5-Azacytidine-treated human mesenchymal stem/progenitor cells derived from umbilical cord, cord blood and bone marrow do not generate cardiomyocytes in vitro at high frequencies

Optimal temperature for the long-term culture of adult porcine islets for xenotransplantation

Porcine islet xenotransplantation represents a promising therapy for severe diabetes mellitus. Long-term culture of porcine islets is a crucial challenge to permit the on-demand provision of islets. We aimed to identify the optimal temperature for the long-term culture of adult porcine islets for xenotransplantation. We evaluated the factors potentially influencing successful 28-day culture of islets at 24°C and 37°C, and found that culture at 37°C contributed to the stability of the morphology of the islets, the proliferation of islet cells, and the recovery of endocrine function, indicated by the expression of genes involved in pancreatic development, hormone production, and glucose-stimulated insulin secretion. These advantages may be provided by islet-derived CD146-positive stellate cells. The efficacy of xenotransplantation using islets cultured for a long time at 37°C was similar to that of overnight-cultured islets. In conclusion, 37°C might be a suitable temperature for the long-term culture of porcine islets, but further modifications will be required for successful xenotransplantation in a clinical setting.

Mesenchymal Stem Cell-Originated Exosomal Lnc A2M-AS1 Alleviates Hypoxia/Reperfusion-Induced Apoptosis and Oxidative Stress in Cardiomyocytes

BACKGROUND

Mesenchymal stem cell (MSC)-derived exosomes play significant roles in ameliorating cardiac damage after myocardial ischemia-reperfusion (I/R) injury. Long non-coding RNA alpha-2-macroglobulin antisense RNA 1 (Lnc A2M-AS1) was found that might protect against myocardial I/R. However, whether Lnc A2M-AS1 delivery via MSC-derived exosomes could also regulate myocardial I/R injury remains unknown.

METHODS

Exosomes were isolated by ultracentrifugation, and qualified by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blot. Hypoxia/reoxygenation (H/R) treatment in human cardiomyocytes was used to mimic the process of myocardial I/R in vitro. The viability and apoptosis of cardiomyocytes were detected using cell counting kit-8, flow cytometry, and Western blot assays. The contents of lactate dehydrogenase (LDH), malondialdehyde (MDA), and superoxide dismutase (SOD) were evaluated using corresponding commercial kits. The quantitative real-time polymerase chain reaction and Western blot were used to determine the expression levels of Lnc A2M-AS1, microRNA (miR)-556-5p, and X-linked inhibitor of apoptosis protein (XIAP). The binding interaction between miR-556-5p and Lnc A2M-AS1 or XIAP was confirmed by the dual-luciferase reporter, RIP and pull-down assays.

RESULTS

Exosomes isolated from hMSCs (hMSCs-exo) attenuated H/R-induced apoptosis and oxidative stress in cardiomyocytes. Lnc A2M-AS1 was lowly expressed in AMI patients and H/R-induced cardiomyocytes. Besides, Lnc A2M-AS1 was detectable in hMSCs-exo, exosomes derived from Lnc A2M-AS1-transfected hMSCs weakened H/R-induced apoptosis and oxidative stress, and enhanced the protective action of hMSCs-exo on H/R-induced cardiomyocytes. Further mechanism analysis showed that Lnc A2M-AS1 acted as a sponge for miR-556-5p to increase XIAP expression level. Importantly, miR-556-5p overexpression or XIAP knockdown reversed the action of exosomal Lnc A2M-AS1 on H/R-induced cardiomyocytes.

CONCLUSION

Lnc A2M-AS1 delivery via MSC-derived exosomes ameliorated H/R-induced cardiomyocyte apoptosis and oxidative stress via regulating miR-556-5p/XIAP, opening a new window into the pathogenesis of myocardial I/R injury.

Expression Profile of New Marker Genes Involved in Differentiation of Human Wharton's Jelly-Derived Mesenchymal Stem Cells into Chondrocytes, Osteoblasts, Adipocytes and Neural-like Cells

Wharton's jelly (WJ) contains mesenchymal stem cells (MSCs) exhibiting broad immunomodulatory properties and differentiation capacity, which makes them a promising tool for cellular therapies. Although the osteogenic, chondrogenic and adipogenic differentiation is a gold standard for proper identification of MSCs, it is important to elucidate the exact molecular mechanisms governing these processes to develop safe and efficient cellular therapies. Umbilical cords were collected from healthy, full-term deliveries, for subsequent MSCs (WJ-MSCs) isolation. WJ-MSCs were cultivated in vitro for osteogenic, chondrogenic, adipogenic and neurogenic differentiation. The RNA samples were isolated and the transcript levels were evaluated using NovaSeq platform, which led to the identification of differentially expressed genes. Expression of H19 and SLPI was enhanced in adipocytes, chondrocytes and osteoblasts, and NPPB was decreased in all analyzed groups compared to the control. KISS1 was down-regulated in adipocytes, chondrocytes, and neural-like cells compared to the control. The most of identified genes were already implicated in differentiation of MSCs; however, some genes (PROK1, OCA2) have not yet been associated with initiating final cell fate. The current results indicate that both osteo- and adipo-induced WJ-MSCs share many similarities regarding the most overexpressed genes, while the neuro-induced WJ-MSCs are quite distinctive from the other three groups. Overall, this study provides an insight into the transcriptomic changes occurring during the differentiation of WJ-MSCs and enables the identification of novel markers involved in this process, which may serve as a reference for further research exploring the role of these genes in physiology of WJ-MSCs and in regenerative medicine.

Research progress of extracellular vesicles and exosomes derived from mesenchymal stem cells in the treatment of oxidative stress-related diseases

There is growing evidence that mesenchymal stem cell-derived extracellular vesicles and exosomes can significantly improve the curative effect of oxidative stress-related diseases. Mesenchymal stem cell extracellular vesicles and exosomes (MSC-EVs and MSC-Exos) are rich in bioactive molecules and have many biological regulatory functions. In this review, we describe how MSC-EVs and MSC-Exos reduce the related markers of oxidative stress and inflammation in various systemic diseases, and the molecular mechanism of MSC-EVs and MSC-Exos in treating apoptosis and vascular injury induced by oxidative stress. The results of a large number of experimental studies have shown that both local and systemic administration can effectively inhibit the oxidative stress response in diseases and promote the survival and regeneration of damaged parenchymal cells. The mRNA and miRNAs in MSC-EVs and MSC-Exos are the most important bioactive molecules in disease treatment, which can inhibit the apoptosis, necrosis and oxidative stress of lung, heart, kidney, liver, bone, skin and other cells, and promote their survive and regenerate.

Stem cell therapy for acute myocardial infarction: Mesenchymal Stem Cells and induced Pluripotent Stem Cells

INTRODUCTION

Acute myocardial infarction (AMI) remains a leading cause of death in the United States. The limited capacity of cardiomyocytes to regenerate and the restricted contractility of scar tissue after AMI are not addressed by current pharmacologic interventions. Mesenchymal stem/stromal cells (MSCs) have emerged as a promising therapeutic approach due to their low antigenicity, ease of harvesting, and efficacy and safety in preclinical and clinical studies, despite their low survival and engraftment rates. Other stem cell types, such as induced pluripotent stem cells (iPSCs) also show promise, and optimizing cardiac repair requires integrating emerging technologies and strategies.

AREAS COVERED

This review offers insights into advancing cell-based therapies for AMI, emphasizing meticulously planned trials with a standardized definition of AMI, for a bench-to-bedside approach. We critically evaluate fundamental studies and clinical trials to provide a comprehensive overview of the advances, limitations and prospects for cell-based therapy in AMI.

EXPERT OPINION

MSCs continue to show potential promise for treating AMI and its sequelae, but addressing their low survival and engraftment rates is crucial for clinical success. Integrating emerging technologies such as pluripotent stem cells and conducting well-designed trials will harness the full potential of cell-based therapy in AMI management. Collaborative efforts are vital to developing effective stem cell therapies for AMI patients.

