Mesenchymal Stem Cells for Cardiac Regenerative Therapy: Optimization of Cell Differentiation Strategy

Mesenchymal Stem Cell-Derived Exosomes and Their MicroRNAs in Heart Repair and Regeneration

Mesenchymal stem cells (MSCs) can be differentiated into cardiac, endothelial, and smooth muscle cells. Therefore, MSC-based therapeutic approaches have the potential to deal with the aftermaths of cardiac diseases. However, transplanted stem cells rarely survive in damaged myocardium, proposing that paracrine factors other than trans-differentiation may involve in heart regeneration. Apart from cytokines/growth factors, MSCs secret small, single-membrane organelles named exosomes. The MSC-secreted exosomes are enriched in lipids, proteins, nucleic acids, and microRNA (miRNA). There has been an increasing amount of data that confirmed that MSC-derived exosomes and their active molecule microRNA (miRNAs) regulate signaling pathways involved in heart repair/regeneration. In this review, we systematically present an overview of MSCs, their cardiac differentiation, and the role of MSC-derived exosomes and exosomal miRNAs in heart regeneration. In addition, biological functions regulated by MSC-derived exosomes and exosomal-derived miRNAs in the process of heart regeneration are reviewed.

Latest Advances in 3D Bioprinting of Cardiac Tissues

Cardiovascular diseases (CVDs) are known as the major cause of death worldwide. In spite of tremendous advancements in medical therapy, the gold standard for CVD treatment is still transplantation. Tissue engineering, on the other hand, has emerged as a pioneering field of study with promising results in tissue regeneration using cells, biological cues, and scaffolds. Three-dimensional (3D) bioprinting is a rapidly growing technique in tissue engineering because of its ability to create complex scaffold structures, encapsulate cells, and perform these tasks with precision. More recently, 3D bioprinting has made its debut in cardiac tissue engineering, and scientists are investigating this technique for development of new strategies for cardiac tissue regeneration. In this review, the fundamentals of cardiac tissue biology, available 3D bioprinting techniques and bioinks, and cells implemented for cardiac regeneration are briefly summarized and presented. Afterwards, the pioneering and state-of-the-art works that have utilized 3D bioprinting for cardiac tissue engineering are thoroughly reviewed. Finally, regulatory pathways and their contemporary limitations and challenges for clinical translation are discussed.

Overexpression of GATA binding protein 4 and myocyte enhancer factor 2C induces differentiation of mesenchymal stem cells into cardiac-like cells

BACKGROUND

Heart diseases are the primary cause of death all over the world. Following myocardial infarction, billions of cells die, resulting in a huge loss of cardiac function. Stem cell-based therapies have appeared as a new area to support heart regeneration. The transcription factors GATA binding protein 4 (GATA-4) and myocyte enhancer factor 2C (MEF2C) are considered prominent factors in the development of the cardiovascular system.

AIM

To explore the potential of GATA-4 and MEF2C for the cardiac differentiation of human umbilical cord mesenchymal stem cells (hUC-MSCs).

METHODS

hUC-MSCs were characterized morphologically and immunologically by the presence of specific markers of MSCs via immunocytochemistry and flow cytometry, and by their potential to differentiate into osteocytes and adipocytes. hUC-MSCs were transfected with GATA-4, MEF2C, and their combination to direct the differentiation. Cardiac differentiation was confirmed by semiquantitative real-time polymerase chain reaction and immunocytochemistry.

RESULTS

hUC-MSCs expressed specific cell surface markers CD105, CD90, CD44, and vimentin but lack the expression of CD45. The transcription factors GATA-4 and MEF2C, and their combination induced differentiation in hUC-MSCs with significant expression of cardiac genes i.e., GATA-4, MEF2C, NK2 homeobox 5 (NKX2.5), MHC, and connexin-43, and cardiac proteins GATA-4, NKX2.5, cardiac troponin T, and connexin-43.

CONCLUSION

Transfection with GATA-4, MEF2C, and their combination effectively induces cardiac differentiation in hUC-MSCs. These genetically modified MSCs could be a promising treatment option for heart diseases in the future.

Emerging Trends in Mesenchymal Stem Cells Applications for Cardiac Regenerative Therapy: Current Status and Advances

Irreversible myocardium infarction is one of the leading causes of cardiovascular disease (CVD) related death and its quantum is expected to grow in coming years. Pharmacological intervention has been at the forefront to ameliorate injury-related morbidity and mortality. However, its outcomes are highly skewed. As an alternative, stem cell-based tissue engineering/regenerative medicine has been explored quite extensively to regenerate the damaged myocardium. The therapeutic modality that has been most widely studied both preclinically and clinically is based on adult multipotent mesenchymal stem cells (MSC) delivered to the injured heart. However, there is debate over the mechanistic therapeutic role of MSC in generating functional beating cardiomyocytes. This review intends to emphasize the role and use of MSC in cardiac regenerative therapy (CRT). We have elucidated in detail, the various aspects related to the history and progress of MSC use in cardiac tissue engineering and its multiple strategies to drive cardiomyogenesis. We have further discussed with a focus on the various therapeutic mechanism uncovered in recent times that has a significant role in ameliorating heart-related problems. We reviewed recent and advanced technologies using MSC to develop/create tissue construct for use in cardiac regenerative therapy. Finally, we have provided the latest update on the usage of MSC in clinical trials and discussed the outcome of such studies in realizing the full potential of MSC use in clinical management of cardiac injury as a cellular therapy module.

