Chemical and physical stimuli induce cardiomyocyte differentiation from stem cells

Human Induced Pluripotent Stem Cell Encapsulation Geometry Impacts Three-Dimensional Developing Human Engineered Cardiac Tissue Functionality

Cardiac tissue engineering has been working to alleviate the immense burden of cardiovascular disease for several decades. To improve cardiac tissue homogeneity and cardiomyocyte (CM) maturation, in this study, we investigated altering initial encapsulation geometry in a three-dimensional (3D) direct cardiac differentiation platform. Traditional engineered cardiac tissue production utilizes predifferentiated CMs to produce 3D cardiac tissue and often involves various cell selection and exogenous stimulation methods to promote CM maturation. Starting tissue formation directly with human induced pluripotent stem cells (hiPSCs), rather than predifferentiated CMs, simplifies the engineered cardiac tissue formation process, making it more applicable for widespread implementation and scale-up. In this study, hiPSCs were encapsulated in poly (ethylene glycol)-fibrinogen in three tissue geometries (disc-shaped microislands, squares, and rectangles) and subjected to established cardiac differentiation protocols. Resulting 3D engineered cardiac tissues (3D-ECTs) from each geometry displayed similar CM populations (∼65%) and gene expression over time. Notably, rectangular tissues displayed less tissue heterogeneity and suggested more advanced features of maturing CMs, including myofibrillar alignment and Z-line formation. In addition, rectangular tissue showed significantly higher anisotropic contractile properties compared to square and microisland tissues (MI 0.28 ± 0.03, SQ 0.35 ± 0.05, RT 0.79 ± 0.04). This study demonstrates a straightforward method for simplifying and improving 3D-ECT production without the use of exogenous mechanical or electrical pacing and has the potential to be utilized in bioprinting and drug testing applications. Impact statement Current methods for improving cardiac maturation postdifferentiation remain tedious and complex. In this study, we examined the impact of initial encapsulation geometry on improvement of three-dimensional engineered cardiac tissue (3D-ECT) production and postdifferentiation maturation for three tissue geometries, including disc-shaped microislands, squares, and rectangles. Notably, rectangular 3D-ECTs displayed less tissue heterogeneity and more advanced features of maturing cardiomyocytes, including myofibrillar alignment, Z-line formation, and anisotropic contractile properties, compared to microisland and square tissues. This study demonstrates an initial human induced pluripotent stem cell-encapsulated rectangular tissue geometry can improve cardiac maturation, rather than implementing cell selection or tedious postdifferentiation manipulation, including exogenous mechanical and/or electrical pacing.

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.

Biophysical and Biochemical Cues of Biomaterials Guide Mesenchymal Stem Cell Behaviors

Mesenchymal stem cells (MSCs) have been widely used in the fields of tissue engineering and regenerative medicine due to their self-renewal capabilities and multipotential differentiation assurance. However, capitalizing on specific factors to precisely guide MSC behaviors is the cornerstone of biomedical applications. Fortunately, several key biophysical and biochemical cues of biomaterials that can synergistically regulate cell behavior have paved the way for the development of cell-instructive biomaterials that serve as delivery vehicles for promoting MSC application prospects. Therefore, the identification of these cues in guiding MSC behavior, including cell migration, proliferation, and differentiation, may be of particular importance for better clinical performance. This review focuses on providing a comprehensive and systematic understanding of biophysical and biochemical cues, as well as the strategic engineering of these signals in current scaffold designs, and we believe that integrating biophysical and biochemical cues in next-generation biomaterials would potentially help functionally regulate MSCs for diverse applications in regenerative medicine and cell therapy in the future.

[Human umbilical cord mesenchymal stem cells differentiate into neuron-like cells after induction with B27-supplemented serum-free medium]

OBJECTIVE

To evaluate the capacity and efficiency of human umbilical cord mesenchymal stem cells (HUCMSCs) to differentiate into neuron- like cells after induction with B27- supplemented serum- free medium.