Administration of stem cells against cardiovascular diseases with a focus on molecular mechanisms: Current knowledge and prospects

Cardiovascular diseases (CVDs) are a serious global concern for public and human health. Despite the emergence of significant therapeutic advances, it is still the leading cause of death and disability worldwide. As a result, extensive efforts are underway to develop practical therapeutic approaches. Stem cell-based therapies could be considered a promising strategy for the treatment of CVDs. The efficacy of stem cell-based therapeutic approaches is demonstrated through recent laboratory and clinical studies due to their inherent regenerative properties, proliferative nature, and their capacity to differentiate into different cells such as cardiomyocytes. These properties could improve cardiovascular functioning leading to heart regeneration. The two most common types of stem cells with the potential to cure heart diseases are induced pluripotent stem cells (iPSCs) and mesenchymal stem cells (MSCs). Several studies have demonstrated the use, efficacy, and safety of MSC and iPSCs-based therapies for the treatment of CVDs. In this study, we explain the application of stem cells, especially iPSCs and MSCs, in the treatment of CVDs with a focus on cellular and molecular mechanisms and then discuss the advantages, disadvantages, and perspectives of using this technology in the treatment of these diseases.

Remodeled CD146+CD271+ Bone Marrow Mesenchymal Stem Cells from Patients with Polycythemia Vera Exhibit Altered Hematopoietic Supportive Activity

An essential component of the hematopoietic microenvironment, bone marrow mesenchymal stem cells (BM-MSCs) play an important role in the homeostasis and pathogenesis of the hematopoietic system by regulating the fate of hematopoietic stem cells (HSCs). Previous studies revealed that BM-MSCs were functionally remodeled by malignant cells in leukemia. However, the alterations in BM-MSCs in polycythemia vera (PV) and their effects on HSCs still need to be elucidated. Our results demonstrated that although BM-MSCs from PV patients shared similar surface markers with those from healthy donors, they exhibited enhanced proliferation, decreased senescence, and abnormal osteogenic differentiation capacities. The CD146⁺CD271⁺ BM-MSC subpopulation, which is considered to give rise to typical cultured BM-MSCs and form bone and the hematopoietic stroma, was then sorted. Compared with those from healthy donors, CD146⁺CD271⁺ BM-MSCs from PV patients showed an impaired mesensphere formation capacity and abnormal differentiation toward osteogenic lineages. In addition, CD146⁺CD271⁺ PV BM-MSCs showed altered hematopoietic supportive activity when cocultured with cord blood CD34⁺ cells. Our study suggested that remodeled CD146⁺CD271⁺ BM-MSCs might contribute to the pathogenesis of PV, a finding that will shed light on potential therapeutic strategies for PV.

The Effect of Tissue Stromal Vascular Fraction as Compared to Cellular Stromal Vascular Fraction to Treat Anal Sphincter Incontinence

BACKGROUND

The long-term prognosis of current treatments for anal sphincter incontinence (ASI) is poor. Here, we explored the efficacy of tissue adipose stromal vascular fraction SVF (tSVF) on ASI and compared it to that of cellular SVF (cSVF). We then investigated possible mechanisms.

METHODS

Rat cSVF and tSVF were isolated and labeled with DIL. One day after modeling, three groups received phosphate-buffered saline (PBS), cSVF, tSVF, respectively. The control group received nil modeling nor any treatments. The effect was assessed by function test for anal pressure and electromyography, and staining for fiber content, proliferation and differentiation at day 5 and day 10.

RESULTS

cSVF injection resulted in faster healing than tSVF. The cSVF group showed significant improvement on anal pressure on day 10. For the electromyography test, cSVF showed significant improvement for the frequencies on day 10, and for the peak values on both time points, while tSVF showed significant improvement for the peak values on day 10. The two SVF both alleviated fibrosis. Immunofluorescence tracing identified differentiation of some injected cells towards myosatellite cells and smooth muscle cells in both SVF groups. For all the tests, the tSVF group tends to have similar or lower effects than the cSVF group with no significant difference.

CONCLUSION

cSVF and tSVF are both safe and effective in treating ASI, while the effect of cSVF is slighter higher than tSVF.

Comparison of Sources and Methods for the Isolation of Equine Adipose Tissue-Derived Stromal/Stem Cells and Preliminary Results on Their Reaction to Incubation with 5-Azacytidine

Simple Summary

The function of the equine heart is different from that in other species, and a species-specific in vitro model would simplify investigations in the field of equine cardiology. The recent advances in stem cell research and the availability of adipose tissue-derived stromal/stem cells (ASCs) could be a promising starting point for the development of such an in vitro model. In order to test the hypothesis that equine ASCs can be differentiated into cells resembling heart cells, we isolated ASCs from abdominal, retrobulbar, and subcutaneous adipose tissue after collagenase digestion or from direct cultivation of explants. Both techniques resulted in similar yields of cells displaying morphological, immunophenotypical, and molecular biological characteristics of mesenchymal stem cells. Abdominal adipose tissue was found to be most suitable for ASC isolation in equines. However, contrasting earlier studies performed with ASCs from other species, equine ASCs were refractory to 5-azacytidine-induced upregulation of markers characteristic for the differentiation into heart cells. Hence, further studies are required to establish equine cardiomyocyte induction.

Abstract

Physiological particularities of the equine heart justify the development of an in vitro model suitable for investigations of the species-specific equine cardiac electrophysiology. Adipose tissue-derived stromal/stem cells (ASCs) could be a promising starting point from which to develop such a cardiomyocyte (CM)-like cell model. Therefore, we compared abdominal, retrobulbar, and subcutaneous adipose tissue as sources for the isolation of ASCs applying two isolation methods: the collagenase digestion and direct explant culture. Abdominal adipose tissue was most suitable for the isolation of ASCs and both isolation methods resulted in comparable yields of CD45-/CD34-negative cells expressing the mesenchymal stem cell markers CD29, CD44, and CD90, as well as pluripotency markers, as determined by flow cytometry and real-time quantitative PCR. However, exposure of equine ASCs to 5-azacytidine (5-AZA), reportedly inducing CM differentiation from rats, rabbits, and human ASCs, was not successful in our study. More precisely, neither the early differentiation markers GATA4 and NKX2-5, nor the late CM differentiation markers TNNI3, MYH6, and MYH7 were upregulated in equine ASCs exposed to 10 µM 5-AZA for 48 h. Hence, further work focusing on the optimal conditions for CM differentiation of equine stem cells derived from adipose tissue, as well as possibly from other origins, are needed.

CD317-Positive Immune Stromal Cells in Human "Mesenchymal Stem Cell" Populations

Heterogeneity of bone marrow mesenchymal stromal cells (MSCs, frequently referred to as "mesenchymal stem cells") clouds biological understanding and hampers their clinical development. In MSC cultures most commonly used in research and therapy, we have identified an MSC subtype characterized by CD317 expression (CD317^pos (29.77 ± 3.00% of the total MSC population), comprising CD317^dim (28.10 ± 4.60%) and CD317^bright (1.67 ± 0.58%) MSCs) and a constitutive interferon signature linked to human disease. We demonstrate that CD317^pos MSCs induced cutaneous tissue damage when applied a skin explant model of inflammation, whereas CD317^neg MSCs had no effect. Only CD317^neg MSCs were able to suppress proliferative cycles of activated human T cells in vitro, whilst CD317^pos MSCs increased polarization towards pro-inflammatory Th1 cells and CD317^neg cell lines did not. Using an in vivo peritonitis model, we found that CD317^neg and CD317^pos MSCs suppressed leukocyte recruitment but only CD317^neg MSCs suppressed macrophage numbers. Using MSC-loaded scaffolds implanted subcutaneously in immunocompromised mice we were able to observe tissue generation and blood vessel formation with CD317^neg MSC lines, but not CD317^pos MSC lines. Our evidence is consistent with the identification of an immune stromal cell, which is likely to contribute to specific physiological and pathological functions and influence clinical outcome of therapeutic MSCs.