Mesenchymal Stem Cell-Based Therapy as a New Approach for the Treatment of Systemic Sclerosis

Systemic sclerosis (SSc) is an intractable autoimmune disease with unmet medical needs. Conventional immunosuppressive therapies have modest efficacy and obvious side effects. Targeted therapies with small molecules and antibodies remain under investigation in small pilot studies. The major breakthrough was the development of autologous haematopoietic stem cell transplantation (AHSCT) to treat refractory SSc with rapidly progressive internal organ involvement. However, AHSCT is contraindicated in patients with advanced visceral involvement. Mesenchymal stem cells (MSCs) which are characterized by immunosuppressive, antifibrotic and proangiogenic capabilities may be a promising alternative option for the treatment of SSc. Multiple preclinical and clinical studies on the use of MSCs to treat SSc are underway. However, there are several unresolved limitations and safety concerns of MSC transplantation, such as immune rejections and risks of tumour formation, respectively. Since the major therapeutic potential of MSCs has been ascribed to their paracrine signalling, the use of MSC-derived extracellular vesicles (EVs)/secretomes/exosomes as a "cell-free" therapy might be an alternative option to circumvent the limitations of MSC-based therapies. In the present review, we overview the current knowledge regarding the therapeutic efficacy of MSCs in SSc, focusing on progresses reported in preclinical and clinical studies using MSCs, as well as challenges and future directions of MSC transplantation as a treatment option for patients with SSc.

Role of Signaling Pathways during Cardiomyocyte Differentiation of Mesenchymal Stem Cells

Multipotent stem cells, including mesenchymal stem cells (MSCs), represent a promising source to be used by regenerative medicine. They are capable of performing myogenic, chondrogenic, osteogenic and adipogenic differentiation. Also, MSCs are characterized by the expression of multiple surface antigens, but none of them appears to be particularly expressed on MSCs. Moreover, the prospect of monitoring and controlling MSC differentiation is a scientifically crucial regulatory and clinical requirement. Different transcription factors and signaling pathways are involved in cardiomyocyte differentiation. Due to the paucity of studies exclusively focused on cardiomyocyte differentiation of MSCs, present study aims at describing the roles of various signaling pathways (FGF, TGF, Wnt, Notch, etc.) in cardiomyocytes differentiation of MSCs. Understanding the signaling pathways that control the commitment and differentiation of cardiomyocyte cells not only will expand our basic understanding of molecular mechanisms of heart development, but also will enable us to develop therapeutic means of intervention in cardiovascular diseases.

Computational and in vitro validation of cardiogenic induction of quercetin on adipose-derived mesenchymal stromal cells through the inhibition of Wnt and non-Smad-dependent TGF-β pathways

Exploiting human mesenchymal stem cells (hMSCs) was proposed as a promising therapeutic approach for cardiovascular disease due to their capacity to differentiate into cardiac cells. Though modulation of the intracellular signaling pathways dominantly WNT/β catenin and transforming growth factor-β (TGF-β) have been reported to promote differentiation of hMSCs into cardiomyocytes in the prevailing literature, a safe and reproducible system for their clinical application has not yet turned into reality. In the present study, the molecular docking-based strategy was first applied for evaluating the potency of some natural phenolic compounds in the modulation of Wnt and TGF-β signaling pathways using a vital class of crystallographic protein structures of WNT signaling regulators such as Frizzled, Disheveled, GSK3-β, β-catenin, LRP 5/6 extracellular domain, Tankyrase and their variety of active pockets. Then, the impacts of plant-derived chemical compounds on the regulation of the relevant signals for the differentiation of hMSCs into the definitive mesoderm lineage and cardiac progenitors were assessed in vitro. Data obtained revealed the synergistic activity of Wnt and TGF-β superfamily to direct cardiac differentiation in human cardiogenesis by comparing cardiac gene expression in the presence and absence of the TGF-β inhibitors. We found that the inhibitory effect of canonical Wnt/β-catenin is sufficient to cause proper cardiomyocyte differentiation, but the TGF-β pathway plays a vital role in enhancing the expression of the cardiomyocyte-specific marker (cTnT). It was found that quercetin, a p38MAPK inhibitor with the high energy dock to the active pocket of Wnt receptors, promotes cardiac differentiation via the inhibition of both Wnt and non-Smad TGF-β pathways. Altogether, data presented here can contribute to the development of a feasible and efficient cardiac differentiation protocol as an "off-the-shelf" therapeutic source using novel natural agents for cardiac repair or regeneration.

Evaluation of an Injectable Hydrogel Based on Hyaluronic Acid-chitosan/β-glycerophosphate-loaded Mesenchymal Stem Cells in Enhancing the Therapeutic Efficacy of Myocardial Infarction

Myocardial infarction (MI), which is due to cardiac dysfunction, results in morbidity and mortality. Moreover, the cellular activity of transplanted mesenchymal stem cells (MSCs)generally limits their therapeutic efficacy in the treatment of MI. Here, inject able hyaluronic acid-chitosan/β-glycerophosphate (HA-CS/β-GP) hydrogel-loaded MSCs were prepared, after which their effects on the treatment of MI were investigated. The synthesized HA-CS/β-GP hydrogels exhibited swelling ratio (SR), an in vitro degradation value, and a gelatin time of 82.19 ± 4.1, 88.18% ± 2.4%, and 9 s, respectively. Further, rheological studies revealed that the elastic modulus of the HA-CS/β-GP hydrogels was ≥230 Pa, exhibiting large elastic to viscous modulus ratio, which indicated their mechanical strength. Furthermore, the in vitro 3T3 cell and MSC culture studies confirmed the good biocompatibility of the HA-CS and HA-CS/β-GP hydrogels. The implantation of the synthesized hydrogels in the mouse MI model considerably improved the therapeutic effect of the MSCs (enhanced cardiac function, reduced cardiomyocyte apoptosis, and increased vascularization) for the first time. The innovative synergistic strategy of combining injectable HA-CS and HA-CS/β-GP hydro gels with MSCs might be suitable for the effective treatment of cardiac morbidity due to MIs. This article is protected by copyright. All rights reserved.