METHODS

HUCMSCs at passage 4 were cultured for 14 days with serum-containing medium (SCM) (group A), SCM supplemented with 20 ng/mL nerve growth factor (NGF) and 10 ng/mL basic fibroblast growth factor (bFGF) (group B), serum-free medium (SFM) (group C), or SFM supplemented with 20 ng/mL NGF and 10 ng/mL bFGF. The culture medium were changed every 3 days and the growth of the neurospheres was observed using an inverted microscope. The cell markers were analyzed with flow cytometry and the expressions of nestin, neuron- specific enolase (NSE), neurofilament heavy polypeptide (NEFH), and glial fibrillary acidic protein (GFAP) were quantified by quantitative real-time PCR (qRT-PCR) and Western blotting.

RESULTS

Before induction, HUCMSCs expressed abundant mesenchymal stem cell surface markers including CD29 (99.5%), CD44 (49.6%) and CD105 (77.7%). Neuron-like cells were observed in the cultures on days 7, 10, and 14, and the cell differentiation was the best in group D, followed by groups C, B and A. In all the 4 groups, the cellular expressions of nestin and GFAP gradually lowered while those of NEFH and NSE increased progressively. The expressions of GFAP, NEFH, nestin and NSE were significantly different between group A and the other 3 groups (P < 0.001 or 0.05).

CONCLUSIONS

B27-supplemented SFM effectively induces the differentiation of HUCMSCs into neuron- like cells, and the supplementation with cytokines (NGF and bFGF) strongly promotes the cell differentiation.

The Extracts of Human Fetal Brain Induce the Differentiation of Human Umbilical Cord Mesenchymal Stem Cells into Dopaminergic Neuron Containing Cells

Mesenchymal stem cells (MSCs) have the potential to differentiate into neuron-like cells, which may provide a new strategy for the clinical treatment of neurodegenerative diseases such as Parkinson's disease (PD). However, the application of MSCs in the patients is still limited as the reason of efficiency and safety of transplantation. The aim of this study is to develop a new method and induce human umbilical cord MSCs (hUCMSCs) into neuron-like cells. Results from flow cytometry indicate that the isolated MSCs from hUCMSCs exhibited a typical phenotype of adult stem cells and express CD44, CD54, CD73, CD90, CD105, CD166, and HLA-ABC. Furthermore, the induced cells from hUCMSCs could spontaneously express different neural cell markers [neuron-specific enolase (NSE) and glial fibrillary acidic protein (GFAP)], even transcription factors related to dopaminergic neuron's development (Nurr1, Wnt-1, and En-1). Moreover, after treatment of EHFBT (extracts of human fetal brain tissue), hUCMSCs can express neuronal markers such as Nestin, LIM homeobox transcription factor 1 beta (LMX1B), dopamine beta hydroxylase (DBH), and dopamine transporter (DAT). In summary, a method that can induce hUCMSCs into dopaminergic neuron containing cells is established in vitro by the treatment of EHFBT. This would provide us a new cell source for PD in clinical treatment in the future.

Biohybrid robotics with living cell actuation

This review comprehensively discusses recent advances in the basic components, controlling methods and especially in the applications of biohybrid robots.

Cardiotrophic Growth Factor-Driven Induction of Human Muse Cells Into Cardiomyocyte-Like Phenotype