Impact of Microenvironmental Changes during Degeneration on Intervertebral Disc Progenitor Cells: A Comparison with Mesenchymal Stem Cells

Intervertebral disc (IVD) degeneration occurs with natural ageing and is linked to low back pain, a common disease. As an avascular tissue, the microenvironment inside the IVD is harsh. During degeneration, the condition becomes even more compromised, presenting a significant challenge to the survival and function of the resident cells, as well as to any regeneration attempts using cell implantation. Mesenchymal stem cells (MSCs) have been proposed as a candidate stem cell tool for IVD regeneration. Recently, endogenous IVD progenitor cells have been identified inside the IVD, highlighting their potential for self-repair. IVD progenitor cells have properties similar to MSCs, with minor differences in potency and surface marker expression. Currently, it is unclear how IVD progenitor cells react to microenvironmental factors and in what ways they possibly behave differently to MSCs. Here, we first summarized the microenvironmental factors presented in the IVD and their changes during degeneration. Then, we analyzed the available studies on the responses of IVD progenitor cells and MSCs to these factors, and made comparisons between these two types of cells, when possible, in an attempt to achieve a clear understanding of the characteristics of IVD progenitor cells when compared to MSCs; as well as, to provide possible clues to cell fate after implantation, which may facilitate future manipulation and design of IVD regeneration studies.

Mesenchymal stromal cells: what have we learned so far about their therapeutic potential and mechanisms of action?

Mesenchymal stromal cells (MSCs) have been found to be safe and effective in a wide range of animal models of human disease. MSCs have been tested in thousands of clinical trials, but results show that while these cells appear to be safe, they tend to lack efficacy. This has raised questions about whether animal models are useful for predicting efficacy in patients. However, a problem with animal studies is that there is a lack of standardisation in the models and MSC therapy regimes used; there appears to be publication bias towards studies reporting positive outcomes; and the reproducibility of results from animal experiments tends not to be confirmed prior to clinical translation. A further problem is that while some progress has been made towards investigating the mechanisms of action (MoA) of MSCs, we still fail to understand how they work. To make progress, it is important to ensure that prior to clinical translation, the beneficial effects of MSCs in animal studies are real and can be repeated by independent research groups. We also need to understand the MoA of MSCs to assess whether their effects are likely to be beneficial across different species. In this review, we give an overview of the current clinical picture of MSC therapies and discuss what we have learned from animal studies. We also give a comprehensive update of what we know about the MoA of MSCs, particularly in relation to their role in immunomodulation.

Exosomes Derived from lncRNA TCTN2-Modified Mesenchymal Stem Cells Improve Spinal Cord Injury by miR-329-3p/IGF1R Axis

Mesenchymal stem cells (MSCs)-derived exosomes play significant roles in alleviating spinal cord injury (SCI). Previous study showed that long non-coding RNA tectonic family member 2 (TCTN2) was able to relieve SCI. Herein, whether TCTN2 exerted its roles in functional recovery after SCI via exosomes derived from MSCs was explored. The SCI model was established in rats, and the neurological function was evaluated using the Basso, Beattie, and Bresnahan (BBB) scoring. Lipopolysaccharide (LPS)-induced differentiated PC12 cells were used as an in vitro model for neurotoxicity research. The expression of genes and proteins was detected by qRT-PCR and Western blot. Exosomes were isolated by ultracentrifugation and qualified by TEM and Western blot. In vitro assays were performed using CCK-8 assay, EdU assay, and flow cytometry, respectively. Dual-luciferase reporter assay and RIP assay were used to confirm the target relationship between miR-329-3p and TCTN2 or insulin-like growth factor1 receptor (IGF1R). TCTN2 expression was down-regulated in SCI model rat and lipopolysaccharide (LPS)-stimulated PC12 cells. MSCs produced exosomes and could package TCTN2 into secreted exosomes. Tail vein injection of TCTN2 exosomes into rats significantly improved functional recovery of SCI. Meanwhile, TCTN2 exosomes treatment alleviated LPS-induced neuronal apoptosis, inflammation, and oxidative stress in vitro. Additionally, TCTN2 targeted miR-329-3p and subsequently regulated the expression of its target IGF1R. Rescue assays suggested that miR-329-3p/IGF1R axis mediated the beneficial effects of TCTN2 exosomes on LPS-treated PC12 cells. In all, exosomes derived from TCTN2-modified MSCs could improve functional recovery of SCI in vivo and attenuate LPS-induced neuronal apoptosis, inflammation, and oxidative stress in vitro via miR-329-3p/IGF1R axis, suggesting a novel insight into the development of MSC-exosomes-based therapy for SCI.

Functions of Mesenchymal Stem Cells in Cardiac Repair

Myocardial infarction (MI) and heart failure (HF) are significant contributors of mortality worldwide. Mesenchymal stem cells (MSCs) hold a great potential for cardiac regenerative medicine-based therapies. Their therapeutic potential has been widely investigated in various in-vitro and in-vivo preclinical models. Besides, they have been tested in clinical trials of MI and HF with various outcomes. Differentiation to lineages of cardiac cells, neovascularization, anti-fibrotic, anti-inflammatory, anti-apoptotic and immune modulatory effects are the main drivers of MSC functions during cardiac repair. However, the main mechanisms regulating these functions and cross-talk between cells are not fully known yet. Increasing line of evidence also suggests that secretomes of MSCs and/or their extracellular vesicles play significant roles in a paracrine manner while mediating these functions. This chapter aims to summarize and highlight cardiac repair functions of MSCs during cardiac repair.

Comparison of the Characteristics of Breast Milk-derived Stem Cells with the Stem Cells Derived from the Other Sources: A Comparative Review

Breast milk (BrM) not only supplies nutrition, but it also contains a diverse population of cells. It has been estimated that up to 6% of the cells in human milk possess the characteristics of mesenchymal stem cells (MSC). Available data also indicate that these cells are multipotent and capable of self-renewal and differentiation with other cells. In this review, we have compared different characteristics, such as CD markers, differentiation capacity, and morphology of stem cells, derived from human breast milk (hBr-MSC) with human bone marrow (hBMSC), Wharton's jelly (WJMSC), and human adipose tissue (hADMSC). Through the literature review, it was revealed that human breast milk-derived stem cells specifically express a group of cell surface markers, including CD14, CD31, CD45, and CD86. Importantly, a group of markers, CD13, CD29, CD44, CD105, CD106, CD146, and CD166, were identified, which were common in the four sources of stem cells. WJMSC, hBMSC, hADMSC, and hBr-MSC are potently able to differentiate into the mesoderm, ectoderm, and endoderm cell lineages. The ability of hBr-MSCs todifferentiate into the neural stem cells, neurons, adipocyte, hepatocyte, chondrocyte, osteocyte, and cardiomyocytes has made these cells a promising source of stem cells in regenerative medicine, while isolation of stem cells from the commonly used sources, such as bone marrow, requires invasive procedures. Although autologous breast milk-derived stem cells are an accessible source for women who are in the lactation period, breast milk can be considered as a source of stem cells with high differentiation potential without any ethical concern.

Prospects for the therapeutic development of umbilical cord blood-derived mesenchymal stem cells

Umbilical cord blood (UCB) is a primitive and abundant source of mesenchymal stem cells (MSCs). UCB-derived MSCs have a broad and efficient therapeutic capacity to treat various diseases and disorders. Despite the high latent self-renewal and differentiation capacity of these cells, the safety, efficacy, and yield of MSCs expanded for ex vivo clinical applications remains a concern. However, immunomodulatory effects have emerged in various disease models, exhibiting specific mechanisms of action, such as cell migration and homing, angiogenesis, anti-apoptosis, proliferation, anti-cancer, anti-fibrosis, anti-inflammation and tissue regeneration. Herein, we review the current literature pertaining to the UCB-derived MSC application as potential treatment strategies, and discuss the concerns regarding the safety and mass production issues in future applications.

