect against degradation or an immune response. Lymph collected from melanoma patients undergoing lymph node dissection was enriched in exosomes containing melanoma proteins and miRNA compared to plasma. Distinct proteomic signatures were identified in patients with extra-nodal spread compared to patients with sentinel lymph node proteome. Notably, the exosomes from the extra-nodal spread were enriched with S100 proteins, a well-characterized melanoma antigen previously shown to promote pre-metastatic niche formation . A study by Ekstrom et al. isolated exosomes from the lymphatic drainage of breast cancer patients during axillary lymph node dissection and identified a subset of markers that contained CSC markers and markers associated with platelets . OverallSome challenges associated with diagnosing and treating metastatic disease are that it can occur before a diagnosis and undergo cellular dormancy before the primary tumor is detected, as well as the difficulty treating dormant cells . SkeletaMetastatic-promoting traits are obtained at the invasive front of the primary tumor and appear to be selective for what is most advantageous for tumor progression at both local and distant sites . It was Subsequent studies have also supported this phenomenon of MSC priming by using metastatic human breast cell lines that secrete exosomes containing miR-23b to induce cellular dormancy chemoresistance by the downregulation of MARCKS, a driver of cell proliferation and motility . Both stBreast cancer dormancy interactions between disseminated metastatic cells and the resident stroma have also been observed in liver metastasis. In a 2D transwell assay, hepatocyte preincubation with MDA-MB-231 primary tumor exosomes increased cancer cell migration and survival. However, in a subsequent 3D human liver micro-physiological system, hepatic milieu preincubation with tumor exosomes increased cancer cell seeding, and hepatic cell proliferation was inhibited. Exosomal miRNA and protein analysis revealed that tumor exosome incubation altered the hepatic niche’s exosomal profile. In addition, the isolation of hepatic niche exosomes and subsequent incubation with aggressive metastatic lines led to the increased expression of E-cadherin, an indicator of a mesenchymal-to-epithelial transition in these cells . This alFor determining whether tumors are present, noninvasive sampling methods such as liquid biopsies are used to isolate tumor-derived exosomes from bodily fluids such as blood, lymphatics, and urine. Circulating exosomes may detect the regression, progression, and recurrence of disease processes. For instance, in bladder cancer, exosomes isolated from urine sub as a liquid easily accessible and consistent with the clinical manifestation of this tumor. Carbonic anhydrase (CA-9) is overexpressed in bladder cancer and is considered a molecular biomarker of this disease. Wen et al. detected CA-9 mRNA in exosomes from 168 bladder cancer patients compared to 90 control patients, with a sensitivity of 85% and specificity of 83% , therebyThe optimal biomarkers have high specificity for disease and allow for early detection to promote prompt intervention. However, biomarker development is limited by the dichotomy that, while protein-rich bodily fluids may contain disease-specific markers, they are minimal and difficult to detect. In contrast, biomarkers found in more advanced diseases are abundant but are no longer necessary for early-stage detection and interventions. Exosomes offer a more organized and tissue-specific approach to biomarker development based on the intricate packaging and secretion process .Multiple studies have shown the value of exosomes in monitoring resistance to therapy. The mechanisms by which this occurs may vary. Previous works from Corcoran and others provide evidence that docetaxel resistance is directly transferable by exosomes using the multidrug resistance-1 protein, known to efflux taxanes out of the cell ,77. ConvPD-L1-derived exosomes [EGFRvIII may be “shared” among glioblastoma cells through exosomes. In this context, Skog et al. confirmed that exosomes might allow for the secretion of pathogenic receptor EGFRvIII and are readily detected in the serum of patients with glioblastoma [PD-L1 and EGFRvIII may serve as plasma markers for cancer prognosis. In addition to serving as direct biomarkers of diseases, it is now evident that exosomes isolated from body fluids can be analyzed for their donor and recipient cell types based on their cargos and surface markers   .In addition to delivering antisense oligonucleotides, exosomes can be loaded with small molecule chemotherapeutics. For example, macrophage-derived exosomes loaded with paclitaxel through sonication were incubated with a malignant canine kidney cell line expressing P-glycoprotein. The loaded exosomes displayed enhanced cytotoxicity compared to free paclitaxel in both drug resistance and sensitivity . FurtherCancer vaccination strategies utilizing exosomes loaded with antigenic peptides have been evaluated in animal and clinical trials . DendritIdentifying the genetic material and its use in promoting cellular reprogramming provides potential therapeutic strategies to reduce metastasis ,91. To aGreat strides have been made to overcome some of the challenges associated with immune cell activation, including engineering exosomes with immune-suppressing agents such as “self” antigens or coating them with molecules that prevent immunogenicity to increase their delivery to recipient cells ,93. AddiTargeting glioblastoma has been challenging due to the blood–brain barrier. Munoz et al. used MSC-mediated delivery to inhibit TMZ resistance , demonstNanocarriers are a type of nanotechnology that is used to deliver drugs or therapeutic agents in a targeted manner and can be engineered to have specific properties, such as size, shape, surface charge, and functional groups, that can enhance their stability, solubility, and targeting ability. Nanocarriers are typically engineered to have specific properties that allow them to encapsulate or attach therapeutic agents and transport them to the desired site in the body. Furthermore, nanocarriers may provide solutions to rectify off-target effects and overcome immune system and blood–brain barriers that thwart clinical exosome applications. For example, core–shell nanocarriers containing miRNA coupled with docetaxel were used as codelivery systems in treating metastatic breast cancer, and miR34a encapsulated in the core of the nanocarrier was shielded from RNase degradation, while the shell interacted with the caveolae-mediated pathway to prevent lysosome degradation . MRX34 is a liposome-encapsulated miRNA that targets tumor suppressors miRNA, miR21, and miR-21 and is overexpressed in many types of cancer, and it plays a role in promoting tumor growth and metastasis. MRX34 works by downregulating miR-21 expression, thereby inhibiting tumor growth and metastasis. MRX34 is relatively safe and is well tolerated in patients. There was a phase I/II trial on pancreatic cancer where MRX34 was shown to reduce tumor sizes in some patients [MRX34 coupled with dexamethasone pretreatment reduced tumor sizes and improved cancer patient outcomes in seven cancer types, including solid tumors and hematology malignancy [Types of nanocarriers include liposomes, polymeric nanoparticles, dendrimers, and micelles . Strategpatients . Furtherlignancy . Desantis et al. specifically provided an overview of three different miR-based nanocarriers, liposomes, polymers, and exosomes, and highlighted their potential as codelivery molecules that were used to increase stability and decrease degradation. Further, they described various nanoparticle systems that incorporated fungoides, non-living bacteria, or locked nucleic acid oligonucleotides complexes with anti-miR or mimic miR responses that have been implemented to treat various types of cancer, including multiple myeloma . AlthougExosomes have been modified and engineered in several ways to deliver targeted drugs, including altering exosome surfaces with specific ligands, vaccines, or antibodies to enhance tumor cell targeting ,107. AddPD-L1 cargo to cells with greater efficacy than dendrimers alone, which seemed to be exosome-driven, thereby evading the concerns associated with exosome transport or premature degradation before reaching its target [Engineered exosomes coupled to liposomes, PEGs, or other molecules have also been reported to increase exosome drug delivery in a controllable way and could circumvent pharmacokinetic drawbacks . Poly(ams target . Nanocarriers can address some challenges associated with exosome therapeutic potential. For example, encapsulating exosomes in nanocarriers would provide a universal size distribution, and their cargo composition would also be uniform. Additionally, adding surface modifications to exosome-loaded nanocarriers could increase the exosome circulation time and biodistribution. Finally, given that nanocarriers can be synthesized and manufactured in large batches, identifying exosome cargo and loading them into nanocarriers could address the concerns regarding the variations in the isolation methods or exosome heterogeneity.Exosome heterogeneity is thought to be a key factor in determining their function and effectiveness in intercellular communication. By displaying different properties and compositions, exosomes can interact with different target cells and activate different signaling pathways . MoreoveA consensus is needed for acceptable purification standards that are well tolerated with a maximum payload. Comparisons of various isolation steps across different cell lines or ex vivo samples such as urine and blood are currently underway ,114,115;Exosomes have limited cargo capacity due to their size, which affects how much and what type of therapeutic agents can be loaded into them, as well as their delivery speed and clearance rate . FurtherTargeting exosomes at breast cancer cells specifically can be challenging without proper selective markers, since exosomes are distributed throughout the body and potentially interact with healthy tissues, leading to off-target effects and reduced therapeutic efficiency. Additionally, exosome instability can also be problematic for cancer treatment, as their components can undergo rapid changes when exposed to different environmental conditions. Exosomes can degrade quickly, making them