TGFβ1 contributes to cardiomyogenic-like differentiation of human bone marrow mesenchymal stem cells

Novel fabrication of bioengineered injectable chitosan hydrogel loaded with conductive nanoparticles to improve therapeutic potential of mesenchymal stem cells in functional recovery after ischemic myocardial infarction

In recent decades, myocardial regeneration through stem cell transplantation and tissue engineering has been viewed as a promising technique for treating myocardial infarction. As a result, the researcher attempts to see whether co-culturing modified mesenchymal stem cells with Au@Ch-SF macro-hydrogel and H9C2 may help with tissue regeneration and cardiac function recovery. The gold nanoparticles (Au) incorporated into the chitosan-silk fibroin hydrogel (Au@Ch-SF) were validated using spectral and microscopic examinations. The most essential elements of hydrogel groups were investigated in detail, including weight loss, mechanical strength, and drug release rate. Initially, the cardioblast cells (H9C2 cells) was incubated with Au@Ch-SF macro-hydrogel, followed by mesenchymal stem cells (2 × 10⁵) were transplanted into the Au@Ch-SF macro-hydrogel+H9C2 culture at the ratio of 2:1. Further, cardiac phenotype development, cytokines expression and tissue regenerative performance of modified mesenchymal stem cells treatment were studied through various in vitro and in vivo analyses. The Au@Ch-SF macro-hydrogel gelation time was much faster than that of Ch and Ch-SF hydrogels, showing that Ch and SF exhibited greater intermolecular interactions. The obtained Au@Ch-SF macro-hydrogel has no toxicity on mesenchymal stem cells (MS) or cardiac myoblast (H9C2) cells, according to the biocompatibility investigation. MS cells co-cultured with Au@Ch-SF macro-hydrogel and H9C2 cells also stimulated cardiomyocyte fiber restoration, which has been confirmed in myocardial infarction rats using -MHC and Cx43 myocardial indicators. We developed a novel method of co-cultured therapy using MS cells, Au@Ch-SF macro-hydrogel, and H9C2 cells which could promote the regenerative activities in myocardial ischemia cells. These study findings show that co-cultured MS therapy might be effective for the treatment of myocardial injury.

Polycaprolactone-co-polylactic acid nanofiber scaffold in combination with 5-azacytidine and transforming growth factor-β to induce cardiomyocyte differentiation of adipose-derived mesenchymal stem cells

Adipose-derived mesenchymal stem cells (Ad-MSCs) are promising candidates for cardiac repair/regeneration. The application of copolymer nanoscaffolds has received great attention in tissue engineering to support differentiation and functional tissue organization toward effective tissue regeneration. The objective of the current study was to develop functional and bioactive scaffolds by combining polycaprolactone (PCL) and polylactic acid (PLA) for cardiomyocyte differentiation of human Ad-MSC (hAd-MSCs) in the absence or presence of 5-azacytidine and transforming growth factor-β (TGF-β). To that end, the human MSCs were extracted from human adipose tissue (AD). The cardiomyocyte differentiation potency of hAd-MSCs was evaluated on the novel synthetic PCL/PLA nanofiber scaffolds prepared in the absence and presence of 5-azacytidine and TGF-β supplements. A PCL/PLA nanofibrous scaffold was fabricated using the electrospinning method and its nanotopography and porous structure were characterized using scanning electron microscopy. In addition, the attachment of hAd-MSCs on the PCL/PLA scaffolds was semiquantitatively investigated. Compared with other treatments, the PCL/PLA nanofibrous scaffold supplemented with both 5-azacytidine and TGF-β was observed to differentiate hAd-MSCs into cardiomyocytes at Day 21 as evidenced by real-time PCR for cardiac-specific genes including cardiac troponin I (cTnI), GATA4, MYH7, and NKX2.5. In addition, flow cytometric analysis of cTnI-positive cells demonstrated that the cardiomyocyte differentiation of hAd-MSCs was more efficient on the PCL/PLA nanofibrous scaffold supplemented with both 5-azacytidine and TGF-β than it was in the other treatment groups. Generally speaking, the results show that PCL/PLA nanofibrous scaffolds may be applied as a platform for efficient differentiation of hAd-MSCs into functional cardiomyocytes.

Cardiomyocyte-specific regression of nitrosative stress-mediated S-Nitrosylation of IKKγ alleviates pathological cardiac hypertrophy

IKKγ prototypically promotes NFκBp65 activity by regulating the assembly of the IKK holocomplex. In hypertrophied cardiomyocytes, the p65-p300 complex-induced regenerative efforts are neutralized by the p53-p300 complex-mediated apoptotic load resulting in compromised cardiac function. The present study reports that nitrosative stress leads to S-Nitrosylation of IKKγ in hypertrophied cardiomyocytes in a pre-clinical model. Using a cardiomyocyte-targeted nanoconjugate, IKKγ S-Nitrosylation-resistant mutant plasmids were delivered to the pathologically hypertrophied heart that resulted in improved cardiac function by amelioration of cardiomyocyte apoptosis and simultaneous induction of their cell cycle re-entry machinery. Mechanistically, in IKKγ S-Nitrosyl mutant-transfected hypertrophied cells, increased IKKγ-p300 binding downregulated the binding of p53 and p65 with p300. This shifted the binding preference of p65 from p300 to HDAC1 resulting in upregulated expression of cyclin D1 and CDK2 via the p27/pRb pathway. This approach has therapeutic advantage over mainstream anti-hypertrophic remedies which concomitantly reduce the regenerative prowess of resident cardiomyocytes during hypertrophy upon downregulation of myocyte apoptosis. Therefore, cardiomyocyte-targeted delivery of IKKγ S-Nitrosyl mutants during hypertrophy can be exploited as a novel strategy to re-muscularize the diseased heart.

Human Acquired Aplastic Anemia Patients' Bone-Marrow-Derived Mesenchymal Stem Cells Are Not Influenced by Hematopoietic Compartment and Maintain Stemness and Immune Properties

Methods

In the current study, we investigated the morphological differences, proliferation capacity, population doubling time (PDT), surface marker profiling, trilineage differentiation potential, and immunosuppressive ability of BM Mesenchymal Stem Cells (BM-MSCs) from untreated aAA patients and in the same number of age- and gender-matched controls.

Results

We observed similar morphology, proliferation capacity, phenotype, trilineage differentiation potential, and immunomodulatory properties of BM-MSCs in aAA patients and control subjects.

