Paracrine action accounts for marked protection of ischemic heart by Akt-modified mesenchymal stem cells

The therapeutic efficacy and clinical translation of mesenchymal stem cell-derived exosomes in cardiovascular diseases

Exosomes, mainly derived from mesenchymal stem cells, provide a good reference for cardiac function repair and clinical application in cardiac and vascular diseases by regulating cardiomyocyte viability, inflammatory levels, angiogenesis, and ventricular remodeling after a heart injury. This review presents the cardioprotective efficacy of mesenchymal stem cell-originated exosomes and explores the underlying molecular mechanisms. Furthermore, we expound on several efficient approaches to transporting exosomes into the heart in clinical application and comment on the advantages and disadvantages of each method.

EV products obtained from iPSC-derived MSCs show batch-to-batch variations in their ability to modulate allogeneic immune responses in vitro

Mesenchymal stromal cells (MSCs) have demonstrated therapeutic potential in diverse clinical settings, largely due to their ability to produce extracellular vesicles (EVs). These EVs play a pivotal role in modulating immune responses, transforming pro-inflammatory cues into regulatory signals that foster a pro-regenerative milieu. Our previous studies identified the variability in the immunomodulatory effects of EVs sourced from primary human bone marrow MSCs as a consistent challenge. Given the limited proliferation of primary MSCs, protocols were advanced to derive MSCs from GMP-compliant induced pluripotent stem cells (iPSCs), producing iPSC-derived MSCs (iMSCs) that satisfied rigorous MSC criteria and exhibited enhanced expansion potential. Intriguingly, even though obtained iMSCs contained the potential to release immunomodulatory active EVs, the iMSC-EV products displayed batch-to-batch functional inconsistencies, mirroring those from bone marrow counterparts. We also discerned variances in EV-specific protein profiles among independent iMSC-EV preparations. Our results underscore that while iMSCs present an expansive growth advantage, they do not overcome the persistent challenge of functional variability of resulting MSC-EV products. Once more, our findings accentuate the crucial need for batch-to-batch functional testing, ensuring discrimination of effective and ineffective MSC-EV products for considered downstream applications.

Prospective applications of extracellular vesicle-based therapies in regenerative medicine: implications for the use of dental stem cell-derived extracellular vesicles

In the 21st century, research on extracellular vesicles (EVs) has made remarkable advancements. Recently, researchers have uncovered the exceptional biological features of EVs, highlighting their prospective use as therapeutic targets, biomarkers, innovative drug delivery systems, and standalone therapeutic agents. Currently, mesenchymal stem cells stand out as the most potent source of EVs for clinical applications in tissue engineering and regenerative medicine. Owing to their accessibility and capability of undergoing numerous differentiation inductions, dental stem cell-derived EVs (DSC-EVs) offer distinct advantages in the field of tissue regeneration. Nonetheless, it is essential to note that unmodified EVs are currently unsuitable for use in the majority of clinical therapeutic scenarios. Considering the high feasibility of engineering EVs, it is imperative to modify these EVs to facilitate the swift translation of theoretical knowledge into clinical practice. The review succinctly presents the known biotherapeutic effects of odontogenic EVs and the underlying mechanisms. Subsequently, the current state of functional cargo loading for engineered EVs is critically discussed. For enhancing EV targeting and in vivo circulation time, the review highlights cutting-edge engineering solutions that may help overcome key obstacles in the clinical application of EV therapeutics. By presenting innovative concepts and strategies, this review aims to pave the way for the adaptation of DSC-EVs in regenerative medicine within clinical settings.

Adipose stromal cells bioproducts as cell-free therapies: manufacturing and therapeutic dose determine in vitro functionality

BACKGROUND

Extracellular vesicles (EV) are considered a cell-free alternative to mesenchymal stromal cell (MSC) therapy. Numerous reports describe the efficacy of EV in conferring immunomodulation and promoting angiogenesis, yet others report these activities to be conveyed in EV-free bioproducts. We hypothesized that this discrepancy may depend either on the method of isolation or rather the relative impact of the individual bioactive components within the MSC secretome.

METHODS

To answer this question, we performed an inter-laboratory study evaluating EV generated from adipose stromal cells (ASC) by either sequential ultracentrifugation (UC) or size-exclusion chromatography (SEC). The effect of both EV preparations on immunomodulation and angiogenesis in vitro was compared to that of the whole secretome and of the EV-free protein fraction after SEC isolation.

RESULTS

In the current study, neither the EV preparations, the secretome or the protein fraction were efficacious in inhibiting mitogen-driven T cell proliferation. However, EV generated by SEC stimulated macrophage phagocytic activity to a similar extent as the secretome. In turn, tube formation and wound healing were strongly promoted by the ASC secretome and protein fraction, but not by EV. Within the secretome/protein fraction, VEGF was identified as a potential driver of angiogenesis, and was absent in both EV preparations.

CONCLUSIONS

Our data indicate that the effects of ASC on immunomodulation and angiogenesis are EV-independent. Specific ASC-EV effects need to be dissected for their use as cell-free therapeutics.

Potential of mesenchymal stem cell-derived conditioned medium/secretome as a therapeutic option for ocular diseases

Research has shown that the therapeutic effect of mesenchymal stem cells (MSCs) is partially due to its secreted factors as opposed to the implantation of the cells into the treated tissue or tissue replacement. MSC secretome, especially in the form of conditioned medium (MSC-CM) is now being explored as an alternative to MSCs transplantation. Despite the observed benefits of MSC-CM, only a few clinical trials have evaluated it and other secretome components in the treatment of eye diseases. This review provides insight into the potential therapeutic use of MSC-CM in eye conditions, such as corneal diseases, dry eye, glaucoma, retinal diseases and uveitis. We discuss the current evidence, some limitations, and the progress that remains to be achieved before clinical translation becomes possible.

New treatment methods for myocardial infarction

For a long time, cardiovascular clinicians have focused their research on coronary atherosclerotic cardiovascular disease and acute myocardial infarction due to their high morbidity, high mortality, high disability rate, and limited treatment options. Despite the continuous optimization of the therapeutic methods and pharmacological therapies for myocardial ischemia-reperfusion, the incidence rate of heart failure continues to increase year by year. This situation is speculated to be caused by the current therapies, such as reperfusion therapy after ischemic injury, drugs, rehabilitation, and other traditional treatments, that do not directly target the infarcted myocardium. Consequently, these therapies cannot fundamentally solve the problems of myocardial pathological remodeling and the reduction of cardiac function after myocardial infarction, allowing for the progression of heart failure after myocardial infarction. Coupled with the decline in mortality caused by acute myocardial infarction in recent years, this combination leads to an increase in the incidence of heart failure. As a new promising therapy rising at the beginning of the twenty-first century, cardiac regenerative medicine provides a new choice and hope for the recovery of cardiac function and the prevention and treatment of heart failure after myocardial infarction. In the past two decades, regeneration engineering researchers have explored and summarized the elements, such as cells, scaffolds, and cytokines, required for myocardial regeneration from all aspects and various levels day and night, paving the way for our later scholars to carry out relevant research and also putting forward the current problems and directions for us. Here, we describe the advantages and challenges of cardiac tissue engineering, a contemporary innovative therapy after myocardial infarction, to provide a reference for clinical treatment.

Biodistribution of mesenchymal stromal cell-derived extracellular vesicles administered during acute lung injury

BACKGROUND

Mesenchymal stromal cell-derived extracellular vesicles (MSC-EVs) are a promising cell-free therapy for acute lung injury (ALI). To date, no studies have investigated their biodistribution in ALI or discerned the timing of administration for maximal lung targeting, which are crucial considerations for clinical translation. Our study aimed to characterize a mouse model of ALI and establish the distribution kinetics and optimal timing of MSC-EV delivery during lung injury.

