Use of priming strategies to advance the clinical application of mesenchymal stromal/stem cell-based therapy

Mesenchymal stromal/stem cells(MSCs)have garnered significant attention in the field of regenerative medicine due to their remarkable therapeutic potential.MSCs play a pivotal role in maintaining tissue homeostasis and possess diverse functions in tissue repair and recovery in various organs.These cells are charac-terized by easy accessibility,few ethical concerns,and adaptability to in vitro cultures,making them a valuable resource for cell therapy in several clinical conditions.Over the years,it has been shown that the true therapeutic power of MSCs lies not in cell engraftment and replacement but in their ability to produce critical paracrine factors,including cytokines,growth factors,and exosomes(EXOs),which modulate the tissue microenvironment and facilitate repair and regeneration processes.Consequently,MSC-derived products,such as condi-tioned media and EXOs,are now being extensively evaluated for their potential medical applications,offering advantages over the long-term use of whole MSCs.However,the efficacy of MSC-based treatments varies in clinical trials due to both intrinsic differences resulting from the choice of diverse cell sources and non-standardized production methods.To address these concerns and to enhance MSC therapeutic potential,researchers have explored many priming strategies,including exposure to inflammatory molecules,hypoxic conditions,and three-dimensional culture techniques.These approaches have optimized MSC secretion of functional factors,empowering them with enhanced immunomodulatory,angiogenic,and regenerative properties tailored to specific medical conditions.In fact,various priming strategies show promise in the treatment of numerous diseases,from immune-related disorders to acute injuries and cancer.Currently,in order to exploit the full therapeutic potential of MSC therapy,the most important challenge is to optimize the modulation of MSCs to obtain adapted cell therapy for specific clinical disorders.In other words,to unlock the complete potential of MSCs in regenerative medicine,it is crucial to identify the most suitable tissue source and develop in vitro manipulation protocols specific to the type of disease being treated.

Fortuitous benefits of activity-based rehabilitation in stem cell-based therapy for spinal cord repair: enhancing graft survival

Traumatic injuries to spinal cord elicit diverse signaling pathways leading to unselective and complex pathological outcomes：death of multiple classes of neural cells,formation of cystic cavities and glial scars,disruption of axonal connections,and demyelination of spared axons,all of which can contribute more or less to debilitating functional impairments found in patients with spinal cord injury.

The potential of stem cell-based therapy for retinal repair

Like injured neurons in the brain or spinal cord, neurons in the retina are incapable to regenerate following injury and ultimately would lead to irreversible neuronal loss and vision impairment. Over decades, extensive effort has been made to develop strategies to protect retinal neurons from death; however, the outcome is limited （Pettmann and Henderson, 1998; Bahr, 2000; Lagali and Picketts, 2011）. Replacing the degenerated retinal neurons by newly generated and functional neurons would be an ideal scenario. The rapid development of stem cell biology has recently demonstrated that stem cells could be a potential source of cells for cell replace- ment therapy because these cells have the self-renewal capacity and could be differentiated into many cell types. This review will dis- cuss the therapeutic potential of stem cell-based therapy to retinal degenerative diseases.

Cell-based therapy in Alzheimer's disease: can human fetal cholinergic neurons “untangle the skein”?

Alzheimer＇s disease（AD）is a devastating neurodegenerative disorder and the most common form of old-age dementia.The disease is characterized by a progressive decline in cognitive functions,gradual loss of memory and ability to perform everyday activities,and leads to inevitable death within 3 to 9 years atter diagnosis.

Tubular conduits,cell-based therapy and exercise to improve peripheral nerve regeneration

Peripheral nerve injuries （PNI） are a major clinical prob- lem. In general, PNI results from motor vehicle accidents, lacerations with sharp objects, penetrating trauma （gunshot wounds） and stretching or crushing trauma and fractures. It is estimated that PNI occur in 2.8% of trauma patients and this number reaches 5% if plexus and root lesions are in- cluded. However, due to lack of recent epidemiological stud- ies, these data probably underestimate the actual number of nerve injuries

Endothelium-specific gene and stem cell-based therapy for erectile dysfunction

Erectile dysfunction （ED） commonly results from endothelial dysfunction of the systemic vasculature. Although phosphodiesterase type 5 （PDE-5） inhibitors are effective at treating most cases of ED, they must be taken routinely and are ineffectual for a meaningful number of men. In recent years gene and stem cell-based therapies targeted at the penile endothelium have been gaining momentum in preclinical studies. These early studies reveal that gene and stem cell-based therapies may be both enduring and efficacious, and may eventually lead to a cure for ED. The following review will highlight our current understanding of endothelial-specific gene and stem cell-based therapies performed to date in a number of experimental animal models.