difficult to transport and store for long periods of time. Perhaps synthesizing exosomes from the same cell type will have the same surface proteins that are recognized and engulfed by the recipient cell. Additionally, using nanocarrier systems will protect exosomes from degradation and enhance their delivery to specific target cells. The large-scale production of exosomes for clinical use can be technically challenging and costly. Standardized manufacturing processes need to be established to ensure the consistent quality, purity, and potency of exosome-based therapeutics. Scaling up production while maintaining batch-to-batch consistency remains a significant hurdle. Moreover, there is a need for standardized methods for the isolation, characterization, and quantification of exosomes to ensure consistency and reproducibility in their use as therapeutic agents.As with any novel therapeutic approach, exosome-based treatments must undergo rigorous testing and regulatory approval processes. Regulatory challenges associated with exosome clinical implementation that include characterization, standardization, and administration are currently under review . EnsurinWhile exosomes hold promise for various therapeutic applications, they also present several disadvantages when treating cancer patients. Here are some of the key drawbacks:Three types of tumor-derived extracellular vesicles are reported to promote cancer metastasis and were discussed in our review, with exosomes as the primary focus. Several proteins overlap between the TD-Evs, regardless of how they are synthesized. Yet, the degree to which these proteins are expressed varies and is regulated by the donor cell. Interestingly, exosomes mainly contain RNA-processing biomolecules, while the other two vesicles contain antigens or plasma proteins that drive rapid responses in the recipient cells by transferring membrane proteins ,31. DespSeveral clinical trials are currently underway to test the safety and efficacy of miRNAs in treating breast cancer. Some of these trials are evaluating the use of miRNAs alone, while others are evaluating the use of miRNAs in combination with other cancer therapies, ultimately choosing which miR nanocarriers will need to consider the microenvironment and bioavailability of the particle to ensure that the miR payload is delivered to the intended cell or tissue. The complexity of tumor progression demands a multi-level therapeutic strategy to inhibit metastasis, which has ushered in a new wave of cancer therapies and diagnostic tools for cancer progression, including exosomes as drug delivery systems. The synergistic effects of combining exosome therapy with other treatment modalities, such as chemotherapy, radiation therapy, or immunotherapy using nanocarriers as delivery vehicles, has proven to be effective in preclinical models, while tumor and interpatient heterogeneity pose challenges to implementing nanomedicines in patients ,99,100. Some approaches include loading exosomes with therapeutic molecules by incubating them with the desired cargo via chemical manipulation, such as diffusion, electrophoresis, or sonication, and then delivering drugs to cancer cells ,121. OthSeveral studies have investigated exosomes’ ability to inhibit cancer metastases; only a small subset of delivery systems has been tested in clinical trials, and none have received FDA approval ,121,124.Given our current understanding of the role of exosome integrins in driving tumor organotropism, it may be fruitful to explore hijacking this process as a therapeutic strategy. As mentioned earlier, integrins A6β4 and αvβ5 were identified in exosomes and established as necessary for lung and liver tropism through shRNA knockdown and antibody neutralization studies. Targeting these integrins may serve to prevent metastasis in high-risk patients. Additionally, designing synthetic exosomes embedded with these integrins may be a strategy for delivering drug cargos to metastatic sites.Furthermore, integrins in exosomes can also be predictors of the metastatic propensity and future sites of metastasis across tumor types. This may have significant clinical benefits in stratifying cancer surveillance, leading to earlier screening during remission and the early initiation of relapse chemotherapy, as well as more accurate prognostics for care decision-making goals. However, future works are needed to help develop and standardize integrins as a cancer biomarker.Exosomes have tremendous potential in cancer drug delivery due to their low immunogenicity, low cellular toxicity, and preferential accumulation in tumor tissues over normal tissues . HoweverAdditionally, exosomes have poor cargo loading and size standardization, leading to a potentially unpredictable biodistribution; a technique currently being investigated to standardize the size involves using semi-continuous size exclusion chromatography . The pliancy of exosomes makes them a promising target for therapeutic intervention. Exosome sizes allow them to easily travel through the bloodstream or enter cells via gap junctions. Their lipid bilayer is also pliable and can be modified to deliver cargos that include crossing the blood–brain barrier. Finally, exosome cargos alter cell functions by regulating gene expression, protein synthesis, and apoptosis; therefore making them an optimal drug delivery system or optimal for developing strategies that target cancer metastasis and chemoresistance. As the field optimizes scalability and administration, while addressing safety and toxicity, nanocarriers will become a game changer for how exosome-based therapies are delivered to cancer patients.


Gait deficits are found in various degenerative central nervous system conditions, and are particularly a hallmark of Parkinson’s disease (PD). While there is no cure for such neurodegenerative disorders, Levodopa is considered as the standard medication in PD patients. Often times, the therapy of severe PD consists of deep brain stimulation (DBS) of the subthalamic nucleus. Earlier research exploring the effect of gait have reported contradictory results or insufficient efficacy. A change in gait includes various parameters, such as step length, cadence, Double-stance phase duration which may be positively affected by DBS. DBS could also be effective in correcting the levodopa-induced postural sway abnormalities. Moreover, during normal walking, interaction among the subthalamic nucleus and cortex —essential regions which exert a role in locomotion— are coupled. However, during the freezing of gait, the activity is desynchronized. The mechanisms underlying DBS-induced neurobehavioral improvements in such scenarios requires further study. The present review discusses DBS in the context of gait, the benefits associated with DBS compared to standard pharmacotherapy options, and provides insights into future research. •Deep brain stimulation (DBS) has been established as an efficacious therapy for Parkinson's disease (PD).•Gait disturbance is implicated in many nervous system disorders.•DBS can enhance the results obtained via standard therapeutic regimen.•The efficacy of DBS should be evaluated, as progression of neurodegeneration limits DBS benefits. Gait needs the integration of locomotion mechanisms with those of balance, motor control, cognition, and musculoskeletal function, even though it can be done automatically and without conscious effort . Gait ab22.1The insertion of electrodes into deep brain areas to manipulate neural function in order to treat neurological disorders is referred to as DBS. These electrodes are electrically connected to an implanted pulse generator (IPG), normally hidden beneath the clavicle. An IPG has a battery and electronic components that produce electrical stimulation and can be adjusted by patients or clinicians . An MRI The origins of DBS can be traced back to as early as 1900 s, when breakthroughs in animal cerebral cortex stimulation set the groundwork for cortical functional localization as we know it today. At that time, the first stereotactic case was established, allowing researchers to experiment with stimulation of deeper brain regions . The firDifferent mechanisms for DBS have been proposed in our review of literature. Neural inhibitory response is one of the mechanisms of effect in DBS that several reports have demonstrated a reduction in neuronal activity nearby the DBS site . HoweverDBS has significant advantages over other neuromodulation surgical techniques as a therapeutic tool. The non-lesional character of DBS, the ability to adjust stimulation parameters to maximize benefit while minimizing detrimental effects, and the ability to directly engage with the circuit pathophysiology that produces the symptoms are just a few of the benefits of DBS. Despite its benefits, DBS is still an invasive surgical procedure with minimal but potentially substantial complications, like cerebral bleeding and infection . DBS is Depending on the condition that we are tackling, different brain regions are targeted during DBS . Some of3Walking is a multidimensional activity that is directed through both voluntary and automatic mechanisms that are influenced by emotions. Acute development of a gait disturbance can imply a cerebrovascular or other acute nervous system impairment, as well as systemic disorders or pharmaceutical side effects . The mosThe mesopontine tegmentum (MPT) is a cellular region located at the intersection of the mesencephalon and the pons. The pedunculopontine tegmental nucleus (PPN) and the laterodorsal tegmental nucleus (LTN) are two cholinergic nuclei in the mesopontine tegmentum . PhysiolIn basal ganglia dysfunction such as Parkinson’s disease, gait deficiency is defined by latency in gait commencement, narrow steps, propulsions, and poor balance when walking . Gait anLatest evidence on the cerebellum's function in PD and its direct disynaptic connections to the basal ganglia attracted attentions to the VIM as a significant cerebellar information relay . VIM stiPrevious systematic reviews and meta-analyses evaluating the eﬀectiveness of GPi-DBS and STN-DBS on PD patients have demonstrated that no significant differences in therapeutic performance on PD motor symptoms between the GPi-DBS and the STN-DBS have been found . MeanwhiWith growing understanding that it may be implicated in the development of several motor diseases, the PPN has sparked a lot of study in