Clinical Trials Based on Mesenchymal Stromal Cells are Exponentially Increasing: Where are We in Recent Years?

Efficient delivery of mesenchymal stem/stromal cells to injured liver by surface PEGylation

BACKGROUND

Mesenchymal stem/stromal cells (MSCs) have been used in clinical trials for various diseases. These have certain notable functions such as homing to inflammation sites, tissue repair, and immune regulation. In many pre-clinical studies, MSCs administered into peripheral veins demonstrated effective therapeutic outcomes. However, most of the intravenously administered MSCs were entrapped in the lung, and homing to target sites was less than 1%. This occurred mainly because of the adhesion of MSCs to vascular endothelial cells in the lung. To prevent this adhesion, we modified the surface of MSCs with polyethylene glycol (PEG; a biocompatible polymer) using the avidin-biotin complex (ABC) method.

METHODS

The surface of MSCs was modified with PEG using the ABC method. Then, the cell adhesion to mouse aortic endothelial cells and the tissue distribution of PEG-modified MSCs were evaluated. Moreover, the homing to the injured liver and therapeutic effect of PEG-modified MSCs were evaluated using carbon tetrachloride-induced acute liver failure model mice.

RESULTS

The PEG modification significantly suppressed the adhesion of MSCs to cultured mouse aortic endothelial cells as well as the entrapment of MSCs in the lungs after intravenous injection in mice. PEG-modified MSCs efficiently homed to the injured liver of carbon tetrachloride-induced acute liver failure model mice. More importantly, the cells significantly suppressed serum transaminase levels and leukocyte infiltration into the injured liver.

CONCLUSION

These results indicate that PEG modification to the surface of MSCs can suppress the lung entrapment of intravenously administered MSCs and improve their homing to the injured liver.

Fetal Muse-based therapy prevents lethal radio-induced gastrointestinal syndrome by intestinal regeneration

BACKGROUND

Human multilineage-differentiating stress enduring (Muse) cells are nontumorigenic endogenous pluripotent-like stem cells that can be easily obtained from various adult or fetal tissues. Regenerative effects of Muse cells have been shown in some disease models. Muse cells specifically home in damaged tissues where they exert pleiotropic effects. Exposition of the small intestine to high doses of irradiation (IR) delivered after radiotherapy or nuclear accident results in a lethal gastrointestinal syndrome (GIS) characterized by acute loss of intestinal stem cells, impaired epithelial regeneration and subsequent loss of the mucosal barrier resulting in sepsis and death. To date, there is no effective medical treatment for GIS. Here, we investigate whether Muse cells can prevent lethal GIS and study how they act on intestinal stem cell microenvironment to promote intestinal regeneration.

METHODS

Human Muse cells from Wharton's jelly matrix of umbilical cord (WJ-Muse) were sorted by flow cytometry using the SSEA-3 marker, characterized and compared to bone-marrow derived Muse cells (BM-Muse). Under gas anesthesia, GIS mice were treated or not through an intravenous retro-orbital injection of 50,000 WJ-Muse, freshly isolated or cryopreserved, shortly after an 18 Gy-abdominal IR. No immunosuppressant was delivered to the mice. Mice were euthanized either 24 h post-IR to assess early small intestine tissue response, or 7 days post-IR to assess any regenerative response. Mouse survival, histological stainings, apoptosis and cell proliferation were studied and measurement of cytokines, recruitment of immune cells and barrier functional assay were performed.

RESULTS

Injection of WJ-Muse shortly after abdominal IR highly improved mouse survival as a result of a rapid regeneration of intestinal epithelium with the rescue of the impaired epithelial barrier. In small intestine of Muse-treated mice, an early enhanced secretion of IL-6 and MCP-1 cytokines was observed associated with (1) recruitment of monocytes/M2-like macrophages and (2) proliferation of Paneth cells through activation of the IL-6/Stat3 pathway.

CONCLUSION

Our findings indicate that a single injection of a small quantity of WJ-Muse may be a new and easy therapeutic strategy for treating lethal GIS.

Chitosan Scaffolds as Microcarriers for Dynamic Culture of Human Neural Stem Cells

Human neural stem cells (hNSCs) possess remarkable potential for regenerative medicine in the treatment of presently incurable diseases. However, a key challenge lies in producing sufficient quantities of hNSCs, which is necessary for effective treatment. Dynamic culture systems are recognized as a powerful approach to producing large quantities of hNSCs required, where microcarriers play a critical role in supporting cell expansion. Nevertheless, the currently available microcarriers have limitations, including a lack of appropriate surface chemistry to promote cell adhesion, inadequate mechanical properties to protect cells from dynamic forces, and poor suitability for mass production. Here, we present the development of three-dimensional (3D) chitosan scaffolds as microcarriers for hNSC expansion under defined conditions in bioreactors. We demonstrate that chitosan scaffolds with a concentration of 4 wt% (4CS scaffolds) exhibit desirable microstructural characteristics and mechanical properties suited for hNSC expansion. Furthermore, they could also withstand degradation in dynamic conditions. The 4CS scaffold condition yields optimal metabolic activity, cell adhesion, and protein expression, enabling sustained hNSC expansion for up to three weeks in a dynamic culture. Our study introduces an effective microcarrier approach for prolonged expansion of hNSCs, which has the potential for mass production in a three-dimensional setting.

Mesenchymal Stromal Cell Therapy in Lung Transplantation

Lung transplantation is often the only viable treatment option for a patient with end-stage lung disease. Lung transplant results have improved substantially over time, but ischemia-reperfusion injury, primary graft dysfunction, acute rejection, and chronic lung allograft dysfunction (CLAD) continue to be significant problems. Mesenchymal stromal cells (MSC) are pluripotent cells that have anti-inflammatory and protective paracrine effects and may be beneficial in solid organ transplantation. Here, we review the experimental studies where MSCs have been used to protect the donor lung against ischemia-reperfusion injury and alloimmune responses, as well as the experimental and clinical studies using MSCs to prevent or treat CLAD. In addition, we outline ex vivo lung perfusion (EVLP) as an optimal platform for donor lung MSC delivery, as well as how the therapeutic potential of MSCs could be further leveraged with genetic engineering.

Single-Cell RNA-Seq Reveals LRRC75A-Expressing Cell Population Involved in VEGF Secretion of Multipotent Mesenchymal Stromal/Stem Cells Under Ischemia

Human multipotent mesenchymal stromal/stem cells (MSCs) have been utilized in cell therapy for various diseases and their clinical applications are expected to increase in the future. However, the variation in MSC-based product quality due to the MSC heterogeneity has resulted in significant constraints in the clinical utility of MSCs. Therefore, we hypothesized that it might be important to identify and ensure/enrich suitable cell subpopulations for therapies using MSC-based products. In this study, we aimed to identify functional cell subpopulations to predict the efficacy of angiogenic therapy using bone marrow-derived MSCs (BM-MSCs). To assess its angiogenic potency, we observed various levels of vascular endothelial growth factor (VEGF) secretion among 11 donor-derived BM-MSC lines under in vitro ischemic culture conditions. Next, by clarifying the heterogeneity of BM-MSCs using single-cell RNA-sequencing analysis, we identified a functional cell subpopulation that contributed to the overall VEGF production in BM-MSC lines under ischemic conditions. We also found that leucine-rich repeat-containing 75A (LRRC75A) was more highly expressed in this cell subpopulation than in the others. Importantly, knockdown of LRRC75A using small interfering RNA resulted in significant inhibition of VEGF secretion in ischemic BM-MSCs, indicating that LRRC75A regulates VEGF secretion under ischemic conditions. Therefore, LRRC75A may be a useful biomarker to identify cell subpopulations that contribute to the angiogenic effects of BM-MSCs. Our work provides evidence that a strategy based on single-cell transcriptome profiles is effective for identifying functional cell subpopulations in heterogeneous MSC-based products.