Cytokine interplay among the diseased retina, inflammatory cells and mesenchymal stem cells-a clue to stem cell-based therapy

Retinal degenerative disorders,such as diabetic retinopathy,retinitis pigmentosa,age-related macular degeneration or glaucoma,represent the most common causes of loss of vision and blindness.In spite of intensive research,treatment options to prevent,stop or cure these diseases are limited.Newer therapeutic approaches are offered by stem cell-based therapy.To date,various types of stem cells have been evaluated in a range of models.Among them,mesenchymal stem/stromal cells(MSCs)derived from bone marrow or adipose tissue and used as autologous cells have been proposed to have the potential to attenuate the negative manifestations of retinal diseases.MSCs delivered to the vicinity of the diseased retina can exert local anti-inflammatory and repairpromoting/regenerative effects on retinal cells.However,MSCs also produce numerous factors that could have negative impacts on retinal regeneration.The secretory activity of MSCs is strongly influenced by the cytokine environment.Therefore,the interactions among the molecules produced by the diseased retina,cytokines secreted by inflammatory cells and factors produced by MSCs will decide the development and propagation of retinal diseases.Here we discuss the interactions among cytokines and other factors in the environment of the diseased retina treated by MSCs,and we present results supporting immunoregulatory and trophic roles of molecules secreted in the vicinity of the retina during MSC-based therapy.

Review:On dendritic cell-based therapy for cancers

Dendritic cells (DCs), the most prevalent antigen-presenting cell in vivo, had been widely characterized in the last three decades. DCs are present in almost all tissues of the body and play cardinal roles in recognition of microbial agents,autoantigens, allergens and alloantigen. DCs process the microbial agents or their antigens and migrate to lymphoid tissues to present the antigenic peptide to lymphocytes. This leads to activation of antigen-specific lymphocytes. Initially, it was assumed that DCs are principally involved in the induction and maintenance of adaptive immune responses, but now it is evident that DCs also have important roles in innate immunity. These features make DCs very good candidates for therapy against various pathological conditions including malignancies. Initially, DC-based therapy was used in animal models of cancers. Data from these studies inspired considerable optimism and DC-based therapies was started in human cancers 8 years ago. In general,DC-based therapy has been found to be safe in patients with cancers, although few controlled trials have been conducted in this regard. Because the fundamentals principles of human cancers and animal models of cancers are different, the therapeutic efficacy of the ongoing regime of DC-based therapy in cancer patients is not satisfactory. In this review, we covered the various aspects that should be considered for developing better regime of DC-based therapy for human cancers.

Biomaterial application strategies to enhance stem cell-based therapy for ischemic stroke

BACKGROUND Ischemic stroke is a condition in which an occluded blood vessel interrupts blood flow to the brain and causes irreversible neuronal cell death.Transplantation of regenerative stem cells has been proposed as a novel therapy to restore damaged neural circuitry after ischemic stroke attack.However,limitations such as low cell survival rates after transplantation remain significant challenges to stem cellbased therapy for ischemic stroke in the clinical setting.In order to enhance the therapeutic efficacy of transplanted stem cells,several biomaterials have been developed to provide a supportable cellular microenvironment or functional modification on the stem cells to optimize their reparative roles in injured tissues or organs.AIM To discuss state-of-the-art functional biomaterials that could enhance the therapeutic potential of stem cell-based treatment for ischemic stroke and provide detailed insights into the mechanisms underlying these biomaterial approaches.METHODS The PubMed,Science Direct and Scopus literature databases were searched using the keywords of“biomaterial”and“ischemic stroke”.All topically-relevant articles were then screened to identify those with focused relevance to in vivo,in vitro and clinical studies related to“stem cells”OR“progenitor cells”OR“undifferentiated cells”published in English during the years of 2011 to 2022.The systematic search was conducted up to September 30,2022.RESULTS A total of 19 articles matched all the inclusion criteria.The data contained within this collection of papers comprehensively represented 19 types of biomaterials applied on seven different types of stem/progenitor cells,namely mesenchymal stem cells,neural stem cells,induced pluripotent stem cells,neural progenitor cells,endothelial progenitor cells,neuroepithelial progenitor cells,and neuroblasts.The potential major benefits gained from the application of biomaterials in stem cell-based therapy were noted as induction of structural and functional modifications,increased stem cell retention rate in the hostile ischemic microenvironment,and promoting the secretion of important cytokines for reparative mechanisms.CONCLUSION Biomaterials have a relatively high potential for enhancing stem cell therapy.Nonetheless,there is a scarcity of evidence from human clinical studies for the efficacy of this bioengineered cell therapy,highlighting that it is still too early to draw a definitive conclusion on efficacy and safety for patient usage.Future in-depth clinical investigations are necessary to realize translation of this therapy into a more conscientious and judicious evidence-based therapy for clinical application.