Conclusion

Our results confirm that the basic and immunosuppressive properties of BM-MSCs from aAA patients do not differ from normal BM-MSCs. Our data suggest that BM-MSCs from aAA patients might not be involved in disease pathogenesis. However, owing to a smaller number of samples, it is not conclusive, and future studies with more exhaustive investigation at transcriptome level are warranted.

Cardiac Differentiation of Mesenchymal Stem Cells: Impact of Biological and Chemical Inducers

Cardiovascular disorders (CVDs) are the leading cause of global death, widely occurs due to irreparable loss of the functional cardiomyocytes. Stem cell-based therapeutic approaches, particularly the use of Mesenchymal Stem Cells (MSCs) is an emerging strategy to regenerate myocardium and thereby improving the cardiac function after myocardial infarction (MI). Most of the current approaches often employ the use of various biological and chemical factors as cues to trigger and modulate the differentiation of MSCs into the cardiac lineage. However, the recent advanced methods of using specific epigenetic modifiers and exosomes to manipulate the epigenome and molecular pathways of MSCs to modify the cardiac gene expression yield better profiled cardiomyocyte like cells in vitro. Hitherto, the role of cardiac specific inducers triggering cardiac differentiation at the cellular and molecular level is not well understood. Therefore, the current review highlights the impact and recent trends in employing biological and chemical inducers on cardiac differentiation of MSCs. Thereby, deciphering the interactions between the cellular microenvironment and the cardiac inducers will help us to understand cardiomyogenesis of MSCs. Additionally, the review also provides an insight on skeptical roles of the cell free biological factors and extracellular scaffold assisted mode for manipulation of native and transplanted stem cells towards translational cardiac research.

Cell-Laden Bioactive Poly(ethylene glycol) Hydrogels for Studying Mesenchymal Stem Cell Behavior in Myocardial Infarct-Stiffness Microenvironments

PURPOSE

Cellular therapy with mesenchymal stem cells (MSCs) shows promise for restoring function after myocardial infarction (MI). However, cellular therapy has yet to be clinically translated, in part because of difficulty in studying how MSCs interact with the post-MI scar microenvironment. This study aimed to design an in vitro model to study MSC behavior in the post-MI scar stiffness microenvironment.

METHODS

Using poly(ethylene glycol)-acrylate (PEG) conjugated to bioactive peptides, rat MSCs were encapsulated in hydrogels of varying stiffnesses and crosslinking densities. Cell viability was assessed through 14 days using calcein and ethidium homodimer staining. To simulate post-MI pro-fibrotic signaling, transforming growth factor-beta (TGFβ) was added to selected cultures. Immunofluorescence and qRT-PCR were used to assess changes in cardiac transdifferentiation or paracrine secretion, two proposed methods of MSCs in cellular therapy.

RESULTS

Bioactivated PEG hydrogels with stiffnesses between 1.6 and 151.0 kPa were prepared. Rat MSCs demonstrated up to 71.6% viability after 3 days of encapsulated culture, and survived within the hydrogels up to 14 days. Encapsulation decreased MSC expression of cardiac troponin T and most growth factors, except interleukin-6. Meanwhile, TGFβ caused increased cardiac troponin T expression but decreased secreted factor expression. Varying hydrogel stiffness did not have an effect on cardiac troponin T or secreted factor expression.

CONCLUSIONS

These findings suggest that a 3D microenvironment hinders two key mechanisms by which MSCs could improve cardiac function after post-MI scar formation, namely cardiac transdifferentiation and secreted factor production. Future studies incorporating MSCs other cell types should broaden understanding of the post-MI scar microenvironment.

Fluorescent conjugated polymer nanovector for in vivo tracking and regulating the fate of stem cells for restoring infarcted myocardium

Stem cell therapy holds great promise for cardiac regeneration. However, the lack of ability to control stem cell fate after in vivo transplantation greatly restricts its therapeutic outcomes. MicroRNA delivery has emerged as a powerful tool to control stem cell fate for enhanced cardiac regeneration. However, the clinical translation of therapy based on gene-transfected stem cells remains challenging, due to the unknown in vivo behaviors of stem cells. Here, we developed a nano-platform (i.e., PFBT@miR-1-Tat NPs) that can achieve triggered release of microRNA-1 to promote cardiac differentiation of mesenchymal stem cells (MSCs), and long-term tracking of transplanted MSCs through bright and ultra-stable fluorescence of conjugated polymer poly(9,9-dioctylfluorene-alt-benzothiadiazole) (PFBT). We found that PFBT@miR-1-Tat NP-treated MSCs significantly restored the infarcted myocardium by promoting stem cell cardiac differentiation and integration with the in situ cardiac tissues. Meanwhile, MSCs without gene delivery improved the infarcted heart functions mainly through a paracrine effect and blood vessel formation. The developed conjugated polymer nanovector should be a powerful tool for manipulating as well as revealing the fate of therapeutic cells in vivo, which is critical for optimizing the therapeutic route of gene and cell combined therapy and therefore for accelerating clinical translation. STATEMENT OF SIGNIFICANCE: The lack of controllability in stem cell fate and the unclear in vivo cellular behaviors restrict the therapeutic outcomes of stem cell therapy. Herein, we engineered fluorescent conjugated polymer nanoparticles as gene delivery nanovectors with controlled release and high intracellular delivery capability to harness the fate of mesenchymal stem cells (MSCs) in vivo, meanwhile to reveal the cellular mechanism of gene-treated stem cell therapy. As compared with only MSC treatment that improves infarcted myocardium functions through paracrine effect, treatment with conjugated polymer nanovector-treated MSCs significantly restored infarcted myocardium through enhancing MSC cardiac differentiation and integration with the in-situ cardiac tissues. These findings demonstrate that the conjugated polymer nanovector would be a powerful tool in optimizing gene and cell combined therapy.

GLP: A requirement in cell therapies - perspectives for the cardiovascular field

In biomedical research, enormous progress is being made and new candidates for putative medicinal products emerge. However, most published preclinical data are not conducted according to the standard Good Laboratory Practice (GLP). GLP is mandatory for preclinical analysis of Advanced Therapy Medicinal Products (ATMP) and thereby a prerequisite for planning and conduction of clinical trials. Not inconsiderable numbers of clinical trials are terminated earlier or fail - do inadequate testing strategies or missing specialized assays during the preclinical development contribute to this severe complex of problems? Unfortunately, there is also a lack of access to GLP testing results and OECD (Organisation for Economic Co-operation and Development) GLP guidelines are not yet adjusted to ATMP specialties. Ultimately, GLP offers possibilities to generate reliable and reproducible data. Therefore, this review elucidates different GLP aspects in drug development, speculates on reasons of putative low GLP acceptance in the scientific community and mentions solution proposals.