Immunophenotypic characteristics of multipotent mesenchymal stromal cells that affect the efficacy of their use in the prevention of acute graft vs host disease

BACKGROUND

Multipotent mesenchymal stromal cells (MSCs) are widely used in the clinic due to their unique properties, namely, their ability to differentiate in all mesenchymal directions and their immunomodulatory activity. Healthy donor MSCs were used to prevent the development of acute graft vs host disease (GVHD) after allogeneic bone marrow transplantation (allo-BMT). The administration of MSCs to patients was not always effective. The MSCs obtained from different donors have individual characteristics. The differences between MSC samples may affect their clinical efficacy.

AIM

To study the differences between effective and ineffective MSCs.

METHODS

MSCs derived from the bone marrow of a hematopoietic stem cells donor were injected intravenously into allo-BMT recipients for GVHD prophylaxis at the moment of blood cell reconstitution. Aliquots of 52 MSC samples that were administered to patients were examined, and the same cells were cultured in the presence of peripheral blood mononuclear cells (PBMCs) from a third-party donor or treated with the pro-inflammatory cytokines IL-1β, IFN and TNF. Flow cytometry revealed the immunophenotype of the nontreated MSCs, the MSCs cocultured with PBMCs for 4 d and the MSCs exposed to cytokines. The proportions of CD25-, CD146-, CD69-, HLA-DR- and PD-1-positive CD4+ and CD8+ cells and the distribution of various effector and memory cell subpopulations in the PBMCs cocultured with the MSCs were also determined.

RESULTS

Differences in the immunophenotypes of effective and ineffective MSCs were observed. In the effective samples, the mean fluorescence intensity (MFI) of HLA-ABC, HLA-DR, CD105, and CD146 was significantly higher. After MSCs were treated with IFN or cocultured with PBMCs, the HLA-ABC, HLA-DR, CD90 and CD54 MFI showed a stronger increase in the effective MSCs, which indicated an increase in the immunomodulatory activity of these cells. When PBMCs were cocultured with effective MSCs, the proportions of CD4+ and CD8+central memory cells significantly decreased, and the proportion of CD8+CD146+ lymphocytes increased more than in the subpopulations of lymphocytes cocultured with MSC samples that were ineffective in the prevention of GVHD; in addition, the proportion of CD8+effector memory lymphocytes decreased in the PBMCs cocultured with the effective MSC samples but increased in the PBMCs cocultured with the ineffective MSC samples. The proportion of CD4+CD146+ lymphocytes increased only when cocultured with the inefficient samples.

CONCLUSION

For the first time, differences were observed between MSC samples that were effective for GVHD prophylaxis and those that were ineffective. Thus, it was shown that the immunomodulatory activity of MSCs depends on the individual characteristics of the MSC population.

Mesenchymal Stem Cells in Cardiac Repair: Effects on Myocytes, Vasculature, and Fibroblasts

PURPOSE

Cardiac pathologies remain a dominant cause of morbidity and mortality within the community. The drive to develop therapies capable of repairing damaged heart tissue to achieve clinically significant restoration of function has motivated the pursuit of novel approaches such as cell therapy. To this end, evidence of therapeutic benefits achieved by using mesenchymal stem cells (MSCs) has captured considerable interest despite a relative lack of information regarding the mechanisms involved. This narrative review synthesizes and interprets the current literature describing mechanisms by which MSCs can elicit cardiac repair, thereby directing attention to avenues of further inquiry.

METHODS

OVID versions of MEDLINE and EMBASE were searched for studies describing the role of MSCs in mammalian cardiac repair. Additional studies were sourced from the reference lists of relevant articles and other personal files.

FINDINGS

MSCs elicit cardiac repair in a range of in vitro systems and animal models of diseases such as myocardial infarction and heart failure. Important mechanisms include the preservation of myocardial contractility, the promotion of angiogenesis, and the modulation of fibrosis. Exposing in vitro MSCs to a microenvironment reflective of that encountered in the injured heart seems to potentiate these therapeutic mechanisms.

IMPLICATIONS

Promising results in animal studies warrant continuation of clinical MSC cardiac therapy studies. Paracrine functions of MSCs seem to be the dominant mechanism of cardiac repair over direct cellular effects. Although integral, the MSC secretome remains poorly defined. In addition, most of the mechanistic data within the literature have been derived from animal MSC research, necessitating more human MSC-based work.

Regenerative potential of Wharton's jelly-derived mesenchymal stem cells: A new horizon of stem cell therapy

Umbilical cord Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs) have recently gained considerable attention in the field of regenerative medicine. Their high proliferation rate, differentiation ability into various cell lineages, easy collection procedure, immuno-privileged status, nontumorigenic properties along with minor ethical issues make them an ideal approach for tissue repair. Besides, the number of WJ-MSCs in the umbilical cord samples is high as compared to other sources. Because of these properties, WJ-MSCs have rapidly advanced into clinical trials for the treatment of a wide range of disorders. Therefore, this paper summarized the current preclinical and clinical studies performed to investigate the regenerative potential of WJ-MSCs in neural, myocardial, skin, liver, kidney, cartilage, bone, muscle, and other tissue injuries.

Human Wharton's Jelly-Cellular Specificity, Stemness Potency, Animal Models, and Current Application in Human Clinical Trials

Stem cell therapies offer a great promise for regenerative and reconstructive medicine, due to their self-renewal and differentiation capacity. Although embryonic stem cells are pluripotent, their utilization involves embryo destruction and is ethically controversial. Therefore, adult tissues that have emerged as an alternative source of stem cells and perinatal tissues, such as the umbilical cord, appear to be particularly attractive. Wharton's jelly, a gelatinous connective tissue contained in the umbilical cord, is abundant in mesenchymal stem cells (MSCs) that express CD105, CD73, CD90, Oct-4, Sox-2, and Nanog among others, and have the ability to differentiate into osteogenic, adipogenic, chondrogenic, and other lineages. Moreover, Wharton's jelly-derived MSCs (WJ-MSCs) do not express MHC-II and exhibit immunomodulatory properties, which makes them a good alternative for allogeneic and xenogeneic transplantations in cellular therapies. Therefore, umbilical cord, especially Wharton's jelly, is a promising source of mesenchymal stem cells.

STAT3 for Cardiac Regenerative Medicine: Involvement in Stem Cell Biology, Pathophysiology, and Bioengineering

Heart disease is the most common cause of death in developed countries, but the medical treatments for heart failure remain limited. In this context, the development of cardiac regeneration therapy for severe heart failure is important. Owing to their unique characteristics, including multiple differentiation and infinitive self-renewal, pluripotent stem cells can be considered as a novel source for regenerative medicine. Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) signaling plays critical roles in the induction, maintenance, and differentiation of pluripotent stem cells. In the heart, JAK/STAT3 signaling has diverse cellular functions, including myocardial differentiation, cell cycle re-entry of matured myocyte after injury, and anti-apoptosis in pathological conditions. Therefore, regulating STAT3 activity has great potential as a strategy of cardiac regeneration therapy. In this review, we summarize the current understanding of STAT3, focusing on stem cell biology and pathophysiology, as they contribute to cardiac regeneration therapy. We also introduce a recently reported therapeutic strategy for myocardial regeneration that uses engineered artificial receptors that trigger endogenous STAT3 signal activation.

RNA-Based Strategies for Cardiac Reprogramming of Human Mesenchymal Stromal Cells

Multipotent adult mesenchymal stromal cells (MSCs) could represent an elegant source for the generation of patient-specific cardiomyocytes needed for regenerative medicine, cardiovascular research, and pharmacological studies. However, the differentiation of adult MSC into a cardiac lineage is challenging compared to embryonic stem cells or induced pluripotent stem cells. Here we used non-integrative methods, including microRNA and mRNA, for cardiac reprogramming of adult MSC derived from bone marrow, dental follicle, and adipose tissue. We found that MSC derived from adipose tissue can partly be reprogrammed into the cardiac lineage by transient overexpression of GATA4, TBX5, MEF2C, and MESP1, while cells isolated from bone marrow, and dental follicle exhibit only weak reprogramming efficiency. qRT-PCR and transcriptomic analysis revealed activation of a cardiac-specific gene program and up-regulation of genes known to promote cardiac development. Although we did not observe the formation of fully mature cardiomyocytes, our data suggests that adult MSC have the capability to acquire a cardiac-like phenotype when treated with mRNA coding for transcription factors that regulate heart development. Yet, further optimization of the reprogramming process is mandatory to increase the reprogramming efficiency.