Cell-based therapy for management of osteoarthritis

Osteoarthritis(OA)is a most common form of degenerative joint disease,primarily characterized by the degradation of articular cartilage,subchondral sclerosis and inflammation of the synovial membrane.Mesenchymal stem cells(MSCs),a multipotent adult stem cell population,can be isolated from many connective tissue lineages,including those of the diarthrodial joint.Joint-resident MSCs or MSC-like progenitor cells contribute to the maintenance of healthy microenvironment or to the response to trauma.The onset of degenerative changes in the joint related to abnormal condition or depletion of these endogenous MSCs and native host hyaline cartilage cells,leading to limited selfrepair potential of the joint and advance of the degradation.To date,no acknowledged medical treatment strategies,including non-operative and classical surgical techniques,are efficient in restoring normal anatomy and function of hyaline cartilage in OA.This highlights an urgent need for better celled-based therapeutic strategies that supplement these functional cel s exogenously to recover the tissue homeostasis and repair in joint cavity via chondrogenic and anti-in fl ammatory functions.In this review we focus on the role of native MSCs in healthy or OA joint and recent progress in cel-based researches utilizing culture-expanded chondrocytes,pluripotent stem cel s,or MSCs from different sources for treating OA.

Importance of the stem cell microenvironment for ophthalmological cell-based therapy

Cell therapy is a promising treatment for diseases that are caused by cell degeneration or death. The cells for clinical transplantation are usually obtained by culturing healthy allogeneic or exogenous tissue invitro. However, for diseases of the eye, obtaining the adequate number of cells for clinical transplantation is difficult due to the small size of tissue donors and the frequent needs of long-term amplification of cells in vitro, which results in low cell viability after transplantation. In addition, the transplanted cells often develop fibrosis or degrade and have very low survival. Embryonic stem cells(ESCs) and induced pluripotent stem cells(i PS) are also promising candidates for cell therapy. Unfortunately, the differentiation of ESCs can bring immune rejection, tumorigenicity and undesired differentiated cells, limiting its clinical application. Although i PS cells can avoid the risk of immune rejection caused by ES cell differentiation post-transplantation, the low conversion rate, the risk of tumor formation and the potentially unpredictable biological changes that could occur through genetic manipulation hinder its clinical application. Thus, the desired clinical effect of cell therapy is impaired by these factors. Recent research findings recognize that the reason for low survival of the implanted cells not only depends on the seeded cells, but also on the cell microenvironment, which determines the cell survival, proliferation and even reverse differentiation. When used for cell therapy, the transplanted cells need a specific three-dimensional structure to anchor and specific extra cellular matrix components in addition to relevant cytokine signaling to transfer the required information to support their growth. These structures present in the matrix in which the stem cells reside are known as the stem cell microenvironment. The microenvironment interaction with the stem cells provides the necessary homeostasis for cell maintenance and growth. A large number of studies suggest that to explore how to reconstruct the stem cell microenvironment and strengthen its combination with the transplanted cells are key steps to successful cell therapy. In this review, we will describe the interactions of the stem cell microenvironment with the stem cells, discuss the importance of the stem cell microenvironment for cell-based therapy in ocular diseases, and introduce the progress of stem cell-basedtherapy for ocular diseases.

Stem cell-based ischemic stroke therapy:Novel modifications and clinical challenges

Ischemic stroke(IS)causes severe disability and high mortality worldwide.Stem cell(SC)therapy exhibits unique therapeutic potential for IS that differs from current treatments.SC’s cell homing,differentiation and paracrine abilities give hope for neuroprotection.Recent studies on SC modification have enhanced therapeutic effects for IS,including gene transfection,nanoparticle modification,biomaterial modification and pretreatment.Thesemethods improve survival rate,homing,neural differentiation,and paracrine abilities in ischemic areas.However,many problems must be resolved before SC therapy can be clinically applied.These issues include production quality and quantity,stability during transportation and storage,as well as usage regulations.Herein,we reviewed the brief pathogenesis of IS,the“multi-mechanism”advantages of SCs for treating IS,various SC modification methods,and SC therapy challenges.We aim to uncover the potential and overcome the challenges of using SCs for treating IS and convey innovative ideas for modifying SCs.