Progression of irradiated mesenchymal stromal cells from early to late senescence: Changes in SASP composition and anti-tumour properties

Genotoxic injuries converge on senescence-executive program that promotes production of a senescence-specific secretome (SASP). The study of SASP is particularly intriguing, since through it a senescence process, triggered in a few cells, can spread to many other cells and produce either beneficial or negative consequences for health. We analysed the SASP of quiescent mesenchymal stromal cells (MSCs) following stress induced premature senescence (SIPS) by ionizing radiation exposure. We performed a proteome analysis of SASP content obtained from early and late senescent cells. The bioinformatics studies evidenced that early and late SASPs, besides some common ontologies and signalling pathways, contain specific factors. In spite of these differences, we evidenced that SASPs can block in vitro proliferation of cancer cells and promote senescence/apoptosis. It is possible to imagine that SASP always contains core components that have an anti-tumour activity, the progression from early to late senescence enriches the SASP of factors that may promote SASP tumorigenic activity only by interacting and instructing cells of the immune system. Our results on Caco-2 cancer cells incubated with late SASP in presence of peripheral white blood cells strongly support this hypothesis. We evidenced that quiescent MSCs following SIPS produced SASP that, while progressively changed its composition, preserved the capacity to block cancer growth by inducing senescence and/or apoptosis only in an autonomous manner.

Progression of irradiated mesenchymal stromal cells from early to late senescence: Changes in SASP composition and anti-tumour properties

Genotoxic injuries converge on senescence-executive program that promotes production of a senescence-specific secretome (SASP). The study of SASP is particularly intriguing, since through it a senescence process, triggered in a few cells, can spread to many other cells and produce either beneficial or negative consequences for health. We analysed the SASP of quiescent mesenchymal stromal cells (MSCs) following stress induced premature senescence (SIPS) by ionizing radiation exposure. We performed a proteome analysis of SASP content obtained from early and late senescent cells. The bioinformatics studies evidenced that early and late SASPs, besides some common ontologies and signalling pathways, contain specific factors. In spite of these differences, we evidenced that SASPs can block in vitro proliferation of cancer cells and promote senescence/apoptosis. It is possible to imagine that SASP always contains core components that have an anti-tumour activity, the progression from early to late senescence enriches the SASP of factors that may promote SASP tumorigenic activity only by interacting and instructing cells of the immune system. Our results on Caco-2 cancer cells incubated with late SASP in presence of peripheral white blood cells strongly support this hypothesis. We evidenced that quiescent MSCs following SIPS produced SASP that, while progressively changed its composition, preserved the capacity to block cancer growth by inducing senescence and/or apoptosis only in an autonomous manner.

Senescence induces fundamental changes in the secretome of mesenchymal stromal cells (MSCs): implications for the therapeutic use of MSCs and their derivates

Mesenchymal stromal cells (MSCs) are a heterogeneous population containing multipotent adult stem cells with a multi-lineage differentiation capacity, which differentiated into mesodermal derivatives. MSCs are employed for therapeutic purposes and several investigations have demonstrated that the positive effects of MSC transplants are due to the capacity of MSCs to modulate tissue homeostasis and repair via the activity of their secretome. Indeed, the MSC-derived secretomes are now an alternative strategy to cell transplantation due to their anti-inflammatory, anti-apoptotic, and regenerative effects. The cellular senescence is a dynamic process that leads to permanent cell cycle arrest, loss of healthy cells' physiological functions and acquiring new activities, which are mainly accrued through the release of many factors, indicated as senescence-associated secretory phenotype (SASP). The senescence occurring in stem cells, such as those present in MSCs, may have detrimental effects on health since it can undermine tissue homeostasis and repair. The analysis of MSC secretome is important either for the MSC transplants and for the therapeutic use of secretome. Indeed, the secretome of MSCs, which is the main mechanism of their therapeutic activity, loses its beneficial functions and acquire negative pro-inflammatory and pro-aging activities when MSCs become senescent. When MSCs or their derivatives are planned to be used for therapeutic purposes, great attention must be paid to these changes. In this review, we analyzed changes occurring in MSC secretome following the switch from healthy to senescence status.

Rps6ka2 enhances iMSC chondrogenic differentiation to attenuate knee osteoarthritis through articular cartilage regeneration in mice

Articular cartilage (AC) is most susceptible to degeneration in knee osteoarthritis (OA); however, the existing treatments for OA do not target the core link of the pathogenesis-"decreased tissue cell function activity and extracellular matrix (ECM) metabolic disorders" for effective intervention. iMSC hold lower heterogeneity and great promise in biological research and clinical applications. Rps6ka2 may play an important role in the iMSC to treat OA. In this study, the CRISPR/Cas9 gene editing Rps6ka2^-/- iMSC were obtained. Effect of Rps6ka2 on iMSC proliferation and chondrogenic differentiation was evaluated in vitro. An OA model was constructed in mice by surgical destabilization of medial meniscus (DMM). The Rps6ka2^-/- iMSC and iMSC were injected into the articular cavity twice-weekly for 8 weeks. In vitro experiments showed that Rps6ka2 could promote iMSC proliferation and chondrogenic differentiation. In vivo results further confirmed that Rps6ka2 could improve iMSC viability to promote ECM production to attenuate OA in mice.

Metformin Ameliorates D-Galactose-Induced Senescent Human Bone Marrow-Derived Mesenchymal Stem Cells by Enhancing Autophagy

Human bone marrow-derived mesenchymal stem cells (hBMSCs) are promising candidates for stem cell therapy in clinical trials. Applications of hBMSCs in clinical therapy are limited by cellular senescence due to long-term ex vivo expansion. Metformin, an oral hypoglycemic drug for type 2 diabetes, has been shown to have antiaging effects. However, the mechanisms of metformin in antiaging treatment remain controversial. Here, we used D-galactose (D-gal) to establish an appropriate model of senescent hBMSCs to explore the antiaging effects of metformin. Following metformin treatment with a low concentration range, senescence phenotypes induced by D-gal significantly changed, including generation of reactive oxygen species (ROS), loss of mitochondrial membrane potential (MMP), and cell cycle arrest. In contrast, no apparent change was found in unsenescent hBMSCs. Furthermore, the results show that activation of 5'AMP-activated protein kinase (AMPK) by metformin enhances cell autophagy in senescent hBMSCs. These findings suggest that metformin exerts antiaging function within the low concentration range by enhancing autophagy and exhibits potential benefits for clinical stem cell therapy by ameliorating the ex vivo replicative senescence of hBMSCs.

Protective effect of bone marrow mesenchymal stem cell-derived exosomes on cardiomyoblast hypoxia-reperfusion injury through the HAND2-AS1/miR-17-5p/Mfn2 axis

BACKGROUND

The exosomes (exos) of bone marrow mesenchymal stem cells (BMSCs) play an important therapeutic role in repairing myocardial injury. The purpose of this study was to explore how the exos of BMSCs can alleviate the myocardial cell injury caused by hypoxia/reoxygenation (H/R) through HAND2-AS1/miR-17-5p/Mfn 2 pathway.

METHODS

Cardiomyocytes H9c2 were damaged by H/R to mimic myocardial damage. Exos were gained from BMSC. The content of HAND2-AS1 and miR-17-5p was assessed by RT-qPCR. Cell survival rate and apoptosis were estimated by MTT assay and flow cytometry. Western blotting was used to detect the expression of protein. The contents of LDH, SOD, and MDA in the cell culture were detected by commercial kits. The luciferase reporter gene method confirmed the targeted relationships.

RESULTS

In H9c2 cells induced by H/R, the level of HAND2-AS1 declined and the expression of miR-17-5p was elevated, but their expression was reversed after exo treatment. Exos improved the cell viability, declined cell apoptosis, controlled the oxidative stress, and repressed inflammation, thus attenuating the damage of H9c2 induced by H/R, whereas, the knockdown of HAND2-AS1 partly alleviated the impacts of exos. MiR-17-5p played the opposite role to HAND2-AS1 on H/R-injured myocardial cells.

CONCLUSION

Exos derived from BMSC could alleviate H/R-induced myocardial injury by activating HAND2-AS1/miR-17-5p/Mfn2 pathway.