the recent decade . PPN-DBS4L-dopa is known as the gold standard therapy for PD from the late 1960’s when Cotzias et al. described L-dopa ’s efficiency for symptomatic management of PD. From then, L-dopa treatment has improved both the life expectancy and quality of life of PD patients. L-dopa could pass the Blood-Brain-Barrier (BBB) and is transformed to DA in the Central Nervous System (CNS) in Dopa Decarboxylase (DDC) expressing neurons. In spites of the fact that multiple DA substitution treatments are now accessible, L-dopa is considered the most efficient medicine for controlling motor signs in PD. Yet, L-dopa treatment has some caveats. As the disease develops long-term therapy with L-dopa is related to motor difficulties, i.e., motor fluctuation (the therapeutic effect duration once each dose diminishes) and dyskinesia (involuntary movements). These motor difficulties are observed in most of PD patients, who are being treated with L-dopa for longer than five years. Furthermore, probable neuroprotective versus neurotoxic impacts of L-dopa are being debated for years (The dopamine (DA) precursor molecule or years .L-dopa and that decrement of drugs ameliorates postoperative dyskinesia. By contrast, drug dose reduction could bring about other difficulties, such as apathy and depression, which induces doubt about forceful reduction of dopaminergic treatments in patients treated with STN-DBS. Taken together, there is a challenging debate regarding STN-DBS in PD  and other dopaminergic drugs is observed profoundly after STN-DBS and is now considered an “anticipated benefit” of such surgical modality. This theory is based on the logic that STN-DBS could decrease PD principal signs to a comparable amount than BS in PD .., appendicular akinesia, tremor, and rigidity is well described, its impact on axial disability is still debated. Some authors demonstrated an enhancement of gait, posture, and balance control subsequent to STN-DBS, or GPi (with a bolder enhancement with STN-DBS). While these signs were sensitive to L-dopa therapy prior to surgery  by which, based on the electrode position, some regions within the STN receive differing stimulus. Through experimentation, researchers observed in a specific set of patients that using stimulation along with L-dopa resulted in dyskinesia in the lower extremities. The symptoms of dyskinesia manifested as walking-evoked hyperkinetic lower extremity movement , walking-induced one-sided foot eversion, along with “ON-freezing” of gait. This observation is backed by several patients whose freezing of gait vanished due to complete discontinuation of L-dopa therapy and stayed treated exclusively with stimulation. Overall, the effect of STN-DBS versus L-dopa shows a paradoxical trend that relies on many factors , as well as developing guidelines and preoperative evaluations to determine the most suitable PD patients for the various surgical procedures.Aside from STN and GPi there are other brain regions that are targeted in DBS surgery for gait problems, including PPN, centro-median thalamic nucleus, and the zona incerta . There aA multifaceted targeting of gait in PD or other important conditions could provide optimal results, it may be beneficial to utilize inflammation modulating pharmaceutical and natural therapies, targeting inflammasomes, toll-like receptors (TLRs) and adaptive immunity, and even opioid brain receptors . Reducti6Gait disturbance is implicated in many nervous system disorders. DBS can enhance the results obtained via standard therapeutic regimen. Also, the efficacy of DBS should be evaluated, considering that as a neurodegenerative condition progresses the nerve cells may be lost, limiting the benefits associated with DBS. The neurodegenerative processes are multifaceted. For instance, even one complication such as gait disturbance results from damage to many brain regions. Ultimately, the clues provided by the rapidly increasing evidence warrants future research utilizing DBS in conjunction with standard treatments that may be symptom relievers or neurodegeneration-slowing for optimal results.Not applicable.Ramtin Pourahmad, Kiarash Saleki, Mohammadreza Esmaili, Arian Abdollahi, Mehrad Zare Gholinejad, and Mohammad Banazadeh drafted the manuscript. Kiarash Saleki and Parsa Alijanizadeh made the figure. Kiarash Saleki prepared the final draft and critically appraised the manuscript. Mona Ahmadi supervised the project, drafted the manuscript, and critically appraised the manuscript. Figure created with BioRender.com.Not applicable.None.The authors report there are no competing interests to declare.


Comparative economic assessments of renal replacement therapies (RRT) are common and often used to inform national policy in the management of end-stage renal disease (ESRD). This study aimed to assess existing cost-effectiveness analyses of dialysis modalities and consider whether the methods applied and results obtained reflect the complexities of the real-world treatment pathway experienced by ESRD patients.A systematic literature review (SLR) was conducted to identify cost-effectiveness studies of dialysis modalities from 2005 onward by searching Embase, MEDLINE, EBM reviews, and EconLit. Economic evaluations were included if they compared distinct dialysis modalities .In total, 19 cost-effectiveness studies were identified. There was considerable heterogeneity in perspectives, time horizon, discounting, utility values, sources of clinical and economic data, and extent of clinical and economic elements included. The vast majority of studies included an incident dialysis patient population. All studies concluded that home dialysis treatment options were cost-effective interventions.Despite similar findings across studies, there are a number of uncertainties about which dialysis modalities represent the most cost-effective options for patients at different points in the care pathway. Most studies included an incident patient cohort; however, in clinical practice, patients may switch between different treatment modalities over time according to their clinical need and personal circumstances.Promoting health policies through financial incentives in renal care should reflect the cost-effectiveness of a comprehensive approach that considers different RRTs along the patient pathway; however, no such evidence is currently available.The online version contains supplementary material available at 10.1007/s10198-022-01478-2. Chronic kidney disease affects up to 16% of the adult population globally, and is associated with poor outcomes upon progression to end-stage renal disease (ESRD) ), have sAppropriate decision-making is fundamental in renal care, for which effective implementation and continuation of care is crucial to prolonging survival and improving a patient’s quality of life. Furthermore, RRT is a significant burden on finite healthcare resources; across Europe RRT accounts for 2% of healthcare expenditure for 0.1% of the population, with an estimated total cost of €15 billion per year . In geneNational guidance and public health policies have emerged that recommend or incentivise specific dialysis modalities based upon conclusions of cost-effectiveness –25. The A systematic literature review (SLR) was conducted to identify published cost-effectiveness studies comparing two or more distinct dialysis techniques in the management of ESRD. Since renal transplant is accepted to be the superior mode of RRT for clinically suitable patients , studiesAbstracts and full texts were screened by two reviewers based on the criteria described in Table The initial search identified 2189 records and the update identified 189 records. In total, 19 publications comparing distinct modalities were eligible for inclusion  revealed that in general, the studies had well defined objectives, study design, and data collection methods. However, key modelling decisions  were not consistently justified. Further, while results were generally clearly reported and included incremental analyses, there was variability in the extent to which individual caveats were discussed and issues relating to the generalisability of results were not often addressed.Whilst in clinical practice, patients may switch between different treatment modalities over time according to their clinical need and personal circumstances –16, noneFew studies noted the applicability of their results to the individual as a limitation; however, Treharne et al. (2014) highlighted that their findings concerning the cost-effectiveness of PD relative to ICHD would only be applicable to those patients who were willing and able to perform PD . The samPrevious reviews of dialysis have highlighted that there is no best dialysis modality for a patient, but rather a combination of different modalities applied at the right time for the right patient, to create an optimal treatment pathway , 16. TheNational guidance and public health policies have emerged that recommend or incentivise specific dialysis modalities based upon conclusions of cost-effectiveness –25. A laDecision-making within renal care should be holistic and comprehensive so that health outcomes are optimised for each patient and resources are allocated appropriately. Future work in this area should consider a pathway-based cost study, mapping costs to data from large care networks to more accurately reflect resource use associated with renal care.Dialysis is a life-saving intervention, but a patient’s care pathway is likely to evolve over time due to a changing lifestyle, increasing age and declining health. Switching between dialysis modalities is often essential. The cost-effectiveness of any intervention is reliant on its effectiveness, which, in the case of dialysis, is inherently linked with patient acceptability of and suitability for a particular modality. Estimates of cost-effectiveness for a particular dialysis modality at a specific point in time should be considered within the context of the holistic ESRD pathway. Each dialysis method is distinct and may be applicable to different points in care; therefore, modalities should be considered complementary and not competitively. Personalised care, including offering the right modality to the right patient at the right time, will maximise patient outcomes and minimise expenditure.Supplementary file1 (DOCX 92 KB)Supplementary file2 (XLSX 43 KB)Below is the link to the electronic supplementary material.