Multilineage-differentiating stress-enduring (Muse) cells are endogenous nontumorigenic stem cells collectable as stage-specific embryonic antigen 3 (SSEA-3) + from various organs including the bone marrow and are pluripotent-like. The potential of human bone marrow-derived Muse cells to commit to cardiac lineage cells was evaluated. We found that (1) initial treatment of Muse cells with 5'-azacytidine in suspension culture successfully accelerated demethylation of cardiac marker Nkx2.5 promoter; (2) then transferring the cells onto adherent culture and treatment with early cardiac differentiation factors including wingless-int (Wnt)-3a, bone morphogenetic proteins (BMP)-2/4, and transforming growth factor (TGF) β1; and (3) further treatment with late cardiac differentiation cytokines including cardiotrophin-1 converted Muse cells into cardiomyocyte-like cells that expressed α-actinin and troponin-I with a striation-like pattern. MLC2a expression in the final step suggested differentiation of the cells into an atrial subtype. MLC2v, a marker for a mature ventricular subtype, was expressed when cells were treated with Dickkopf-related protein 1 (DKK-1) and Noggin, inhibitors of Wnt3a and BMP-4, respectively, between steps (2) and (3). None of the steps included exogenous gene transfection, making induced cells feasible for future clinical application.

Uniaxial Cyclic Tensile Stretching at 8% Strain Exclusively Promotes Tenogenic Differentiation of Human Bone Marrow-Derived Mesenchymal Stromal Cells

The present study was conducted to establish the amount of mechanical strain (uniaxial cyclic stretching) required to provide optimal tenogenic differentiation expression in human mesenchymal stromal cells (hMSCs) in vitro, in view of its potential application for tendon maintenance and regeneration. Methods. In the present study, hMSCs were subjected to 1 Hz uniaxial cyclic stretching for 6, 24, 48, and 72 hours; and were compared to unstretched cells. Changes in cell morphology were observed under light and atomic force microscopy. The tenogenic, osteogenic, adipogenic, and chondrogenic differentiation potential of hMSCs were evaluated using biochemical assays, extracellular matrix expressions, and selected mesenchyme gene expression markers; and were compared to primary tenocytes. Results. Cells subjected to loading displayed cytoskeletal coarsening, longer actin stress fiber, and higher cell stiffness as early as 6 hours. At 8% and 12% strains, an increase in collagen I, collagen III, fibronectin, and N-cadherin production was observed. Tenogenic gene expressions were highly expressed (p < 0.05) at 8% (highest) and 12%, both comparable to tenocytes. In contrast, the osteoblastic, chondrogenic, and adipogenic marker genes appeared to be downregulated. Conclusion. Our study suggests that mechanical loading at 8% strain and 1 Hz provides exclusive tenogenic differentiation; and produced comparable protein and gene expression to primary tenocytes.

Enhancement of Cardiomyogenesis in Murine Stem Cells by Low-Intensity Ultrasound

OBJECTIVES

Low-intensity ultrasound (LIUS) has been shown to enhance bone and cartilage regeneration from stem cells. The ease of its incorporation makes it an attractive mechanical stimulus for not only osteogenesis and chondrogenesis, but also cardiomyogenesis. However, to date, no study has investigated its effects on cardiomyogenesis from embryonic stem cells.

METHODS

In this study, murine embryonic stem cells were differentiated via embryoid body formation and plating, and after 3 days they were subjected to daily 10 minutes of LIUS treatment with various conditions: (1) low-pulsed (21 mW/cm² , 20% duty cycle), (2) low-continuous, (3) high-pulsed (147 mW/cm² , 20% duty cycle), and (4) high-continuous LIUS.

RESULTS

Low-pulsed and high-continuous LIUS had improved beating rates of contractile areas as well as increased late cardiac gene expressions, such as α- and β-myosin heavy chain and cardiac troponin T, showing its benefits on cardiomyocyte differentiation. Meanwhile, an early endodermal marker, α-fetoprotein, was significantly attenuated after LIUS treatments.

CONCLUSIONS

With these observations, it is demonstrated that LIUS simulation could enhance cardiomyogenesis from embryonic stem cells and increase its selectivity toward cardiomyocytes by reducing spontaneous differentiation.