Mesenchymal Stem Cells in Acquired Aplastic Anemia: The Spectrum from Basic to Clinical Utility

Aplastic anemia (AA), a rare but potentially life-threatening disease, is a paradigm of bone marrow failure syndromes characterized by pancytopenia in the peripheral blood and hypocellularity in the bone marrow. The pathophysiology of acquired idiopathic AA is quite complex. Mesenchymal stem cells (MSCs), an important component of the bone marrow, are crucial in providing the specialized microenvironment for hematopoiesis. MSC dysfunction may result in an insufficient bone marrow and may be associated with the development of AA. In this comprehensive review, we summarized the current understanding about the involvement of MSCs in the pathogenesis of acquired idiopathic AA, along with the clinical application of MSCs for patients with the disease. The pathophysiology of AA, the major properties of MSCs, and results of MSC therapy in preclinical animal models of AA are also described. Several important issues regarding the clinical use of MSCs are discussed finally. With evolving knowledge from basic studies and clinical applications, we anticipate that more patients with the disease can benefit from the therapeutic effects of MSCs in the near future.

Cytochalasin B Influences Cytoskeletal Organization and Osteogenic Potential of Human Wharton's Jelly Mesenchymal Stem Cells

Among perinatal stem cells of the umbilical cord, human Wharton's jelly mesenchymal stem cells (hWJ-MSCs) are of great interest for cell-based therapy approaches in regenerative medicine, showing some advantages over other MSCs. In fact, hWJ-MSCs, placed between embryonic and adult MSCs, are not tumorigenic and are harvested with few ethical concerns. Furthermore, these cells can be easily cultured in vitro, maintaining both stem properties and a high proliferative rate for several passages, as well as trilineage capacity of differentiation. Recently, it has been demonstrated that cytoskeletal organization influences stem cell biology. Among molecules able to modulate its dynamics, Cytochalasin B (CB), a cyto-permeable mycotoxin, influences actin microfilament polymerization, thus affecting several cell properties, such as the ability of MSCs to differentiate towards a specific commitment. Here, we investigated for the first time the effects of a 24 h-treatment with CB at different concentrations (0.1-3 μM) on hWJ-MSCs. CB influenced the cytoskeletal organization in a dose-dependent manner, inducing changes in cell number, proliferation, shape, and nanomechanical properties, thus promoting the osteogenic commitment of hWJ-MSCs, as confirmed by the expression analysis of osteogenic/autophagy markers.

Regulatory cells and the effect of cancer immunotherapy

Several mechanisms and cell types are involved in the regulation of the immune response. These include mostly regulatory T cells (Tregs), regulatory macrophages (Mregs), myeloid suppressor cells (MDSCs) and other regulatory cell types such as tolerogenic dendritic cells (tolDCs), regulatory B cells (Bregs), and mesenchymal stem cells (MSCs). These regulatory cells, known for their ability to suppress immune responses, can also suppress the anti-tumor immune response. The infiltration of many regulatory cells into tumor tissues is therefore associated with a poor prognosis. There is growing evidence that elimination of Tregs enhances anti-tumor immune responses. However, the systemic depletion of Treg cells can simultaneously cause deleterious autoimmunity. Furthermore, since regulatory cells are characterized by their high level of expression of immune checkpoints, it is also expected that immune checkpoint inhibitors perform part of their function by blocking these molecules and enhancing the immune response. This indicates that immunotherapy does not only act by activating specific effector T cells but can also directly or indirectly attenuate the suppressive activity of regulatory cells in tumor tissues. This review aims to draw together our current knowledge about the effect of immunotherapy on the various types of regulatory cells, and how these effects may be beneficial in the response to immunotherapy.

Therapeutic Perspectives for the Clinical Application of Umbilical Cord Hematopoietic and Mesenchymal Stem Cells: Overcoming Complications Arising After Allogeneic Hematopoietic Stem Cell Transplantation

This review focuses on the therapeutic features of umbilical cord blood (UCB) cells as a source for allogeneic hematopoietic stem cell transplantation (aHSCT) in adult and child populations to treat malignant and nonmalignant hematologic diseases, genetic disorders, or pathologies of the immune system, when standard treatment (e.g., chemotherapy) is not effective or clinically contraindicated. In this article, we summarize the immunological properties and the advantages and disadvantages of using UCB stem cells and discuss a variety of treatment outcomes using different sources of stem cells from different donors both in adults and pediatric population. We also highlight the critical properties (total nucleated cell dose depending on HLA compatibility) of UCB cells that reach better survival rates, reveal the advantages of double versus single cord blood unit transplantation, and present recommendations from the most recent studies. Moreover, we summarize the mechanism of action and potential benefit of mesenchymal umbilical cord cells and indicate the most common posttransplantation complications.

Improved efficacy of mesenchymal stromal cells stably expressing CXCR4 and IL-10 in a xenogeneic graft versus host disease mouse model

Previous clinical trials have shown that mesenchymal stromal cells (MSCs) can modulate graft versus host disease (GvHD) after allogeneic hematopoietic transplantation, although with variable efficacy. To improve the anti-GvHD effect of these cells, adipose tissue derived-human MSCs (Ad-MSCs) were transduced with a lentiviral vector conferring stable expression of CXCR4, a molecule involved in cell migration to inflamed sites, and IL-10, a cytokine with potent anti-inflammatory properties. In vitro experiments showed that the expression of these molecules in Ad-MSCs (named CXCR4-IL10-MSCs) efficiently enhanced their migration towards SDF-1α and also improved their immunomodulatory properties compared to unmodified Ad-MSCs (WT-MSCs). Moreover, using a humanized GvHD mouse model, CXCR4-IL10-MSCs showed improved therapeutic effects, which were confirmed by histopathologic analysis in the target organs. Additionally, compared to WT-MSCs, CXCR4-IL10-MSCs induced a more marked reduction in the number of pro-inflammatory Th1 and Th17 cells, a higher polarization towards an anti-inflammatory T cell profile (CD3⁺-IL10⁺ cells), and increased the number of regulatory T and B cells. Our in vitro and in vivo studies strongly suggest that CXCR4-IL10-MSCs should constitute an important new generation of MSCs for the treatment of GvHD in patients transplanted with allogeneic hematopoietic grafts.

Conglomeration of T- and B-Cell Matrix Responses Determines the Potency of Human Bone Marrow Mesenchymal Stromal Cells

Cell manufacturing facilities need to define the potency of mesenchymal stromal cells (MSCs) as cellular therapeutics in advanced clinical trials or marketing approval. Since MSCs' mechanism of action in humans is not well defined, more than a single functional property of MSCs needs to be captured as a surrogate measure of potency utilizing assay matrix technologies. However, the current limitation is the sole investigation of MSC-mediated T-cell suppression as a surrogate measure of potency. We investigated the effect of MSCs on B-cell matrix responses to be incorporated into the assay matrix potency analytical system. Our results demonstrate that MSCs inhibit B-cell differentiation and block pan-antibody secretion upon activation of B cells in the PBMCs. In contrast, MSCs are inferior in blocking B-cell matrix responses when purified B cells are used. Mechanistic analysis has demonstrated that MSC-mediated inhibition of B-cell matrix responses is non-contact dependent and Tryptophan metabolic pathway plays a major role, akin to the mechanism of MSC-mediated T-cell suppression. MSCs also inhibit both T-cell and B-cell responses when both of these lymphoid populations are concurrently activated in the PBMCs. Secretome analysis of MSC and T/B cell-activated PBMC cocultures identified direct and inverse correlative matrix signatures between humoral antibody isotypes and secretory molecules. The current analysis of the combined and concomitant investigation of T-cell and B-cell matrix responses fulfills the potency assay matrix strategy by incorporating MSCs' interaction with more than a single inflammatory immune responder.