C-kit-derived CD11b+ cells are critical for cardiac allograft prolongation by autologous C-kit+ progenitor cells

Autologous C-kit⁺ cells robustly prolong cardiac allografts. As C-kit⁺ cells can transdifferentiate to hematopoietic cells as well as non-hematopoietic cells, we aimed to clarify the class(es) of C-kit-derived cell(s) required for cardiac allograft prolongation. Autologous C-kit⁺ cells were administered post-cardiac transplantation and allografts were evaluated for C-kit⁺ inoculum-derived cells. Results suggested that alloimmunity was a major signal for trafficking of C-kit-derived cells to the allograft and demonstrated that C-kit⁺ inoculum-derived cells expressed CD11b early after transfer. Allograft survival studies with CD11b-DTR C-kit⁺ cells demonstrated a requirement for C-kit⁺-derived CD11b⁺ cells. Co-therapy studies demonstrated near complete abrogation of acute rejection with concomitant CTLA4-Ig therapy and no loss of prolongation in combination with Cyclosporine A. These results strongly implicate a C-kit-derived myeloid population as critical for allograft preservation and demonstrate the potential therapeutic application of autologous C-kit⁺ progenitor cells as calcineurin inhibitor-sparing agents and possibly as co-therapeutics for durable graft survival.

Comparison of the Cardiomyogenic Potency of Human Amniotic Fluid and Bone Marrow Mesenchymal Stem Cells

Background and Objectives

Most studies in cardiac regeneration have explored bone marrow mesenchymal stem cells (BM-MSC) with variable therapeutic effects. Amniotic fluid MSC (AF-MSC) having extended self-renewal and multipotent properties may be superior to bone marrow MSC (BM-MSC). However, a comparison of their cardiomyogenic potency has not been studied yet.

Methods

The 5-azacytidine (5-aza) treated AF-MSC and BM-MSC were evaluated for the expression of GATA-4, Nkx2.5 and ISL-1 transcripts and proteins by quantitative RT-PCR and Western blotting, respectively as well as for the expression of cardiomyogenic differentiation markers cardiac troponin-T (cTNT), beta myosin heavy chain (βMHC) and alpha sarcomeric actinin (ASA) by immunocytochemistry.

Results

The AF-MSC as compared to BM-MSC had significantly higher expression of GATA-4 (183.06±29.85 vs. 9.80±0.05; p<0.01), Nkx2.5 (8.3±1.4 vs. 1.82±0.32; p<0.05), and ISL-1 (39.59±4.05 vs. 4.36±0.39; p<0.01) genes as well as GATA-4 (2.01±0.5 vs. 0.6±0.1; p<0.05), NKx2.5 (1.9±0.14 vs. 0.8±0.2; p<0.01) and ISL-1 (1.7±0.3 vs. 0.9±0.1; p<0.05) proteins. The AF-MSC also had significantly elevated expression of cTNT (5.0×10⁴±0.6×10⁴ vs. 3.5 ×10⁴±0.8×10⁴; p<0.01), β-MHC (15.7×10⁴±0.9×10⁴ vs. 8.2×10⁴±0.6×10⁴; p<0.01) and ASA (18.6×10⁴±4.9×10⁴ vs. 13.1×10⁴±3.0×10⁴; p<0.05) than BM-MSC.

Conclusions

Our data suggest that AF-MSC have greater cardiomyogenic potency than BM-MSC, and thus may be a better source of MSC for therapeutic applications in cardiac regenerative medicine.

Chemically Defined Conditions Mediate an Efficient Induction of Mesodermal Lineage from Human Umbilical Cord- and Bone Marrow- Mesenchymal Stem Cells and Dental Pulp Pluripotent-Like Stem Cells

The human umbilical cord Wharton's Jelly- and the bone marrow- mesenchymal stem cells (WJ-MSCs and BM-MSCs, respectively) and the newly identified dental pulp pluripotent-like stem cells (DPPSCs) are new sources for stem cells with prospective use in cell regeneration and therapy. These cells are self-renewable, can be differentiated into several lineages, and can potentiate the immune responses. We hypothesized that three-dimensional (3D) culture conditions and directed differentiation using specific signaling regulators will enhance an efficient generation of mesoderm (MD) lineage independent from the origin or source of the stem cells. For a period of 3-days, cell aggregates were generated in a serum-free media containing ascorbic acid, retinoic acid, and keratinocyte growth factor; sonic hedgehog and bone morphogenic protein-4 signaling were inhibited using small molecules. In all cell types used, the biochemical and molecular analysis revealed a time course-dependent induction of the mesodermal, but not endodermal or ectodermal makers. In this study, we utilized a novel and efficient serum-free protocol to differentiate WJ-MSCs, BM-MSCs, and DPPSCs into MD-cells. Successful development of an efficient differentiation protocol can further be utilized and expanded on to obtain MD- derivative cell lineages.

Cellular Therapy for Ischemic Heart Disease: An Update

Ischemic heart disease (IHD), which includes heart failure (HF) induced by heart attack (myocardial infarction, MI), is a significant cause of morbidity and mortality worldwide (Benjamin, et al. Circulation 139:e56-e66, 2019). MI occurs at an alarmingly high rate in the United States (approx. One case every 40 seconds), and the failure to repair damaged myocardium is the leading cause of recurrent heart attacks, heart failure (HF), and death within 5 years of MI (Benjamin, et al. Circulation 139:e56-e66, 2019). At present, HF represents an unmet need with no approved clinical therapies to replace the damaged myocardium. As the population ages, the number of heart failure patients is projected to increase, doubling the annual cost by 2030 (Benjamin, et al. Circulation 139:e56-e66, 2019). In the past decades, stem cell therapy has become a promising strategy for cardiac regeneration. However, stem cell-based therapy yielded modest success in human clinical trials. This chapter examines the types of cells examined in cardiac therapy in the setting of IHD, with a brief introduction to ongoing research aiming at enhancing the therapeutic potential of transplanted cells.

The Winding Road of Cardiac Regeneration-Stem Cell Omics in the Spotlight

Despite significant progress in treating ischemic cardiac disease and succeeding heart failure, there is still an unmet need to develop effective therapeutic strategies given the persistent high-mortality rate. Advances in stem cell biology hold great promise for regenerative medicine, particularly for cardiac regeneration. Various cell types have been used both in preclinical and clinical studies to repair the injured heart, either directly or indirectly. Transplanted cells may act in an autocrine and/or paracrine manner to improve the myocyte survival and migration of remote and/or resident stem cells to the site of injury. Still, the molecular mechanisms regulating cardiac protection and repair are poorly understood. Stem cell fate is directed by multifaceted interactions between genetic, epigenetic, transcriptional, and post-transcriptional mechanisms. Decoding stem cells’ “panomic” data would provide a comprehensive picture of the underlying mechanisms, resulting in patient-tailored therapy. This review offers a critical analysis of omics data in relation to stem cell survival and differentiation. Additionally, the emerging role of stem cell-derived exosomes as “cell-free” therapy is debated. Last but not least, we discuss the challenges to retrieve and analyze the huge amount of publicly available omics data.