METHODS

MSC-EVs were isolated by ultracentrifugation alone (U/C) or tangential flow filtration with ultracentrifugation (TFF-U/C) and characterized by nanoparticle tracking analysis and western blot. A lipopolysaccharide (LPS)-induced mouse model of ALI was established to study the inflammatory response over 72 h. ALI was assessed by histological lung injury score, bronchoalveolar lavage fluid cell count and inflammatory cytokines. For biodistribution studies, ALI mice were intravenously administered fluorescently labeled MSC-EVs to determine the optimal timing of administration and organ-specific biodistribution. Live in vivo and ex vivo fluorescence imaging was conducted at various timepoints post-EV injection.

RESULTS

EVs isolated by either ultracentrifugation alone or TFF-U/C displayed comparable size distribution (~ 50-350 nm) and EV marker expression (CD63/81). TFF-U/C generated a 5.4-fold higher particle concentration and 3.9-fold higher total protein when compared to ultracentrifugation alone. From the inflammatory time-course study, cell count and IL-1β peaked in bronchoalveolar lavage fluid at 24 h after ALI induction. MSC-EVs delivered at 24 h (as opposed to 0.5 h, 5 h or 10 h) after disease induction resulted in a 2.7-4.4-fold higher lung uptake of EVs. Biodistribution studies comparing organ-specific MSC-EV uptake showed progressive lung accumulation up to 48 h post-delivery (threefold higher than the spleen/liver), with a decline at 72 h. Importantly, lung EV fluorescence at 48 h in ALI mice was significantly elevated as compared to control mice. The lung tropism of MSC-EVs was further validated as therapeutically inert EVs derived from HEK293T cells accumulated mainly to the spleen and liver with a 5.5-fold lower distribution to the lungs as compared to MSC-EVs.

CONCLUSION

MSC-EVs exhibit maximal lung accumulation when administered during heightened inflammation at 24 h after ALI induction. This lung tropism suggests that MSC-EVs may serve as a practical rescue treatment for acute inflammatory respiratory conditions.

Mesenchymal STRO-1/STRO-3+ precursor cells for the treatment of chronic heart failure with reduced ejection fraction

The heart is susceptible to proinflammatory and profibrotic responses after myocardial injury, leading to further worsening of cardiac dysfunction. Important developments in the management of heart failure with reduced ejection fraction have reduced morbidity and mortality; however, these therapies focus on optimizing cardiac function through hemodynamic and neurohormonal pathways and not by repairing the underlying cardiac injury. The potential of cell-based therapy to reverse cardiac injury has received substantial attention. Herein are examined the phase II and III studies of bone marrow-derived mesenchymal STRO-1+ or STRO-1/STRO-3+ precursor cells in patients with ischemic and nonischemic heart failure with reduced ejection fraction, addressing the safety and efficacy of cell-based therapy throughout multiple clinical trials, the optimal dose and the steps toward revolutionizing the treatment of heart failure.

Extracellular Vesicle Heterogeneity and Its Impact for Regenerative Medicine Applications

Extracellular vesicles (EVs) are cell-derived membrane-enclosed particles that are involved in physiologic and pathologic processes. EVs are increasingly being studied for therapeutic applications in the field of regenerative medicine. Therapeutic application of stem cell-derived EVs has shown great potential to stimulate tissue repair. However, the exact mechanisms through which they induce this effect have not been fully clarified. This may to a large extent be attributed to a lack of knowledge on EV heterogeneity. Recent studies suggest that EVs represent a heterogeneous population of vesicles with distinct functions. The heterogeneity of EVs can be attributed to differences in their biogenesis, and as such, they can be classified into distinct populations that can then be further subcategorized into various subpopulations. A better understanding of EV heterogeneity is crucial for elucidating their mechanisms of action in tissue regeneration. This review provides an overview of the latest insights on EV heterogeneity related to tissue repair, including the different characteristics that contribute to such heterogeneity and the functional differences among EV subtypes. It also sheds light on the challenges that hinder clinical translation of EVs. Additionally, innovative EV isolation techniques for studying EV heterogeneity are discussed. Improved knowledge of active EV subtypes would promote the development of tailored EV therapies and aid researchers in the translation of EV-based therapeutics to the clinic. SIGNIFICANCE STATEMENT: Within this review we discuss the differences in regenerative properties of extracellular vesicle (EV) subpopulations and implications of EV heterogeneity for development of EV-based therapeutics. We aim to provide new insights into which aspects are leading to heterogeneity in EV preparations and stress the importance of EV heterogeneity studies for clinical applications.

Stem cell-conditioned medium is a promising treatment for Alzheimer's disease

BACKGROUND AND AIM

Alzheimer's disease (AD), a prevalent progressive neurodegenerative disease, is mainly characterized by dementia, memory loss, and cognitive disorder. Rising research was performed to develop pharmacological or non-pharmacological approaches to treat or improve AD complications. Mesenchymal stem cells (MSCs) are stromal cells that can self-renew and exhibit multilineage differentiation. Recent evidence suggested that some of the therapeutic effects of MSCs are mediated by the secreted paracrine factors. These paracrine factors, called MSC- conditioned medium (MSC-CM), may stimulate endogenous repair, promote angio- and artery genesis, and reduce apoptosis through paracrine mechanisms. The current study aims to systematically review the advantages of MSC-CM to the development of research and therapeutic concepts for AD management.

MATERIAL AND METHODS

The present systematic review was performed using PubMed, Web of Science, and Scopus from April 2020 to May 2022 following the "Preferred Reporting Items for Systematic Reviews" (PRISMA) guidelines. The keywords, including "Conditioned medium OR Conditioned media OR Stem cell therapy" AND "Alzheimer's," was searched, and finally, 13 papers were extracted.

RESULTS

The obtained data revealed that MSC-CMs might positively affect neurodegenerative diseases prognosis, especially AD, through various mechanisms, including a decrease in neuro-inflammation, reduction of oxidative stress and Aβ formation, modulation of Microglia function and count, reduction of apoptosis, induction of synaptogenesis and neurogenesis. Also, the results showed that MSC-CM administration could significantly improve cognitive and memory function, increase the expression of neurotrophic factors, decrease the production of pro-inflammatory cytokines, improve mitochondrial function, reduce cytotoxicity, and increase neurotransmitter levels.

CONCLUSION

While inhibiting the induction of neuroinflammation could be considered the first therapeutic effect of CMs, the prevention of apoptosis could be regarded as the most crucial effect of CMs on AD improvement.

Genetic and Pharmacological YAP Activation Induces Proliferation and Improves Survival in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Cardiomyocyte loss following myocardial infarction cannot be addressed with current clinical therapies. Cell therapy with induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) is a potential approach to replace cardiomyocyte loss. However, engraftment rates in pre-clinical studies have been low, highlighting a need to refine current iPSC-CM technology. In this study, we demonstrated that inducing Yes-associated protein (YAP) by genetic and pharmacological approaches resulted in increased iPSC-CM proliferation and reduced apoptosis in response to oxidative stress. Interestingly, iPSC-CM maturation was differently affected by each strategy, with genetic activation of YAP resulting in a more immature cardiomyocyte-like phenotype not witnessed upon pharmacological YAP activation. Overall, we conclude that YAP activation in iPSC-CMs enhances cell survival and proliferative capacity. Therefore, strategies targeting YAP, or its upstream regulator the Hippo signalling pathway, could potentially be used to improve the efficacy of iPSC-CM technology for use as a future regenerative therapy in myocardial infarction.

Mesenchymal Stromal Cells: Heterogeneity and Therapeutical Applications

Mesenchymal stromal cells nowadays emerge as a major player in the field of regenerative medicine and translational research. They constitute, with their derived products, the most frequently used cell type in different therapies. However, their heterogeneity, including different subpopulations, the anatomic source of isolation, and high donor-to-donor variability, constitutes a major controversial issue that affects their use in clinical applications. Furthermore, the intrinsic and extrinsic molecular mechanisms underlying their self-renewal and fate specification are still not completely elucidated. This review dissects the different heterogeneity aspects of the tissue source associated with a distinct developmental origin that need to be considered when generating homogenous products before their usage for clinical applications.