Fate of tenogenic differentiation potential of human bone marrow stromal cells by uniaxial stretching affected by stretch-activated calcium channel agonist gadolinium

The role for mechanical stimulation in the control of cell fate has been previously proposed, suggesting that there may be a role of mechanical conditioning in directing mesenchymal stromal cells (MSCs) towards specific lineage for tissue engineering applications. Although previous studies have reported that calcium signalling is involved in regulating many cellular processes in many cell types, its role in managing cellular responses to tensile loading (mechanotransduction) of MSCs has not been fully elucidated. In order to establish this, we disrupted calcium signalling by blocking stretch-activated calcium channel (SACC) in human MSCs (hMSCs) in vitro. Passaged-2 hMSCs were exposed to cyclic tensile loading (1 Hz + 8% for 6, 24, 48, and 72 hours) in the presence of the SACC blocker, gadolinium. Analyses include image observations of immunochemistry and immunofluorescence staining from extracellular matrix (ECM) production, and measuring related tenogenic and apoptosis gene marker expression. Uniaxial tensile loading increased the expression of tenogenic markers and ECM production. However, exposure to strain in the presence of 20 μM gadolinium reduced the induction of almost all tenogenic markers and ECM staining, suggesting that SACC acts as a mechanosensor in strain-induced hMSC tenogenic differentiation process. Although cell death was observed in prolonged stretching, it did not appear to be apoptosis mediated. In conclusion, the knowledge gained in this study by elucidating the role of calcium in MSC mechanotransduction processes, and that in prolonged stretching results in non-apoptosis mediated cell death may be potential useful for regenerative medicine applications.

Ascorbic acid-mediated enhanced cardiomyocyte differentiation of mouse ES-cells involves interplay of DNA methylation and multiple-signals

Embryonic stem cells (ES-cells) provide a good model system to study lineage-specific differentiation. Though, the differentiation of ES-cells to cardiomyocytes is documented, a clear understanding of the molecular mechanism of differentiation and improved functional-differentiation efficiency are yet to be achieved. In this regard, ascorbic acid (Aa) is shown to be one of the effective cardiac inducers in ES-cells. But, its mechanism is poorly understood. We therefore, investigated the mechanism of Aa-mediated cardiomyocyte differentiation of ES-cells. Here, we describe the potential involvement of epigenetic (DNA methylation) as well as integrin- and Erk- signaling systems during cardiomyocyte differentiation. Transgenic GS-2 ES-cells and wild-type D3 ES-cells were differentiated to cardiomyocytes, in the presence or absence of Aa and with or without inhibitors of Erk-, collagen- and integrin- pathways. At specific time points, differentiated states of ES-cells were scored by gene expression analyses and the proportion of functional cTnI⁺ cardiomyocytes. DNA methylation changes of Isl-1, BMP-2, GATA-4 and α-MHC in cardiogenic cells, following stimulation with Aa, were analyzed by using methylation specific PCR (MSP). We observed that Aa, when applied in initial phase of ES-cell differentiation, consistently enhanced cardiac differentiation (99%) over that observed during spontaneous differentiation (70%). This was associated with enhanced expressions of cardiogenesis-associated genes. A two-fold increase in cTnI⁺ cells was observed, with appropriate myofibril arrangement. The observed effect of Aa was due to enhanced collagen and integrin signaling, coupled with a high p-ERK1/2 expression, downstream. Besides, the involvement of DNA methylation in regulating the expression of cardiac genes i.e., Isl-1 and α-MHC was also observed. Overall, this study, for the first time, demonstrates that Aa-mediated cardiac enhancement is brought about, mechanistically, through the interplay of epigenetic changes in DNA methylation of cardiac genes (Isl-1 and α-MHC) and integrin signaling system.