Functional Outcomes of Nerve Allografts Seeded with Undifferentiated and Differentiated Mesenchymal Stem Cells in a Rat Sciatic Nerve Defect Model

BACKGROUND

Mesenchymal stem cells have the potential to produce neurotrophic growth factors and establish a supportive microenvironment for neural regeneration. The purpose of this study was to determine the effect of undifferentiated and differentiated mesenchymal stem cells dynamically seeded onto decellularized nerve allografts on functional outcomes when used in peripheral nerve repair.

METHODS

In 80 Lewis rats, a 10-mm sciatic nerve defect was reconstructed with (1) autograft, (2) decellularized allograft, (3) decellularized allograft seeded with undifferentiated mesenchymal stem cells, or (4) decellularized allograft seeded with mesenchymal stem cells differentiated into Schwann cell-like cells. Nerve regeneration was evaluated over time by cross-sectional tibial muscle ultrasound measurements, and at 12 and 16 weeks by isometric tetanic force measurements, compound muscle action potentials, muscle mass, histology, and immunofluorescence analyses.

RESULTS

At 12 weeks, undifferentiated mesenchymal stem cells significantly improved isometric tetanic force measurement and compound muscle action potential outcomes compared to decellularized allograft alone, whereas differentiated mesenchymal stem cells significantly improved compound muscle action potential outcomes. The autografts outperformed both stem cell groups histologically at 12 weeks. At 16 weeks, functional outcomes normalized between groups. At both time points, the effect of undifferentiated versus differentiated mesenchymal stem cells was not significantly different.

CONCLUSIONS

Undifferentiated and differentiated mesenchymal stem cells significantly improved functional outcomes of decellularized allografts at 12 weeks and were similar to autograft results in the majority of measurements. At 16 weeks, outcomes normalized as expected. Although differences between both cell types were not statistically significant, undifferentiated mesenchymal stem cells improved functional outcomes of decellularized nerve allografts to a greater extent and had practical benefits for clinical translation by limiting preparation time and costs.

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.

Dielectrophoretic Characterization of Tenogenically Differentiating Mesenchymal Stem Cells

Tendons are collagenous musculoskeletal tissues that connect muscles to bones and transfer the forces necessary for movement. Tendons are susceptible to injury and heal poorly, with long-term loss of function. Mesenchymal stem cell (MSC)-based therapies are a promising approach for treating tendon injuries but are challenged by the difficulties of controlling stem cell fate and of generating homogenous populations of stem cells optimized for tenogenesis (differentiation toward tendon). To address this issue, we aim to explore methods that can be used to identify and ultimately separate tenogenically differentiated MSCs from non-tenogenically differentiated MSCs. In this study, baseline and tenogenically differentiating murine MSCs were characterized for dielectric properties (conductivity and permittivity) of their outer membrane and cytoplasm using a dielectrophoretic (DEP) crossover technique. Experimental results showed that unique dielectric properties distinguished tenogenically differentiating MSCs from controls after three days of tenogenic induction. A single shell model was used to quantify the dielectric properties and determine membrane and cytoplasm conductivity and permittivity. Together, cell responses at the crossover frequency, cell morphology, and shell models showed that changes potentially indicative of early tenogenesis could be detected in the dielectric properties of MSCs as early as three days into differentiation. Differences in dielectric properties with tenogenesis indicate that the DEP-based label-free separation of tenogenically differentiating cells is possible and avoids the complications of current label-dependent flow cytometry-based separation techniques. Overall, this work illustrates the potential of DEP to generate homogeneous populations of differentiated stem cells for applications in tissue engineering and regenerative medicine.

Gene expression profiles of human adipose-derived mesenchymal stem cells dynamically seeded on clinically available processed nerve allografts and collagen nerve guides