Driving force of deteriorated cellular environment in heart failure: Metabolic remodeling

Heart Failure (HF) has been one of the leading causes of death worldwide. Though its latent mechanism and therapeutic manipulation are updated and developed ceaselessly, there remain great gaps in the cognition of heart failure. High morbidity and readmission rates among HF patients are waiting to be addressed. Recent studies have found that myocardial energy metabolism was closely related to heart failure, in which substrate utilization, as well as intermediate metabolism disorders, insulin resistance, oxidative stress, and mitochondrial dysfunction, might underlie systolic dysfunction and progression of HF. This article centers on the changes and counteraction of cardiac energy metabolism in the failing heart. Therefore, targeting impaired energy provision is of great potential in the treatment of HF. And shifting the objective from traditional neurohormones to improving the cellular environment is expected to further optimize the management of HF.

HSF-1 enhances cardioprotective potential of stem cells via exosome biogenesis and their miRNA cargo enrichment

Stem cell therapy provides a hope to no option heart disease patient group. Stem cells work via different mechanisms of which paracrine mechanism is reported to justify most of the effects. Therefore, identifying the control arms for paracrine cocktail production is necessary to tailor stem cell functions in disease contextual manner. In this study, we describe a novel paracrine cocktail regulatory axis, in stem cells, to enhance their cardioprotective abilities. We identified that HSF1 knockout resulted in reduced cardiac regenerative abilities of mesenchymal stem cells (MSCs) while its overexpression had opposite effects. Altered exosome biognesis and their miRNA cargo enrichment were found to be underlying these altered regenerative abilities. Decreased production of exosomes by MSCs accompanied their loss of HSF1 and vice versa. Moreover, the exosomes derived from HSF1 depleted MSCs showed significantly reduced candidate miRNA expression (miR-145, miR-146, 199-3p, 199b and miR-590) compared to those obtained from HSF1 overexpressing MSCs. We further discovered that HSF1 mediates miRNAs' enrichment into exosomes via Y binding protein 1 (YBX1) and showed, by loss and gain of function strategies, that miRNAs' enrichment in mesenchymal stem cell derived exosomes is deregulated with altered YBX1 expression. It was finally demonstrated that absence of YBX1 in MSCs, with normal HSF1 expression, resulted in significant accumulation of candidate miRNAs into the cells. Together, our data shows that HSF1 plays a critical role in determining the regenerative potential of stem cells. HSF1 does that by affecting exosome biogenesis and miRNA cargo sorting via regulation of YBX1 gene expression.

A roadmap from research to clinical testing of mesenchymal stromal cell exosomes in the treatment of psoriasis

The most clinically trialed cells, mesenchymal stromal cells (MSCs), are now known to mainly exert their therapeutic activity through paracrine secretions, which include exosomes. To mitigate potential regulatory concerns on the scalability and reproducibility in the preparations of MSC exosomes, MSC exosomes were produced using a highly characterized MYC-immortalized monoclonal cell line. These cells do not form tumors in athymic nude mice or exhibit anchorage-independent growth, and their exosomes do not carry MYC protein or promote tumor growth. Unlike intra-peritoneal injections, topical applications of MSC exosomes in a mouse model of IMQ-induced psoriasis alleviate interleukin (IL)-17, IL-23 and terminal complement complex, C5b9 in psoriatic skin. When applied on human skin explants, fluorescence from covalently labeled fluorescent MSC exosomes permeated and persisted in the stratum corneum for about 24 hours with negligible exit out of the stratum corneum into the underlying epidermis. As psoriatic stratum corneums are uniquely characterized by activated complements and Munro microabscesses, we postulated that topically applied exosomes permeate the psoriatic stratum corneum to inhibit C5b9 complement complex through CD59, and this inhibition attenuated neutrophil secretion of IL-17. Consistent with this, we demonstrated that assembly of C5b9 on purified human neutrophils induced IL-17 secretion and this induction was abrogated by MSC exosomes, which was in turn abrogated by a neutralizing anti-CD 59 antibody. We thus established the mechanism of action for the alleviation of psoriatic IL-17 by topically applied exosomes.

Stem cell-derived extracellular vesicle-based therapy for nerve injury: A review of the molecular mechanisms

Recent evidence suggests that stem cell therapy has beneficial effects on nerve damage. These beneficial effects were subsequently found to be exerted in part in a paracrine manner by the release of extracellular vesicles. Stem cell-secreted extracellular vesicles have shown great potential to reduce inflammation and apoptosis, optimize the function of Schwann cells, regulate genes related to regeneration, and improve behavioral performance after nerve damage. This review summarizes the current knowledge on the effect of stem cell-derived extracellular vesicles on neuroprotection and regeneration along with their molecular mechanisms after nerve damage.

Mesenchymal Stem Cell Conditioned Medium Modulates Inflammation in Tenocytes: Complete Conditioned Medium Has Superior Therapeutic Efficacy than Its Extracellular Vesicle Fraction

Tendinopathy, a prevalent overuse injury, lacks effective treatment options, leading to a significant impact on quality of life and socioeconomic burden. Mesenchymal stem/stromal cells (MSCs) and their secretome, including conditioned medium (CM) and extracellular vesicles (EVs), have shown promise in tissue regeneration and immunomodulation. However, it remains unclear which components of the secretome contribute to their therapeutic effects. This study aimed to compare the efficacy of CM, EVs, and the soluble protein fraction (PF) in treating inflamed tenocytes. CM exhibited the highest protein and particle concentrations, followed by PF and EVs. Inflammation significantly altered gene expression in tenocytes, with CM showing the most distinct separation from the inflamed control group. Treatment with CM resulted in the most significant differential gene expression, with both upregulated and downregulated genes related to inflammation and tissue regeneration. EV treatment also demonstrated a therapeutic effect, albeit to a lesser extent. These findings suggest that CM holds superior therapeutic efficacy compared with its EV fraction alone, emphasizing the importance of the complete secretome in tendon injury treatment.

Stress-induced senescence in mesenchymal stem cells: Triggers, hallmarks, and current rejuvenation approaches

Mesenchymal stem cells (MSCs) have emerged as promising cell-based therapies in the treatment of degenerative and inflammatory conditions. However, despite accumulating evidence of the breadth of MSC functional potency, their broad clinical translation is hampered by inconsistencies in therapeutic efficacy, which is at least partly due to the phenotypic and functional heterogeneity of MSC populations as they progress towards senescence in vitro. MSC senescence, a natural response to aging and stress, gives rise to altered cellular responses and functional decline. This review describes the key regenerative properties of MSCs; summarises the main triggers, mechanisms, and consequences of MSC senescence; and discusses current cellular and extracellular strategies to delay the onset or progression of senescence, or to rejuvenate biological functions lost to senescence.

Revolutionizing Radiotoxicity Management with Mesenchymal Stem Cells and Their Derivatives: A Focus on Radiation-Induced Cystitis

Although radiation therapy plays a crucial role in cancer treatment, and techniques have improved continuously, irradiation induces side effects in healthy tissue. Radiation cystitis is a potential complication following the therapeutic irradiation of pelvic cancers and negatively impacts patients' quality of life (QoL). To date, no effective treatment is available, and this toxicity remains a therapeutic challenge. In recent times, stem cell-based therapy, particularly the use of mesenchymal stem cells (MSC), has gained attention in tissue repair and regeneration due to their easy accessibility and their ability to differentiate into several tissue types, modulate the immune system and secrete substances that help nearby cells grow and heal. In this review, we will summarize the pathophysiological mechanisms of radiation-induced injury to normal tissues, including radiation cystitis (RC). We will then discuss the therapeutic potential and limitations of MSCs and their derivatives, including packaged conditioned media and extracellular vesicles, in the management of radiotoxicity and RC.