Angiotensin II and TGF-β1 Induce Alterations in Human Amniotic Fluid-Derived Mesenchymal Stem Cells Leading to Cardiomyogenic Differentiation Initiation

Background and Objectives

Human amniotic fluid-derived mesenchymal stem cells (AF-MSCs) may be a valuable source for cardiovascular tissue engineering and cell therapy. The aim of this study is to verify angiotensin II and transforming growth factor-beta 1 (TGF-β1) as potential cardiomyogenic differentiation inducers of AF-MSCs.

Methods and Results

AF-MSCs were obtained from amniocentesis samples from second-trimester pregnant women, isolated and characterized by the expression of cell surface markers (CD44, CD90, CD105 positive; CD34 negative) and pluripotency genes (OCT4, SOX2, NANOG, REX1). Cardiomyogenic differentiation was induced using different concentrations of angiotensin II and TGF-β1. Successful initiation of differentiation was confirmed by alterations in cell morphology, upregulation of cardiac genes-markers NKX2-5, TBX5, GATA4, MYH6, TNNT2, DES and main cardiac ion channels genes (sodium, calcium, potassium) as determined by RT-qPCR. Western blot and immunofluorescence analysis revealed the increased expression of Connexin43, the main component of gap junctions, and Nkx2.5, the early cardiac transcription factor. Induced AF-MSCs switched their phenotype towards more energetic and started utilizing oxidative phosphorylation more than glycolysis for energy production as assessed using Agilent Seahorse XF analyzer. The immune analysis of chromatin-modifying enzymes DNMT1, HDAC1/2 and Polycomb repressive complex 1 and 2 (PRC1/2) proteins BMI1, EZH2 and SUZ12 as well as of modified histones H3 and H4 indicated global chromatin remodeling during the induced differentiation.

Conclusions

Angiotensin II and TGF-β1 are efficient cardiomyogenic inducers of human AF-MSCs; they initiate alterations at the gene and protein expression, metabolic and epigenetic levels in stem cells leading towards cardiomyocyte- like phenotype formation.

Human tissue-specific MSCs demonstrate differential mitochondria transfer abilities that may determine their regenerative abilities

BACKGROUND

Recent studies have demonstrated mesenchymal stem cells (MSCs) as effective mitochondrial donors with therapeutic success in multiple experimental models of human disease. MSCs obtained from different tissue sources such as bone marrow (BM), adipose (AD), dental pulp (DP), and Wharton's jelly (WJ) are routinely used in clinical trials with no known study of their mitochondrial donor capacity. Here, we show for the first time that MSCs derived from different tissue sources have different mitochondrial donor properties and that this is correlated with their intrinsic respiratory states.

METHODS

MitoTracker^®-labeled MSCs were co-cultured with Cell Trace-labeled U87-MG cells or rat cardiomyocytes. Mitochondrial transfer abilities of MSCs were assessed by using flow cytometry analysis and fluorescence imaging. Mitochondrial reactive oxygen species (mtROS) levels were analyzed by using MitoSOX red-based staining, and mitochondrial respiration parameters were analyzed by using a Seahorse XF Analyzer.

RESULTS

AD-MSCs and BM-MSCs displayed higher mitochondrial transfer than DP-MSCs and WJ-MSCs. Counterintuitively, DP-MSCs and WJ-MSCs were more effective in suppressing mtROS levels in stressed recipient cells than AD-MSCs or BM-MSCs. Interestingly, the oxygen consumption rates and intrinsic mitochondrial respiration parameters like ATP levels, basal and maximal respiration, and mitochondrial DNA copy number in donor MSCs showed a highly significant inverse correlation with their mitochondrial donation.

CONCLUSIONS

We find that there are intrinsic differences in the mitochondrial respiration, donation capacity, and therapeutic efficacy among MSCs of different tissue origin. MSCs with high mitochondrial respiration capacities are associated with lower mitochondrial transfer but more effective suppression of mtROS in stressed recipient cells. This is most compatible with a model where recipient cells optimally regulate mitochondrial transfer such that they take more mitochondria from MSCs with lower mitochondrial function. Furthermore, it appears to be advantageous to use MSCs such as DP-MSCs or WJ-MSCs with higher mitochondrial respiratory abilities that achieved better therapeutic effect with lower mitochondrial transfer in our study. This opens up a new direction in stem cell therapeutics.

Specific Cell (Re-)Programming: Approaches and Perspectives

Many disorders are manifested by dysfunction of key cell types or their disturbed integration in complex organs. Thereby, adult organ systems often bear restricted self-renewal potential and are incapable of achieving functional regeneration. This underlies the need for novel strategies in the field of cell (re-)programming-based regenerative medicine as well as for drug development in vitro. The regenerative field has been hampered by restricted availability of adult stem cells and the potentially hazardous features of pluripotent embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). Moreover, ethical concerns and legal restrictions regarding the generation and use of ESCs still exist. The establishment of direct reprogramming protocols for various therapeutically valuable somatic cell types has overcome some of these limitations. Meanwhile, new perspectives for safe and efficient generation of different specified somatic cell types have emerged from numerous approaches relying on exogenous expression of lineage-specific transcription factors, coding and noncoding RNAs, and chemical compounds.It should be of highest priority to develop protocols for the production of mature and physiologically functional cells with properties ideally matching those of their endogenous counterparts. Their availability can bring together basic research, drug screening, safety testing, and ultimately clinical trials. Here, we highlight the remarkable successes in cellular (re-)programming, which have greatly advanced the field of regenerative medicine in recent years. In particular, we review recent progress on the generation of cardiomyocyte subtypes, with a focus on cardiac pacemaker cells. Graphical Abstract.

Direct Cardiac Reprogramming: A Novel Approach for Heart Regeneration

Cardiac diseases are among the most common causes of death globally. Cardiac muscle has limited proliferative capacity, and regenerative therapies are highly in demand as a new treatment strategy. Although pluripotent reprogramming has been developed, it has obstacles, such as a potential risk of tumor formation, poor survival of the transplanted cells, and high cost. We previously reported that fibroblasts can be directly reprogrammed to cardiomyocytes by overexpressing a combination of three cardiac-specific transcription factors (Gata4, Mef2c, Tbx5 (together, GMT)). We and other groups have promoted cardiac reprogramming by the addition of certain miRNAs, cytokines, and epigenetic factors, and unraveled new molecular mechanisms of cardiac reprogramming. More recently, we discovered that Sendai virus (SeV) vector expressing GMT could efficiently and rapidly reprogram fibroblasts into integration-free cardiomyocytes in vitro via robust transgene expression. Gene delivery of SeV-GMT also improves cardiac function and reduces fibrosis after myocardial infarction in mice. Through direct cardiac reprogramming, new cardiomyocytes can be generated and scar tissue reduced to restore cardiac function, and, thus, direct cardiac reprogramming may serve as a powerful strategy for cardiac regeneration. Here, we provide an overview of the previous reports and current challenges in this field.