Rebuilding the Damaged Heart: Mesenchymal Stem Cells, Cell-Based Therapy, and Engineered Heart Tissue

Mesenchymal stem cells (MSCs) are broadly distributed cells that retain postnatal capacity for self-renewal and multilineage differentiation. MSCs evade immune detection, secrete an array of anti-inflammatory and anti-fibrotic mediators, and very importantly activate resident precursors. These properties form the basis for the strategy of clinical application of cell-based therapeutics for inflammatory and fibrotic conditions. In cardiovascular medicine, administration of autologous or allogeneic MSCs in patients with ischemic and nonischemic cardiomyopathy holds significant promise. Numerous preclinical studies of ischemic and nonischemic cardiomyopathy employing MSC-based therapy have demonstrated that the properties of reducing fibrosis, stimulating angiogenesis, and cardiomyogenesis have led to improvements in the structure and function of remodeled ventricles. Further attempts have been made to augment MSCs' effects through genetic modification and cell preconditioning. Progression of MSC therapy to early clinical trials has supported their role in improving cardiac structure and function, functional capacity, and patient quality of life. Emerging data have supported larger clinical trials that have been either completed or are currently underway. Mechanistically, MSC therapy is thought to benefit the heart by stimulating innate anti-fibrotic and regenerative responses. The mechanisms of action involve paracrine signaling, cell-cell interactions, and fusion with resident cells. Trans-differentiation of MSCs to bona fide cardiomyocytes and coronary vessels is also thought to occur, although at a nonphysiological level. Recently, MSC-based tissue engineering for cardiovascular disease has been examined with quite encouraging results. This review discusses MSCs from their basic biological characteristics to their role as a promising therapeutic strategy for clinical cardiovascular disease.

Direct Mechanical Stimulation of Stem Cells: A Beating Electromechanically Active Scaffold for Cardiac Tissue Engineering

The combination of stem cell therapy with a supportive scaffold is a promising approach to improving cardiac tissue engineering. Stem cell therapy can be used to repair nonfunctioning heart tissue and achieve myocardial regeneration, and scaffold materials can be utilized in order to successfully deliver and support stem cells in vivo. Current research describes passive scaffold materials; here an electroactive scaffold that provides electrical, mechanical, and topographical cues to induced human pluripotent stem cells (iPS) is presented. The poly(lactic-co-glycolic acid) fiber scaffold coated with conductive polymer polypyrrole (PPy) is capable of delivering direct electrical and mechanical stimulation to the iPS. The electroactive scaffolds demonstrate no cytotoxic effects on the iPS as well as an increased expression of cardiac markers for both stimulated and unstimulated protocols. This study demonstrates the first application of PPy as a supportive electroactive material for iPS and the first development of a fiber scaffold capable of dynamic mechanical actuation.

Electrical and mechanical stimulation of cardiac cells and tissue constructs

The field of cardiac tissue engineering has made significant strides over the last few decades, highlighted by the development of human cell derived constructs that have shown increasing functional maturity over time, particularly using bioreactor systems to stimulate the constructs. However, the functionality of these tissues is still unable to match that of native cardiac tissue and many of the stem-cell derived cardiomyocytes display an immature, fetal like phenotype. In this review, we seek to elucidate the biological underpinnings of both mechanical and electrical signaling, as identified via studies related to cardiac development and those related to an evaluation of cardiac disease progression. Next, we review the different types of bioreactors developed to individually deliver electrical and mechanical stimulation to cardiomyocytes in vitro in both two and three-dimensional tissue platforms. Reactors and culture conditions that promote functional cardiomyogenesis in vitro are also highlighted. We then cover the more recent work in the development of bioreactors that combine electrical and mechanical stimulation in order to mimic the complex signaling environment present in vivo. We conclude by offering our impressions on the important next steps for physiologically relevant mechanical and electrical stimulation of cardiac cells and engineered tissue in vitro.

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.