Barriers to mesenchymal stromal cells for low back pain

Intervertebral disc degeneration is the main cause of low back pain. In the past 20 years, the injection of mesenchymal stromal cells (MSCs) into the nucleus pulposus of the degenerative disc has become the main approach for the treatment of low back pain. Despite the progress made in this field, there are still many barriers to overcome. First, intervertebral disc is a highly complex load-bearing composite tissue composed of annulus fibrosus, nucleus pulposus and cartilaginous endplates. Any structural damage will change its overall biomechanical function, thereby causing progressive degeneration of the entire intervertebral disc. Therefore, MSC-based treatment strategies should not only target the degenerated nucleus pulposus but also include degenerated annulus fibrosus or cartilaginous endplates. Second, to date, there has been relatively little research on the basic biology of annulus fibrosus and cartilaginous endplates, although their pathological changes such as annular tears or fissures, Modic changes, or Schmorl's nodes are more commonly associated with low back pain. Given the high complexity of the structure and composition of the annulus fibrosus and cartilaginous endplates, it remains an open question whether any regeneration techniques are available to achieve their restorative regeneration. Finally, due to the harsh microenvironment of the degenerated intervertebral disc, the delivered MSCs die quickly. Taken together, current MSC-based regenerative medicine therapies to regenerate the entire disc complex by targeting the degenerated nucleus pulposus alone are unlikely to be successful.

Extracellular Vesicles in Inner Ear Therapies-Pathophysiological, Manufacturing, and Clinical Considerations

(1) Background: Sensorineural hearing loss is a common and debilitating condition. To date, comprehensive pharmacologic interventions are not available. The complex and diverse molecular pathology that underlies hearing loss may limit our ability to intervene with small molecules. The current review foccusses on the potential for the use of extracellular vesicles in neurotology. (2) Methods: Narrative literature review. (3) Results: Extracellular vesicles provide an opportunity to modulate a wide range of pathologic and physiologic pathways and can be manufactured under GMP conditions allowing for their application in the human inner ear. The role of inflammation in hearing loss with a focus on cochlear implantation is shown. How extracellular vesicles may provide a therapeutic option for complex inflammatory disorders of the inner ear is discussed. Additionally, manufacturing and regulatory issues that need to be addressed to develop EVs as advanced therapy medicinal product for use in the inner ear are outlined. (4) Conclusion: Given the complexities of inner ear injury, novel therapeutics such as extracellular vesicles could provide a means to modulate inflammation, stress pathways and apoptosis in the inner ear.

Transcription Factors STAT3 and MYC Are Key Players of Human Platelet Lysate-Induced Cell Proliferation

Human platelet lysate (HPL) is an efficient alternative for animal serum supplements, significantly enhancing stromal cell proliferation. However, the molecular mechanism behind this growth-promoting effect remains elusive. The aim of this study was to investigate the effect of HPL on cell cycle gene expression in different human stromal cells and to identify the main key players that mediate HPL's growth-enhancing effect. RT-qPCR and an antibody array revealed significant upregulation of cell cycle genes in stromal cells cultured in HPL. As HPL is rich in growth factors that are ligands of tyrosine kinase receptor (TKR) pathways, we used TKR inhibitors and could significantly reduce cell proliferation. Genome profiling, RT-qPCR and Western blotting revealed an enhanced expression of the transcription factors signal transducer and activator of transcription 3 (STAT3) and MYC, both known TKR downstream effectors and stimulators of cell proliferation, in response to HPL. In addition, specifically blocking STAT3 resulted in reduced cell proliferation and expression of cell cycle genes. Our data indicate that HPL-enhanced cell proliferation can, at least in part, be explained by the TKR-enhanced expression of STAT3 and MYC, which in turn induce the expression of genes being involved in the promotion and control of the cell cycle.

Small Extracellular Vesicles Released from Bioglass/Hydrogel Scaffold Promote Vascularized Bone Regeneration by Transferring miR-23a-3p

BACKGROUND

The treatment of critical-size bone defect is a great difficulty in orthopedics. Osteogenesis and angiogenesis are critical issue during the process of bone repair and remodeling. Mesenchymal stem cells (MSCs)-derived exosomes have the same therapeutic effect to MSCs-based therapies. The effect of human umbilical cord MSCs-derived sEVs (hUC-MSCs-sEVs) on vascularized bone regeneration and the potential mechanism remains to be investigated. Herein, we aimed to explore the therapeutic effect and the mechanism of hUC-MSCs-sEVs on critical-size bone defect.

METHODS

To investigate the potential osteogenesis and angiogenesis effects of sEVs in vitro, we extracted sEVs from hUC-MSCs, and then sEVs were co-incubated with BMSCs and HUVECs. We next investigated the effect and potential mechanism of sEVs on the effects of osteogenesis and angiogenesis. We fabricated 3D-printed bioglass scaffold with Gelma/nanoclay hydrogel coatings to load sEVs (BG-gel-sEVs) to ensure in vivo sustained efficacy of sEVs. Finally, the skull defect model was used to evaluate the capacity of vascularized bone regeneration of the composited scaffolds.

RESULTS

hUC-MSCs-sEVs facilitated calcium deposition and the endothelial network formation, inducing osteogenic differentiation and angiogenesis by delivering miR-23a-3p to activate PTEN/AKT signaling pathway. Additionally, the BG-gel-sEVs composited scaffold achieved vascularized bone regeneration in vivo.

CONCLUSION

This finding illuminated that hUC-MSCs-sEVs promoted osteogenesis and angiogenesis by delivering miR-23a-3p to activate PTEN/AKT signaling pathway, achieving vascularized bone regeneration.

Circulating Endothelial Progenitor and Mesenchymal Stromal Cells as Biomarkers for Monitoring Disease Status and Responses to Exercise

Noncommunicable chronic diseases, such as obesity, cardiovascular disease (CVD), and type 2 diabetes (T2D), pose significant health challenges globally. Important advances have been made in the understanding of the pathophysiologal mechanisms and treatment of noncommunicable diseases in recent years. Lack of physical activity is a primary contributor to many noncommunicable diseases including metabolic syndrome, T2D, CVD, and obesity. Certain diabetes medications and non-pharmaceutical interventions, such as physical activity and exercise, are shown to be effective in decreasing the CVD risks associated with heart disease, stroke, obesity, prediabetes, and T2D. The ability to measure and analyze circulating adult stem cells (ASCs) has gained particular interest due to their potential to identify at-risk individuals and implications in various therapeutics. Therefore, the purpose of this narrative review is to (1) provide an overview of ASCs; specifically endothelial progenitor cells (EPCs) and mesenchymal stromal cells (MSCs), (2) describe the responses of these cells to acute and chronic exercise, and (3) highlight the potential effect of exercise on EPCs and MSCs in aging and disease. EPCs are circulating cells, abundantly available in peripheral blood, bone marrow, and umbilical cord, and are defined by cell surface markers such as CD34+. EPCs are expected to play an important role in angiogenesis and neovascularization and have been implicated in the treatment of CVD. MSCs are essential for maintaining tissue and organ homeostasis. MSCs are defined as multipotent heterogeneous cells that can proliferate in vitro as plastic-adherent cells, have fibroblast-like morphology, form colonies in vitro, and can differentiate into ostyeoblasts, adipocytes, chondroblasts, and myoblasts. In the presence of aging and disease, EPCs and MSCs decrease in quantity and functional capacity. Importantly, exercise facilitates EPC differentiation and production from bone marrow and also helps to promote migration and homing to the hypoxic and damaged tissue which in turn improve angiogenesis and vasculogenesis. Similarly, exercise stimulates increases in proliferation and migratory activity of MSCs. Despite the reported benefits of exercise on EPC and MSC number and function, little is known regarding the optimal exercise prescription for aging and clinical populations. Moreover, the interactions between medications and exercise on EPCs and MSCs is currently unclear. Use of ASCs as a biomarker have the potential to revolutionize the management of patients with a variety of metabolic and obesity related disorders and also pro-inflammatory diseases. Further investigation of clinical entities are urgently needed to understand the implications of interventions such as exercise, diet, and various medications on EPC and MSC quantity and function in aging and clinical populations.