Mobility limitation is common among older populations and is a major burden to public health. While lower extremity dysfunction is a known contributor, the influence of shoulder dysfunction on mobility is less well understood. Shoulder pain and rotator cuff tear are common causes of shoulder dysfunction, and both ailments are highly prevalent in older adults. This article discusses shoulder pain and rotator cuff tear as contributors to shoulder dysfunction and describes the association of shoulder dysfunction with mobility limitation in older adults. Mobility limitation is a major burden on public health, affecting more than 1 in 3 older adults in the United States -8. The aInvestigators have called for development of more holistic research strategies to provide greater scientific understanding of reduced mobility in older populations . For exaThe potential association of shoulder dysfunction with mobility limitation has been mostly overlooked and remains not well understood. Conceptually, the shoulder is the mobile link between the upper limb and trunk, facilitating arm swing during ambulation. Swinging of the arms during ambulation provides dynamic stability via coupled rhythmic interlimb coordination among the upper and lower extremities -16. The Shoulder dysfunction is common among older adults and may accelerate functional decline ,18. PopuShoulder pain is highly prevalent in older populations. The 2011 National Health and Aging Study estimated a nearly 20% prevalence of pain at the shoulder among adults aged 65 years and older in the United States, only trailing the back (30%) and knee 25%) as the most common source of musculoskeletal pain . Shoulde% as the The burden of shoulder dysfunction among older populations on public health is likely under-estimated. Nearly one-half of older clinical patients with chronic bouts of shoulder pain do not report their symptoms to their primary care providers ,25. EvenHowever, pain is not required to harbor a functional deficit. Populations of older adults with asymptomatic RC tears display inferior ROM at the shoulder on physical examination compared to peers who lack RC tear ,31.The rotator cuff is a myotendinous structure that provides dynamic stability at the shoulder. Working in synchronized concert with static stabilizers—the glenoid labrum, bone morphology, glenohumeral capsule-ligamentous complex, and negative intra-articular pressure, the rotator cuff facilitates stability of the glenohumeral joint through all phases of motion -35.RC tear is the physical manifestation of an acquired anatomic defect in the tendon of the myotendinous unit which potentially compromises dynamic stability of the glenohumeral joint. RC tear is primarily a disease of aging ,37. SomePain, limited ROM and weakness at the shoulder are common symptoms of RC tear, although not all individuals with RC experience symptoms . SymptomImaging is central for establishing the clinical diagnosis and prognosis for patients presenting with either traumatic acute-onset shoulder dysfunction or non-traumatic shoulder disorders which are not self-limited ,44,45. MThe prevalence of shoulder dysfunction among older adults in the general population is likely under-estimated, as the number of older adults with symptoms of shoulder dysfunction who do not seek evaluation from healthcare providers is unknown. Given that nearly-one half of the population of older adults with non-acute shoulder dysfunction do not report shoulder complaints to their primary care provider ,25, a reShoulder dysfunction’s effect on functional decline may be under-recognized by current screening paradigms for disability in older populations. Traditional self-reported screening tools used to screen for level of disability in older populations, such as the Katz ADLs and Lawton-Brody instrumental ADLs surveys, may exhibit ceiling effect and be insensitive to detect shoulder-specific disability in the population of community-dwelling older adults at large . In contPractice standards vary among healthcare providers for diagnosis and treatment of older adults who present as clinical patients with chief complaint of shoulder symptoms. Older adults may initially seek care from a variety of healthcare professionals, including physical therapists, primary care providers, emergency medicine physicians, orthopaedic surgeons, sports medicine physician specialists, rheumatologists, and chiropractors. Physical therapists, for example, are often the first to encounter older adults with shoulder complaints through direct access, also known as patient self-referral without prior evaluation by another healthcare provider. Physical therapists most often establish a clinical diagnosis through history and physical examination alone -57. GiveTreatment of shoulder dysfunction in clinical patients is dependent on presenting symptoms, which commonly include pain, weakness and decreased ROM ,42,58,59Best treatment practices for RC tear among older persons is controversial, and non-operative management with physical therapy remains in a state of equipoise with RCR surgery ,60-62. TThe annual cost of RCR surgery has been estimated to be as high as $12 billion dollars for the nearly 300,000 performed each year in the Unites States . The burEarly detection of mobility limitation is an important factor to enable prevention or mitigation of subsequent mobility-related disability among community-dwelling older adults. Valid and reliable screening methods toward this goal improve healthcare providers’ ability to stratify this population by mobility performance. The Short Physical Performance Battery (SPPB), for example, is a well-known tool used in research and clinical practice to quantify lower extremity performance. The SPPB is a feasible performance-based categorical screening tool to quantify lower extremity function, on a scale from 0 (worst performance) to 12 (best performance). The SPPB score is the sum of 3 components, each scored on a scale of 0 (worst performance) to 4 (best performance) which rate static balance, chair rise, and gait speed performance, respectively . A scorePerformance-based measures, such as the expanded Short Physical Performance Battery (eSPPB), were developed to raise the measurement ceiling of SPPB to evaluate a broader range of lower extremity performance on a continuous scale . ResearcThe United States Center for Disease Control and Prevention promotes additional common feasible mobility performance screening instruments for older populations as part of its Stopping Elderly Accidents, Deaths & Injuries program. Examples include the 30-second chair stand test , a test Quantifying the contribution of shoulder dysfunction towards development of mobility limitation in community-dwelling older populations is a relatively novel concept, in line with the need to develop newer innovative, holistic strategies to prevent or to mitigate mobility limitation . Investip = 0.001) to manifest a SPPB score <10, relative to participants in the best quartile of shoulder coordination [In a cross-sectional study of 130 community-dwelling older adults, James et al. assessed the association of shoulder coordination with SPPB score by testing rhythmic interlimb coordination between shoulders using non-ambulatory function testing via auditory metronome tones in a supine position via three-dimensional motion capture kinematics. These investigators reported that study participants in the poorest quartile of shoulder coordination had a 6.7 times adjusted odds  also may abnormally influence arm swing and coordination of the extremities during ambulation, although there is a current knowledge gap in this area. Dysfunction local to the shoulder secondary to pain or structural abnormality, such as RC tear, has a known consequence of limited ROM or loss of strength ,27,41,42p = 0.020) to perform poorly on the fast-paced 400-meter walk test and also as high as a 3.2 times adjusted odds (p = 0.004) to perform poorly on the eSPPB, relative to participants with full ROM at both shoulders [The link between shoulder ROM and mobility limitation in older populations is nascent in description. In a cross-sectional analysis of 613 participants 60 years or older in the Baltimore Longitudinal Study of Aging, Davis et al. examined the association of restricted shoulder elevation and external rotation ROM with measures of lower extremity performance and walking endurance capacity. These investigators found that participants who failed to demonstrate full ROM at both shoulders on physical examination had as high as a 4.5 times adjusted odds (houlders .Additional research is needed to further examine the strength of association between shoulder dysfunction and mobility performance measures relevant to the daily lives of community-dwelling older adults. One current study funded by the National Institute on Aging “Shoulder Pain, Rotator Cuff Tear, Coordination, and Mobility in Aging” is underway which seeks to establish preliminary data on the association of shoulder coordination while overground walking with mobility performance measures, and also the association between of shoulder coordination while walking overground with RC tear or shoulder pain, in a population of community-dwelling older adults .In conclusion, shoulder dysfunction and mobility limitation are common conditions that contribute to functional decline in older populations. The idea that lower extremity dysfunction does not fully explain all mechanisms of mobility limitation is gaining acceptance in the scientific community. Holistic research strategies that investigate the influence of shoulder dysfunction on mobility offer the potential for development of future novel interventions that improve prevention or mitigation of mobility limitation in older adults.