Optimization of the cardiovascular therapeutic properties of mesenchymal stromal/stem cells-taking the next step

Despite current treatment options, cardiac failure is associated with significant morbidity and mortality highlighting a compelling clinical need for novel therapeutic approaches. Based on promising pre-clinical data, stem cell therapy has been suggested as a possible therapeutic strategy. Of the candidate cell types evaluated, mesenchymal stromal/stem cells (MSCs) have been widely evaluated due to their ease of isolation and ex vivo expansion, potential allogeneic utility and capacity to promote neo-angiogenesis and endogenous cardiac repair. However, the clinical application of MSCs for mainstream cardiovascular use is currently hindered by several important limitations, including suboptimal retention and engraftment and restricted capacity for bona fide cardiomyocyte regeneration. Consequently, this has prompted intense efforts to advance the therapeutic properties of MSCs for cardiovascular disease. In this review, we consider the scope of benefit from traditional plastic adherence-isolated MSCs and the lessons learned from their conventional use in preclinical and clinical studies. Focus is then given to the evolving strategies aimed at optimizing MSC therapy, including discussion of cell-targeted techniques that encompass the preparation, pre-conditioning and manipulation of these cells ex vivo, methods to improve their delivery to the heart and innovative substrate-directed strategies to support their interaction with the host myocardium.

Cardiomyocyte culture - an update on the in vitro cardiovascular model and future challenges

The success of any work with isolated cardiomyocytes depends on the reproducibility of cell isolation, because the cells do not divide. To date, there is no suitable in vitro model to study human adult cardiac cell biology. Although embryonic stem cells and induced pluripotent stem cells are able to differentiate into cardiomyocytes in vitro, the efficiency of this process is low. Isolation and expansion of human cardiomyocyte progenitor cells from cardiac surgical waste or, alternatively, from fetal heart tissue is another option. However, to overcome various issues related to human tissue usage, especially ethical concerns, researchers use large- and small-animal models to study cardiac pathophysiology. A simple model to study the changes at the cellular level is cultures of cardiomyocytes. Although primary murine cardiomyocyte cultures have their own advantages and drawbacks, alternative strategies have been developed in the last two decades to minimise animal usage and interspecies differences. This review discusses the use of freshly isolated murine cardiomyocytes and cardiomyocyte alternatives for use in cardiac disease models and other related studies.

Mechanostimulation protocols for cardiac tissue engineering

Owing to the inability of self-replacement by a damaged myocardium, alternative strategies to heart transplantation have been explored within the last decades and cardiac tissue engineering/regenerative medicine is among the present challenges in biomedical research. Hopefully, several studies witness the constant extension of the toolbox available to engineer a fully functional, contractile, and robust cardiac tissue using different combinations of cells, template bioscaffolds, and biophysical stimuli obtained by the use of specific bioreactors. Mechanical forces influence the growth and shape of every tissue in our body generating changes in intracellular biochemistry and gene expression. That is why bioreactors play a central role in the task of regenerating a complex tissue such as the myocardium. In the last fifteen years a large number of dynamic culture devices have been developed and many results have been collected. The aim of this brief review is to resume in a single streamlined paper the state of the art in this field.

Tanshinone IIA and astragaloside IV promote the migration of mesenchymal stem cells by up-regulation of CXCR4

Mesenchymal stem cells (MSCs) have a therapeutic potential to treat cardiovascular diseases. However, a significant barrier to MSC therapy is insufficient MSC engraftment in ischemic myocardium after systemic administration. Here, we investigated the modulatory effects of tanshinone IIA and astragaloside IV on the migration of MSCs and further defined the underlying mechanisms. CXCR4 expression in MSCs was determined by using flow cytometry, real-time PCR, and western blotting. The results showed that CXCR4 expression was significantly higher in tanshinone IIA- and astragaloside IV-stimulated MSCs than that of the control. MSC migration toward stromal cell-derived factor-1α (SDF-1α) was studied using a transwell system. MSCs treated with tanshinone IIA and astragaloside IV showed stronger migration than that of the control. Moreover, this enhanced migration ability was abrogated by a CXCR4 inhibitor. In a rat acute myocardial infarction model, MSCs stimulated with tanshinone IIA and astragaloside IV were stained with Dio and injected into model rats via the tail vein. Dio-labeled cells in myocardium sections were observed by fluorescence microscopy. Tanshinone IIA- and astragaloside IV-stimulated MSCs showed enhanced capacities to home to ischemic myocardium sites. In addition, there was no significant difference in the SDF-1α expression among groups. These data suggest that tanshinone IIA and astragaloside IV regulate MSC mobilization, at least partially via modulation of the CXCR4 expression.