Differential reduction of reactive oxygen species by human tissuespecific mesenchymal stem cells from different donors under oxidative stress

Clinical trials using human Mesenchymal Stem Cells (MSCs) have shown promising results in the treatment of various diseases. Different tissue sources, such as bone marrow, adipose tissue, dental pulp and umbilical cord, are being routinely used in regenerative medicine. MSCs are known to reduce increased oxidative stress levels in pathophysiological conditions. Differences in the ability of MSCs from different donors and tissues to ameliorate oxidative damage have not been reported yet. In this study, for the first time, we investigated the differences in the reactive oxygen species (ROS) reduction abilities of tissue-specific MSCs to mitigate cellular damage in oxidative stress. Hepatic Stellate cells (LX-2) and cardiomyocytes were treated with Antimycin A (AMA) to induce oxidative stress and tissue specific MSCs were co-cultured to study the reduction in ROS levels. We found that both donor's age and source of tissue affected the ability of MSCs to reduce increased ROS levels in damaged cells. In addition, the abilities of same MSCs differed in LX-2 and cardiomyocytes in terms of magnitude of reduction of ROS, suggesting that the type of recipient cells should be kept in consideration when using MSCs in regenerative medicine for treatment purposes.

Mesenchymal Stem Cells in Cardiology

Cardiovascular disease (CVD) accounts for more deaths globally than any other single disease. There are on average 1.5 million episodes of myocardial infarction (heart attack) each year in the United States alone with roughly one-third resulting in death. There is therefore a major need for developing new and effective strategies to promote cardiac repair. Intramyocardial transplantation of mesenchymal stem cells (MSCs) has emerged as a leading contender in the pursuit of clinical intervention and therapy. MSCs are potent mediators of cardiac repair and are therefore an attractive tool in the development of preclinical and clinical trials. MSCs are capable of secreting a large array of soluble factors, which have had demonstrated effects on pathogenic cardiac remolding, fibrosis, immune activation, and cardiac stem cell proliferation within the damaged heart. MSCs are also capable of differentiation into cardiomyocytes, endothelial cells, and vascular smooth muscle cells, although the relative contribution of trilineage differentiation and paracrine effectors on cardiac repair remains the subject of active investigation.

(Re-)programming of subtype specific cardiomyocytes

Adult cardiomyocytes (CMs) possess a highly restricted intrinsic regenerative potential - a major barrier to the effective treatment of a range of chronic degenerative cardiac disorders characterized by cellular loss and/or irreversible dysfunction and which underlies the majority of deaths in developed countries. Both stem cell programming and direct cell reprogramming hold promise as novel, potentially curative approaches to address this therapeutic challenge. The advent of induced pluripotent stem cells (iPSCs) has introduced a second pluripotent stem cell source besides embryonic stem cells (ESCs), enabling even autologous cardiomyocyte production. In addition, the recent achievement of directly reprogramming somatic cells into cardiomyocytes is likely to become of great importance. In either case, different clinical scenarios will require the generation of highly pure, specific cardiac cellular-subtypes. In this review, we discuss these themes as related to the cardiovascular stem cell and programming field, including a focus on the emergent topic of pacemaker cell generation for the development of biological pacemakers and in vitro drug testing.

Stem cell therapies for myocardial infarction in clinical trials: bioengineering and biomaterial aspects

Cardiovascular disease remains the leading cause of death and disability in advanced countries. Stem cell transplantation has emerged as a promising therapeutic strategy for acute and chronic ischemic cardiomyopathy. The current status of stem cell therapies for patients with myocardial infarction is discussed from a bioengineering and biomaterial perspective in this review. We describe (a) the current status of clinical trials of human pluripotent stem cells (hPSCs) compared with clinical trials of human adult or fetal stem cells, (b) the gap between fundamental research and application of human stem cells, (c) the use of biomaterials in clinical and pre-clinical studies of stem cells, and finally (d) trends in bioengineering to promote stem cell therapies for patients with myocardial infarction. We explain why the number of clinical trials using hPSCs is so limited compared with clinical trials using human adult and fetal stem cells such as bone marrow-derived stem cells.

Synergistic Effect of BDNF and FGF2 in Efficient Generation of Functional Dopaminergic Neurons from human Mesenchymal Stem Cells

To understand the process of neurogenesis, generation of functional dopaminergic (DAergic) neurons from human mesenchymal stem cells (hMSCs) is important. BDNF has been reported to be responsible for inducing neuronal maturation and functionality. Previously, we have reported the efficient generation of neurons from human bone marrow derived MSCs using FGF2 alone. We hypothesize that hMSCs from various tissues [(bone marrow (BM), adipose tissue (AD) and dental pulp (DP)], if treated with BDNF on 9th day of induction, alongwith FGF2 will generate functional DAergic neurons. Hence, cells were characterized at morphometric, transcription and translational levels for various markers like MAP2, TH, NGN2, PITX3, DAT, synaptophysin, Kv4.2 and SCN5A. Functionality of in vitro generated neurons was studied by calcium ion imaging. Result analysis depicted that BDNF has effect on expression of dopaminergic neuronal markers at gene and protein levels and functionality of neurons. Among these hMSCs, DP-MSC showed significantly better neuronal characteristics in terms of morphology, expression of neuronal markers and foremost, functionality of neurons. From the present study, therefore, we concluded that i) BDNF has additive effect on neuronal characteristics and functionality ii) DP-MSC are better MSC candidate to study DAergic neurogenesis and perform future studies.