We also concluded that there is suggestive evidence of no association between genital talc application and endometrial cancer, and insufficient evidence to determine whether a causal association exists between genital talc application and cervical cancer based on a smaller but largely null body of literature.Talc is a hydrous magnesium sheet silicate used in cosmetic powders, ceramics, paints, rubber, and many other products. We conducted a systematic review of the potential carcinogenicity of genitally applied talc in humans. Our systematic review methods adhere to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and incorporated aspects from the US Institute of Medicine  and several US EPA frameworks for systematic reviews, evaluating and integrating the epidemiological, animal, and mechanistic literature on talc and cancer. We conducted a comprehensive literature search. Detailed data abstraction and study quality evaluation, adapting the Toxic Substances Control Act (TSCA) framework, were central to our analysis. The literature search and selection process identified 40 primary studies that assessed exposure to talc and female reproductive cancer risks in humans (n = 36) and animals (n = 4). The results of our evaluation emphasize the importance of considering biological plausibility and study quality in systematic review. Integrating all streams of evidence according to the IOM framework yielded classifications of  Extracted talcs contain pure talc as well as a variety of potential accessory minerals. Pharmaceutical-grade talc is the purest  followed by cosmetic-grade talc and industrial-grade talc  between perineal exposure to talc-containing products  and female reproductive tract cancer(s), critically assessing and integrating evidence from epidemiology, toxicology, and studies informing potential underlying MOAs.This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist, using a hybrid systematic review framework, incorporating aspects from several recognized systems. Specifically, we relied most heavily on the United States Environmental Protection Agency’s (EPA) protocol for systematic reviews conducted under the Toxic Substances Control Act (TSCA) and the Draft Handbook for the Integrated Risk Information System . Hazard a priori inclusion and exclusion criteria specific to each realm of evidence, including epidemiological studies, experimental animal studies in mammalian species, and mechanistic studies in vivo or in mammalian or bacterial cell lines  yielded a total of 1,229 publications. After eliminating duplicate entries or studies that were subsequently updated and applying the inclusion and exclusion criteria, 36 epidemiological and four animal studies remained and were selected for review. Additional searches in Web of Science identified no additional publications. The results of the literature search and study identification and selection are summarized in Four experimental animal studies evaluated the potential for talc externally applied or introduced vaginally to reach the internal reproductive organs: these studies are summarized in brief below. Unfortunately, the four identified studies did not provide comprehensive details regarding the physiochemical nature of the talc used. Thus, it was not possible to elucidate the effect of variation in physiochemical talc properties on the biological effects observed.Similarly, Five small studies of human subjects (n = 5–25) detected talc (among other particles) in ovarian tissue of women with ovarian cancer . In the Four studies evaluated talc carcinogenicity in rodents . HoweverWe classified no evidence that talc causes ovarian or other reproductive tumors in rodents after perineal exposure based on limited evidence–a single negative study utilizing a subchronic exposure duration. Other non-cancer potentially adverse effects were noted in this study, though the authors stated that these effects were not indicators of pre-cancerous lesions or associated with increased cancer risk.Animal evidence informing the potential association between talc and reproductive cancer is very limited. The single study with perineal talc application was judged to be of medium quality and reported no indication of carcinogenicity in any reproductive organs. Overall, there is Because it is inert, talc is unlikely to induce systemic toxicity or exert carcinogenicity via MOAs typical of many chemical carcinogens . As with other poorly soluble low toxicity particles, one postulated potential carcinogenic MOA for talc is chronic inflammation, long-term tissue irritation and release of inflammatory chemokines and cytokines, and reactive oxygen species (ROS) formation. In sufficient quantities, ROS can cause secondary genotoxic effects (DNA damage), and potentially, tumor development . AnotherGsr and Sod1 were statistically significantly increased in talc-exposed animals relative to controls; other markers were not statistically significantly altered. miRNA associated with both apoptosis and apoptosis inhibition  were statistically significantly increased in talc-exposed rats. Critically, this study is considered unreliable because the control group had no incisions or sham exposures, so it is not possible to determine whether effects were independent of the stress induced from the administration route.per se” and that additional studies would be needed to determine whether the effect of phagocytosis occurs in vivo, particularly in humans (n humans .p = 0.04); in tests of trend by talc use frequency , there was a borderline significant (p = 0.11) association between genital talc use and decreased anti-MUC1 antibodies. In another study of ovulation, MUC1 and ovarian cancer, talc use was not associated with an increased number of ovulatory cycles or anti-MUC1 antibodies . Unfortunately, several of the available talc genotoxicity studies are low quality, employing methodologies now thought less informative for predicting genotoxicity  cohort, comparing “ever” vs. “never” genital talc use, reported an elevated relative risk  for invasive serous ovarian cancer after adjusting for several potential confounders . CovariaAll cohort studies received a medium quality score overall, although there were differences in quality ratings across assessed domains . In brieLower quality study ratings primarily were driven by the talcum powder perineal exposure characterization approach and exposure metrics used. Four of the cohort studies collected information on lifetime genital talc use as of baseline only .Details regarding cohort members’ genital talc use were sparse. Nevertheless, due to their prospective design, all of the cohort studies ascertained genital tac use among large numbers of women free of ovarian cancer and in advance of those diagnosed with ovarian cancer during follow-up, ensuring that the self-reporting of genital talc use could not be influenced by the ovarian cancer diagnosis.Of the 26 case-control studies evaluated, 18 (69%) reported at least one statistically significant odds ratio for ovarian cancer and genital talcum powder use . There wEight case-control studies evaluated genital talc use by histological subtypes of ovarian cancer, six of which reported statistically significant odds ratios for serous ovarian cancer , and oneAlthough generally weak associations between reported genital talc use and ovarian cancer were reported by more than half of the case-control studies, estimated odds ratios were inconsistent in terms of strength, precision, and talc exposure surrogate. The rest of the case-control studies reported no positive associations. Some studies reported associations with genital application of talc in general, or for dusting of sanitary napkins or underwear; however, few associations were seen for talc applied to diaphragms or cervical caps , and one  reportedOf the 26 case-control studies assessed, none was rated high overall quality, 11 (42%) were rated medium, and 15 (58%) were rated low overall quality see . In mostpost hoc, many of the case-control studies attempted to characterize genital talc use by level, frequency or duration . However, a substantial proportion of case-control studies  only evaluated “ever” vs. “never” genital use of talcum powder, precluding evaluation of possible relationships with exposure characteristics or exploring indicators of recall or reporting bias .Low overall quality scores for case-control studies primarily were driven by limitations in exposure assessment. Recall and self-reporting of historical talc exposure and other risk factors can be influenced by cases’ knowledge of their ovarian cancer diagnosis, especially if an association with a risk factor such as genital talc use is suspected or has been highlighted in the public media . Such anLimitations related to the control of potential confounding factors or other analytical issues  also contributed to lower-quality ratings see . As the Most case-control studies (n = 18) reported positive associations between ovarian cancer and genital talc use; however, the quality of the studies was mixed, with most studies assigned low-quality ratings specifically for exposure characterization and risk of bias. Among these studies, there were no consistent associations seen between ovarian cancer and reported talc application type, frequency, or duration of use; in other words, no consistent exposure-response relationships were identified in any studies.Cohort studies that evaluated genital talc use by histological subtype of ovarian cancer reported no statistically significant associations for endometrioid, mucinous, ‘other’ ovarian cancer subtypes or invasive serous ovarian cancer  See Fig. OverallThe cohort studies included in the systematic review consistently reported no associations between genital talc use and epithelial ovarian cancer overall, in contrast with the case-control studies, many of which reported inconsistent associations with the remaining studies reporting no statistically significant associations. For specific histologic types of ovarian cancer, a few studies reported associations with invasive serous ovarian cancer. However, except for one statistically significant relative risk estimate for ever use of genital talc and invasive serous ovarian cancer  that wasAlthough application of talc to contraceptive diaphragms or cervical caps may represent a more direct route of exposure compared to external application or dusting, cohort and case-control studies evaluating such internal talc exposures failed to demonstrate any association with ovarian cancer. The only statistically significant association between talc use on diaphragms or cervical caps was a statistically significantly decreased relative risk of ovarian cancer  . Most ofAcross both cohort and case-control studies, low-quality ratings primarily were driven by substantial limitations in the talc exposure assessment. Regardless of study design, studies assessing talc exposure at one time point via self-report are subject to inaccurate recall and reporting, leading to exposure misclassification; however, the expected direction