Notch signaling regulates CXCR4 expression and the migration of mesenchymal stem cells

Mesenchymal stem cells (MSCs) have been used to repair injured tissues through immune-suppression and/or cell replace mechanisms. However, a significant barrier to MSC therapy is insufficient MSC engraftment in injured tissues after systemic administration. Here, we report that cell surface, total protein, and mRNA levels of CXCR4 were significantly increased in MSCs when Notch signaling was interrupted by γ-secretase inhibitor (GSI) or knockout of the transcription factor RBP-J, which mediates signaling from all four mammalian Notch receptors. The GSI-treated or RBP-J deficient MSCs showed stronger migration toward stromal cell-derived factor-1α (SDF-1α) than that of the control. In a mouse hepatic ischemia/reperfusion model, RBP-J deficient MSCs migrated into the injured liver tissues at a significantly higher efficiency than that of the control MSCs. Mice transfused with RBP-J deficient MSCs showed reduced liver damage. Therefore, Notch signaling regulates MSC migration and function, at least partially via the modulation of CXCR4 expression.

Guiding Differentiation of Stem Cells in Vivo by Tetracycline-Controlled Expression of Key Transcription Factors

Transplantation of stem or progenitor cells is an attractive strategy for cell replacement therapy. However, poor long-term survival and insufficiently reproducible differentiation to functionally appropriate cells in vivo still present major obstacles for translation of this methodology to clinical applications. Numerous experimental studies have revealed that the expression of just a few transcription factors can be sufficient to drive stem cell differentiation toward a specific cell type, to transdifferentiate cells from one fate to another, or to dedifferentiate mature cells to pluripotent stem/progenitor cells (iPSCs). We thus propose here to apply the strategy of expressing the relevant key transcription factors to guide the differentiation of transplanted cells to the desired cell fate in vivo. To achieve this requires tools allowing us to control the expression of these genes in the transplant. Here, we describe drug-inducible systems that allow us to sequentially and timely activate gene expression from the outside, with a particular emphasis on the Tet system, which has been widely and successfully used in stem cells. These regulatory systems offer a tool for strictly limiting gene expression to the respective optimal stage after transplantation. This approach will direct the differentiation of the immature stem/progenitor cells in vivo to the desired cell type.

Human umbilical cord perivascular cells exhibit enhanced cardiomyocyte reprogramming and cardiac function after experimental acute myocardial infarction

We were interested in evaluating the ability of the mesenchymal stromal cell (MSC) population, human umbilical cord perivascular cells (HUCPVCs), to undergo cardiomyocyte reprogramming in an established coculture system with rat embryonic cardiomyocytes. Results were compared with human bone marrow-derived (BM) MSCs. The transcription factors GATA4 and Mef 2c were expressed in HUCPVCs but not BM-MSCs at baseline and, at 7 days, increased 7.6- and 3.5-fold, respectively, compared with BM-MSCs. Although cardiac-specific gene expression increased in both cell types in coculture, upregulation was more significant in HUCPVCs, consistent with Mef 2c-GATA4 synergism. Using a lentivector with eGFP transcribed from the α-myosin heavy chain (α-MHC) promoter, we found that cardiac gene expression was greater in HUCPVCs than BM-MSCs after 14 days coculture (52±17% vs. 29±6%, respectively). A higher frequency of HUCPVCs expressed α-MHC protein compared with BM-MSCs (11.6±0.9% vs. 5.3±0.3%); however, both cell types retained MSC-associated determinants. We also assessed the ability of the MSC types to mediate cardiac regeneration in a NOD/SCID γ mouse model of acute myocardial infarction (AMI). Fourteen days after AMI, cardiac function was significantly better in cell-treated mice compared with control animals and HUCPVCs exhibited greater improvement. Although human cells persisted in the infarct area, the frequency of α-MHC expression was low. Our results indicate that HUCPVCs exhibit a greater degree of cardiomyocyte reprogramming but that differentiation for both cell types is partial. We conclude that HUCPVCs may be preferable to BM-MSCs in the cell therapy of AMI.