It was hypothesized that mesenchymal stem cells (MSCs) could provide necessary trophic factors when seeded onto the surfaces of commonly used nerve graft substitutes. We aimed to determine the gene expression of MSCs when influenced by Avance® Nerve Grafts or NeuraGen® Nerve Guides. Human adipose-derived MSCs were cultured and dynamically seeded onto 30 Avance® Nerve Grafts and 30 NeuraGen® Nerve Guides for 12 hours. At six time points after seeding, quantitative polymerase chain reaction analyses were performed for five samples per group. Neurotrophic [nerve growth factor (NGF), glial cell line-derived neurotrophic factor (GDNF), pleiotrophin (PTN), growth associated protein 43 (GAP43) and brain-derived neurotrophic factor (BDNF)], myelination [peripheral myelin protein 22 (PMP22) and myelin protein zero (MPZ)], angiogenic [platelet endothelial cell adhesion molecule 1 (PECAM1/CD31) and vascular endothelial cell growth factor alpha (VEGFA)], extracellular matrix (ECM) [collagen type alpha I (COL1A1), collagen type alpha III (COL3A1), Fibulin 1 (FBLN1) and laminin subunit beta 2 (LAMB2)] and cell surface marker cluster of differentiation 96 (CD96) gene expression was quantified. Unseeded Avance® Nerve Grafts and NeuraGen® Nerve Guides were used to evaluate the baseline gene expression, and unseeded MSCs provided the baseline gene expression of MSCs. The interaction of MSCs with the Avance® Nerve Grafts led to a short-term upregulation of neurotrophic (NGF, GDNF and BDNF), myelination (PMP22 and MPZ) and angiogenic genes (CD31 and VEGFA) and a long-term upregulation of BDNF, VEGFA and COL1A1. The interaction between MSCs and the NeuraGen® Nerve Guide led to short term upregulation of neurotrophic (NGF, GDNF and BDNF) myelination (PMP22 and MPZ), angiogenic (CD31 and VEGFA), ECM (COL1A1) and cell surface (CD96) genes and long-term upregulation of neurotrophic (GDNF and BDNF), angiogenic (CD31 and VEGFA), ECM genes (COL1A1, COL3A1, and FBLN1) and cell surface (CD96) genes. Analysis demonstrated MSCs seeded onto NeuraGen® Nerve Guides expressed significantly higher levels of neurotrophic (PTN), angiogenic (VEGFA) and ECM (COL3A1, FBLN1) genes in the long term period compared to MSCs seeded onto Avance® Nerve Grafts. Overall, the interaction between human MSCs and both nerve graft substitutes resulted in a significant upregulation of the expression of numerous genes important for nerve regeneration over time. The in vitro interaction of MSCs with the NeuraGen® Nerve Guide was more pronounced, particularly in the long term period (> 14 days after seeding). These results suggest that MSC-seeding has potential to be applied in a clinical setting, which needs to be confirmed in future in vitro and in vivo research.

Differentiation of cardiomyocyte-like cells from human amniotic fluid mesenchymal stem cells by combined induction with human platelet lysate and 5-azacytidine

Human amniotic fluid mesenchymal stem cells (hAF-MSCs) have been shown to be effective in the treatment of many diseases. Platelet lysate (PL) contains multiple growth and differentiation factors; therefore, it can be used as a differentiation inducer. In this study, we attempted to evaluate the efficiency of human platelet lysate (hPL) on cell viability and the effects on cardiomyogenic differentiation of hAF-MSCs. When treating the cells with hPL, the result showed an increase in cell viability. Expressions of cardiomyogenic specific genes, including GATA4, cTnT, Cx43 and Nkx2.5, were higher in the combined treatment groups of 5-azacytidine (5-aza) and hPL than the expressions of cardiomyogenic specific genes in the control group and in the 5-aza treatment group. In terms of the results of immunofluorescence and immunoenzymatic staining, the highest expressions of cardiomyogenic specific proteins were revealed in combined treatment groups. It can be summarized that hPL may be an effective supporting cardiomyogenic supplementary factor for cardiomyogenic differentiation in hAF-MSCs.

Stem Cells: A Review Encompassing the Literature with a Special Focus on the Side-Lined Miraculous Panacea; Pre-Morula Stem Cells

Stem cells are the undifferentiated cells in the body that possess the ability to differentiate and give rise to any type of cells in the body. In recent years, there has been a growing interest in therapies involving stem cells as different treatment methods got developed. Depending on the source, there are two major kinds of stem cells, embryonic and adult stem cells. The former type is found in the embryo at the different developmental stages before the implantation and excels the latter owing to pluripotency. On the premise of the attributes of stem cells, they are touted as the "panacea for all ills" and are extensively sought for their potential therapeutic roles. There are a lot of robust pieces of evidence that have proved to cure the different ailments in the body like Huntington disease, Parkinson's disease, and Spinal cord injury with stem cell therapy but associated with adverse effects like immune rejection and teratoma formation. In this regard, the pre-morula (isolated at an early pre-morula stage) stem cells (PMSCs) are one of its kind of embryonic stem cells that are devoid of the aforementioned adverse effects. Taking the beneficial factor into account, they are being used for the treatment of disorders like Cerebral palsy, Parkinson's disorder, Aplastic anemia, Multiple sclerosis and many more. However, it is still illegal to use stem cells in the abovementioned disorders. This review encompasses different stem cells and emphasizes on PMSCs for their uniqueness in therapy as no other previously published literature reviews have taken these into consideration. Later in the review, current regulatory aspects related to stem cells are also considered.

Exosomes derived from pro-inflammatory bone marrow-derived mesenchymal stem cells reduce inflammation and myocardial injury via mediating macrophage polarization

Exosomes are served as substitutes for stem cell therapy, playing important roles in mediating heart repair during myocardial infarction injury. Evidence have indicated that lipopolysaccharide (LPS) pre-conditioning bone marrow-derived mesenchymal stem cells (BMSCs) and their secreted exosomes promote macrophage polarization and tissue repair in several inflammation diseases; however, it has not been fully elucidated in myocardial infarction (MI). This study aimed to investigate whether LPS-primed BMSC-derived exosomes could mediate inflammation and myocardial injury via macrophage polarization after MI. Here, we found that exosomes derived from BMSCs, in both Exo and L-Exo groups, increased M2 macrophage polarization and decreased M1 macrophage polarization under LPS stimulation, which strongly depressed LPS-dependent NF-κB signalling pathway and partly activated the AKT1/AKT2 signalling pathway. Compared with Exo, L-Exo had superior therapeutic effects on polarizing M2 macrophage in vitro and attenuated the post-infarction inflammation and cardiomyocyte apoptosis by mediating macrophage polarization in mice MI model. Consequently, we have confidence in the perspective that low concentration of LPS pre-conditioning BMSC-derived exosomes may develop into a promising cell-free treatment strategy for clinical treatment of MI.