Single-cell RNA sequencing reveals different signatures of mesenchymal stromal cell pluripotent-like and multipotent populations

Somatic stem cells are advantageous research targets for understanding the properties required to maintain stemness. Human bone marrow-mesenchymal stromal cells (BM-MSCs) were separated into pluripotent-like SSEA-3(+) Muse cells (Muse-MSCs) and multipotent SSEA-3(−) MSCs (MSCs) and were subjected to single-cell RNA sequencing analysis. Compared with MSCs, Muse-MSCs exhibited higher expression levels of the p53 repressor MDM2; signal acceptance-related genes EGF, VEGF, PDGF, WNT, TGFB, INHB, and CSF; ribosomal protein; and glycolysis and oxidative phosphorylation. Conversely, MSCs had higher expression levels of FGF and ANGPT; Rho family and caveola-related genes; amino acid and cofactor metabolism; MHC class I/II, and lysosomal enzyme genes than Muse-MSCs. Unsupervised clustering further divided Muse-MSCs into two clusters stratified by the expression of cell cycle-related genes, and MSCs into three clusters stratified by the expression of cell cycle-, cytoskeleton-, and extracellular matrix-related genes. This study evaluating the differentiation ability of BM-MSC subpopulations provides intriguing insights for understanding stemness.

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MSCs were separated into pluripotent-like Muse-MSCs and multipotent MSCs

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Gene expressions of Muse-MSCs and MSCs were analyzed by single-cell RNA sequencing

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p53 suppressor, ribosomal protein, and energy metabolism were higher in Muse-MSCs

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Genes related to the cytoskeleton, amino acid metabolism, and MHC were higher in MSCs

Molecular and Physiological Effects of Browning Agents on White Adipocytes from Bone Marrow Mesenchymal Stromal Cells

Two different types of adipose depots can be observed in mammals: white adipose tissue (WAT) and brown adipose tissue (BAT). The primary role of WAT is to deposit surplus energy in the form of triglycerides, along with many metabolic and hormonal activities; as thermogenic tissue, BAT has the distinct characteristic of using energy and glucose consumption as a strategy to maintain the core body temperature. Under specific stimuli—such as exercise, cold exposure, and drug treatment—white adipocytes can utilize their extraordinary flexibility to transdifferentiate into brown-like cells, called beige adipocytes, thereby acquiring new morphological and physiological characteristics. For this reason, the process is identified as the ‘browning of WAT’. We evaluated the ability of some drugs, including GW501516, sildenafil, and rosiglitazone, to induce the browning process of adult white adipocytes obtained from differentiated mesenchymal stromal cells (MSCs). In addition, we broadened our investigation by evaluating the potential browning capacity of IRISIN, a myokine that is stimulated by muscular exercises. Our data indicate that IRISIN was effective in promoting the browning of white adipocytes, which acquire increased expression of UCP1, increased mitochondrial mass, and modification in metabolism, as suggested by an increase of mitochondrial oxygen consumption, primarily in presence of glucose as a nutrient. These promising browning agents represent an appealing focus in the therapeutic approaches to counteracting metabolic diseases and their associated obesity.

Mesenchymal Stem Cell-Derived Extracellular Vesicles as an Advanced Therapy for Chronic Wounds

Chronic wounds are a significant challenge for patients, healthcare providers, and healthcare systems. Chronic wounds develop due to a complex interplay between chronic inflammation, tissue hypoxia, and oxidative stress, often occurring in the setting of advancing age. Ideally, new therapeutics should address all the components of chronic wound pathophysiology. Mesenchymal stem cell (MSC) therapies show significant promise to promote healing of chronic wounds. Extracellular vesicles (EVs) secreted by MSCs mediate many of their beneficial effects. We review the evidence demonstrating that MSC-EVs target the processes leading to chronic wounds. Additionally, we discuss how MSCs can be influenced to generate more potent wound healing EVs. Finally, we highlight the current state of EV clinical trials for wound healing and important preclinical studies that will lead to optimal use of MSC-EVs for patient care.

Stem Cells in Clinical Trials on Neurological Disorders: Trends in Stem Cells Origins, Indications, and Status of the Clinical Trials

Neurological diseases can significantly reduce the quality and duration of life. Stem cells provide a promising solution, not only due to their regenerative features but also for a variety of other functions, including reducing inflammation and promoting angiogenesis. Although only hematopoietic cells have been approved by the FDA so far, the number of trials continues to expand. We analyzed 492 clinical trials and illustrate the trends in stem cells origins, indications, and phase and status of the clinical trials. The most common neurological disorders treated with stem cells were injuries of brain, spinal cord, and peripheral nerves (14%), stroke (13%), multiple sclerosis (12%), and brain tumors (11%). Mesenchymal stem cells dominated (83%) although the choice of stem cells was highly dependent on the neurological disorder. Of the 492 trials, only two trials have reached phase 4, with most of all other trials being in phases 1 or 2, or transitioning between them (83%). Based on a comparison of the obtained results with similar works and further analysis of the literature, we discuss some of the challenges and future directions of stem cell therapies in the treatment of neurological diseases.

Recent advances to enhance the immunomodulatory potential of mesenchymal stem cells

Considering the unique therapeutic potential of mesenchymal stem cells (MSCs), including their immunosuppressive and immunomodulatory properties as well as their ability to improve tissue regeneration, these cells have attracted the attention of scientists and clinicians for the treatment of different inflammatory and immune system mediated disorders. However, various clinical trials using MSCs for the therapeutic purpose are conflicting and differ from the results of promising preclinical studies. This inconsistency is caused by several factors such as poor migration and homing capacities, low survival rate, low level of proliferation and differentiation, and donor-dependent variation of the cells. Enhancement and retention of persistent therapeutic effects of the cells remain a challenge to overcome in MSC-based therapy. In this review, we summarized various approaches to enhance the clinical outcomes of MSC-based therapy as well as revised current and future perspectives for the creation of cellular products with improved potential for diverse clinical applications.

Amniotic Fluid-Derived Mesenchymal Stem/Stromal Cell-Derived Secretome and Exosomes Improve Inflammation in Human Intestinal Subepithelial Myofibroblasts

Inflammatory Bowel Diseases (IBDs) are characterized by chronic relapsing inflammation of the gastrointestinal tract. The mesenchymal stem/stromal cell-derived secretome and secreted extracellular vesicles may offer novel therapeutic opportunities in patients with IBD. Thus, exosomes may be utilized as a novel cell-free approach for IBD therapy. The aim of our study was to examine the possible anti-inflammatory effects of secretome/exosomes on an IBD-relevant, in vitro model of LPS-induced inflammation in human intestinal SubEpithelial MyoFibroblasts (SEMFs). The tested CM (Conditioned Media)/exosomes derived from a specific population of second-trimester amniotic fluid mesenchymal stem/stromal cells, the spindle-shaped amniotic fluid MSCs (SS-AF-MSCs), and specifically, their secreted exosomes could be utilized as a novel cell-free approach for IBD therapy. Therefore, we studied the effect of SS-AF-MSCs CM and exosomes on LPS-induced inflammation in SEMF cells. SS-AF-MSCs CM and exosomes were collected, concentrated, and then delivered into the cell cultures. Administration of both secretome and exosomes derived from SS-AF-MSCs reduced the severity of LPS-induced inflammation. Specifically, IL-1β, IL-6, TNF-α, and TLR-4 mRNA expression was decreased, while the anti-inflammatory IL-10 was elevated. Our results were also verified at the protein level, as secretion of IL-1β was significantly reduced. Overall, our results highlight a cell-free and anti-inflammatory therapeutic agent for potential use in IBD therapy.

Global scientific trends on the immunomodulation of mesenchymal stem cells in the 21st century: A bibliometric and visualized analysis

Background

Since the discovery of the immunomodulatory functions of mesenchymal stem cells (MSCs), their application in immunomodulation has attracted considerable attention, and an increasing number of studies have been conducted worldwide. Our research aimed to investigate the global status and trends in this field.

Methods

Publications on the immunomodulatory functions of MSCs from 1 January 2000 to 7 March 2022 were retrieved from the Web of Science Core Collection. The data were studied and indexed using the bibliometric methodology. Visualization analysis, co-authorship, co-occurrence analysis, and publication trends in MSC immunomodulation were conducted using the VOSviewer software.

Results

In total, 4,227 papers were included in the study. The number of publications and research interests has significantly increased globally. China published the highest number of related articles, while the US published articles with the highest number of citations. Stem Cell Research & Therapy had the highest number of publications. Sun Yat-sen University, Shanghai Jiao Tong University, Harvard University, and Seoul National University were the most contributive institutions. Furthermore, the studies were divided into four research hotspots for MSC immunomodulation: MSC immunomodulation in regenerative medicine, the effects and mechanisms of MSC immunomodulation, MSC therapy for immune diseases, and the cell source of MSCs.