Cardiomyogenic differentiation of human bone marrow-derived mesenchymal stem cell spheroids within electrospun collagen nanofiber mats

Collagen is the major structural protein in myocardium and contributes to tissue strength and integrity, cellular orientation, and cell-cell and cell-matrix interactions. Significant post-myocardial infarction related loss of cardiomyocytes and cardiac tissue, and their subsequent replacement with fibrous scar tissue, negatively impacts endogenous tissue repair and regeneration capabilities. To overcome such limitations, tissue engineers are working toward developing a 3D cardiac patch which not only mimics the structural, functional, and biological hierarchy of the native cardiac tissue, but also could deliver autologous stem cells and encourage their homing and differentiation. In this study, we examined the utility of electrospun, randomly-oriented, type-I collagen nanofiber (dia = 789 ± 162 nm) mats on the cardiomyogenic differentiation of human bone marrow-derived mesenchymal stem cells (BM-MSC) spheroids, in the presence or absence of 10 μM 5-azacytidine (aza). Results showed that these scaffolds are biocompatible and enable time-dependent evolution of early (GATA binding protein 4: GATA4), late (cardiac troponin I: cTnI), and mature (myosin heavy chain: MHC) cardiomyogenic markers, with a simultaneous reduction in CD90 (stemness) expression, independent of aza-treatment. Aza-exposure improved connexin-4 expression and sustained sarcomeric α-actin expression, but provided only transient improvement in cardiac troponin T (cTnT) expression. Cell orientation and alignment significantly improved in these nanofiber scaffolds over time and with aza-exposure. Although further quantitative in vitro and in vivo studies are needed to establish the clinical applicability of such stem-cell laden collagen nanofiber mats as cardiac patches for cardiac tissue regeneration, our results underscore the benefits of 3D milieu provided by electrospun collagen nanofiber mats, aza, and spheroids on the survival, cardiac differentiation and maturation of human BM-MSCs. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 3303-3312, 2018.

Guided evaluation and standardisation of mesenchymal stem cell culture conditions to generate conditioned medium favourable to cardiac c-kit cell growth

Mesenchymal stem cells (MSCs) are known to secrete cardioprotective paracrine factors that can potentially activate endogenous cardiac c-kit cells (CCs). This study aims to optimise MSC growth conditions and medium formulation for generating the conditioned medium (CdM) to facilitate CC growth and expansion in vitro. The quality of MSC-CdM after optimisation of seeding density during MSC stabilisation and medium formulation used during MSC stimulation including glucose, ascorbic acid, serum and oxygen levels and the effects of treatment concentration and repeated CdM harvesting were assessed based on CC viability in vitro under growth factor- and serum-deprived condition. Our data showed that functional CdM can be produced from MSCs with a density of 20,000 cells/cm², which were stimulated using high glucose (25 mM), ascorbic acid supplemented, serum-free medium under normoxic condition. The generated CdM, when applied to growth factor- and serum-deprived medium at 1:1 ratio, improved CC viability, migration and proliferation in vitro. Such an effect could further be augmented by generating CdM concentrates without compromising CC gene and protein expressions, while retaining its capability to undergo differentiation to form endothelial, smooth muscle and cardiomyocytes. Nevertheless, CdM could not be repeatedly harvested from the same MSC culture, as the protein content and its effect on CC viability deteriorated after the first harvest. In conclusion, this study provides a proof-of-concept strategy to standardise the production of CdM from MSCs based on rapid, stepwise assessment of CC viability, thus enabling production of CdM favourable to CC growth for in vitro or clinical applications.

CD105+ Porcine Endometrial Stromal Mesenchymal Stem Cells Possess Differentiation Potential Toward Cardiomyocyte-Like Cells and Insulin-Producing β Cell-Like Cells In Vitro

Porcine mesenchymal stem cells (MSCs) are similar to human MSCs, hence considered a valuable model for assessing potential for cell therapy. Porcine adipose-derived MSCs (AD-MSCs) and endometrial stromal MSCs (EMSCs) displayed fibroblast-like morphology and were positive for MSC markers CD73, CD90, and CD105 and negative for hematopoietic markers CD34 and CD45. The EMSCs had similar or slightly higher growth rate compared to AD-MSCs, and similar percentage of cells of both EMSCs and AD-MSCs were at G0/G1 and G2/M phases; however, EMSCs had significantly ( P < .05) higher percentage of cells at S phase of cell cycle than AD-MSCs. Transdifferentiation ability to cardiomyocyte-like cells was confirmed in differentiated cells by the expression of lineage-specific marker genes such as DES, ACTA2, cTnT, and ACTC1 by real-time quantitative polymerase chain reaction (RT-qPCR). Furthermore, cardiomyocyte-specific protein markers cTnT and ACTC1 were expressed in completely differentiated cells. Endodermal differentiation capacity of EMSCs to pancreatic β cell-like cells was evident with the changes in morphology and the expression of β-cell-specific marker genes such as PDX1, GLUT2, SST, NKX6.1, PAX4, and NGN3 as analyzed by RT-qPCR. The differentiated cells secreted insulin and C-peptide upon glucose challenge and also they expressed insulin, PDX1, PAX4, NGN3, and GLUT2 at protein level as assessed by immunostaining confirming the successful differentiation to β cell-like cells. Porcine EMSCs possess all the characteristics of MSCs and are suitable model for studying molecular mechanisms of cellular differentiation.

Three-dimensional collagenous niche and azacytidine selectively promote time-dependent cardiomyogenesis from human bone marrow-derived MSC spheroids

Endogenous adult cardiac regenerative machinery is not capable of replacing the lost cells following myocardial infarction, often leading to permanent alterations in structure-function-mechanical properties. Regenerative therapies based on delivering autologous stem cells within an appropriate 3D milieu could meet such demand, by enabling homing and directed differentiation of the transplanted cells into lost specialized cell populations. Since type I collagen is the predominant cardiac tissue matrix protein, we here optimized the 3D niche which could promote time-dependent evolution of cardiomyogenesis from human bone marrow-derived mesenchymal stem cells (BM-MSC). 3D collagen gel physical and mechanical characteristics were assessed using SEM and AFM, respectively, while the standalone and combined effects of collagen concentration, culture duration, and 5-azacytidine (aza) dose on the phenotype and genotype of MSC spheroids were quantified using immunofluorescence labeling and RT-PCR analysis. Increasing collagen concentration led to a significant increase in Young's modulus (p < 0.01) but simultaneous decrease in the mean pore size, resulting in stiffer gels. Spheroid formation significantly modulated MSC differentiation and genotype, mostly due to better cell-cell interactions. Among the aza dosages tested, 10 μM appears to be optimal, while 3 mg/ml gels resulted in significantly lower cell viability compared to 1 or 2 mg/ml gels. Stiffer gels (2 and 3 mg/ml) and exposure to 10 μM aza upregulated early and late cardiac marker expressions in a time-dependent fashion. On the other hand, cell-cell signaling within the MSC spheroids seem to have a strong role in influencing mature cardiac markers expression, since neither aza nor gel stiffness seem to significantly improve their expression. Western blot analysis suggested that canonical Wnt/β-catenin signaling pathway might be primarily mediating the observed benefits of aza on cardiac differentiation of MSC spheroids. In conclusion, 2 mg/ml collagen and 10 μM aza appears to offer optimal 3D microenvironment in terms of cell viability and time-dependent evolution of cardiomyogenesis from human BM-MSCs, with significant applications in cardiac tissue engineering and stem cell transplantation for regenerating lost cardiac tissue.