An innovative stand-alone bioreactor for the highly reproducible transfer of cyclic mechanical stretch to stem cells cultured in a 3D scaffold

Much evidence in the literature demonstrates the effect of cyclic mechanical stretch in maintaining, or addressing, a muscle phenotype. Such results were obtained using several technical approaches, useful for the experimental collection of proofs of principle but probably unsuitable for application in clinical regenerative medicine. Here we aimed to design a reliable innovative bioreactor, acting as a stand-alone cell culture incubator, easy to operate and effective in addressing mesenchymal stem cells (MSCs) seeded onto a 3D bioreabsorbable scaffold, towards a muscle phenotype via the transfer of a controlled and highly-reproducible cyclic deformation. Electron microscopy, immunohistochemistry and biochemical analysis of the obtained pseudotissue constructs showed that cells 'trained' over 1 week: (a) displayed multilayer organization and invaded the 3D mesh of the scaffold; and (b) expressed typical markers of muscle cells. This effect was due only to physical stimulation of the cells, without the need of any other chemical or genetic manipulation. This device is thus proposed as a prototypal instrument to obtain pseudotissue constructs to test in cardiovascular regenerative medicine, using good manufacturing procedures.

Mesenchymal stem cells for cardiac cell therapy

Despite refinements of medical and surgical therapies, heart failure remains a fatal disease. Myocardial infarction is the most common cause of heart failure, and only palliative measures are available to relieve symptoms and prolong the patient's life span. Because mammalian cardiomyocytes irreversibly exit the cell cycle at about the time of birth, the heart has traditionally been considered to lack any regenerative capacity. This paradigm, however, is currently shifting, and the cellular composition of the myocardium is being targeted by various regeneration strategies. Adult progenitor and stem cell treatment of diseased human myocardium has been carried out for more than 10 years (Menasche et al., 2001; Stamm et al., 2003), and it has become clear that, in humans, the regenerative capacity of hematopoietic stem cells and endothelial progenitor cells, despite potent proangiogenic effects, is limited (Stamm et al., 2009). More recently, mesenchymal stem cells (MSCs) and related cell types are being evaluated in preclinical models of heart disease as well as in clinical trials (see Published Clinical Trials, below). MSCs have the capacity to self-renew and to differentiate into lineages that normally originate from the embryonic mesenchyme (connective tissues, blood vessels, blood-related organs) (Caplan, 1991; Prockop, 1997; Pittenger et al., 1999). The current definition of MSCs includes plastic adherence in cell culture, specific surface antigen expression (CD105(+)/CD90(+)/CD73(+), CD34(-)/CD45(-)/CD11b(-) or CD14(-)/CD19(-) or CD79α(-)/HLA-DR1(-)), and multilineage in vitro differentiation potential (osteogenic, chondrogenic, and adipogenic) (Dominici et al., 2006 ). If those criteria are not met completely, the term "mesenchymal stromal cells" should be used for marrow-derived adherent cells, or other terms for MSC-like cells of different origin. For the purpose of this review, MSCs and related cells are discussed in general, and cell type-specific properties are indicated when appropriate. We first summarize the preclinical data on MSCs in models of heart disease, and then appraise the clinical experience with MSCs for cardiac cell therapy.