Conclusion

This study indicates that the number of publications on MSC immunomodulation will increase in the future, and MSC immunomodulation mechanisms and clinical applications of MSC immunotherapy should be the next hotspots in this research field.

An Appearance Data-Driven Model Visualizes Cell State and Predicts Mesenchymal Stem Cell Regenerative Capacity

Mesenchymal stem cells (MSCs) are widely used in treating various diseases. However, lack of a reliable evaluation approach to characterize the potency of MSCs has dampened their clinical applications. Here, a function-oriented mathematical model is established to evaluate and predict the regenerative capacity (RC) of MSCs. Processed by exhaustive testing, the model excavates four optimal fitted indices, including nucleus roundness, nucleus/cytoplasm ratio, side-scatter height, and ERK1/2 from the given index combinations. Notably, three of them except ERK1/2 are cell appearance-associated features. The predictive power of the model is validated via screening experiments of these indices by predicting the RC of newly enrolled and chemical inhibitor-treated MSCs. Further RNA-sequencing analysis reveals that cell appearance-based indices may serve as major indicators to visualize the results of integration-weighted signals in and out of cells and reflect MSC stemness. In general, this study proposes an appearance data-driven predictive model for the RC and stemness of MSCs.

Intravenously transplanted mesenchymal stromal cells: a new endocrine reservoir for cardioprotection

Background

Intravenous administration of mesenchymal stromal cells (MSCs) has an acknowledged competence of cardiac repair, despite a lack of systematic description of the underlying biological mechanisms. The lung, but not the heart, is the main trapped site for intravenously transplanted MSCs, which leaves a spatial gap between intravenously transplanted MSCs and the injured myocardium. How lung-trapped MSCs after intravenous transplantation rejuvenate the injured myocardium remains unknown.

Methods

MSCs were isolated from human placenta tissue, and DF-MSCs or Gluc-MSCs were generated by transduced with firefly luciferase (Fluc)/enhanced green fluorescence protein (eGFP) or Gaussia luciferase (Gluc) lactadherin fusion protein. The therapeutic efficiency of intravenously transplanted MSCs was investigated in a murine model of doxorubicin (Dox)-induced cardiotoxicity. Trans-organ communication from the lung to the heart with the delivery of blood was investigated by testing the release of MSC-derived extracellular vesicles (MSC-EVs), and the potential miRNA inner MSC-EVs were screened out and verified. The potential therapeutic miRNA inner MSC-EVs were then upregulated or downregulated to assess the further therapeutic efficiency

Results

Dox-induced cardiotoxicity, characterized by cardiac atrophy, left ventricular dysfunction, and injured myocardium, was alleviated by consecutive doses of MSCs. These cardioprotective effects might be attributed to suppressing GRP78 triggering endoplasmic reticulum (ER) stress-induced apoptosis in cardiomyocytes. Our results confirmed that miR-181a-5p from MSCs-derived EVs (MSC-EVs) inhibited GRP78. Intravenous DF-MSCs were trapped in lung vasculature, secreted a certain number of EVs into serum, which could be confirmed by the detection of eGFP⁺ EVs. GLuc activity was increased in serum EVs from mice administrated with GLuc-MSCs. MiR-181a-5p, inhibiting GRP78 with high efficacy, was highly expressed in serum EVs and myocardium after injecting consecutive doses of MSCs into mice treated with Dox. Finally, upregulation or downregulation of miR-181a-5p levels in MSC-EVs enhanced or weakened therapeutic effects on Dox-induced cardiotoxicity through modulating ER stress-induced apoptosis.

Conclusions

This study identifies intravenously transplanted MSCs, as an endocrine reservoir, to secrete cardioprotective EVs into blood continuously and gradually to confer the trans-organ communication that relieves Dox-induced cardiotoxicity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02922-z.

Heterogeneity of In Vitro Expanded Mesenchymal Stromal Cells and Strategies to Improve Their Therapeutic Actions

Beneficial properties of mesenchymal stromal cells (MSCs) have prompted their use in preclinical and clinical research. Accumulating evidence has been provided for the therapeutic effects of MSCs in several pathologies, including neurodegenerative diseases, myocardial infarction, skin problems, liver disorders and cancer, among others. Although MSCs are found in multiple tissues, the number of MSCs is low, making in vitro expansion a required step before MSC application. However, culture-expanded MSCs exhibit notable differences in terms of cell morphology, physiology and function, which decisively contribute to MSC heterogeneity. The changes induced in MSCs during in vitro expansion may account for the variability in the results obtained in different MSC-based therapy studies, including those using MSCs as living drug delivery systems. This review dissects the different changes that occur in culture-expanded MSCs and how these modifications alter their therapeutic properties after transplantation. Furthermore, we discuss the current strategies developed to improve the beneficial effects of MSCs for successful clinical implementation, as well as potential therapeutic alternatives.

One of the Primary Functions of Tissue-Resident Pluripotent Pericytes Cells May Be to Regulate Normal Organ Growth and Maturation: Implications for Attempts to Repair Tissues Later in Life

Adult mesenchymal stem cells were reported more than 30 years ago. Since then, their potential to repair and regenerate damaged or diseased tissues has been studied intensively in both preclinical models and human trials. Most of the need for such tissue repair/regeneration is in older populations, so much of the effort has been performed with autologous cells in older patients. However, success has been difficult to achieve. In the literature, it has been noted that such progenitor cells from younger individuals often behave with more vigorous activity and are functionally enhanced compared to those from older individuals or animals. In addition, cells with the characteristics of mesenchymal stem cells or pluripotent mesenchymal regulatory cells exist in nearly all tissues and organs as pericytes since fetal life. Such evidence raises the possibility that one of the primary roles of these organ-specific cells is to regulate organ growth and maturation, and then subsequently play a role in the maintenance of organ integrity. This review will discuss the evidence to support this concept and the implications of such a concept regarding the use of these progenitor cells for the repair and regeneration of tissues damaged by injury or disease later in life. For the latter, it may be necessary to return the organ-specific progenitor cells to the functional state that contributed to their effectiveness during growth and maturation rather than attempting to use them after alterations imposed during the aging process have been established and their function compromised.

A Comparative Study on the Adipogenic Differentiation of Mesenchymal Stem/Stromal Cells in 2D and 3D Culture

Mesenchymal stem/stromal cells (MSC) are capable of renewing the progenitor cell fraction or differentiating in a tissue-specific manner. Adipogenic differentiation of adipose-tissue-derived MSC (adMSC) is important in various pathological processes. Adipocytes and their progenitors are metabolically active and secrete molecules (adipokines) that have both pro- and anti-inflammatory properties. Cell culturing in 2D is commonly used to study cellular responses, but the 2D environment does not reflect the structural situation for most cell types. Therefore, 3D culture systems have been developed to create an environment considered more physiological. Since knowledge about the effects of 3D cultivation on adipogenic differentiation is limited, we investigated its effects on adipogenic differentiation and adipokine release of adMSC (up to 28 days) and compared these with the effects in 2D. We demonstrated that cultivation conditions are crucial for cell behavior: in both 2D and 3D culture, adipogenic differentiation occurred only after specific stimulation. While the size and structure of adipogenically stimulated 3D spheroids remained stable during the experiment, the unstimulated spheroids showed signs of disintegration. Adipokine release was dependent on culture dimensionality; we found upregulated adiponectin and downregulated pro-inflammatory factors. Our findings are relevant for cell therapeutic applications of adMSC in complex, three-dimensionally arranged tissues.