Bioreactor-induced mesenchymal progenitor cell differentiation and elastic fiber assembly in engineered vascular tissues

In vitro maturation of engineered vascular tissues (EVT) requires the appropriate incorporation of smooth muscle cells (SMC) and extracellular matrix (ECM) components similar to native arteries. To this end, the aim of the current study was to fabricate 4mm inner diameter vascular tissues using mesenchymal progenitor cells seeded into tubular scaffolds. A dual-pump bioreactor operating either in perfusion or pulsatile perfusion mode was used to generate physiological-like stimuli to promote progenitor cell differentiation, extracellular elastin production, and tissue maturation. Our data demonstrated that pulsatile forces and perfusion of 3D tubular constructs from both the lumenal and ablumenal sides with culture media significantly improved tissue assembly, effectively inducing mesenchymal progenitor cell differentiation to SMCs with contemporaneous elastin production. With bioreactor cultivation, progenitor cells differentiated toward smooth muscle lineage characterized by the expression of smooth muscle (SM)-specific markers smooth muscle alpha actin (SM-α-actin) and smooth muscle myosin heavy chain (SM-MHC). More importantly, pulsatile perfusion bioreactor cultivation enhanced the synthesis of tropoelastin and its extracellular cross-linking into elastic fiber compared with static culture controls. Taken together, the current study demonstrated progenitor cell differentiation and vascular tissue assembly, and provides insights into elastin synthesis and assembly to fibers.

STATEMENT OF SIGNIFICANCE

Incorporation of elastin into engineered vascular tissues represents a critical design goal for both mechanical and biological functions. In the present study, we seeded porous tubular scaffolds with multipotent mesenchymal progenitor cells and cultured in dual-pump pulsatile perfusion bioreactor. Physiological-like stimuli generated by bioreactor not only induced mesenchymal progenitor cell differentiation to vascular smooth muscle lineage but also actively promoted elastin synthesis and fiber assembly. Gene expression and protein synthesis analyses coupled with histological and immunofluorescence staining revealed that elastin-containing vascular tissues were fabricated. More importantly, co-localization and co-immunoprecipitation experiments demonstrated that elastin and fibrillin-1 were abundant throughout the cross-section of the tissue constructs suggesting a process of elastin protein crosslinking. This study paves a way forward to engineer elastin-containing functional vascular substitutes from multipotent progenitor cells in a bioreactor.

Differentiation of cardiomyocytes from amniotic fluid‑derived mesenchymal stem cells by combined induction with transforming growth factor β1 and 5‑azacytidine

As a novel type of seed cell, amniotic fluid-derived mesenchymal stem cells (AFMSCs) are promising for the regeneration of myocardial cells. A focus of cardiovascular regenerative medicine is to improve the efficiency of AFMSC differentiation. The present study replaced the traditional method of AFMSC differentiation with a combined induction method, in order to improve the efficiency of directional differentiation. AFMSCs were obtained from rabbit amniotic fluid samples, and western blot analysis was performed to analyze the expression of octamer-binding transcription factor 4 (OCT4), and tumorigenicity experiments were conducted. AFMSCs were divided into the following 4 groups: Induction with transforming growth factor β1 (TGFβ1); induction with 5-azacytidine (5Aza); induction with TGFβ1 and 5Aza combined; and untreated controls. Reverse transcription-quantitative polymerase chain reaction was performed to analyze the expression of cardiac-specific GATA binding protein 4 (GATA4), and immunofluorescence was employed to analyze the expression of cardiac troponin T (cTnT). In addition, western blotting was performed to analyze the expression of connexin 43, and transmission electron microscopy was used to observe the ultrastructure of the differentiated cells. AFMSCs exhibited positive OCT4 expression and were not observed to induce tumor development in nude mice. The expression levels of GATA4, cTnT, and connexin 43 in the combined induction group were markedly higher when compared with the remaining groups. Transmission electron microscopy analysis revealed that differentiated cells exhibited myocardial cell characteristics. In conclusion, AFMSCs are multipotent, non-tumorigenic cells that are capable of differentiating into cardiomyocyte-like cells. This combined induction method may improve the efficiency of directed differentiation.

DNA Methyltransferases Modulate Hepatogenic Lineage Plasticity of Mesenchymal Stromal Cells

The irreversibility of developmental processes in mammalian cells has been challenged by rising evidence that de-differentiation of hepatocytes occurs in adult liver. However, whether reversibility exists in mesenchymal stromal cell (MSC)-derived hepatocytes (dHeps) remains elusive. In this study, we find that hepatogenic differentiation (HD) of MSCs is a reversible process and is modulated by DNA methyltransferases (DNMTs). DNMTs are regulated by transforming growth factor β1 (TGFβ1), which in turn controls hepatogenic differentiation and de-differentiation. In addition, a stepwise reduction in TGFβ1 concentrations in culture media increases DNMT1 and decreases DNMT3 in primary hepatocytes (Heps) and confers Heps with multi-differentiation potentials similarly to MSCs. Hepatic lineage reversibility of MSCs and lineage conversion of Heps are regulated by DNMTs in response to TGFβ1. This previously unrecognized TGFβ1-DNMTs-MSC-HD axis may further increase the understanding the normal and pathological processes in the liver, as well as functions of MSCs after transplantation to treat liver diseases.

Differentiation of Bone Marrow Mesenchymal Stem Cells to Cardiomyocyte-Like Cells Is Regulated by the Combined Low Dose Treatment of Transforming Growth Factor-β1 and 5-Azacytidine

Bone marrow mesenchymal stem cells (BMMSCs) are used in cardiac tissue engineering for the regeneration of diseased hearts. We examined the differentiation of rat BMMSCs into cardiomyocyte-like cells when induced with a combined low dose treatment of transforming growth factor-β1 (TGF-β1) and 5-azacytidine (5-AZA). Results showed that cell proliferation in the combined low dose treatment group of TGF-β1 and 5-AZA was increased compared with the TGF-β1 group or the 5-AZA group. The cell apoptosis was relieved by combined TGF-β1 and 5-AZA treatment compared to 5-AZA treatment alone. The number of cells positive for myosin heavy chain, connexin-43, α-actin, and troponin I in the combined treatment group was higher than those observed in the TGF-β1 group or the 5-AZA group. Moreover, the combined low dose treatment group of TGF-β1 and 5-AZA reveals the strongest expression of troponin I, α-actin, and phosphorylated extracellular signal-regulated protein kinases 1 and 2 (p-ErK1/2) among the treatment groups. These results suggest that the combined low dose treatment of TGF-β1 and 5-AZA can improve the differentiation potential of rat BMMSCs into cardiomyocyte-like cells and alleviate cell damage effects in vitro. The mechanism that is involved in influencing differentiation may be associated with p-ErK1/2.