Effect of ascorbic acid on differentiation of human amniotic fluid mesenchymal stem cells into cardiomyocyte-like cells

The aim of this study was to evaluate the efficiency of ascorbic acid (AA) on cell viability, cytotoxicity and the effects on cardiomyogenic differentiation of the human amniotic fluid mesenchymal stem cells (hAF-MSCs). The results of methylthiazole tetrazolium (MTT) assay and cell apoptosis assay indicated that after 24, 48 and 72 h of treatment, AA had no effect on cells viability and cytotoxicity. After treating the hAF-MSCs with 5-azacytidine (5-aza) and a combination of AA and 5-aza, the alamar blue cells proliferation assay showed the normal growth characteristic similar to control group. Especially, the morphological changes were observed between day 0 and day 21, and it was revealed that the hAF-MSCs exhibited myotube-like morphology after 7 days of cell culturing. Moreover, the treatment with a combination of AA and 5-aza was able to up-regulate the cardiomyogenic specific gene levels, which are known to play an important role in cardiomyogenesis. This was specifically notable with the results of immunofluorescence and immunoenzymatic staining in the AA combined with 5-aza treatment group, the highest expression of cardiomyogenic specific proteins was revealed including for GATA4, cTnT, Cx43 and Nkx2.5. It could be concluded that AA may be a good alternative cardiomyogenic inducing factor for hAF-MSCs and may open new insights into future biomedical applications for a clinically treatment.

Mesenchymal stem cell therapy for the treatment of inflammatory diseases: Challenges, opportunities, and future perspectives

Mesenchymal stem cells (MSCs) are promising alternative agents for the treatment of inflammatory disorders due to their immunomodulatory functions, and several clinical trials on MSC-based products are currently being conducted. In this review, we discuss recent progress made on the use of MSCs as immunomodulatory agents, developmental challenges posed by MSC-based therapy, and the strategies being used to overcome these challenges. In this context, current understanding of the mechanisms responsible for MSC interactions with the immune system and the molecular responses of MSCs to inflammatory signals are discussed. The immunosuppressive activities of MSCs are initiated by cell-to-cell contact and the release of immuno-regulatory molecules. By doing so, MSCs can inhibit the proliferation and function of T cells, natural killer cells, B cells, and dendritic cells, and can also increase the proliferation of regulatory T cells. However, various problems, such as low transplanted cell viability, poor homing and engraftment into injured tissues, MSC heterogeneity, and lack of adequate information on optimum MSC doses impede clinical applications. On the other hand, it has been shown that the immunomodulatory activities and viabilities of MSCs might be enhanced by 3D-cultured systems, genetic modifications, preconditioning, and targeted-delivery.

Mechanism of Action of Icariin in Bone Marrow Mesenchymal Stem Cells

Osteoporosis, femoral head necrosis, and congenital bone defects are orthopedic disorders characterized by reduced bone generation and insufficient bone mass. Bone regenerative therapy primarily relies on the bone marrow mesenchymal stem cells (BMSCs) and their ability to differentiate osteogenically. Icariin (ICA) is the active ingredient of Herba epimedii, a common herb used in traditional Chinese medicine (TCM) formulations, and can effectively enhance BMSC proliferation and osteogenesis. However, the underlying mechanism of ICA action in BMSCs is not completely clear. In this review, we provide an overview of the studies on the role and mechanism of action of ICA in BMSCs, to provide greater insights into its potential clinical use in bone regeneration.

Insulin gene enhancer binding protein 1 induces adipose tissue‑derived stem cells to differentiate into pacemaker‑like cells

Hybrid approaches combining gene- and cell-based therapies to make biological pacemakers are a promising therapeutic avenue for bradyarrhythmia. The present study aimed to direct adipose tissue-derived stem cells (ADSCs) to differentiate specifically into cardiac pacemaker cells by overexpressing a single transcription factor, insulin gene enhancer binding protein 1 (ISL-1). In the present study, the ADSCs were transfected with ISL‑1 or mCherry fluorescent protein lentiviral vectors and co-cultured with neonatal rat ventricular cardiomyocytes (NRVMs) in vitro for 5-7 days. The feasibility of regulating the differentiation of ADSCs into pacemaker-like cells by overexpressing ISL-1 was evaluated by observation of cell morphology and beating rate, reverse transcription-quantitative polymerase chain reaction analysis, western blotting, immunofluorescence and analysis of electrophysiological activity. In conclusion, these data indicated that the overexpression of ISL-1 in ADSCs may enhance the pacemaker phenotype and automaticity in vitro, features which were significantly increased following co‑culture induction.

Dynamic Cultivation of Mesenchymal Stem Cell Aggregates

Mesenchymal stem cells (MSCs) are considered as primary candidates for cell-based therapies due to their multiple effects in regenerative medicine. Pre-conditioning of MSCs under physiological conditions—such as hypoxia, three-dimensional environments, and dynamic cultivation—prior to transplantation proved to optimize their therapeutic efficiency. When cultivated as three-dimensional aggregates or spheroids, MSCs display increased angiogenic, anti-inflammatory, and immunomodulatory effects as well as improved stemness and survival rates after transplantation, and cultivation under dynamic conditions can increase their viability, proliferation, and paracrine effects, alike. Only few studies reported to date, however, have utilized dynamic conditions for three-dimensional aggregate cultivation of MSCs. Still, the integration of dynamic bioreactor systems, such as spinner flasks or stirred tank reactors might pave the way for a robust, scalable bulk expansion of MSC aggregates or MSC-derived extracellular vesicles. This review summarizes recent insights into the therapeutic potential of MSC aggregate cultivation and focuses on dynamic generation and cultivation techniques of MSC aggregates.