and magnitude of such biases differ by study design. For cohort studies, participants reported genital talc use prior to ovarian cancer diagnosis, likely closer to the period of actual use and unaffected by any subsequent ovarian cancer diagnosis, thereby reducing potential bias whereas recall bias for case-control studies increases potential bias. Further, many cohort and case-control studies only or primarily analyzed ever talc use, which provided minimal information about possible changes in use patterns over time. These methods most likely result in random error, expected to be similar among women who subsequently develop ovarian cancer and those who do not. In contrast, case-control studies obtain information on talc use after cases have been diagnosed with ovarian cancer, and these women – especially if they believe that their cancer might have been caused by their genital talcum powder use–may better recall or possibly over-report their talc use compared with controls necessarily without ovarian cancer. Overall, more case-control studies included multiple surrogates of talc use including frequency and duration, than did the cohort studies; however, all such historical recall and reporting followed the ovarian cancer diagnosis, and required recall of use over previous decades rather than current or recent use.Despite their limitations, the cohort studies on genital talc use and risk of ovarian cancer provide higher quality evidence overall compared to the case-control studies. Given the prospective design, inclusion of large national cohorts, and consistent medium quality ratings of the cohort studies (compared with a mix of medium and low ratings for the case-control studies), it is likely that the cohort studies collectively were better able to mitigate the effects of errors in recalling and reporting genital talc use, as these would not be expected to differ by any future cancer diagnosis.Among the case-control studies assessed as medium quality, statistically significant associations between any talc use and epithelial ovarian cancer were more consistently reported in the recent studies, i.e., those published since 2012 . The casDespite the modest number of high-quality epidemiological studies addressing genital use of talc and ovarian cancer, the better-quality studies tend to be negative, providing insufficient evidence and an inadequate basis for concluding with any confidence that there is a causal connection. The several case-control studies reporting statistically significant associations between ovarian cancer and genital talc use all are overshadowed by recall and reporting bias, enhanced by the unavoidable exposure to news stories, social media and advertisements purporting that talcum powder causes cancer.We identified and systematically reviewed five publications evaluating potential associations between cosmetic talcum powder exposure and endometrial cancer, including four cohort studies  and one Four studies utilized data from large, national cohorts, including the NHS , the SisNone of the four cohort studies and one case-control study reviewed that evaluated genital talc use and endometrial cancer reported a statistically significant overall association . DespiteThe case-control study by Although quality domain scores varied across studies, all studies evaluating the potential association between genital talc use and endometrial cancer received a medium overall quality score . The oneThe endometrial and cervical cancer studies generally used appropriate and reproducible analysis methods, including adjustment for potential confounders. Covariates, however, typically were self-reported, and only one cohort study re-assessed covariates throughout study follow-up . Most stConsistent with the study quality patterns observed across the body of literature addressing ovarian cancer, lower quality ratings largely were driven by exposure characterization methods. Genital talc use was self-reported by participants at one time point in all studies, which could have resulted in inaccurate or biased reporting and misclassification of the exposure. Recall bias remains a particular concern for the one case-control study  and the All studies included at least one talc exposure estimate with three or more levels, although the definition and level of detail varied. For example, All endometrial studies reviewed were of similar quality overall with some differences in specific domains. No clear or consistent relationships were identified between genital talc use and endometrial cancer overall or by quality characteristics, although a few positive associations were reported  were considered of limited relevance to in vivo exposures and to human exposures. The epidemiological evidence included numerous studies of ovarian cancer and genital talc use, but most of those reporting associations were case-control studies, most of which were considered of low quality primarily due to post-diagnosis historical self-reporting of talc use by women or even next-of-kin. Evidence of recall and reporting bias was greatest in the more recent studies after the possible association between talcum powder use and ovarian cancer risk was widely publicized. One meta-analysis reported an increased meta-RR estimate for invasive serous ovarian cancer, but risk was unrelated to various talc exposure indicators, suggesting that the overall association may not be due to talcum powder use . Talc increased cell proliferation and decreased apoptosis in cancer cells and some normal cells wder use . Goodmansuggestive evidence of no association between genital talc use and endometrial cancer at human relevant exposure levels. Given the limited body of literature assessing the potential relationship between genital talc use and cervical cancer, we conclude there is insufficient evidence to determine whether a causal association exists for cervical cancer.The body of evidence for endometrial and especially cervical cancer is somewhat sparse. However, study results from all lines of scientific inquiry largely mimic those for ovarian cancer. No endometrial or cervical tumors were observed in the sub-chronic animal study of perineal talc application. Mechanistic studies in animals indicate there may be some movement of talc from the external genital area to the cervix, but not into the uterus or beyond. No information was available regarding inflammatory or immune MOAs in endometrial or cervical cells or tissues. The five epidemiological studies evaluated, all of which were rated medium quality, demonstrated no association between genital talc use and endometrial or cervical cancer. Therefore, we again conclude that there is suggestive evidence of no association for exposure to talc and ovarian cancer, as well as suggestive evidence of no association for endometrial cancer. We found insufficient evidence to determine whether a causal association exists for genital talc use and cervical cancer based on a limited body of literature. The body of epidemiological evidence is larger and more robust for ovarian cancer and provides critical information, complemented by high-quality experimental animal carcinogenicity bioassays and no convincing mechanistic evidence. Although the paucity of mechanistic information remains a limitation, the balance of evidence, especially the negative animal studies and body of higher-quality cohort studies demonstrating no increased cancer risks, provides the best scientific evidence of lack of carcinogenicity, at least at “real world” human-relevant exposures.Our systematic review of talc and cancer finds No prior reviews were identified on talc and endometrial or cervical cancers; however, a number of prior reviews have evaluated perineal talc use and ovarian cancer. Our systematic review is in general agreement with the critical review and weight-of-evidence assessment of ovarian cancer and talc exposure published by The comprehensive searches and detailed methods we followed are documented in this report and the We believe that this comprehensive systematic review will be useful to researchers, regulators, policymakers, and other stakeholders concerned with the carcinogenicity of talc and talcum powder products under human-relevant exposure conditions, as well as help identify remaining research gaps. Nevertheless, based on the integration of evidence from animal experiments, mechanistic evaluations and epidemiological studies of reasonable methodological quality, this systematic review demonstrates that talc and cosmetic talcum powders unlikely cause female reproductive cancers at human-relevant exposures.


The extracellular microenvironment regulates many of the mechanical and biochemical cues that direct musculoskeletal development and are involved in musculoskeletal disease. The extracellular matrix (ECM) is a main component of this microenvironment. Tissue engineered approaches towards regenerating muscle, cartilage, tendon, and bone target the ECM because it supplies critical signals for regenerating musculoskeletal tissues. Engineered ECM–material scaffolds that mimic key mechanical and biochemical components of the ECM are of particular interest in musculoskeletal tissue engineering. Such materials are biocompatible, can be fabricated to have desirable mechanical and biochemical properties, and can be further chemically or genetically modified to support cell differentiation or halt degenerative disease progression. In this review, we survey how engineered approaches using natural and ECM-derived materials and scaffold systems can harness the unique characteristics of the ECM to support musculoskeletal tissue regeneration, with a focus on skeletal muscle, cartilage, tendon, and bone. We summarize the strengths of current approaches and look towards a future of materials and culture systems with engineered and highly tailored cell–ECM–material interactions to drive musculoskeletal tissue restoration. The works highlighted in this review strongly support the continued exploration of ECM and other engineered materials as tools to control cell fate and make large-scale musculoskeletal regeneration a reality.  