Nanothin Coculture Membranes with Tunable Pore Architecture and Thermoresponsive Functionality for Transfer-Printable Stem Cell-Derived Cardiac Sheets

Coculturing stem cells with the desired cell type is an effective method to promote the differentiation of stem cells. The features of the membrane used for coculturing are crucial to achieving the best outcome. Not only should the membrane act as a physical barrier that prevents the mixing of the cocultured cell populations, but it should also allow effective interactions between the cells. Unfortunately, conventional membranes used for coculture do not sufficiently meet these requirements. In addition, cell harvesting using proteolytic enzymes following coculture impairs cell viability and the extracellular matrix (ECM) produced by the cultured cells. To overcome these limitations, we developed nanothin and highly porous (NTHP) membranes, which are ∼20-fold thinner and ∼25-fold more porous than the conventional coculture membranes. The tunable pore size of NTHP membranes at the nanoscale level was found crucial for the formation of direct gap junctions-mediated contacts between the cocultured cells. Differentiation of the cocultured stem cells was dramatically enhanced with the pore size-customized NTHP membrane system compared to conventional coculture methods. This was likely due to effective physical contacts between the cocultured cells and the fast diffusion of bioactive molecules across the membrane. Also, the thermoresponsive functionality of the NTHP membranes enabled the efficient generation of homogeneous, ECM-preserved, highly viable, and transfer-printable sheets of cardiomyogenically differentiated cells. The coculture platform developed in this study would be effective for producing various types of therapeutic multilayered cell sheets that can be differentiated from stem cells.

TGF-β1 induces apoptosis of bone marrow-derived mesenchymal stem cells via regulation of mitochondrial reactive oxygen species production

Bone marrow-derived mesenchymal stem cells (BMSCs) are the most promising seed cells in regenerative medicine. Our previous study demonstrated that transforming growth factor (TGF)-β1 induced BMSC senescence in vitro. Whether TGF-β1 affects the apoptosis of BMSCs has not been examined; therefore the aim of the present study was to investigate this effect. BMSCs were isolated from mouse bone marrow, and the third-passage cells were exposed to 0, 10 and 20 ng/ml TGF-β1 for 24 h. Cell proliferation was measured by MTT assay; apoptosis was assessed using DAPI staining; and the apoptotic signals Annexin V, B-cell lymphoma (Bcl)-2 and Bcl-2-associated X protein (Bax) were measured using western blotting. Mitochondrial reactive oxygen species (ROS) were measured by flow cytometry following staining with MitoSOX™ Red mitochondrial superoxide indicator. The MTT assay showed that 10 and 20 ng/ml TGF-β1 inhibited BMSC proliferation. DAPI staining demonstrated that 10 and 20 ng/ml TGF-β1 promoted BMSC apoptosis, which was further confirmed by a western blotting assay showing a significant increase in the pro-apoptotic signals Annexin V and Bax but a decrease in the anti-apoptotic signal Bcl-2. It was also found that TGF-β1 markedly increased the mitochondrial ROS levels in BMSCs. It is well known that mitochondrial ROS are strong stimulators of cell apoptosis. These findings indicate that TGF-β1 can induce BMSC apoptosis, and the mechanism may involve mitochondrial ROS generation.

Pretreatment of mesenchymal stem cells with angiotensin II enhances paracrine effects, angiogenesis, gap junction formation and therapeutic efficacy for myocardial infarction

BACKGROUND

Pretreatment of mesenchymal stem cells (MSCs) with growth factors is reported to be an effective route for improving cell-based therapy of myocardial infarction (MI). Angiotensin II (Ang II) triggers vascular endothelial growth factor (VEGF) synthesis in MSCs. This study aimed to investigate the effects and mechanisms of Ang II pretreatment in enhancing the therapeutic efficacy of MSCs in MI.

METHODS

MSCs and endothelial cells (ECs) were isolated from Sprague-Dawley rats. After pretreated with or without 100 nM of Ang II for 24 h, the MSCs were directly injected into the border zones of the ischemic heart. Cardiac function, fibrosis, infarct size, VEGF expression, angiogenesis, and cell differentiation in the infarcted myocardium were determined after 30 days. The cell apoptosis of MSCs post hypoxia was assessed using flow cytometry. The angiogenic activity of MSCs was analyzed using tube formation assay. The gap junction protein connexin-43 (Cx43) expression was detected.

RESULTS

Compared with the MSC group, pretreatment of MSCs with Ang II resulted in better cardiac function, less cardiac fibrosis, smaller infarct size, and higher expression of VEGF and Von Willebrand Factor in ischemic myocardium, but no promotion of cardiomyocyte-like differentiation of MSCs. Ang II pretreatment enhanced the survival of MSCs and the H9c2 cells surrounding MSCs, and augmented the tube formation of ECs and MSCs. Ang II pretreatment up-regulated the Cx43 expression.

CONCLUSIONS

The pretreatment of MSCs with Ang II improved the outcome of MSC-based therapy for MI via the mechanisms of enhancing the paracrine production of VEGF, angiogenesis, and gap junction formation.

Iron oxide nanoparticle-mediated development of cellular gap junction crosstalk to improve mesenchymal stem cells' therapeutic efficacy for myocardial infarction

Electrophysiological phenotype development and paracrine action of mesenchymal stem cells (MSCs) are the critical factors that determine the therapeutic efficacy of MSCs for myocardial infarction (MI). In such respect, coculture of MSCs with cardiac cells has windowed a platform for cardiac priming of MSCs. Particularly, active gap junctional crosstalk of MSCs with cardiac cells in coculture has been known to play a major role in the MSC modification through coculture. Here, we report that iron oxide nanoparticles (IONPs) significantly augment the expression of connexin 43 (Cx43), a gap junction protein, of cardiomyoblasts (H9C2), which would be critical for gap junctional communication with MSCs in coculture for the generation of therapeutic potential-improved MSCs. MSCs cocultured with IONP-harboring H9C2 (cocultured MSCs: cMSCs) showed active cellular crosstalk with H9C2 and displayed significantly higher levels of electrophysiological cardiac biomarkers and a cardiac repair-favorable paracrine profile, both of which are responsible for MI repair. Accordingly, significantly improved animal survival and heart function were observed upon cMSC injection into rat MI models compared with the injection of unmodified MSCs. The present study highlights an application of IONPs in developing gap junctional crosstalk among the cells and generating cMSCs that exceeds the reparative potentials of conventional MSCs. On the basis of our finding, the potential application of IONPs can be extended in cell biology and stem cell-based therapies.

Induced pluripotent stem cell transplantation in the treatment of porcine chronic myocardial ischemia

BACKGROUND

This study was designed to test the effects of induced pluripotent stem cell (iPSC) in the treatment of chronic myocardial ischemia.