The anti-fecundity effect of 5-azacytidine (5-AzaC) on Schistosoma mansoni is linked to dis-regulated transcription, translation and stem cell activities

Uncontrolled host immunological reactions directed against tissue-trapped eggs precipitate a potentially lethal, pathological cascade responsible for schistosomiasis. Blocking schistosome egg production, therefore, presents a strategy for simultaneously reducing immunopathology as well as limiting disease transmission in endemic or emerging areas. We recently demonstrated that the ribonucleoside analogue 5-azacytidine (5-AzaC) inhibited Schistosoma mansoni oviposition, egg maturation and ovarian development. While these anti-fecundity effects were associated with a loss of DNA methylation, other molecular processes affected by 5-AzaC were not examined at the time. By comparing the transcriptomes of 5-AzaC-treated females to controls, we provide evidence that this ribonucleoside analogue also modulates other crucial aspects of schistosome egg-laying biology. For example, S. mansoni gene products associated with amino acid-, carbohydrate-, fatty acid-, nucleotide- and tricarboxylic acid (TCA)- homeostasis are all dysregulated in 5-AzaC treated females. To validate the metabolic pathway most significantly affected by 5-AzaC, amino acid metabolism, nascent protein synthesis was subsequently quantified in adult schistosomes. Here, 5-AzaC inhibited this process by 68% ±16.7% (SEM) in male- and 81% ±4.8% (SEM) in female-schistosomes. Furthermore, the transcriptome data indicated that adult female stem cells were also affected by 5-AzaC. For instance, 40% of transcripts associated with proliferating schistosome cells were significantly down-regulated by 5-AzaC. This finding correlated with a considerable reduction (95%) in the number of 5-ethynyl-2'-deoxyuridine (EdU) positive cells found in 5-AzaC-treated females. In addition to protein coding genes, the effect that 5-AzaC had on repetitive element expression was also assessed. Here, 46 repeats were found differentially transcribed between 5-AzaC-treated and control females with long terminal repeat (LTR) and DNA transposon classes being amongst the most significant. This study demonstrates that the anti-fecundity activity of 5-AzaC affects more than just DNA methylation in schistosome parasites. Further characterisation of these processes may reveal novel targets for schistosomiasis control.

Cardiomyocyte differentiation of mesenchymal stem cells from bone marrow: new regulators and its implications

In the past years, cardiac mortality has decreased, but cardiac diseases are still responsible for millions of deaths every year worldwide. Bone-marrow mesenchymal stem cells (BMSCs) transplantation may be a promising therapeutic strategy because of its capacity to differentiate into cardiac cells. Current research indicates that chemical substances, microRNAs, and cytokines have biological functions that regulate the cardiomyocytes differentiation of BMSCs. In this review, we chiefly summarize the regulatory factors that induce BMSCs to differentiate into cardiomyocytes.

Paracrine Mechanisms of Mesenchymal Stem Cells in Tissue Repair

Tissue regeneration from transplanted mesenchymal stromal cells (MSC) either through transdifferentiation or cell fusion was originally proposed as the principal mechanism underlying their therapeutic action. However, several studies have now shown that both these mechanisms are very inefficient. The low MSC engraftment rate documented in injured areas also refutes the hypothesis that MSC repair tissue damage by replacing cell loss with newly differentiated cells. Indeed, despite evidence of preferential homing of MSC to the site of myocardial ischemia, exogenously administered MSC show poor survival and do not persist in the infarcted area. Therefore, it has been proposed that the functional benefits observed after MSC transplantation in experimental models of tissue injury might be related to the secretion of soluble factors acting in a paracrine fashion. This hypothesis is supported by pre-clinical studies demonstrating equal or even improved organ function upon infusion of MSC-derived conditioned medium (MSC-CM) compared with MSC transplantation. Identifying key MSC-secreted factors and their functional role seems a reasonable approach for a rational design of nextgeneration MSC-based therapeutics. Here, we summarize the major findings regarding both different MSC-mediated paracrine actions and the identification of paracrine mediators.

Oxidized low-density lipoprotein (ox-LDL) promotes cardiac differentiation of bone marrow mesenchymal stem cells via activating ERK1/2 signaling

BACKGROUND/AIMS

The differentiation efficiency of bone marrow mesenchymal stem cells (BM-MSCs) is low in vivo after transplantation. Therefore, it is necessary to look for effective reagents for enhancing cardiac differentiation of BM-MSCs. It has been reported that cardiac differentiation of stem cells depends on the activation of extracellular signal-regulated protein 1/2 (ERK1/2) signaling. Oxidized low-density lipoprotein (ox-LDL) is a potent reagent for ERK1/2 activation. This indicates that ox-LDL may be a potential reagent to stimulate cardiac differentiation of stem cells. In this study, we investigated the effect of ox-LDL on cardiac differentiation of BM-MSCs and its relationship with ERK1/2 signaling.

METHODS

BM-MSCs were isolated from mouse bone marrow, cultured in DMEM supplemented with 15% FBS, and passaged up to the 3rd passage. Following culture with 5 μg/mL ox-LDL for 3 weeks, the cardiac differentiation of the 3rd passage BM-MSCs was identified by immunostaining, Western blotting, and RT-PCR assays for measuring the expression of cardiac-specific markers. To further explore the role of ERK1/2 signaling in cardiac differentiation of BM-MSCs, we simultaneously exposed BM-MSCs to ERK1/2 inhibitor (U0126) and ox-LDL, and identified the cardiac differentiation again.

RESULTS

The expressions of cardiac-specific markers including α-cardiac actin, α-MHC, β-MHC, ANP, and BNP were markedly increased in BM-MSCs following treatment with ox-LDL (P < .05), which indicates a directional differentiation of BM-MSCs to cardiac cells. Further, ox-LDL could also activate ERK1/2 in BM-MSCs, and application of U0126 markedly inhibited ox-LDL-induced cardiac transformation of BM-MSCs.

CONCLUSIONS

Ox-LDL induces cardiac differentiation of BM-MSCs via activation of ERK1/2 signaling.

Cardiac Stem Cells for Myocardial Regeneration: They Are Not Alone

Heart failure is the number one killer worldwide with ~50% of patients dying within 5 years of prognosis. The discovery of stem cells, which are capable of repairing the damaged portion of the heart, has created a field of cardiac regenerative medicine, which explores various types of stem cells, either autologous or endogenous, in the hope of finding the “holy grail” stem cell candidate to slow down and reverse the disease progression. However, there are many challenges that need to be overcome in the search of such a cell candidate. The ideal cells have to survive the harsh infarcted environment, retain their phenotype upon administration, and engraft and be activated to initiate repair and regeneration in vivo. Early bench and bedside experiments mostly focused on bone marrow-derived cells; however, heart regeneration requires multiple coordinations and interactions between various cell types and the extracellular matrix to form new cardiomyocytes and vasculature. There is an observed trend that when more than one cell is coadministered and cotransplanted into infarcted animal models the degree of regeneration is enhanced, when compared to single-cell administration. This review focuses on stem cell candidates, which have also been tested in human trials, and summarizes findings that explore the interactions between various stem cells in heart regenerative therapy.

Programming cells for cardiac repair

Because the heart is a poorly regenerative organ, there has been considerable interest in developing novel cell-based approaches to restore lost contractile function after myocardial infarction (MI). While a wide variety of candidate cell types have been tested in animal MI models, the vast majority of clinical trials have used adult stem cell types, usually derived from bone marrow. These studies have generally yielded disappointing results, an outcome that may reflect in part the limited cardiogenic potential of the adult stem cell sources employed. Post-MI heart failure is ultimately a disease of cardiomyocyte deficiency, so better outcomes may be possible with more cardiogenic approaches that may 'remuscularize' the infarct scar with new, electrically-integrated myocardium. In this review, we summarize work in the field to 'program' exogenous or endogenous cells into such a cardiogenic state, as well as efforts to test their capacity to mediate true heart regeneration.

Stem cell therapy for chronic ischaemic heart disease and congestive heart failure

BACKGROUND

A promising approach to the treatment of chronic ischaemic heart disease and congestive heart failure is the use of stem cells. The last decade has seen a plethora of randomised controlled trials developed worldwide, which have generated conflicting results.

OBJECTIVES

The critical evaluation of clinical evidence on the safety and efficacy of autologous adult bone marrow-derived stem/progenitor cells as a treatment for chronic ischaemic heart disease and congestive heart failure.

SEARCH METHODS

We searched CENTRAL in the Cochrane Library, MEDLINE, Embase, CINAHL, LILACS, and four ongoing trial databases for relevant trials up to 14 December 2015.