Transcriptome Sequencing Reveals Key Genes in Three Early Phases of Osteogenic, Adipogenic, and Chondrogenic Differentiation of Bone Marrow Mesenchymal Stem Cells in Rats

Bone mesenchymal stem cells (BMSCs) of multi-directional differentiation and reproductive activity are attractive candidates for bone and cartilage repair. However, the molecular mechanisms underlying the early phase of osteogenesis, adipogenesis, and chondrogenesis of BMSCs are still far from understood. In the current study, BMSCs are isolated from rats, and the gene expressions during the initiation of differentiation (phase I), lineage acquisition (phase II), and early lineage progression (phase III) of three-directional differentiation of BMSCs were detected by using high-throughput sequencing. Then, 356, 540, and 299 differentially expressed genes (DEGs) were identified in phases I, II, and III of osteogenesis, respectively. The numbers are 507, 287, and 428 for adipogenesis, respectively, and 412, 336, and 513 for chondrogenesis, respectively. Time-dependent expression patterns of genes were also validated during three-directional differentiation in BMSCs. Hub genes including Ccna2, Cdc20, and Il6 may act as common participants in initiating osteogenesis, adipogenesis, and chondrogenesis. Mex3b, Sertad1, and Hopx showed an enhanced expression throughout three early phases during the osteogenic differentiation but no significant change in other two-directional differentiation. A similar pattern of Dtx4 and Ibsp expression occurred in adipogenesis and chondrogenesis, respectively. Our findings will help understand the underlying mechanism determining the differentiation fate of BMSCs and provide theoretical support for the clinical treatment of osteoporosis, osteoarthritis, and other age-related bone diseases.

Extracellular vesicles from hypoxia-preconditioned mesenchymal stem cells alleviates myocardial injury by targeting thioredoxin-interacting protein-mediated hypoxia-inducible factor-1α pathway

BACKGROUND

Extracellular vesicles (EVs) derived from hypoxia-preconditioned (HP) mesenchymal stem cells (MSCs) have better cardioprotective effects against myocardial infarction (MI) in the early stage than EVs isolated from normoxic (NC)-MSCs. However, the cardioprotective mechanisms of HP-EVs are not fully understood.

AIM

To explore the cardioprotective mechanism of EVs derived from HP MSCs.

METHODS

We evaluated the cardioprotective effects of HP-EVs or NC-EVs from mouse adipose-derived MSCs (ADSCs) following hypoxia in vitro or MI in vivo, in order to improve the survival of cardiomyocytes (CMs) and restore cardiac function. The degree of CM apoptosis in each group was assessed by the terminal deoxynucleotidyl transferase dUTP nick end-labeling and Annexin V/PI assays. MicroRNA (miRNA) sequencing was used to investigate the functional RNA diversity between HP-EVs and NC-EVs from mouse ADSCs. The molecular mechanism of EVs in mediating thioredoxin-interacting protein (TXNIP) was verified by the dual-luciferase reporter assay. Co-immunoprecipitation, western blotting, and immunofluorescence were performed to determine if TXNIP is involved in hypoxia-inducible factor-1 alpha (HIF-1α) ubiquitination and degradation via the chromosomal region maintenance-1 (CRM-1)-dependent nuclear transport pathway.

RESULTS

HP-EVs derived from MSCs reduced both infarct size (necrosis area) and apoptotic degree to a greater extent than NC-EVs from CMs subjected to hypoxia in vitro and mice with MI in vivo. Sequencing of EV-associated miRNAs showed the upregulation of 10 miRNAs predicted to bind TXNIP, an oxidative stress-associated protein. We showed miRNA224-5p, the most upregulated miRNA in HP-EVs, directly combined the 3’ untranslated region of TXNIP and demonstrated its critical protective role against hypoxia-mediated CM injury. Our results demonstrated that MI triggered TXNIP-mediated HIF-1α ubiquitination and degradation in the CRM-1-mediated nuclear transport pathway in CMs, which led to aggravated injury and hypoxia tolerance in CMs in the early stage of MI.

CONCLUSION

The anti-apoptotic effects of HP-EVs in alleviating MI and the hypoxic conditions of CMs until reperfusion therapy may partly result from EV miR-224-5p targeting TXNIP.

Vitamin D3 Stimulates Proliferation Capacity, Expression of Pluripotency Markers, and Osteogenesis of Human Bone Marrow Mesenchymal Stromal/Stem Cells, Partly through SIRT1 Signaling

The biology of vitamin D3 is well defined, as are the effects of its active metabolites on various cells, including mesenchymal stromal/stem cells (MSCs). However, the biological potential of its precursor, cholecalciferol (VD3), has not been sufficiently investigated, although its significance in regenerative medicine—mainly in combination with various biomaterial matrices—has been recognized. Given that VD3 preconditioning might also contribute to the improvement of cellular regenerative potential, the aim of this study was to investigate its effects on bone marrow (BM) MSC functions and the signaling pathways involved. For that purpose, the influence of VD3 on BM-MSCs obtained from young human donors was determined via MTT test, flow cytometric analysis, immunocytochemistry, and qRT-PCR. Our results revealed that VD3, following a 5-day treatment, stimulated proliferation, expression of pluripotency markers (NANOG, SOX2, and Oct4), and osteogenic differentiation potential in BM-MSCs, while it reduced their senescence. Moreover, increased sirtuin 1 (SIRT1) expression was detected upon treatment with VD3, which mediated VD3-promoted osteogenesis and, partially, the stemness features through NANOG and SOX2 upregulation. In contrast, the effects of VD3 on proliferation, Oct4 expression, and senescence were SIRT1-independent. Altogether, these data indicate that VD3 has strong potential to modulate BM-MSCs’ features, partially through SIRT1 signaling, although the precise mechanisms merit further investigation.

Transcriptome Sequencing Reveals Key Genes in Three Early Phases of Osteogenic, Adipogenic, and Chondrogenic Differentiation of Bone Marrow Mesenchymal Stem Cells in Rats

Bone mesenchymal stem cells (BMSCs) of multi-directional differentiation and reproductive activity are attractive candidates for bone and cartilage repair. However, the molecular mechanisms underlying the early phase of osteogenesis, adipogenesis, and chondrogenesis of BMSCs are still far from understood. In the current study, BMSCs are isolated from rats, and the gene expressions during the initiation of differentiation (phase I), lineage acquisition (phase II), and early lineage progression (phase III) of three-directional differentiation of BMSCs were detected by using high-throughput sequencing. Then, 356, 540, and 299 differentially expressed genes (DEGs) were identified in phases I, II, and III of osteogenesis, respectively. The numbers are 507, 287, and 428 for adipogenesis, respectively, and 412, 336, and 513 for chondrogenesis, respectively. Time-dependent expression patterns of genes were also validated during three-directional differentiation in BMSCs. Hub genes including Ccna2, Cdc20, and Il6 may act as common participants in initiating osteogenesis, adipogenesis, and chondrogenesis. Mex3b, Sertad1, and Hopx showed an enhanced expression throughout three early phases during the osteogenic differentiation but no significant change in other two-directional differentiation. A similar pattern of Dtx4 and Ibsp expression occurred in adipogenesis and chondrogenesis, respectively. Our findings will help understand the underlying mechanism determining the differentiation fate of BMSCs and provide theoretical support for the clinical treatment of osteoporosis, osteoarthritis, and other age-related bone diseases.

Mesenchymal Stem/Stromal Cells Derived from Human and Animal Perinatal Tissues-Origins, Characteristics, Signaling Pathways, and Clinical Trials

Mesenchymal stem/stromal cells (MSCs) are currently one of the most extensively researched fields due to their promising opportunity for use in regenerative medicine. There are many sources of MSCs, of which cells of perinatal origin appear to be an invaluable pool. Compared to embryonic stem cells, they are devoid of ethical conflicts because they are derived from tissues surrounding the fetus and can be safely recovered from medical waste after delivery. Additionally, perinatal MSCs exhibit better self-renewal and differentiation properties than those derived from adult tissues. It is important to consider the anatomy of perinatal tissues and the general description of MSCs, including their isolation, differentiation, and characterization of different types of perinatal MSCs from both animals and humans (placenta, umbilical cord, amniotic fluid). Ultimately, signaling pathways are essential to consider regarding the clinical applications of MSCs. It is important to consider the origin of these cells, referring to the anatomical structure of the organs of origin, when describing the general and specific characteristics of the different types of MSCs as well as the pathways involved in differentiation.