Genetically Engineered Artificial Microvesicles Carrying Nerve Growth Factor Restrains the Progression of Autoimmune Encephalomyelitis in an Experimental Mouse Model

Multiple sclerosis (MS) is an incurable, progressive chronic autoimmune demyelinating disease. Therapy for MS is based on slowing down the processes of neurodegeneration and suppressing the immune system of patients. MS is accompanied by inflammation, axon-degeneration and neurogliosis in the central nervous system. One of the directions for a new effective treatment for MS is cellular, subcellular, as well as gene therapy. We investigated the therapeutic potential of adipose mesenchymal stem cell (ADMSC) derived, cytochalasin B induced artificial microvesicles (MVs) expressing nerve growth factor (NGF) on a mouse model of multiple sclerosis experimental autoimmune encephalomyelitis (EAE). These ADMSC-MVs-NGF were tested using histological, immunocytochemical and molecular genetic methods after being injected into the tail vein of animals on the 14th and 21st days post EAE induction. ADMSC-MVs-NGF contained the target protein inside the cytoplasm. Their injection into the caudal vein led to a significant decrease in neurogliosis at the 14th and 21st days post EAE induction. Artificial ADMSC-MVs-NGF stimulate axon regeneration and can modulate gliosis in the EAE model.

Mesenchymal stromal cell-derived secretome-based therapy for neurodegenerative diseases: overview of clinical trials

BACKGROUND

Over the past few years, mesenchymal stromal cells (MSCs) have attracted a great deal of scientific attention owing to their promising results in the treatment of incurable diseases. However, there are several concerns about their possible side effects after direct cell transplantation, including host immune response, time-consuming cell culture procedures, and the dependence of cell quality on the donor, which limit the application of MSCs in clinical trials. On the other hand, it is well accepted that the beneficial effects of MSCs are mediated by secretome rather than cell replacement. MSC secretome refers to a variety of bioactive molecules involved in different biological processes, specifically neuro-regeneration.

MAIN BODY

Due to the limited ability of the central nervous system to compensate for neuronal loss and relieve disease progress, mesenchymal stem cell products may be used as a potential cure for central nervous system disorders. In the present study, the therapeutic effects of MSC secretome were reviewed and discussed the possible mechanisms in the three most prevalent central nervous system disorders, namely Alzheimer's disease, multiple sclerosis, and Parkinson's disease. The current work aimed to help discover new medicine for the mentioned complications.

CONCLUSION

The use of MSC-derived secretomes in the treatment of the mentioned diseases has encouraging results, so it can be considered as a treatment option for which no treatment has been introduced so far.

Extracellular vesicles: From bone development to regenerative orthopedics

Regenerative medicine aims to promote the replacement of tissues lost to damage or disease. While positive outcomes have been observed experimentally, challenges remain in their clinical translation. This has led to growing interest in applying extracellular vesicles (EVs) to augment or even replace existing approaches. Through the engineering of culture environments or direct/indirect manipulation of EVs themselves, multiple avenues have emerged to modulate EV production, targeting, and therapeutic potency. Drives to modulate release using material systems or functionalize implants for improved osseointegration have also led to outcomes that could have real-world impact. The purpose of this review is to highlight advantages in applying EVs for the treatment of skeletal defects, outlining the current state of the art in the field and emphasizing avenues for further investigation. Notably, the review identifies inconsistencies in EV nomenclature and outstanding challenges in defining a reproducible therapeutic dose. Challenges also remain in the scalable manufacture of a therapeutically potent and pure EV product, with a need to address scalable cell sources and optimal culture environments. Addressing these issues will be critical if we are to develop regenerative EV therapies that meet the demands of regulators and can be translated from bench to bedside.

Bioengineering extracellular vesicles: smart nanomaterials for bone regeneration

In the past decade, extracellular vesicles (EVs) have emerged as key regulators of bone development, homeostasis and repair. EV-based therapies have the potential to circumnavigate key issues hindering the translation of cell-based therapies including functional tissue engraftment, uncontrolled differentiation and immunogenicity issues. Due to EVs' innate biocompatibility, low immunogenicity, and high physiochemical stability, these naturally-derived nanoparticles have garnered growing interest as potential acellular nanoscale therapeutics for a variety of diseases. Our increasing knowledge of the roles these cell-derived nanoparticles play, has made them an exciting focus in the development of novel pro-regenerative therapies for bone repair. Although these nano-sized vesicles have shown promise, their clinical translation is hindered due to several challenges in the EV supply chain, ultimately impacting therapeutic efficacy and yield. From the biochemical and biophysical stimulation of parental cells to the transition to scalable manufacture or maximising vesicles therapeutic response in vivo, a multitude of techniques have been employed to improve the clinical efficacy of EVs. This review explores state of the art bioengineering strategies to promote the therapeutic utility of vesicles beyond their native capacity, thus maximising the clinical potential of these pro-regenerative nanoscale therapeutics for bone repair.

Conditioned media of deer antler stem cells accelerate regeneration of alveolar bone defects in rats

The destruction of periodontal alveolar bone (AB) caused by periodontitis is regarded as one of the major reasons for tooth loss. The inhibition of bone resorption and regeneration of lost AB are the desirable outcomes in clinical practice but remain in challenge. The use of mesenchymal stem cells (MSCs) is one current approach for achieving true restoration of AB defects (ABD). Antler stem cells (AnSC) are capable of renewing a huge mammalian bony appendage, the deer antler, suggesting an unparalleled potential for bone regeneration. Herein, we investigated the effectiveness of deer AnSCs conditioned medium (CM, AnSC-CM) for repair of surgically-created ABD using a rat model and sought to define the underlying mechanisms. The results showed that AnSC-CM effectively induced regeneration of AB tissue; the outcome was significantly better than human bone marrow mesenchymal stem cell conditioned medium (hBMSC-CM). AnSC-CM treatment upregulated osteogenic factors and downregulated osteoclastic differentiation factors; stimulated proliferation, migration and differentiation of resident MSCs toward osteogenic lineage cells; modulated macrophage polarization toward the M2 phenotype and suppressed osteoclastogenesis. That AnSC-CM resulted in better outcomes than hBMSC-CM in treating ABD was attributed to the cell compatibility as both AnSCs and AB tissue are neural crest-derived. In conclusion, the effects of AnSC-CM on AB tissue regeneration were achieved through both promotion of osteogenesis and inhibition of osteoclastogenesis. We believe that AnSC-CM is a candidate for effective treatment of ABD in dental clinical practice but will require investment in further development.

DPSC-Derived Extracellular Vesicles Promote Rat Jawbone Regeneration

Repair and functional reconstruction of large jawbone defects remain one of the challenges in the field of head and neck surgery. The recent progress in tissue engineering technologies and stem cell biology has significantly promoted the development of regenerative reconstruction of jawbone defects. The multiple trophic activities of extracellular vesicles (EVs) produced by mesenchymal stem cells (MSCs) may play a critical role in their therapeutic effects. Accumulating evidence has shown the promise of dental pulp stem cells (DPSCs) in bone regeneration, but less is known about the regenerative effects of DPSC-EVs on jawbone defects. The purpose of this study is to explore the osteogenic effects of DPSC-EVs on jawbone marrow-derived MSCs (JB-MSCs) in vitro and their osteoinductive effects in a mandibular bone defect model in rats. Our results showed that JB-MSCs could efficiently uptake DPSC-EVs, which in turn significantly promoted the expression of osteogenic genes, such as runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP), and osteocalcin (OCN), as well as the osteogenic differentiation capability of JB-MSCs. Meanwhile, we found that the pro-osteogenic effect in vitro induced by DPSC-EVs was comparable to that induced by BMP-2 (bone morphogenetic protein 2), currently the only Food and Drug Administration-approved osteoinductive growth factor. In vivo, animals that were locally treated with DPSC-EVs laden with a commercially available collagen membrane exhibited a relatively fast wound closure and increased new bone density at the mandible defects. Our results provide evidence for the osteogenic and osteoinductive effects of DPSC-EVs on jawbone regeneration. Due to the accessibility, rapid proliferation, and osteogenic propensity of DPSCs, DPSC-EVs may represent a safe cell-free therapeutic approach for craniofacial bone regeneration.