Engineering cell-extracellular matrix (ECM) interactions to achieve desired regenerative outcomes are promising approaches in musculoskeletal tissue engineering. Musculoskeletal tissue injuries are a common and increasing clinical problem in the US and around the world . InjurieEngineering the ECM to facilitate desired cell–cell and cell–material interactions is a relatively new approach in tissue engineering. In the last decade, biomaterial fabrication methods have progressed to enable precise control over the mechanical, chemical, and biological properties of the extracellular microenvironment . Thanks The cell- and tissue-derived extracellular matrix (ECM) has been extensively characterized for uses in tissue engineering, and it has been reviewed elsewhere ,17. To gThe value of engineering the ECM to foster specific cell–ECM interactions extends beyond its use in regenerative approaches and into its widespread potential applications in directing cell function throughout entire tissue and organ systems . EngineeSelected approaches utilizing cell–ECM–material interactions to regenerate skeletal muscle are summarized in The highly organized, hierarchical structure of skeletal muscle has made it a particularly challenging tissue to engineer, as its structure provides unique mechanical properties. Replicating muscle structure and the complex multi-tissue interfaces required for muscle function, such as neuromuscular junctions (NMJs) and tendons, has proven elusive. While muscle cells from human and non-human sources readily grow and differentiate in vitro, and they can be successfully implanted in numerous animal models, the resulting muscle tissue often lacks the force production, growth, and vascularization capacities of native muscle. A significant limitation of several regenerative approaches for restoring skeletal muscle is the inability to replicate the structural and spatial components of healthy muscle tissue. This problem is especially pronounced in research attempting to reverse volumetric muscle loss (VML) . VML resEngineered approaches replicating the organized ECM of muscle have seen some success in terms of the force production of the regenerated muscle  and haveAlthough decellularized ECM has been shown to aid tissue regeneration, it may require additional materials for effective tissue delivery. A recent study coupled the use of ECM with extracellular vesicles (EVs), cell-secreted nanoparticles that convey intercellular signals to propagate tissue repair. Decellularized muscle ECM was combined with human EVs derived from Wharton Jelly mesenchymal stromal cells (MSC EVs) to boost tissue regeneration in a murine VML model . Thirty Xenogeneic ECM  scaffolds were tested as platforms for skeletal muscle restoration in another complex injury model . A scaffEngineered muscle ECM is a crucial component of recently developed and highly accurate in vitro disease models, which are of significant interest as personalized test platforms for novel muscle-targeting therapeutics. Collagen VI- related dystrophies (COL6-RDs) are rare congenital neuromuscular dystrophies where alterations in one of the three collagen VI genes change the collagen’s incorporation into the ECM, severely impacting the mechanical coherence of the matrix . COL6-RDThe future of engineered cell–ECM interactions in skeletal muscle tissue engineering extends to personalized injury models. ECM–cell materials can potentially recreate the tissue structure that is destroyed during VML, with the goal of restoring the large quantities of the specific muscle tissue  lost in VML, thus reversing the associated disability. Recreating the highly organized mechanical and biological structure of muscle tissue remains a significant challenge. Both natural and engineered ECM, as a standalone biomaterial or in combination with other scaffolds, is uniquely suited to providing a culture environment that mimics native muscle. Though much exploration is still needed regarding the role of ECM in directing cell behavior in degenerative or muscle wasting diseases, improved in vitro and in vivo models of engineered ECM–cell interactions will advance our knowledge of which mechanical, biochemical, and genetic factors synergize to initiate skeletal muscle pathologies. To prevent or reverse skeletal muscle atrophy, a viable strategy may be targeted hypertrophy using ECM-based materials to stimulate muscle cells. Matricellular proteins play key roles in ECM–cell communication and are necessary to understand in engineering ECM–cell interactions for musculoskeletal regeneration. A recent study indicated that matricellular protein cellular communication network factor 2 (CCN2), also known as connective tissue growth factor (CTGF), is induced during a time course of overload-driven skeletal muscle hypertrophy in mice and may be a useful addition to current strategies. Genetically engineered mouse models for myofiber-specific CCN2 gain- and loss-of-function were subjected to mechanical stimuli via muscle overload. Testing showed that myofiber-specific deletion of CCN2 blunted the muscle’s hypertrophic response to overload without interfering with ECM deposition. Conversely, CCN2 overexpression was efficient in promoting overload-induced aberrant ECM accumulation without affecting myofiber growth . The stu+) was seen in placenta-derived matrices compared to muscle derived matrices . Pr. Pr84]. Overuse injuries are common in tendons. Tendon overuse gradually degrades the ECM and alters its crucial mechanotransductive properties, causing pain and disability . MechanoMechanical force regulates tendon ECM organization, as well as tendon growth factor signaling through the transforming growth factor beta (TGFβ) family , indicatAn engineered tendon ECM can also be used to direct stem cell differentiation towards the tendon phenotype. The extracellular compartment is responsible for tendon morphogenesis during early development, in part due to the spatial cues it provides . ECM elaBeyond its mechanical properties, tendon ECM has been engineered to support tissue function via enhancement of its structural and compositional functions. Solubilized tendon ECM was recently used to induce tenogenesis (differentiation towards tendon) in human adipose-derived stem cells . ExtractAs tendon ECM provides essentially all the mechanical functions of tendon tissue, replicating its structure and function is of particular importance to regenerative and tissue engineered approaches for treating tendon injuries. The acellular matrix has been explored as a means of augmenting rotator cuff repairs, where disruption to the gradated tendon-mineralized fibrocartilage-bone matrix is associated with complex recoveries and long-term loss of function. Human acellular dermal matrix (ADM) used as a patch was shown to be a viable option based on results in canine large rotator cuff defect models . More reAnother promising approach in tendon repair is the use of ECM to address post-operative fibrosis. Tendon surgery can lead to fibrosis of the affected or implanted tissue due to the graft adhering to surrounding native tissues. This adherence is the most common post-surgery complication in tendon repair , but decIt is worthwhile to consider the interactions between the cells and the non-collagenous components of tendons. While collagens and their hierarchical structural formations make up 70 to 90% of the total tissue volume in tendon, its less abundant components also provide crucial functions. These include proteoglycans, glycosaminoglycans, and non-collagenous proteins that are incompletely understood and poorly characterized, particularly with respect to their roles in mechanotransduction and their contributions to the mechanical properties of tendon ,102. TheEngineered cell–ECM–material interactions may also benefit tendon wound repair. The tendon has limited healing capacity, but prior work has shown that biglycan and fibromodulin, two non-collagenous components of the tendon ECM, can enhance the wound healing capacity of tendon progenitor cells . Recent Ultimately, though the tendon may be the least explored tissue in the context of engineered ECM approaches for regeneration, we see rapid advancements in the use of natural and engineered ECM and ECM-composite materials for uses in tendon tissue engineering. As ongoing research elucidates the impact of the ECM in tendon development, maintenance, and injury, engineered ECM-material approaches will provide useful interventions for improved tendon healing and regeneration. Tendon ECM is responsible for many of the tissues’ mechanical and biochemical properties, and expanding the capabilities of engineered ECM to drive cell behavior is a critical and ongoing area of investigation.Selected approaches utilizing cell–ECM–material interactions to regenerate bone are summarized in The well-defined composition and structure of bone ECM facilitates biofabrication of bone ECM scaffolds for uses in tissue engineering. Mimicking the porosity, permeability, and tortuosity of bone ECM is relatively straightforward and may enhance cell migration, as show in a recent computational study . AnotherOriented ECM scaffolds have also been fabricated to imitate the material and structural properties of the natural bone growth plate, utilizing bone marrow stromal cells (BMSCs) to prevent bone bridge formation and growth plate injuries . Growth 23–144peptide-fused bone morphogenetic protein 2 (pBMP2) [ECM from non-musculoskeletal tissues has also been successfully used to induce in situ bone regeneration. Porous polycaprolactone (PCL)/decellularized small interesting submucosa (SIS) scaffolds were fabricated using cryogenic free-form extrusion, followed by surface modification with aptamer and PlGF-21 (pBMP2) . Rats we (pBMP2) . At eighAnother promising scaffold for bone regeneration was recently developed using polylactic glycolic acid, bone ECM, and magnesium hydroxide. Magnesium is an emerging scaffold material that resists the loading from human activities and has potential uses as an orthopedic implant due to its porosity and robustness . To mediIn addition to serving as a scaffold material, ECM can functionalize existing scaffolds to enhance osteogenic potential for bone regeneration applications. As a recent example, ECM was functionalized onto the surface of multi-channel biphasic calcium phosphate granules (MCG) to increase osteogenesis and regeneration. The collagen, sulfated glycosaminoglycan, and trace amounts of growth factors, such as BMP2, vascular endothelial growth factor (VEGF), transforming growth factor TGFβ, and fibroblast growth factor (FGF), were found in the ECM supported proliferation of MC3T3-E1 cells over seven days . ProteinIn a unique formatting approach, bone ECM was configured into demineralized bone paper (DBP) as a material to direct osteoblasts to deposit structural mineralized bone tissue . DBP effOther notable in vitro bone models work towards elucidating the mechanisms necessary for proper bone–ECM interactions . It was recently established that many ECM-associated proteins contain thrombospondin type 1 repeat (TSR) motifs that play critical roles in cellular processes, such as cell–cell attachment, extracellular matrix (ECM) remodeling, cell proliferation, and apoptosis . TSRs arWhile this review has already discussed the widely accepted premise that ECM stiffness is important in the regulation of stem cell differentiation, how cells sense stiffness cues and adapt their metabolic activities remains less understood. Recent research explores the role of mitochondrial phosphoenolpyruvate carboxykinase (PCK2) in enhancing osteogenesis in three-dimensional ECM via glycolysis in the context of stem cell osteogenesis . The thrA similar study used a mouse model of trauma-induced heterotopic ossification (HO) to examine how cell-extrinsic forces impact mesenchymal progenitor cell (MPC) fate. Mice were given a partial thickness scald burn injury to produce a burn/tenotomy HO model. Post injury, mice had their hind limbs