The advantages of multi-level omics research on stem cell-based therapies for ischemic stroke

Stem cell transplantation is a potential therapeutic strategy for ischemic stroke. However, despite many years of preclinical research, the application of stem cells is still limited to the clinical trial stage. Although stem cell therapy can be highly beneficial in promoting functional recovery, the precise mechanisms of action that are responsible for this effect have yet to be fully elucidated. Omics analysis provides us with a new perspective to investigate the physiological mechanisms and multiple functions of stem cells in ischemic stroke. Transcriptomic, proteomic, and metabolomic analyses have become important tools for discovering biomarkers and analyzing molecular changes under pathological conditions. Omics analysis could help us to identify new pathways mediated by stem cells for the treatment of ischemic stroke via stem cell therapy, thereby facilitating the translation of stem cell therapies into clinical use. In this review, we summarize the pathophysiology of ischemic stroke and discuss recent progress in the development of stem cell therapies for the treatment of ischemic stroke by applying multi-level omics. We also discuss changes in RNAs, proteins, and metabolites in the cerebral tissues and body fluids under stroke conditions and following stem cell treatment, and summarize the regulatory factors that play a key role in stem cell therapy. The exploration of stem cell therapy at the molecular level will facilitate the clinical application of stem cells and provide new treatment possibilities for the complete recovery of neurological function in patients with ischemic stroke.

Emerging Human Pluripotent Stem Cell-Based Human–Animal Brain Chimeras for Advancing Disease Modeling and Cell Therapy for Neurological Disorders

Human pluripotent stem cell(hPSC)models provide unprecedented opportunities to study human neurological disorders by recapitulating human-specific disease mechanisms.In particular,hPSC-based human–animal brain chimeras enable the study of human cell pathophysiology in vivo.In chimeric brains,human neural and immune cells can maintain human-specific features,undergo maturation,and functionally integrate into host brains,allowing scientists to study how human cells impact neural circuits and animal behaviors.The emerging human–animal brain chimeras hold promise for modeling human brain cells and their interactions in health and disease,elucidating the disease mechanism from molecular and cellular to circuit and behavioral levels,and testing the efficacy of cell therapy interventions.Here,we discuss recent advances in the generation and applications of using human–animal chimeric brain models for the study of neurological disorders,including disease modeling and cell therapy.

The potential of a combined cell-based therapy and rehabilitation approach for stroke recovery

Activation of neuroprotective and particularly later neurorestorative mechanisms after stroke attempts to restore or compensate for lost functions.This potentially opens a wide window for restorative therapies to promote brain repair and improve long-term functional recovery.Although extensively demonstrated in the preclinical setting,the efficacy of cell-based therapies in stroke patients has been modest at best,if any at all.Translational failure may be due to the ineffective survival and integration of transplanted cells in pro-death stroke microenvironments that are not conducive for the structural reconstruction of damaged brain tissue and repair-related network reorganization.Optimal systemic delivery,timing,cell product,and dose remain open as well.Fortunately,a better understanding of the brain plasticity mechanisms underlying stroke recovery has ushered in a combination approach of cell-based therapy and rehabilitation that is aimed at achieving additive,synergistic,or even maximal beneficial effects.This novel combination therapy is not only targeted at promoting exogenous and endogenous cell survival and augmenting stand-alone restorative mechanisms but also at utilizing rehabilitation to facilitate a graft–host structural and functional integration and plasticity that would effectively remodel stroke tissue and restitute lost functions.This review presents an overview of the combination of cell-based therapy and experimental rehabilitation in stroke models.It also discusses associated shortcomings as well as proposes strategies to address them and help facilitate the advancement of this combination approach.