Ovarian rescue in women with premature ovarian insufficiency: facts and fiction

The ovary has a comparatively short functional lifespan compared with other organs, and genetic and pathological injuries can further shorten its functional life. Thus, preserving ovarian function should be considered in the context of women with threats to ovarian reserve, such as ageing, premature ovarian insufficiency (POI) and diminished ovarian reserve (DOR). Indeed, one-third of women with POI retain resting follicles that can be reactivated to produce competent oocytes, as proved by the in-vitro activation of dormant follicles. This paper discusses mechanisms and clinical data relating to new therapeutic strategies using ovarian fragmentation, stem cells or platelet-rich plasma to regain ovarian function in women of older age (>38 years) or with POI or DOR. Follicle reactivation techniques show promising experimental outcomes and have been successful in some cases, when POI is established or DOR diagnosed; however, there is scarce clinical evidence to warrant their widespread clinical use. Beyond these contexts, also discussed is how new insights into the biological mechanisms governing follicular dynamics and oocyte competence may play a role in reversing ovarian damage, as no technique modifies oocyte quality. Additional studies should focus on increasing follicle number and quality. Finally, there is a small but important subgroup of women lacking residual follicles and requiring oocyte generation from stem cells.

Bone-Targeting Exosome Mimetics Engineered by Bioorthogonal Surface Functionalization for Bone Tissue Engineering

Extracellular vesicles have received a great interest as safe biocarriers in biomedical engineering. There is a need to develop more efficient delivery strategies to improve localized therapeutic efficacy and minimize off-target adverse effects. Here, exosome mimetics (EMs) are reported for bone targeting involving the introduction of hydroxyapatite-binding moieties through bioorthogonal functionalization. Bone-binding ability of the engineered EMs is verified with hydroxyapatite-coated scaffolds and an ex vivo bone-binding assay. The EM-bound construct provided a biocompatible substrate for cell adhesion, proliferation, and osteogenic differentiation. Particularly, the incorporation of Smoothened agonist (SAG) into EMs greatly increased the osteogenic capacity through the activation of hedgehog signaling. Furthermore, the scaffold integrated with EM/SAG significantly improved in vivo reossification. Lastly, biodistribution studies confirmed the accumulation of systemically administered EMs in bone tissue. This facile engineering strategy could be a versatile tool to promote bone regeneration, offering a promising nanomedicine approach to the sophisticated treatment of bone diseases.

Stem cell-derived extracellular vesicles: A novel and potential remedy for primary ovarian insufficiency

Primary ovarian insufficiency (POI) is an essential cause of young female fertility loss. At present, there are many treatments for primary ovarian insufficiency, but due to the complexity of the pathogenesis of primary ovarian insufficiency, the efficacy still could not be satisfactory. Stem cell transplantation is a feasible intervention protocol for primary ovarian insufficiency. However, its wide application in the clinic is limited by some defects such as tumorigenic and controversial ethical issues. Stem cell-derived extracellular vesicles (EVs) represent an important mode of intercellular communication attracting increasing interest. It is well documented that stem cell-derived extracellular vesicles for primary ovarian insufficiency with exciting therapeutic effects. Studies have found that stem cell-derived extracellular vesicles could improve ovarian reserve, increase the growth of follicles, reduce follicle atresia, and restore hormone levels of FSH and E2. Its mechanisms include inhibiting ovarian granulosa cells (GCs) apoptosis, reactive oxygen species, and inflammatory response and promoting granulosa cells proliferation and angiogenesis. Thus, stem cell-derived extracellular vesicles are a promising and potential method for primary ovarian insufficiency patients. However, stem cell-derived extracellular vesicles are still a long way from clinical translation. This review will provide an overview of the role and the mechanisms of stem cell-derived extracellular vesicles in primary ovarian insufficiency, and further elaborate on the current challenges. It may suggest new directions for future research.

EVs vs. EVs: MSCs and Tregs as a source of invisible possibilities

Extracellular vesicles (EVs) are produced by various cells and exist in most biological fluids. They play an important role in cell-cell signaling, immune response, and tumor metastasis, and also have theranostic potential. They deliver many functional biomolecules, including DNA, microRNAs (miRNA), messenger RNA (mRNA), long non-coding RNA (lncRNA), lipids, and proteins, thus affecting different physiological processes in target cells. Decreased immunogenicity compared to liposomes or viral vectors and the ability to cross through physiological barriers such as the blood-brain barrier make them an attractive and innovative option as diagnostic biomarkers and therapeutic carriers. Here, we highlighted two types of cells that can produce functional EVs, namely, mesenchymal stem/stromal cells (MSCs) and regulatory T cells (Tregs), discussing MSC/Treg-derived EV-based therapies for some specific diseases including acute respiratory distress syndrome (ARDS), autoimmune diseases, and cancer.

Microneedle system for tissue engineering and regenerative medicine

Global increasing demand for high life quality and length facilitates the development of tissue engineering and regenerative medicine, which apply multidisciplinary theories and techniques to achieve the structural reconstruction and functional recovery of disordered or damaged tissues and organs. However, the clinical performances of adopted drugs, materials, and powerful cells in the laboratory are inescapably limited by the currently available technologies. To tackle the problems, versatile microneedles are developed as the new platform for local delivery of diverse cargos with minimal invasion. The efficient delivery, as well as painless and convenient procedure endow microneedles with good patient compliance in clinic. In this review, we first categorize different microneedle systems and delivery models, and then summarize their applications in tissue engineering and regenerative medicine mainly involving maintenance and rehabilitation of damaged tissues and organs. In the end, we discuss the advantages, challenges, and prospects of microneedles in depth for future clinical translations.

Bone marrow-derived mesenchymal stem cell-conditioned medium ameliorates diabetic foot ulcers in rats

OBJECTIVES

This study aimed to explore the effects of bone marrow-derived Mesenchymal Stem Cell-Conditioned Medium (MSC-CM) treating diabetic foot ulcers in rats.

METHODS

Models of T2DM rats were induced by a high-fat diet and intraperitoneal injection of STZ in SD rats. Models of Diabetic Foot Ulcers (DFUs) were made by operation on hind limbs in diabetic rats. Rats were divided into four groups (n = 6 for each group), i.e., Normal Control group (NC), Diabetes Control group (DM-C), MSC-CM group and Mesenchymal Stem Cells group (MSCs). MSC-CM group was treated with an injection of conditioned medium derived from preconditioned rats' bone marrow MSCs around ulcers. MSCs group were treated with an injection of rats' bone marrow MSCs. The other two groups were treated with an injection of PBS. After the treatment, wound closure, re-epithelialization (thickness of the stratum granulosums of the skin, by H&E staining), cell proliferation (Ki67, by IHC), angiogenesis (CD31, by IFC), autophagy (LC3B, by IFC and WB; autolysosome, by EM) and pyroptosis (IL-1β, NLRP3, Caspase-1, GSDMD and GSDMD-N, by WB) in ulcers were evaluated.

RESULTS

After the treatment wound area rate, IL-1β by ELISA, and IL-1β, Caspase-1, GSDMD and GSDMD-N by WB of MSC-CM group were less than those of DM group. The thickness of the stratum granulosums of the skin, proliferation index of Ki67, mean optic density of CD31 and LC3B by IFC, and LC3B by WB of MSC-CM group were more than those of DM group. The present analysis demonstrated that the injection of MSC-CM into rats with DFUs enhanced the wound-healing process by accelerating wound closure, promoting cell proliferation and angiogenesis, enhancing cell autophagy, and reducing cell pyroptosis in ulcers.

CONCLUSIONS

Studies conducted indicate that MSC-CM administration could be a novel cell-free therapeutic approach to treat DFUs accelerating the wound healing process and avoiding the risk of living cells therapy.