TGF-β1 combined with Sal-B promotes cardiomyocyte differentiation of rat mesenchymal stem cells

Transforming growth factor β1 (TGF-β1) and salvianolic acid B (Sal-B) are key signaling factors for stem cell differentiation into cardiomyocytes (CMs). The present study compared the biological effect of TGF-β1 and Sal-B, alone or in combination, on bone marrow mesenchymal stromal cells (BMSCs) that differentiate into myocardial-like cells in a simulated myocardial microenvironment in vitro. BMSCs were isolated from bones of limbs of 10 male Sprague Dawley rats and cultured. The 2nd-generation BMSCs were co-incubated with TGF-β1 and Sal-B, alone or in combination, for 72 h. The control group was BMSCs cultured without any inductive substance. The levels GATA binding protein 4 (GATA4) and homeobox protein NKx2.5 were determined by reverse-transcription quantitative polymerase chain reaction and immunofluorescence staining was used to evaluate α-sarcomeric actin and cardiac troponin I (cTNI) as cardiomyogenic differentiation markers. The ultrastructure of BMSCs in each group was also observed. BMSCs were initially spindle-shaped with irregular processes. The cells gradually increased in number 24 h post-inoculation and proliferated 7 days later. Compared with the control group, BMSCs in the treatment groups had fusiform shapes, orientating with one accord and were connected with adjoining cells forming myotube-like structures on day 28. The morphology and architecture/myotubes of BMSCs was similar among the treatment groups, but the amount of cells in the combined group was comparatively higher. The results of immunofluorescence staining revealed the expression of the CM-specific proteins α-sarcomeric actin and cTNI in these cells. The expression of these cardiac-specific markers in the combined group was significantly higher than that in the other groups (P<0.01 or P<0.05). In addition, the transcriptional expression of GATA4 and NKx2.5 in the treatment groups was stable and significantly higher than that in the control group on day 7. Transmission electron microscopy showed that BMSCs in the treatment groups all had myofilaments, rough endoplasmic reticulum and mitochondria in the cytoplasm when compared with the control group. Taken together, these results indicated that the combination of TGF-β1 and Sal-B effectively promotes cardiomyogenic differentiation of BMSCs in vitro and their application may represent a therapeutic strategy for the treatment of ischemic heart disease.

Regenerative Therapy for Cardiomyopathies

Despite substantial advances in the development of medical and interventional strategies in ischemic and non-ischemic heart diseases, cardiovascular diseases (CVDs) remain the leading cause of mortality and morbidity worldwide. Stem cell therapy for heart disease has gained traction over the past two decades and is an emerging option for the treatment of myocardial dysfunction. In this review, we summarize the current literature on different types of stem cells and their potential usage in ischemic and non-ischemic heart diseases. We emphasize the clinical utility of stem cells to improve myocardial structural and function, promote microvascular angiogenesis, and diminish scar size and major adverse cardiovascular events. We also discuss the therapeutic potential of microvesicles, such as exosomes, in the treatment of CVDs, which may open novel avenues for further clinical studies.

Phenolic compounds apigenin, hesperidin and kaempferol reduce in vitro lipid accumulation in human adipocytes

BACKGROUND

Adipocytes derived from human mesenchymal stem cells (MSCs) are widely used to investigate adipogenesis. Taking into account both the novelty of these MSCs and the scarcity of studies focused on the effects of phenolic compounds, the aim of the present study was to analyze the effect of apigenin, hesperidin and kaempferol on pre-adipocyte and mature adipocytes derived from this type of cells. In addition, the expression of genes involved in TG accumulation was also measured.

METHODS

Pre-adipocytes were cultured from day 0 to day 8 and mature adipocytes for 48 h with the polyphenols at doses of 1, 10 and 25 µM.

RESULTS

Apigenin did not show an anti-adipogenic action. Pre-adipocytes treated with hesperidin and kaempferol showed reduced TG content at the three experimental doses. Apigenin did not modify the expression of the main adipogenic genes (c/ebpβ, c/ebpα, pparγ and srebp1c), hesperidin inhibited genes involved in the three phases of adipogenesis (c/ebpβ, srebp1c and perilipin) and kaempferol reduced c/ebpβ. In mature adipocytes, the three polyphenols reduced TG accumulation at the dose of 25 µM, but not at lower doses. All compounds increased mRNA levels of atgl. Apigenin and hesperidin decreased fasn expression. The present study shows the anti-adipogenic effect and delipidating effects of apigenin, hesperidin and kaempferol in human adipocytes derived from hMSCs. While hesperidin blocks all the stages of adipogenesis, kaempferol only inhibits the early stage. Regarding mature adipocytes, the three compounds reduce TG accumulation by activating, at least in part, lipolysis, and in the case of hesperidin and apigenin, also by reducing lipogenesis.

CONCLUSIONS

The present study shows for the first time the anti-adipogenic effect and delipidating effect of apigenin, hesperidin and kaempferol in human adipocytes derived from MSCs for the first time.