Cell-based therapies for limbal stem cell deficiency: a literature review

Background and Objective:Limbal stem cell deficiency(LSCD)is characterized by the insufficiency of limbal stem cells to maintain the corneal epithelium.Severe cases of LSCD may be treated with limbal transplantation from healthy autologous or allogeneic limbal tissue.Multiple cell-based therapies have been studied as alternative treatments to improve success rates and minimize immunosuppressive regimens after allogeneic transplants.In this review,we describe the success rates,and complications of different cell-based therapies for LSCD.We also discuss each therapy’s relative strengths and weaknesses,their history in animal and human studies,and their effectiveness compared to traditional transplants.Methods:PubMed was searched for publications using the terms LSCD,cell-based therapy,cultivated limbal epithelial transplantation(CLET),cultivated oral mucosal epithelial transplantation(COMET),and mesenchymal stem cells from 1989 to August 2022.Inclusion criteria were English language articles.Exclusion criteria were non-English language articles.Key Content and Findings:current cell-based therapies for LSCD are CLET and non-limbal epithelial cells.Non-limbal epithelial cell methods include COMET,conjunctival epithelial autografts,and mesenchymal stem/stromal cells(MSCs).Moreover,several alternative potential sources of non-limbal cells have described,including induced pluripotent stem cells(iPSCs),human embryonic stem cells(hESCs),human dental pulp stem cells,hair follicle bulge-derived epithelial stem cells,amniotic membrane epithelial cells,and human umbilical cord lining epithelial cells.Conclusions:Cell-based therapies are a promising treatment modality for LSCD.While CLET is currently the only approved cell-based therapy and is only approved in the European Union,more novel methods have also been shown to be effective in human or animal studies thus far.Non-limbal epithelial cells such as COMET are also an alternative treatment to allogeneic transplants especially as a surface stabilizing procedure.iPSCs are currently being studied in early phase trials and have the potential to revolutionize the way LSCD is treated.Lastly,cell-based therapies for restoring the limbal niche such as mesenchymal stem cells have also shown promising results in the first human proof-of-concept study.Several potential sources of non-limbal cells are under investigation.

Three-dimensional cell-based strategies for liver regeneration

Liver regeneration and the development of effective therapies for liver failure remain formidable challenges in modern medicine.In recent years,the utilization of 3D cell-based strategies has emerged as a promising approach for addressing these urgent clinical requirements.This review provides a thorough analysis of the application of 3D cell-based approaches to liver regeneration and their potential impact on patients with end-stage liver failure.Here,we discuss various 3D culture models that incorporate hepatocytes and stem cells to restore liver function and ameliorate the consequences of liver failure.Furthermore,we explored the challenges in transitioning these innovative strategies from preclinical studies to clinical applications.The collective insights presented herein highlight the significance of 3D cell-based strategies as a transformative paradigm for liver regeneration and improved patient care.

Mesenchymal stem cell-based therapy for burn wound healing

Burns,with their high incidence and mortality rates,have a devastating effect on patients.There are still huge challenges in the management of burns.Mesenchymal stem cells(MSCs),which have multidirectional differentiation potential,have aroused interest in exploring the capacity for treating different intractable diseases due to their strong proliferation,tissue repair,immune tolerance and paracrine abilities,among other features.Currently,several animal studies have shown that MSCs play various roles and have beneficial effects in promoting wound healing,inhibiting burn inflammation and preventing the formation of pathological scars during burn healing process.The substances MSCs secrete can act on peripheral cells and promote burn repair.According to preclinical research,MSC-based treatments can effectively improve burn wound healing and reduce pain.However,due to the small number of patients and the lack of controls,treatment plans and evaluation criteria vary widely,thus limiting the value of these clinical studies.Therefore,to better evaluate the safety and effectiveness of MSC-based burn treatments,standardization of the application scheme and evaluation criteria of MSC therapy in burn treatment is required in the future.In addition,the combination of MSC pretreatment and dressing materials are also conducive to improving the therapeutic effect of MSCs on burns.In this article,we review current animal research and clinical trials based on the use of stem cell therapy for treating burns and discuss the main challenges and coping strategies facing future clinical applications.

Potential of transposon-mediated cellular reprogramming towards cell-based therapies

Induced pluripotent stem(iPS)cells present a seminal discovery in cell biology and promise to support innovative treatments of so far incurable diseases.To translate iPS technology into clinical trials,the safety and stability of these reprogrammed cells needs to be shown.In recent years,different non-viral transposon systems have been developed for the induction of cellular pluripotency,and for the directed differentiation into desired cell types.In this review,we summarize the current state of the art of different transposon systems in iPS-based cell therapies.

Drug-and cell-based therapies for targeting neuroinflammation in traumatic brain injury

TBI pathology： Traumatic brain injury （TBI） is caused by an external force to the head, resulting in trauma to the brain. Approximately 1.7 million Americans suffer from TBI every year. Out of the 1.7 million suffering from TBI, an estimated 52,000 injuries result in death, leaving a mass amount of peo- ple with symptoms that could last a few days, a few years, or their entire life （Faul et al., 2010）. TBI can be classified as mild, moderate and severe. Depending on the classification and the extent of the injury, TBI can cause both physical symptoms and cognitive disorders （Lozano et al., 2015）.