Extracellular Vesicles in Coronary Artery Disease

Coronary artery disease (CAD) is the leading cause of death and disability worldwide. Despite recent progress in the diagnosis and treatment of CAD, evidence gaps remain, including pathogenesis, the most efficient diagnostic strategy, prognosis of individual patients, monitoring of therapy, and novel therapeutic strategies. These gaps could all be filled by developing novel, minimally invasive, blood-based biomarkers. Potentially, extracellular vesicles (EVs) could fill such gaps. EVs are lipid membrane particles released from cells into blood and other body fluids. Because the concentration, composition, and functions of EVs change during disease, and because all cell types involved in the development and progression of CAD release EVs, currently available guidelines potentially enable reliable and reproducible measurements of EVs in clinical trials, offering a wide range of opportunities. In this chapter, we provide an overview of the associations reported between EVs and CAD, including (1) the role of EVs in CAD pathogenesis, (2) EVs as biomarkers to diagnose CAD, predict prognosis, and monitor therapy in individual patients, and (3) EVs as new therapeutic targets and/or drug delivery vehicles. In addition, we summarize the challenges encountered in EV isolation and detection, and the lack of standardization, which has hampered real clinical applications of EVs. Since most conclusions are based on animal models and single-center studies, the knowledge and insights into the roles and opportunities of EVs as biomarkers in CAD are still changing, and therefore, the content of this chapter should be seen as a snapshot in time rather than a final and complete compendium of knowledge on EVs in CAD.

Mesenchymal "stem" cells, or facilitators for the development of regenerative macrophages? Pericytes at the interface of wound healing

Cultured mesenchymal stromal cells are among the most used cells in clinical trials. Currently, their potential benefits include provision of mature cell types through differentiation, and secretion of various types of paracrine signaling molecules. Even though research on these cells has spanned some decades now, surprisingly, their therapeutic potential has not been fully translated into clinical practice yet, which calls for further understanding of their intrinsic nature and modes of action. In this review, after discussing pieces of evidence that suggest that some perivascular cells may exhibit mesenchymal stem cell characteristics in vivo, we examine the possibility that subpopulations of perivascular and/or adventitial cells activated after tissue injury behave as MSCs and contribute to the resolution of tissue injury by providing cues for the development of regenerative macrophages at injured sites. Under this perspective, an important contribution of cultured MSCs (or their acellular products, such as extracellular vesicles) used in cell therapies would be to instigate the development of M2-like macrophages that support the tissue repair process.

TNF-α Enhances the Therapeutic Effects of MenSC-Derived Small Extracellular Vesicles on Inflammatory Bowel Disease through Macrophage Polarization by miR-24-3p

Human menstrual blood-derived mesenchymal stem cells (MenSCs) and their secreted small extracellular vesicles (EVs) had been proven to relieve inflammation, tissue damage, and fibrosis in various organs. The microenvironment induced by inflammatory cytokines can promote mesenchymal stem cells (MSCs) to secrete more substances (including EVs) that could regulate inflammation. Inflammatory bowel disease (IBD) is a chronic idiopathic intestinal inflammation, the etiology and mechanism of which are unclear. At present, the existing therapeutic methods are ineffective for many patients and have obvious side effects. Hence, we explored the role of tumor necrosis factor α- (TNF-α-) pretreated MenSC-derived small EV (MenSCs-sEV^TNF-α ) in a mouse model of dextran sulfate sodium- (DSS-) induced colitis, expecting to find better therapeutic alterations. In this research, the small EVs of MenSCs were obtained by ultracentrifugation. MicroRNAs of small EVs derived from MenSCs before and after TNF-α treatment were sequenced, and the differential microRNAs were analyzed by bioinformatics. The small EVs secreted by TNF-α-stimulating MenSCs were more effective in colonic mice than those secreted directly by MenSCs, as evidenced by the results of histopathology analysis of colonic tissue, immunohistochemistry for tight junction proteins, and enzyme-linked immunosorbent assay (ELISA) for cytokine expression profiles in vivo. The process of MenSCs-sEV^TNF-α relieving colonic inflammation was accompanied by the polarization of M2 macrophages in the colon and miR-24-3p upregulation in small EVs. In vitro, both MenSC-derived sEV (MenSCs-sEV) and MenSCs-sEV^TNF-α reduced the expression of proinflammatory cytokines, and MenSCs-sEV^TNF-α can increase the portion of M2 macrophages. In conclusion, after TNF-α stimulation, the expression of miR-24-3p in small EVs derived from MenSCs was upregulated. MiR-24-3p was proved to target and downregulate interferon regulatory factor 1 (IRF1) expression in the murine colon and then promoted the polarization of M2 macrophages. The polarization of M2 macrophages in colonic tissues then reduced the damage caused by hyperinflammation.

New Opportunities in Heart Failure with Preserved Ejection Fraction: From Bench to Bedside… and Back

Heart failure with preserved ejection fraction (HFpEF) is a growing public health problem in nearly 50% of patients with heart failure. Therefore, research on new strategies for its diagnosis and management has become imperative in recent years. Few drugs have successfully improved clinical outcomes in this population. Therefore, numerous attempts are being made to find new pharmacological interventions that target the main mechanisms responsible for this disease. In recent years, pathological mechanisms such as cardiac fibrosis and inflammation, alterations in calcium handling, NO pathway disturbance, and neurohumoral or mechanic impairment have been evaluated as new pharmacological targets showing promising results in preliminary studies. This review aims to analyze the new strategies and mechanical devices, along with their initial results in pre-clinical and different phases of ongoing clinical trials for HFpEF patients. Understanding new mechanisms to generate interventions will allow us to create methods to prevent the adverse outcomes of this silent pandemic.

High yield engineered nanovesicles from ADSC with enriched miR-21-5p promote angiogenesis in adipose tissue regeneration

BACKGROUND

Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs) have been found to have a great potential for soft tissue repair due to various biological functions, including pro-angiogenesis and low immunogenicity. However, the low yield and heterogeneity of MSC-EVs limited their clinical transformation. This study was designed to develop a novel adipose-derived stem cell engineered nanovesicles (ADSC-NVs) with high production and explore its pro-angiogenetic effect and application in adipose tissue regeneration.

METHODS

Adipose-derived stem cell-derived extracellular vesicles (ADSC-EVs) were isolated from an EVs-free culture medium for human ADSCs (hADSCs). ADSC-NVs were prepared by sequentially extruding ADSCs followed by iodixanol density gradient ultracentrifugation and were compared with ADSC-EVs in morphology, size distribution, protein contents and yield. The pro-angiogenetic effect of ADSC-NVs in different doses (0, 5, 20 and 80 μg/mL) in vitro was determined using transwell assay, tube formation assay, western blot and qRT-PCR. In vivo, BALB/c nude mice were administered injection of a mixture of fat granules and different dose of ADSC-NVs and grafts were harvested at 12 weeks post-transplantation for further analysis. By analyzing the weight and volume of grafts and histological evaluation, we investigated the effect of ADSC-NVs in vessel formation and adipose tissue regeneration.

RESULTS

Our results showed yield of purified ADSC-NVs was approximately 20 times more than that of ADSC-EVs secreted by the same number of ADSCs. In vitro, both ADSC-NVs and ADSC-EVs exhibited a dose-dependent pro-angiogenetic effect, despite their distinct miRNA profiles. These effects of ADSC-NVs may be mediated by enriched miR-21-5p via PTEN inhibition and PI3K/p-Akt signaling activation. Furthermore, after a mixed injection of ADSC-NVs, vessel formation and adipose regeneration were observed in vivo in fat implants.

CONCLUSIONS

Our study developed a potent alternative of ADSC-EVs. ADSC-NVs have a high pro-angiogenesis potential and can be used as cell-free therapeutic biomaterials in soft tissue regeneration.