Mechanisms of stem cell based cardiac repair-gap junctional signaling promotes the cardiac lineage specification of mesenchymal stem cells

Different subtypes of bone marrow-derived stem cells are characterized by varying functionality and activity after transplantation into the infarcted heart. Improvement of stem cell therapeutics requires deep knowledge about the mechanisms that mediate the benefits of stem cell treatment. Here, we demonstrated that co-transplantation of mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs) led to enhanced synergistic effects on cardiac remodeling. While HSCs were associated with blood vessel formation, MSCs were found to possess transdifferentiation capacity. This cardiomyogenic plasticity of MSCs was strongly promoted by a gap junction-dependent crosstalk between myocytes and stem cells. The inhibition of cell-cell coupling significantly reduced the expression of the cardiac specific transcription factors NKX2.5 and GATA4. Interestingly, we observed that small non-coding RNAs are exchanged between MSCs and cardiomyocytes in a GJ-dependent manner that might contribute to the transdifferentiation process of MSCs within a cardiac environment. Our results suggest that the predominant mechanism of HSCs contribution to cardiac regeneration is based on their ability to regulate angiogenesis. In contrast, transplanted MSCs have the capability for intercellular communication with surrounding cardiomyocytes, which triggers the intrinsic program of cardiogenic lineage specification of MSCs by providing cardiomyocyte-derived cues.

Differentiation of mesenchymal stem cells from human amniotic fluid to cardiomyocyte‑like cells

Ischemic heart disease (IHD) is a major factor influencing worldwide mortality rates. Furthermore, IHD has become a significant health problem among the Thai population. Stem cell therapy using mesenchymal stem cells (MSCs) is an alternative therapeutic method that has been applied to improve the quality of life of patients. Amniotic fluid (AF) contains a heterogeneous cell population, including MSCs, which are multipotent stem cells that have the capability to differentiate into mesenchymal lineages. The purpose of the present study was to evaluate the MSC characteristics of human (h)AF and determine its potency regarding cardiogenic differentiation. MSC characterization following flow cytometric analysis revealed that the cells expressed MSC markers, cluster of differentiation (CD)44, CD90, human leukocyte antigen-ABC and CD73. The results of the alamar blue assay demonstrated that cell proliferation rate continuously increased from the early cultivation phase up to 5-fold during days 1 to 5 of cell culturing. The highest rate of cell proliferation was observed on day 17 with a 30-fold increase compared with that on day 1. During the cardiogenic induction stage, morphological changes were observed between day 0 and day 21, and it was revealed that the hAF derived-MSCs in the cardiogenic-induced group exhibited myotube-like morphology after 7 days of cell culturing. Following cardiogenic induction, immunohistochemistry staining was performed on day 21, and reverse transcription-quantitative polymerase chain reaction on day 7 and 21. These steps were performed to detect the protein and gene expression levels of cardiac specific proteins (GATA4, cardiac troponin T, Nkx2.5 and Connexin43). The results of the present study indicated that hAF-MSCs possess the potential to differentiate into cardiomyocyte-like cells. Thus, it was concluded that hAF may be a suitable source of MSCs for stem cell therapy and tissue engineering.

A three-dimensional assemblage of gingiva-derived mesenchymal stem cells and NO-releasing microspheres for improved differentiation

Stem cell therapy is an attractive approach to bone tissue regeneration. Nitric oxide (NO) has been reported to facilitate osteogenic differentiation of stem cells. To enhance osteogenic differentiation of gingiva-derived mesenchymal stem cells (GMSCs), we designed a method for in situ delivery of exogenous NO to these cells. A NO donor, polyethylenimine/NONOate, was incorporated into poly(lactic-co-glycolic acid) microspheres to deliver NO to the cells for an extended period of time under in vitro culture conditions. A hybrid aggregate of GMSCs and NO-releasing microspheres was prepared by the hanging drop technique. Confocal microscopy revealed homogeneous arrangement of the stem cells and microspheres in heterospheroids. Western blot analysis and live-dead imaging showed no significant change in cell viability. Importantly, the in situ delivery of NO within the heterospheroids enhanced osteogenic differentiation indicated by a 1.2-fold increase in alkaline phosphatase activity and an approximately 10% increase in alizarin red staining. In addition, a low dose of NO promoted proliferation of the GMSCs in this 3D system. Thus, delivery of the NO-releasing microsphers to induce differentiation of stem cells within this three dimensional system may be one of possible strategies to direct differentiation of a stem cell-based therapeutic agent toward a specific lineage.

Therapeutic effects of intranigral transplantation of mesenchymal stem cells in rat models of Parkinson's disease

Stem cell transplantation is a promising tool for the treatment of neurodegenerative disorders, including Parkinson's disease (PD); however, the therapeutic routes and mechanisms of mechanical approaches to stem cell transplantation must be explored. This study tests the therapeutic effect of transplantation of rat bone marrow mesenchymal stem cells (MSCs) into the substantia nigra (SN) of the PD rat. 5-Bromo-2-deoxyuridine-labeled rat MSCs were transplanted into the SN of the 6-hydroxydopamine-injected side of PD rat brains. The behavioral changes in PD rats were examined before and 4 and 8 weeks after MSC transplantation. The expression of tyrosine hydroxylase (TH) in the SN and the striatum and the survival and differentiation of MSCs were assessed by immunohistochemical and double immunofluorescence techniques. Abnormal behavior of PD rats was significantly improved by the administration of bone marrow MSCs, and the number of TH-positive cells in the SN and the optical density of TH-positive fibers in the striatum were markedly increased. Transplanted MSCs can survive and migrate in the brain and differentiate into nestin-, neuron-specific enolase-, and GFAP-positive cells. Our findings suggest that transplantation of rat bone marrow MSCs into the SN of PD rats may provide therapeutic effects. © 2016 Wiley Periodicals, Inc.