Mesenchymal Stromal Cells for the Treatment of Graft Versus Host Disease

Graft versus host disease (GvHD) is a life-threating complication of allogeneic hematopoietic stem cell transplantation, which is initially treated with high dose corticosteroids. Approximately 50% of acute GvHD cases are resistant to steroid treatment, and two-year mortality rates in those steroid-resistant patients exceed 80%. Chronic GvHD necessitates prolonged corticosteroid use, which is typically associated with limited efficacy and troublesome adverse effects. No agent has yet been established as an optimal second line therapy for either acute or chronic GvHD, but mesenchymal stromal cells (MSCs) have shown substantial promise. MSCs promote an immunosuppressive and immunoregulatory environment via multifactorial mechanisms, including: secretion of proteins/peptides/hormones; transfer of mitochondria; and transfer of exosomes or microvesicles containing RNA and other molecules. A large number of clinical studies have investigated MSCs from various sources as a treatment for acute and/or chronic GvHD. MSCs are generally safe and well tolerated, and most clinical studies have generated encouraging efficacy results, but response rates have varied. Confounding factors include variability in MSC donor types, production methodology and dose regimens, as well as variations in study design. It is well-established that extensive culture expansion of primary donor-derived MSCs leads to marked changes in functionality, and that there is a high level of inter-donor variability in MSC properties. However, recent manufacturing innovations may be capable of overcoming these problems. Further adequately powered prospective studies are required to confirm efficacy and establish the place of MSC therapy in the treatment of this condition.

Targeting Brain Tumors with Mesenchymal Stem Cells in the Experimental Model of the Orthotopic Glioblastoma in Rats

Despite multimodal approaches for the treatment of multiforme glioblastoma (GBM) advances in outcome have been very modest indicating the necessity of novel diagnostic and therapeutic strategies. Currently, mesenchymal stem cells (MSCs) represent a promising platform for cell-based cancer therapies because of their tumor-tropism, low immunogenicity, easy accessibility, isolation procedure, and culturing. In the present study, we assessed the tumor-tropism and biodistribution of the superparamagnetic iron oxide nanoparticle (SPION)-labeled MSCs in the orthotopic model of C6 glioblastoma in Wistar rats. As shown in in vitro studies employing confocal microscopy, high-content quantitative image cytometer, and xCelligence system MSCs exhibit a high migratory capacity towards C6 glioblastoma cells. Intravenous administration of SPION-labeled MSCs in vivo resulted in intratumoral accumulation of the tagged cells in the tumor tissues that in turn significantly enhanced the contrast of the tumor when high-field magnetic resonance imaging was performed. Subsequent biodistribution studies employing highly sensitive nonlinear magnetic response measurements (NLR-M₂) supported by histological analysis confirm the retention of MSCs in the glioblastoma. In conclusion, MSCs due to their tumor-tropism could be employed as a drug-delivery platform for future theranostic approaches.

Biomolecular Evaluation of Piceatannol's Effects in Counteracting the Senescence of Mesenchymal Stromal Cells: A New Candidate for Senotherapeutics?

Several investigations on senescence and its causative role in aging have underscored the importance of developing senotherapeutics, a field focused on killing senescent cells and/or preventing their accumulation within tissues. Using polyphenols in counteracting senescence may facilitate the development of senotherapeutics given their presence in the human diet, their confirmed tolerability and absence of severe side effects, and their role in preventing senescence and inducing the death of senescent cells. Against that background, we evaluated the effect of piceatannol, a natural polyphenol, on the senescence of mesenchymal stromal cells (MSCs), which play a key role in the body's homeostasis. Among our results, piceatannol reduced the number of senescent cells both after genotoxic stress that induced acute senescence and in senescent replicative cultures. Such senotherapeutics activity, moreover, promoted the recovery of cell proliferation and the stemness properties of MSCs. Altogether, our findings demonstrate piceatannol's effectiveness in counteracting senescence by targeting its associated pathways and detecting and affecting P53-dependent and P53-independent senescence. Our study thus suggests that, given piceatannol's various mechanisms to accomplish its pleiotropic activities, it may be able to counteract any senescent phenotypes.

Molecular Mechanisms of Mesenchymal Stem Cell-Based Therapy in Acute Kidney Injury

Acute kidney injury (AKI) causes a lot of harm to human health but is treated by only supportive therapy in most cases. Recent evidence shows that mesenchymal stem cells (MSCs) benefit kidney regeneration through releasing paracrine factors and extracellular vesicles (EVs) to the recipient kidney cells and are considered to be promising cellular therapy for AKI. To develop more efficient, precise therapies for AKI, we review the therapeutic mechanism of MSCs and MSC-derived EVs in AKI and look for a better understanding of molecular signaling and cellular communication between donor MSCs and recipient kidney cells. We also review recent clinical trials of MSC-EVs in AKI. This review summarizes the molecular mechanisms of MSCs' therapeutic effects on kidney regeneration, expecting to comprehensively facilitate future clinical application for treating AKI.

Application of Mesenchymal Stem Cells in Targeted Delivery to the Brain: Potential and Challenges of the Extracellular Vesicle-Based Approach for Brain Tumor Treatment

Treating brain tumors presents enormous challenges, and there are still poor prognoses in both adults and children. Application of novel targets and potential drugs is hindered by the function of the blood-brain barrier, which significantly restricts therapeutic access to the tumor. Mesenchymal stem cells (MSCs) can cross biological barriers, migrate to sites of injuries to exert many healing effects, and be engineered to incorporate different types of cargo, making them an ideal vehicle to transport anti-tumor agents to the central nervous system. Extracellular vesicles (EVs) produced by MSCs (MSC-EVs) have valuable innate properties from parent cells, and are being exploited as cell-free treatments for many neurological diseases. Compared to using MSCs, targeted delivery via MSC-EVs has a better pharmacokinetic profile, yet avoids many critical issues of cell-based systems. As the field of MSC therapeutic applications is quickly expanding, this article aims to give an overall picture for one direction of EV-based targeting of brain tumors, with updates on available techniques, outcomes of experimental models, and critical challenges of this concept.

Mesenchymal Stem Cells in the Treatment of COVID-19, a Promising Future

Mesenchymal stem cells (MSCs) are multipotent adult stem cells present in virtually all tissues; they have a potent self-renewal capacity and can differentiate into multiple cell types. They also affect the ambient tissue by the paracrine secretion of numerous factors in vivo, including the induction of other stem cells’ differentiation. In vitro, the culture media supernatant is named secretome and contains soluble molecules and extracellular vesicles that retain potent biological function in tissue regeneration. MSCs are considered safe for human treatment; their use does not involve ethical issues, as embryonic stem cells do not require genetic manipulation as induced pluripotent stem cells, and after intravenous injection, they are mainly found in the lugs. Therefore, these cells are currently being tested in various preclinical and clinical trials for several diseases, including COVID-19. Several affected COVID-19 patients develop induced acute respiratory distress syndrome (ARDS) associated with an uncontrolled inflammatory response. This condition causes extensive damage to the lungs and may leave serious post-COVID-19 sequelae. As the disease may cause systemic alterations, such as thromboembolism and compromised renal and cardiac function, the intravenous injection of MSCs may be a therapeutic alternative against multiple pathological manifestations. In this work, we reviewed the literature about MSCs biology, focusing on their function in pulmonary regeneration and their use in COVID-19 treatment.

Extracellular Vesicles as Therapeutic Tools for the Treatment of Chronic Wounds

Chronic wounds develop when the orderly process of cutaneous wound healing is delayed or disrupted. Development of a chronic wound is associated with significant morbidity and financial burden to the individual and health-care system. Therefore, new therapeutic modalities are needed to address this serious condition. Mesenchymal stem cells (MSCs) promote skin repair, but their clinical use has been limited due to technical challenges. Extracellular vesicles (EVs) are particles released by cells that carry bioactive molecules (lipids, proteins, and nucleic acids) and regulate intercellular communication. EVs (exosomes, microvesicles, and apoptotic bodies) mediate key therapeutic effects of MSCs. In this review we examine the experimental data establishing a role for EVs in wound healing. Then, we explore techniques for designing EVs to function as a targeted drug delivery system and how EVs can be incorporated into biomaterials to produce a personalized wound dressing. Finally, we discuss the status of clinically deploying EVs as a therapeutic agent in wound care.