Epicardial transplantation of autologous atrial appendage micrografts: evaluation of safety and feasibility in pigs after coronary artery occlusion

Objectives. Several approaches devised for clinical utilization of cell-based therapies for heart failure often suffer from complex and lengthy preparation stages. Epicardial delivery of autologous atrial appendage micrografts (AAMs) with a clinically used extracellular matrix (ECM) patch provides a straightforward therapy alternative. We evaluated the operative feasibility and the effect of micrografts on the patch-induced epicardial foreign body inflammatory response in a porcine model of myocardial infarction. Design. Right atrial appendages were harvested and mechanically processed into AAMs. The left anterior descending coronary artery was ligated to generate acute infarction. Patches of ECM matrix with or without AAMs were transplanted epicardially onto the infarcted area. Four pigs received the ECM and four received the AAMs patch. Cardiac function was studied by echocardiography both preoperatively and at 3-week follow-up. The primary outcome measures were safety and feasibility of the therapy administration, and the secondary outcome was the inflammatory response to ECM. Results. Neither AAMs nor ECM patch-related complications were detected during the follow-up time. AAMs patch preparation was feasible according to time and safety. Inflammation was greatly reduced in AAMs when compared with ECM patches as measured by the amount of infiltrated inflammatory cells and area of inflammation. Immunohistochemistry demonstrated an increased CD3+ cell density in the AAMs patch infiltrate. Conclusions. Epicardial AAMs transplantation demonstrated safety and clinical feasibility. The use of micrografts significantly inhibited ECM-induced foreign body inflammatory reactivity. Transplantation of AAMs shows good clinical applicability as adjuvant therapy to cardiac surgery and can suppress acute inflammatory reactivity.

LPS preconditioning of MSC-CM improves protection against hypoxia/reoxygenation-induced damage in H9c2 cells partly via HMGB1/Bach1 signalling

Mesenchymal stem cell-derived conditioned medium (MSC-CM) improves cardiac function after myocardial infarction; however, this cardioprotective effect is moderate and transient. Lipopolysaccharide (LPS) pretreatment partially improves MSC-CM-mediated cardioprotective effects owing to the presence of paracrine factors. However, the mechanism underlying these improved effects remains unknown. To study the effect of LPS-pretreated MSC-CM on hypoxia/reoxygenation (H/R)-induced injury, MSCs were treated with or without LPS (400 ng/mL) for 48 h, and the supernatant was collected (MSC-CM). Subsequently, H9c2 cells were co-cultured with Nor-CM (CM derived from LPS-untreated MSCs) and LPS-CM (CM derived from LPS-pretreated MSCs) for 24 h and subjected to H/R. MSC-CM inhibited the progression of H/R-induced injury in H9c2 cells, and this protective effect was enhanced via LPS pretreatment as evidenced by the improved apoptosis assessment index (i.e. caspase-3 and B-cell lymphoma-2 [Bcl-2] expression) and decreased levels of lactic dehydrogenase (LDH) and cardiac troponin (cTn). In addition, the results of haematoxylin-eosin staining (H&E), transmission electron microscopy (TEM) and TdT-mediated dUTP nick-end labelling (TUNEL) validated that MSC-CM inhibited H/R-induced injury in H9c2 cardiomyocytes. LPS pretreatment downregulated the expression of high mobility group box-1 (HMGB1) and BTB and CNC homology-1 (Bach1) proteins in MSCs but upregulated the expression of vascular endothelial growth factor (VEGF), hepatocyte growth factor (HGF) and insulin-like growth factor (IGF). HMGB1 knockdown (MSC/siHMGB1-CM) significantly decreased the expression of Bach1 and increased the expression of VEGF, HGF and IGF. Bach1 knockdown (MSC/siBach1-CM) did not alter the production of HMGB1 but increased the expression of VEGF and IGF. LPS pretreatment did not alter the expression of the paracrine factors VEGF and HGF in the MSC/siHMGB1 group but increased their expression in the MSC/siBach1 group. The myocyte anti-apoptotic effects of MSCs/siBach1-CM were similar to those of untreated MSCs, which were not enhanced by LPS. LPS-pretreated MSC-CM protects H9c2 cells against H/R-induced injury partly through the HMGB1/Bach1 signalling pathway.

Exosomes as a Cell-free Therapy for Myocardial Injury Following Acute Myocardial Infarction or Ischemic Reperfusion

Exosomes, which contain miRNA, have been receiving growing attention in cardiovascular therapy because of their role in mediating cell-cell communication, autophagy, apoptosis, inflammation, and angiogenesis. Several studies have suggested that miRNA derived from exosomes can be used to detect myocardial infarctions (MI) in patients. Basic research also suggests that exosomes could serve as a potential therapeutic target for treating acute myocardial infarction. Ischemia/reperfusion (IR) injury is associated with adverse cardiac events after acute MI. We aim to review the potential benefits and mechanisms of exosomes in treating MI and IR injury.

Extracellular Vesicle-Based Therapeutics in Neurological Disorders

Neurological diseases remain some of the major causes of death and disability in the world. Few types of drugs and insufficient delivery across the blood-brain barrier limit the treatment of neurological disorders. The past two decades have seen the rapid development of extracellular vesicle-based therapeutics in many fields. As the physiological and pathophysiological roles of extracellular vesicles are recognized in neurological diseases, they have become promising therapeutics and targets for therapeutic interventions. Moreover, advanced nanomedicine technologies have explored the potential of extracellular vesicles as drug delivery systems in neurological diseases. In this review, we discussed the preclinical strategies for extracellular vesicle-based therapeutics in neurological disorders and the struggles involved in their clinical application.

Emerging role of mesenchymal stem cell-derived extracellular vesicles in oral and craniomaxillofacial tissue regenerative medicine

Mesenchymal stem cells (MSCs) are multipotent stem cells with differentiation potential and paracrine properties, drawing significant attention in the field of regenerative medicine. Extracellular vesicles (EVs), mainly including exosomes, microvesicles and apoptotic bodies (ABs), are predominantly endosomal in origin and contain bioactive molecules, such as miRNAs, mRNAs, and proteins, which are transferred from their original cells to target cells. Recently it has emerged that MSC-derived EVs (MSC-EVs) combine the advantages of MSCs and EVs, which may be used as a promising MSC-based therapy in tissue repair and regeneration. Oral and craniomaxillofacial diseases are clinically complications containing the soft and hard tissues in craniofacial and dental arches. These diseases are often induced by various factors, such as chemical, microbiological, physical factors, and systemic disorders. For decades, tissue repair and regeneration in oral and craniomaxillofacial regions provide substantial improvements in the prevention and treatment of some severe diseases. In this review we discuss MSC-EVs and their therapeutic potential in oral and craniomaxillofacial tissue regenerative medicine.

From Promise to Reality: Bioengineering Strategies to Enhance the Therapeutic Potential of Extracellular Vesicles

Extracellular vesicles (EVs) have been the focus of great attention over the last decade, considering their promising application as next-generation therapeutics. EVs have emerged as relevant mediators of intercellular communication, being associated with multiple physiological processes, but also in the pathogenesis of several diseases. Given their natural ability to shuttle messages between cells, EVs have been explored both as inherent therapeutics in regenerative medicine and as drug delivery vehicles targeting multiple diseases. However, bioengineering strategies are required to harness the full potential of EVs for therapeutic use. For that purpose, a good understanding of EV biology, from their biogenesis to the way they are able to shuttle messages and establish interactions with recipient cells, is needed. Here, we review the current state-of-the-art on EV biology, complemented by representative examples of EVs roles in several pathophysiological processes, as well as the intrinsic therapeutic properties of EVs and paradigmatic strategies to produce and develop engineered EVs as next-generation drug delivery systems.