Intramyocardial implantation of differentiated rat bone marrow mesenchymal stem cells enhanced by TGF-β1 improves cardiac function in heart failure rats

The present study tested the hypotheses that i) transforming growth factor beta 1 (TGF-β1) enhances differentiation of rat bone marrow mesenchymal stem cells (MSCs) towards the cardiomyogenic phenotype and ii) intramyocardial implantation of the TGF-β1-treated MSCs improves cardiac function in heart failure rats. MSCs were treated with different concentrations of TGF-β1 for 72 h, and then morphological characteristics, surface antigens and mRNA expression of several transcription factors were assessed. Intramyocardial implantation of these TGF-β1-treated MSCs to infarcted heart was also investigated. MSCs were initially spindle-shaped with irregular processes. On day 28 after TGF-β1 treatment, MSCs showed fusiform shape, orientating parallel with one another, and were connected with adjoining cells forming myotube-like structures. Immunofluorescence revealed the expression of cardiomyocyte-specific proteins, α-sarcomeric actin and troponin T, in these cells. The mRNA expression of GATA4 and Nkx2.5 genes was slightly increased on day 7, enhanced on day 14 and decreased on day 28 while α-MHC gene was not expressed on day 7, but expressed slightly on day 14 and enhanced on day 28. Transmission electron microscopy showed that the induced cells had myofilaments, z line-like substances, desmosomes, and gap junctions, in contrast with control cells. Furthermore, intramyocardial implantation of TGF-β1-treated MSCs to infarcted heart reduced scar area and increased the number of muscle cells. This structure regeneration was concomitant with the improvement of cardiac function, evidenced by decreased left ventricular end-diastolic pressure, increased left ventricular systolic pressure and increased maximal positive pressure development rate. Taken together, these results indicate that intramyocardial implantation of differentiated MSCs enhanced by TGF-β1 improved cardiac function in heart failure rats.

Harnessing the secretome of cardiac stem cells as therapy for ischemic heart disease

Adult stem cells continue to promise opportunities to repair damaged cardiac tissue. However, precisely how adult stem cells accomplish cardiac repair, especially after ischemic damage, remains controversial. It has been postulated that the clinical benefit of adult stem cells for cardiovascular disease results from the release of cytokines and growth factors by the transplanted cells. Studies in animal models of myocardial infarction have reported that such paracrine factors released from transplanted adult stem cells contribute to improved cardiac function by several processes. These include promoting neovascularization of damaged tissue, reducing inflammation, reducing fibrosis and scar formation, as well as protecting cardiomyocytes from apoptosis. In addition, these factors might also stimulate endogenous repair by activating cardiac stem cells. Interestingly, stem cells discovered to be resident in the heart appear to be functionally superior to extra-cardiac adult stem cells when transplanted for cardiac repair and regeneration. In this review, we discuss the therapeutic potential of cardiac stem cells and how the proteins secreted from these cells might be harnessed to promote repair and regeneration of damaged cardiac tissue. We also highlight how recent controversies about the efficacy of adult stem cells in clinical trials of ischemic heart disease have not dampened enthusiasm for the application of cardiac stem cells and their paracrine factors for cardiac repair: the latter have proved superior to the mesenchymal stem cells used in most clinical trials in the past, some of which appear to have been conducted with sub-optimal rigor.

Cardiomyogenic Differentiation of Human Dental Follicle-derived Stem Cells by Suberoylanilide Hydroxamic Acid and Their In Vivo Homing Property

The purpose of the present study was to investigate the in vitro cardiomyogenic differentiation potential of human dental follicle-derived stem cells (DFCs) under the influence of suberoylanilide hydroxamic acid (SAHA), a member of the histone deacetylase inhibitor family, and analyze the in vivo homing capacity of induced cardiomyocytes (iCMs) when transplanted systemically. DFCs from extracted wisdom teeth showed mesenchymal stem cell (MSC) characteristics such as plate adherent growing, expression of MSC markers (CD44, CD90, and CD105), and mesenchymal lineage-specific differentiation potential. Adding SAHA to the culture medium induced the successful in vitro differentiation of DFCs into cardiomyocytes. These iCMs expressed cardiomyogenic markers, including alpha-smooth muscle actin (α-SMA), cardiac muscle troponin T (TNNT2), Desmin, and cardiac muscle alpha actin (ACTC1), at both the mRNA and protein level. For the assessment of homing capacity, PKH26 labeled iCMs were intraperitoneally injected (1×10⁶ cells in 100 µL of PBS) into the experimental mice, and the ratios of PKH26 positive cells to the total number of injected cells, in multiple organs were determined. The calculated homing ratios, 14 days after systemic cell transplantation, were 5.6 ± 1.0%, 3.6 ± 1.1%, and 11.6 ± 2.7% in heart, liver, and kidney respectively. There was no difference in the serum levels of interleukin-2 and interleukin-10 at 14 days after transplantation, between the experimental (iCM injected) and control (no injection or PBS injection) groups. These results demonstrate that DFCs can be an excellent source for cardiomyocyte differentiation and regeneration. Moreover, the iCMs can be delivered into heart muscle via systemic administration without eliciting inflammatory or immune response. This can serve as the pilot study for further investigations into the in vitro cardiomyogenic differentiation potential of DFCs under the influence of SAHA and the in vivo homing capacity of the iCMs into the heart muscle, when injected systemically.