SELECTION CRITERIA

Eligible studies were randomised controlled trials comparing autologous adult stem/progenitor cells with no cells in people with chronic ischaemic heart disease and congestive heart failure. We included co-interventions, such as primary angioplasty, surgery, or administration of stem cell mobilising agents, when administered to treatment and control arms equally.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened all references for eligibility, assessed trial quality, and extracted data. We undertook a quantitative evaluation of data using random-effects meta-analyses. We evaluated heterogeneity using the I2 statistic and explored substantial heterogeneity (I2 greater than 50%) through subgroup analyses. We assessed the quality of the evidence using the GRADE approach. We created a 'Summary of findings' table using GRADEprofiler (GRADEpro), excluding studies with a high or unclear risk of selection bias. We focused our summary of findings on long-term follow-up of mortality, morbidity outcomes, and left ventricular ejection fraction measured by magnetic resonance imaging.

MAIN RESULTS

We included 38 randomised controlled trials involving 1907 participants (1114 cell therapy, 793 controls) in this review update. Twenty-three trials were at high or unclear risk of selection bias. Other sources of potential bias included lack of blinding of participants (12 trials) and full or partial commercial sponsorship (13 trials).Cell therapy reduced the incidence of long-term mortality (≥ 12 months) (risk ratio (RR) 0.42, 95% confidence interval (CI) 0.21 to 0.87; participants = 491; studies = 9; I2 = 0%; low-quality evidence). Periprocedural adverse events associated with the mapping or cell/placebo injection procedure were infrequent. Cell therapy was also associated with a long-term reduction in the incidence of non-fatal myocardial infarction (RR 0.38, 95% CI 0.15 to 0.97; participants = 345; studies = 5; I2 = 0%; low-quality evidence) and incidence of arrhythmias (RR 0.42, 95% CI 0.18 to 0.99; participants = 82; studies = 1; low-quality evidence). However, we found no evidence that cell therapy affects the risk of rehospitalisation for heart failure (RR 0.63, 95% CI 0.36 to 1.09; participants = 375; studies = 6; I2 = 0%; low-quality evidence) or composite incidence of mortality, non-fatal myocardial infarction, and/or rehospitalisation for heart failure (RR 0.64, 95% CI 0.38 to 1.08; participants = 141; studies = 3; I2 = 0%; low-quality evidence), or long-term left ventricular ejection fraction when measured by magnetic resonance imaging (mean difference -1.60, 95% CI -8.70 to 5.50; participants = 25; studies = 1; low-quality evidence).

AUTHORS' CONCLUSIONS

This systematic review and meta-analysis found low-quality evidence that treatment with bone marrow-derived stem/progenitor cells reduces mortality and improves left ventricular ejection fraction over short- and long-term follow-up and may reduce the incidence of non-fatal myocardial infarction and improve New York Heart Association (NYHA) Functional Classification in people with chronic ischaemic heart disease and congestive heart failure. These findings should be interpreted with caution, as event rates were generally low, leading to a lack of precision.

Mesenchymal stem cell subpopulations: phenotype, property and therapeutic potential

Mesenchymal stem cells (MSC) are capable of differentiating into cells of multiple cell lineages and have potent paracrine effects. Due to their easy preparation and low immunogenicity, MSC have emerged as an extremely promising therapeutic agent in regenerative medicine for diverse diseases. However, MSC are heterogeneous with respect to phenotype and function in current isolation and cultivation regimes, which often lead to incomparable experimental results. In addition, there may be specific stem cell subpopulations with definite differentiation capacity toward certain lineages in addition to stem cells with multi-differentiation potential. Recent studies have identified several subsets of MSC which exhibit distinct features and biological activities, and enhanced therapeutic potentials for certain diseases. In this review, we give an overview of these subsets for their phenotypic, biological and functional properties.

Simultaneous engagement of mechanical stretching and surface pattern promotes cardiomyogenic differentiation of human mesenchymal stem cells

It has been widely recognized and proved that biophysical factors for mimicking in vivo conditions should be also considered to have stem cells differentiated into desired cell type in vitro along with biochemical factors. Biophysical factors include substrate and biomechanical conditions. This study focused on the effect of biomimetic mechanical stretching along with changes in substrate topography to influence on cardiomyogenic differentiation of human mesenchymal stem cells (hMSCs). Elastic micropatterned substrates were made to mimic the geometric conditions surrounding cells in vivo. To mimic biomechanical conditions due to beating of the heart, mechanical stretching was applied parallel to the direction of the pattern (10% elongation, 0.5 Hz, 4 h/day). Suberoylanilide hydroxamic acid (SAHA) was used as a biochemical factor. The micropatterned substrate was found more effective in the alignment of cytoskeleton and cardiomyogenic differentiation compared with flat substrate. Significantly higher expression levels of related markers [GATA binding protein 4 (GATA4), troponin I, troponin T, natriuretic peptide A (NPPA)] were observed when mechanical stretching was engaged on micropatterned substrate. In addition, 4 days of mechanical stretching was associated with higher levels of expression than 2 days of stretching. These results indicate that simultaneous engagement of biomimetic environment such as substrate pattern and mechanical stimuli effectively promotes the cardiomyogenic differentiation of hMSCs in vitro. The suggested method which tried to mimic in vivo microenvironment would provide systematic investigation to control cardiomyogenic differentiation of hMSCs.

Comparative evaluation of cardiac markers in differentiated cells from menstrual blood and bone marrow-derived stem cells in vitro

In recent years, menstrual blood-derived stem cells (MenSCs) have been introduced as easily accessible and refreshing stem cell source without ethical considerations in the field of regenerative medicine. The aim of this study was to investigate in vitro cardiac differentiation capacity of MenSCs compared to bone marrow-derived stem cells (BMSCs) under two protocols using 5-aza-2'-deoxycytidine (5-aza) and basic fibroblast growth factor (bFGF). Our data revealed that differentiated MenSCs and BMSCs acquired some features of cardiomyocytes; however, degree of differentiation was dependent on the protocol. In a similar manner with BMSCs, differentiated MenSCs showed upper levels of mRNA/protein of late-stage cardiac markers under 5-aza stimulation and continuous treatment with bFGF (protocol 2) compared to those induced by 5-aza alone (protocol 1) evidencing the key role of bFGF in cardiac development of stem cells. Compared to corresponding undifferentiated cells differentiated MenSCs under protocol 2 showed remarkable expression of connexin-43 and TNNT2 at both gene and protein levels, whereas developed BMSCs under the same condition only expressed connextin-43 at the higher level. Superiority of protocol 2 over protocol 1 was confirmed by assessment of LDH and cTnI production by differentiated cells. Based on the accumulative data, our study provided convincing evidence that MenSCs have relatively higher capability to be differentiated toward cardiomyocyte compared with BMSCs. Furthermore, usage of bFGF and 5-aza to induce in vitro cardiac differentiation of MenSCs is highly recommended.

CD146+ mesenchymal stem cells display greater therapeutic potential than CD146- cells for treating collagen-induced arthritis in mice

Background

The characteristics and therapeutic potential of subtypes of mesenchymal stem cells (MSCs) are largely unknown. In this study, CD146⁺ and CD146^– MSCs were separated from human umbilical cords, and their effects on regulatory T cells (Tregs), Th17 cells, chondrogenesis, and osteogenesis were investigated.

Methods

Flow cytometry was used to quantify IL-6 and TGF-β1 expressed on CD146⁺ and CD146^– MSCs. The therapeutic potential of both subpopulations was determined by measuring the clinical score and joint histology after intra-articular (IA) transfer of the cells into mice with collagen-induced arthritis (CIA).

Results

Compared with CD146^– MSCs, CD146⁺ MSCs expressed less IL-6 and had a significantly greater effect on chondrogenesis. After T lymphocyte activation, Th17 cells were activated when exposed to CD146^– cells but not when exposed to CD146⁺ cells both in vitro and in vivo. IA injection of CD146⁺ MSCs attenuated the progression of CIA. Immunohistochemistry showed that only HLA-A⁺ CD146⁺ cells were detected in the cartilage of CIA mice. These cells may help preserve proteoglycan expression.

Conclusions

This study suggests that CD146⁺ cells have greater potency than CD146^– cells for cartilage protection and can suppress Th17 cell activation. These data suggest a potential therapeutic application for CD146⁺ cells in treating inflammatory arthritis.