Extracellular vesicles derived from neural EGFL-Like 1-modified mesenchymal stem cells improve acellular bone regeneration via the miR-25-5p-SMAD2 signaling axis

Stem cell based transplants effectively regenerate tissues; however, limitations such as immune rejection and teratoma formation prevent their application. Extracellular vesicles (EVs)-mediated acellular tissue regeneration is a promising alternative to stem cell based transplants. Although neural EGFL-like 1 (Nell1) is known to contribute to the osteogenic differentiation of bone marrow stem cells (BMSCs), it remains unknown whether EVs are involved in this process. Here, we present that EVs derived from Nell1-modified BMSCs (Nell1/EVs) have a stronger ability to promote BMSC osteogenesis owing to miR-25–5p downregulation. MiR-25–5p inhibits osteogenesis by targeting Smad2 and suppressing the SMAD and extracellular signal-related kinase 1 and 2 (ERK1/2) pathway activation. In addition, we demonstrate that the 3D-Nell1/EV-hydrogel system is beneficial for bone regeneration in vivo, probably stemming from a slow, continuous release and high concentration of EVs in the bone defect area. Thus, our results have shown the potential of Nell1/EVs as a novel acellular bone regeneration strategy. Mechanistically, the identification of miR-25-5p-SMAD2 signaling axis expands the knowledge of Nell1/EVs induced osteogenesis.

•

Extracellular vesicles contributed to the Nell1-induced osteoblast lineage commitment program of BMSCs.

•

The miRNA profile of Nell1-modified-EVs remarkably changed after genetic modification of their parental cells.

•

miRNA-25–5p downregulation of Nell1-modifed-EVs helped with osteogenic effect via the SMAD and ERK pathway.

•

Hydrogel captured with Nell1-modified-EVs showed potential to repair large bone defect.

Cellular-Based Therapies in Systemic Sclerosis: From Hematopoietic Stem Cell Transplant to Innovative Approaches

Systemic sclerosis (SSc) is a systemic disease characterized by autoimmune responses, vasculopathy and tissue fibrosis. The pathogenic mechanisms involve a wide range of cells and soluble factors. The complexity of interactions leads to heterogeneous clinical features in terms of the extent, severity, and rate of progression of skin fibrosis and internal organ involvement. Available disease-modifying drugs have only modest effects on halting disease progression and may be associated with significant side effects. Therefore, cellular therapies have been developed aiming at the restoration of immunologic self-tolerance in order to provide durable remissions or to foster tissue regeneration. Currently, SSc is recommended as the 'standard indication' for autologous hematopoietic stem cell transplantation by the European Society for Blood and Marrow Transplantation. This review provides an overview on cellular therapies in SSc, from pre-clinical models to clinical applications, opening towards more advanced cellular therapies, such as mesenchymal stem cells, regulatory T cells and potentially CAR-T-cell therapies.

Bone Marrow Culture-Derived Conditioned Medium Recovers Endothelial Function of Vascular Grafts following In Vitro Ischemia/Reperfusion Injury in Diabetic Rats

Ischemia/reperfusion injury (IRI) remains a challenge in coronary artery bypass grafting (CABG). Diabetic patients with coronary artery disease are more likely to require CABG and therefore run a high risk for cardiovascular complications. Conditioned medium (CM) from bone marrow-derived mesenchymal stem cells has been shown to have beneficial effects against IRI. We hypothesized that adding CM to physiological saline protects vascular grafts from IRI in diabetic rats. Bone-marrow derived cells were isolated from nondiabetic rat femurs/tibias, and CM was generated. As we previously reported, CM contains 23 factors involved in inflammation, oxidative stress, and apoptosis. DM was induced by streptozotocin administration. Eight weeks later, to measure vascular function, aortic rings were isolated and mounted in organ bath chambers (DM group) or stored in 4°C saline, supplemented either with a vehicle (DM-IR group) or CM (DM-IR+CM group). Although DM was associated with structural changes compared to controls, there were no functional alterations. However, compared to the DM group, in the DM-IR aortas, impaired maximum endothelium-dependent vasorelaxation in response to acetylcholine (DM 86.7 ± 0.1% vs. DM-IR 42.5 ± 2.5% vs. DM-IR+CM 61.9 ± 2.0%, p < 0.05) was improved, caspase-3, caspase-8, caspase-9, and caspase-12 immunoreactivity was decreased, and DNA strand breakage, detected by the TUNEL assay, was reduced by CM. We present the experimental finding that the preservation of vascular grafts with CM prevents endothelial dysfunction after IRI in diabetic rats. Targeting apoptosis by CM may contribute to its protective effect.

Paracrine Effects of Mesenchymal Stem Cells in Ischemic Stroke: Opportunities and Challenges

It is well acknowledged that neuroprotective effects of transplanted mesenchymal stem cells (MSCs) in ischemic stroke are attributed to their paracrine-mediated actions or bystander effects rather than to cell replacement in infarcted areas. This therapeutic plasticity is due to MSCs' ability to secrete a broad range of bioactive molecules including growth factors, trophic factors, cytokines, chemokines, and extracellular vesicles, overall known as the secretome. The secretome derivatives, such as conditioned medium (CM) or purified extracellular vesicles (EVs), exert remarkable advantages over MSC transplantation in stroke treating. Here, in this review, we used published information to provide an overview on the secretome composition of MSCs, underlying mechanisms of therapeutic effects of MSCs, and preclinical studies on MSC-derived products application in stroke. Furthermore, we discussed current advantages and challenges for successful bench-to-bedside translation.

Perinatal derivatives: How to best validate their immunomodulatory functions

Perinatal tissues, mainly the placenta and umbilical cord, contain a variety of different somatic stem and progenitor cell types, including those of the hematopoietic system, multipotent mesenchymal stromal cells (MSCs), epithelial cells and amnion epithelial cells. Several of these perinatal derivatives (PnDs), as well as their secreted products, have been reported to exert immunomodulatory therapeutic and regenerative functions in a variety of pre-clinical disease models. Following experience with MSCs and their extracellular vesicle (EV) products, successful clinical translation of PnDs will require robust functional assays that are predictive for the relevant therapeutic potency. Using the examples of T cell and monocyte/macrophage assays, we here discuss several assay relevant parameters for assessing the immunomodulatory activities of PnDs. Furthermore, we highlight the need to correlate the in vitro assay results with preclinical or clinical outcomes in order to ensure valid predictions about the in vivo potency of therapeutic PnD cells/products in individual disease settings.

Cell-Based and Selected Cell-Free Therapies for Myocardial Infarction: How Do They Compare to the Current Treatment Options?

Because of cardiomyocyte death or dysfunction frequently caused by myocardial infarction (MI), heart failure is a leading cause of morbidity and mortality in modern society. Paradoxically, only limited and non-curative therapies for heart failure or MI are currently available. As a result, over the past two decades research has focused on developing cell-based approaches promoting the regeneration of infarcted tissue. Cell-based therapies for myocardial regeneration include powerful candidates, such as multipotent stem cells (mesenchymal stem cells (MSCs), bone-marrow-derived stem cells, endothelial progenitor cells, and hematopoietic stem cells) and induced pluripotent stem cells (iPSCs). These possess unique properties, such as potency to differentiate into desired cell types, proliferation capacity, and patient specificity. Preclinical and clinical studies have demonstrated modest improvement in the myocardial regeneration and reduced infarcted areas upon transplantation of pluripotent or multipotent stem cells. Another cell population that need to be considered as a potential source for cardiac regeneration are telocytes found in different organs, including the heart. Their therapeutic effect has been studied in various heart pathologies, such as MI, arrhythmias, or atrial amyloidosis. The most recent cell-free therapeutic tool relies on the cardioprotective effect of complex cargo carried by small membrane-bound vesicles-exosomes-released from stem cells via exocytosis. The MSC/iPSC-derived exosomes could be considered a novel exosome-based therapy for cardiovascular diseases thanks to their unique content. There are also other cell-free approaches, e.g., gene therapy, or acellular cardiac patches. Therefore, our review provides the most recent insights into the novel strategies for myocardial repair based on the regenerative potential of different cell types and cell-free approaches.