immobilized. Single-cell (sc) RNA sequencing of the injury site revealed an early increase in MPC genes associated with pathways of cell adhesion and ECM-receptor interactions, as well as MPC trajectories to cartilage and bone . InteresFaulty skeletal muscle repair can also result in HO. A recent study used fibrodysplasia ossificans progressiva (FOP), a disease of progressive HO caused by an activin receptor type-1 (ACVR1) mutation, to elucidate how ACVR1 affects skeletal muscle repair . Primary2+ levels [Bone ECM stiffness has also been implicated in pathologies of the spine. Intervertebral disc degeneration (IDD) is thought to be initiated by the mechanical stimulation provided by the ECM stiffness. ECM defines the mechanical microenvironment of the nucleus pulposus (NP). The mechanosensitive ion channel Piezo1 mediates mechanical transduction within the disc, and a recent study explored the function of Piezo1 in human NP cells subjected stiffness levels comparable to those found in the ECM. The expression of Piezo1 and the ECM elasticity modulus increased in degenerative NP tissues, and stiff ECM activated the Piezo1 channel and increased intracellular Ca+ levels . Increas+ levels . By inhiMoving forward, as the use of scaffolds containing cell-derived ECM continues to be a viable strategy for mediating bone regeneration, a mechanistic understanding of the benefits of ECM compared to other scaffolding techniques is needed. A recent study used ECM-loaded three-dimensional printed gelatin (Gel), sodium alginate (SA), and 58s bioglass (58sBG) gels seeded with either rat aortic endothelial cells (RAOECs) or rat bone mesenchymal stem cells (RBMSCs) were used to explore the mechanisms underlying the advantages of ECM-containing scaffolds. In vitro osteogenic differentiation results showed that scaffolds coated with ECM significantly increased the expression of osteogenic and angiogenic genes compared to uncoated control scaffolds, likely due to the presence of native ECM proteins . In vivoLooking towards the future, with large proportions of the population aging in the United States, China, Japan, and globally, the clinical need for regenerative bone therapies will continue to grow exponentially. We have highlighted unique strategies for exploiting the existing cellular ability to remineralize and regenerate bone, without the need for invasive surgical grafts or drug combinations with side effects that reduce the patients’ quality of life. As research continues to elucidate the mechanisms by which bone ECM supports and regulates bone function, paracrine and endocrine signaling, and homeostasis, engineered ECM approaches will provide novel and exciting platforms for regenerative bone therapies. Enhanced understanding of micro- and nanoscale mechanical properties of engineered ECM materials are considered here. Significant research has already been conducted to understand the mechanics and topography of ECM, as well as how these properties relate to cellular changes at a macroscopic level ,128,129.Atomic force microscopy (AFM) is a promising imaging modality for the study of the topography, mechanical properties, and other ECM characteristics at the micro- and nanoscopic levels. AFM is capable of precisely resolving the nano-topography of diverse surfaces and mapping the spatial distribution of their physicochemical properties to include charge density and potential in a variety of hard and soft materials, including hydrogels ,134. ThiAFM can quantify the stiffness of natural ECM and synthesized ECM scaffolds, which allows for correlations between the nanomechanical characteristics of surfaces and their impact on cellular interactions and behaviors. Cell behavior can then be compared to what has been observed in the context of the material’s bulk characteristics. AFM also offers a method of mechanical testing that is less destructive than standard techniques . AFM can probe multiple mechanical properties simultaneously to produce accurate measurements that include stiffness, maximum indentation, indentation at maximum force, hysteresis, hardness, compliance, adhesion force, detachment distance, detachment energy, and Young’s modulus. As precise attributes of the ECM are engineered to elicit specific responses from cells or create individualized patient disease models, techniques, such as AFM, may prove invaluable in determining the exact properties of various ECM scaffolds.While AFM stands as an incredibly powerful tool to analyze ECM at the microscopic and nanoscopic level, several experimental limitations remain. The long imaging time required for a high-resolution image, potential damages exerted by the probe tip, imaging artifacts, and quantitative interpretation of the results have constrained AFM’s utility in tissue engineering research. However, AFM has already been successfully used before to obtain quality concerning engineered graft surfaces . This saIn addition to using highly sensitive mechanical testing, such as AFM, to inform engineered ECM and biomaterial scaffold design, we expect the role of genetic engineering to expand into the fabrication of custom, genetically-modified ECM for use in biomaterial scaffolds. As highlighted extensively in this review, a critical role of ECM is mechanotransduction. It stands to reason that engineered ECM from genetically modified cells/organisms that contains a specific array of mechanotransduction proteins may be a useful and desirable component of newly developed scaffolds. Techniques, such as CRISPR-based genome editing, may support the fabrication of custom ECMs that can replicate features of diseases that, until now, have been difficult or impossible to mimic in vitro. Alongside genetic engineering, novel composite materials, such as ECM-silk and ECM-titanium constructs, and ECM-based bioinks ,101,140,Until recently, most printers were unable to produce the slightly heterogeneous morphologies observed in native tissues. Recent gains in printer accuracy, porosity, and random structure generation are supporting the fabrication of biomaterials that mimic the native structure of small soft tissues, including musculoskeletal tissues. While ink availability has limited the application of this technology, new inks are rapidly emerging and enable multilayer printing while also incorporating growth factors, such as TGFβs and BMPs ,141. AdvAn underexplored application of engineered ECM is in understanding fibrotic disease, both in regards to musculoskeletal tissues and in the rest of the body. Significant interest in controlling ECM mechanics, and particularly ECM stiffening, has emerged in research related to idiopathic pulmonary fibrosis (IPF). IPF is a progressive scarring disease characterized by extracellular matrix accumulation and altered mechanical properties of lung tissue. Recent studies support the hypothesis that these compositional and mechanical changes create a progressive feed-forward loop, in which enhanced matrix deposition and tissue stiffening contribute to fibroblast and myofibroblast differentiation and activation, which further perpetuates matrix production and stiffening . As the Additional evidence of the critical role of matrix mechanics in fibrotic diseases comes from the field of vascular regeneration. Novel engineered ECM and polyethylene glycol- based materials were recently utilized to understand the pathophysiology of pulmonary artery hypertension (PAH), a progressive disease of the lung vasculature that is characterized by elevated pulmonary blood pressure, remodeling of the pulmonary arteries, and ultimately right ventricular failure. Therapeutic interventions for PAH are limited in part by the lack of in vitro screening platforms that accurately reproduce dynamic arterial wall mechanical properties. In this study, the ECM of the pulmonary arteries was engineered to mimic disease progression. The engineered ECM and polyethylene glycol-based model allowed for unprecedented recreation of the mechanical properties of both PAH and healthy tissue ,149,150,As with any literature summary, we intend for this review to be a brief survey of each of these commonly studied tissues, rather than a comprehensive guide to every engineered ECM-based approach in the field of musculoskeletal regeneration. This review fills a gap in the existing literature by uniting a diverse array of experimental approaches under the common theme of musculoskeletal regeneration. While highlighting every recent and exciting use of engineered ECM-cell interactions in the context of musculoskeletal regeneration is outside of the scope of this review, and we show the expansive promise of ECM in musculoskeletal tissue engineering. We believe this grouping serves readers who may work in more than one musculoskeletal tissue system, which is an increasingly common theme in musculoskeletal tissue engineering.Throughout the last decade, the expanding ability to direct cell behavior for musculoskeletal tissue regeneration via the use of engineered ECM and ECM-based materials has greatly expanded our knowledge of musculoskeletal development, disease, and healing. This review has focused on recent and noteworthy advances that incorporate cell, ECM, and material interactions to increase the regenerative capacity of muscle, cartilage, bone, and tendon. We examined approaches focused on a single tissue, as well as studies that incorporated two or more musculoskeletal tissues, to more faithfully recreate the in vivo environment. The works we highlight suggest that single- and multi-tissue approaches can generate valuable insights into how the physical, mechanical, and biochemical attributes of the ECM, alone and in combination with innovative engineered materials of natural and synthetic origins, can be harnessed to direct cellular behavior towards maximizing the regenerative capacity of musculoskeletal tissues. Human and animal ECM both deserve continued exploration, as continuous improvements to decellularization techniques reduce the danger of systemic immune response or rejection.We concluded with predictions of the future of engineered cell–ECM–material interactions. The implementation of advanced manufacturing techniques, such as three-dimensional printing, as well as improvements in decellularization protocols that decrease the likelihood of adverse immune reactions, have paved the way for expanded use of ECM in musculoskeletal tissue engineering. Renewed interest in harnessing the ECM both as a standalone material and in combination with other well-established biomaterials is driven by studies showing that ECM instructs cells to behave more closely to how they do in native tissue. We show the expansive promise of ECM in musculoskeletal tissue engineering, and we look forward to the advancements of the coming decade. Ultimately, we expect meaningful and exciting advances in bioprinting, improved decellularization techniques, genetic engineering of both the ECM and cells, and the further determination of how ECM mechanics at multiple length scales can be exploited to precisely direct cell behavior towards regenerative phenotypes.