METHODS

The reprogramming of passage 3 myocardial fibroblasts was performed by using the lentiviral vector containing 4 human factors: OCT4, SOX2, KLF4, and c-MYC. The iPSC colonies at P12-17 were allogeneically transplanted into ischemic myocardium of 10 swine by direct injection. Cohorts of 2 animals were sacrificed at 2, 4, 6, 8, and 12 weeks after injection.

RESULTS

No signs of graft versus host disease were evident at any time points. At 2 weeks, clusters of SSEA-4-positive iPSCs were detected in the injected area. At 4 to 8 weeks, these cells started to proliferate into small spheres surrounded by thin capsules. At 12 weeks the cell clusters still existed, but decreased in size and numbers. The cells inside these masses were homogeneous with no sign of differentiation into any specific lineage. Increased smooth muscle actin or vWF positive cells were found inside and around the iPSC clusters, compared with non-injected areas. By real-time polymerase chain reaction, the levels of VEGF, basic FGF, and ANRT expression were significantly higher in the iPSC-treated myocardium compared with untreated areas. These results suggest that iPSCs contributed to angiogenesis.

CONCLUSIONS

Allogeneically transplanted pig iPSCs proliferated despite an ischemic environment in the first 2 months and survived for at least 3 months in immunocompetent hosts. Transplanted iPSCs were also proangiogenic and thus might have beneficial effects on the ischemic heart diseases.

Fibroblast Growth Factor-2 alone as an efficient inducer for differentiation of human bone marrow mesenchymal stem cells into dopaminergic neurons

Background

The reported efficiency of differentiation of human bone marrow derived Mesenchymal Stem Cells (hBM MSC) into dopaminergic neurons with different inducers is found to vary. Thus, in the current study we have investigated the response of hBM MSC to some of the neuronal inducers and their combinations. Neuronal differentiation inducing agents Fibroblastic Growth Factor 2 (FGF2), Sonic Hedge Hog (Shh), Fibroblastic Growth Factor 8 (FGF8) & All Trans Retinoic Acid (ATRA) were used either singly or in varied combinations.

Results

The differentiated and undifferentiated hBM MSC were characterized in terms of morphology, expression of cell markers at transcriptional and translational levels, amount of dopamine secreted by the cells in the media and changes in cell membrane potential by calcium ions imaging. Induced hBM MSC revealed neuron like morphology and expressed cellular markers suggesting neuronal differentiation with all the inducing agents. However, upon quantitative analysis through qPCR, cells induced with FGF2 were found to show maximum expression of tyrosine hydroxylase (TH) by 47.5 folds. Immunofluorescence analysis of differentiated and undifferentiated cells also revealed expression of nestin, neurofilament, microtubule associated protein- 2, beta tubulin III and TH in differentiated cells, at translational level. This data was supported by immunoblotting analysis. Further, ELISA study also supported the release of dopamine by cultures induced with FGF2. When the cells were depolarised with KCl solution, those induced with Shh & FGF8 showed maximum calcium ion trafficking, followed by the cells induced with FGF2 only.

Conclusions

We conclude that hBM MSC can be coaxed to differentiate efficiently into dopaminergic neurons in the presence of a very simple media cocktail containing only one main inducer like FGF2 and thus contribute towards cellular therapy in Parkinson's and other related disorders. These dopaminergic neurons are also functionally active, as shown by calcium ion trafficking.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-014-0083-1) contains supplementary material, which is available to authorized users.

Adipose-derived stem cell adhesion on laminin-coated microcarriers improves commitment toward the cardiomyogenic lineage

For tissue-engineering studies of the infarcted heart it is essential to identify a source of cells that may provide cardiomyocyte progenitors, which is easy to amplify, accessible in adults, and allowing autologous grafts. Preclinical studies have shown that human adipose-derived stem cells (ADSCs) can differentiate into cardiomyocyte-like cells and improve heart function in myocardial infarction. We have developed pharmacologically active microcarriers (PAMs) which are biodegradable and biocompatible polymeric microspheres conveying cells on their biomimetic surface, therefore providing an adequate three-dimensional (3D) microenvironment. Moreover, they can release a growth factor in a prolonged manner. In order to implement ADSCs and PAMs for cardiac tissue engineering we first defined the biomimetic surface by studying the influence of matrix molecules laminin (LM) and fibronectin (FN), in combination with growth factors present in the cardiogenic niche, to further enhance the in vitro cardiac differentiation of ADSCs. We demonstrated that LM increased the expression of cardiac markers (Nkx2.5, GATA4, MEF2C) by ADSCs after 2 weeks in vitro. Interestingly, our results suggest that the 3D support provided by PAMs with a LM biomimetic surface (LM-PAMs) further enhanced the expression of cardiac markers and induced the expression of a more mature contractile protein, cardiac troponin I, compared with the 2D differentiating conditions after only 1 week in culture. The enrichment of the growth-factor cocktail with TGF-β1 potentiated the cardiomyogenic differentiation. These results suggest that PAMs offering a LM biomimetic surface may be efficiently used for applications combining adult stem cells in tissue-engineering strategies of the ischemic heart.

Protective role of 5-azacytidine on myocardial infarction is associated with modulation of macrophage phenotype and inhibition of fibrosis

We examined whether a shift in macrophage phenotype could be therapeutic for myocardial infarction (MI). The mouse macrophage cell line RAW264.7 was stimulated with peptidoglycan (PGN), with or without 5-azacytidine (5AZ) treatment. MI was induced by ligation of the left anterior descending coronary artery in rats, and the rats were divided into two groups; a saline-injection group and a 5AZ-injection group (2.5 mg/kg/day, intraperitoneal injection). LV function was evaluated and immunohistochemical analyses were performed 2 weeks after MI. Cardiac fibrosis was induced by angiotensin II (AngII) infusion with or without 5AZ (5 mg/kg/day) in mice. Nitric oxide was produced by PGN, which was reduced by 77.87% after 5AZ treatment. Both induction of inducible nitric oxide synthase (iNOS) and iNOS promoter activity by PGN were inhibited by 5AZ. Ejection fraction (59.00 ± 8.03% versus 42.52 ± 2.58%), contractility (LV dP/dt-max, 8299.76 ± 411.56 mmHg versus 6610.36 ± 282.37 mmHg) and relaxation indices (LV dP/dt-min, −4661.37 ± 210.73 mmHg versus −4219.50 ± 162.98 mmHg) were improved after 5AZ administration. Cardiac fibrosis in the MI+5AZ was 8.14 ± 1.00%, compared with 14.93 ± 2.98% in the MI group (P < 0.05). Arginase-1(+)CD68(+) macrophages with anti-inflammatory phenotype were predominant in the infarct border zone of the MI+5AZ group, in comparison with the MI group. AngII-induced cardiac fibrosis was also attenuated after 5AZ administration. In cardiac fibroblasts, pro-fibrotic mediators and cell proliferation were increased by AngII, and these increases were attenuated after 5AZ treatment. 5AZ exerts its cardiac protective role through modulation of macrophages and cardiac fibroblasts.

Reprogramming for cardiac regeneration

Treatment of cardiovascular diseases remains challenging considering the limited regeneration capacity of the heart muscle. Developments of reprogramming strategies to create in vitro and in vivo cardiomyocytes have been the focus point of a considerable amount of research in the past decades. The choice of cells to employ, the state-of-the-art methods for different reprogramming strategies, and their promises and future challenges before clinical entry, are all discussed here.

Human embryonic stem cell derived mesenchymal progenitors express cardiac markers but do not form contractile cardiomyocytes

Mesenchymal progenitors or stromal cells have shown promise as a therapeutic strategy for a range of diseases including heart failure. In this context, we explored the growth and differentiation potential of mesenchymal progenitors (MPs) derived in vitro from human embryonic stem cells (hESCs). Similar to MPs isolated from bone marrow, hESC derived MPs (hESC-MPs) efficiently differentiated into archetypical mesenchymal derivatives such as chondrocytes and adipocytes. Upon treatment with 5-Azacytidine or TGF-β1, hESC-MPs modified their morphology and up-regulated expression of key cardiac transcription factors such as NKX2-5, MEF2C, HAND2 and MYOCD. Nevertheless, NKX2-5⁺ hESC-MP derivatives did not form contractile cardiomyocytes, raising questions concerning the suitability of these cells as a platform for cardiomyocyte replacement therapy. Gene profiling experiments revealed that, although hESC-MP derived cells expressed a suite of cardiac related genes, they lacked the complete repertoire of genes associated with bona fide cardiomyocytes. Our results suggest that whilst agents such as TGF-β1 and 5-Azacytidine can induce expression of cardiac related genes, but treated cells retain a mesenchymal like phenotype.

The promotion of cardiogenic differentiation of hMSCs by targeting epidermal growth factor receptor using microRNA-133a

Human bone marrow-derived mesenchymal stem cells (hMSCs) are an attractive candidate for cell therapy in heart disease. Low survival and incomplete electromechanical integration between resident cardiomyocytes and transplanted hMSCs remain unsolved. In order for an infarcted heart to tolerate transplantation, differentiation capacity in stem cells must be reinforced. In this study, we found that compound 56, an epidermal growth factor receptor (EGFR) inhibitor, promotes cardiogenic differentiation of hMSCs and the transplantation of hMSCs treated with compound 56 resulted in enhancement of heart functions. Furthermore, hMSCs transfected with microRNA-133a (miR-133a), which targets EGFR, were observed to express cardiac-specific markers. We also discovered that luciferase activity is exclusively decreased by targeting EGFR in hMSCs transfected with miR-133a mimic. These results suggest that EGFR plays a key role in the regulation of cardiogenic differentiation in hMSCs.

Induction of cardiac myogenic lineage development differs between mesenchymal and satellite cells and is accelerated by bone morphogenetic protein-4

Our aim was to further elucidate the cardiac lineage development of bone marrow-derived mesenchymal stem cells (MSC) and to identify cells which had the potential for cardiac myogenic differentiation when compared to skeletal muscle satellite (Sk-sat) myogenesis. Unlike Sk-sat, MSC expressed the early cardiac markers Nkx2.5 and GATA4. Their expression was significantly increased by culturing MSC with Bone Morphogenetic Protein 4 (BMP4). Enhanced cardiac myogenic lineage differentiation and loss of stem cell characteristics induced by BMP4 were further confirmed by flow cytometry of cells stained for Nkx2.5 and Sca-1 expression. MSC also expressed skeletal genes (MyoG, ssTnI, Sk-Act) early in culture but their expression was suppressed when BMP4 was added from day 0 to day 6 (p<0.05). BMP4 treated MSC also exhibited a 6-fold increase in cTnI expression by day 12 in culture. The average MSC action potential time duration at 90% (APD90) was 32.3±4ms, with some cells exhibiting action potentials closer to Sk-sat APD90 of 13.7±0.9ms. After treatment with BMP4, MSC significantly increased their APD90 to 54.4±7.6ms, shifting from the shorter skeletal-like signature, towards a longer action potential duration more characteristic of a cardiomyocyte signature. Our results show that MSC and Sk-sat exhibit similarities in myogenic lineage development early in culture but that BMP4 clearly enhances cardiac myogenic development, suppresses skeletal myogenesis, and leads to loss of "stemness" in MSC. These findings provide novel information regarding the use of BMP4 to accelerate cardiac myogenic development in harvested MSC and further support the use of MSC in cardiac regenerative therapy.

Bone marrow-derived human mesenchymal stem cells express cardiomyogenic proteins but do not exhibit functional cardiomyogenic differentiation potential

Despite their paracrine activites, cardiomyogenic differentiation of bone marrow (BM)-derived mesenchymal stem cells (MSCs) is thought to contribute to cardiac regeneration. To systematically evaluate the role of differentiation in MSC-mediated cardiac regeneration, the cardiomyogenic differentiation potential of human MSCs (hMSCs) and murine MSCs (mMSCs) was investigated in vitro and in vivo by inducing cardiomyogenic and noncardiomyogenic differentiation. Untreated hMSCs showed upregulation of cardiac tropopin I, cardiac actin, and myosin light chain mRNA and protein, and treatment of hMSCs with various cardiomyogenic differentiation media led to an enhanced expression of cardiomyogenic genes and proteins; however, no functional cardiomyogenic differentiation of hMSCs was observed. Moreover, co-culturing of hMSCs with cardiomyocytes derived from murine pluripotent cells (mcP19) or with murine fetal cardiomyocytes (mfCMCs) did not result in functional cardiomyogenic differentiation of hMSCs. Despite direct contact to beating mfCMCs, hMSCs could be effectively differentiated into cells of only the adipogenic and osteogenic lineage. After intramyocardial transplantation into a mouse model of myocardial infarction, Sca-1(+) mMSCs migrated to the infarcted area and survived at least 14 days but showed inconsistent evidence of functional cardiomyogenic differentiation. Neither in vitro treatment nor intramyocardial transplantation of MSCs reliably generated MSC-derived cardiomyocytes, indicating that functional cardiomyogenic differentiation of BM-derived MSCs is a rare event and, therefore, may not be the main contributor to cardiac regeneration.