Effect of 5-azacytidine on the protein expression of porcine bone marrow mesenchymal stem cells in vitro

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

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

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

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

Cardiac Stem Cells for Myocardial Regeneration: They Are Not Alone

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

Promoting effect of small molecules in cardiomyogenic and neurogenic differentiation of rat bone marrow-derived mesenchymal stem cells

Small molecules, growth factors, and cytokines have been used to induce differentiation of stem cells into different lineages. Similarly, demethylating agents can trigger differentiation in adult stem cells. Here, we investigated the in vitro differentiation of rat bone marrow mesenchymal stem cells (MSCs) into cardiomyocytes by a demethylating agent, zebularine, as well as neuronal-like cells by β-mercaptoethanol in a growth factor or cytokines-free media. Isolated bone marrow-derived MSCs cultured in Dulbecco's Modified Eagle's Medium exhibited a fibroblast-like morphology. These cells expressed positive markers for CD29, CD44, and CD117 and were negative for CD34 and CD45. After treatment with 1 μM zebularine for 24 hours, the MSCs formed myotube-like structures after 10 days in culture. Expression of cardiac-specific genes showed that treated MSCs expressed significantly higher levels of cardiac troponin-T, Nkx2.5, and GATA-4 compared with untreated cells. Immunocytochemical analysis showed that differentiated cells also expressed cardiac proteins, GATA-4, Nkx 2.5, and cardiac troponin-T. For neuronal differentiation, MSCs were treated with 1 and 10 mM β-mercaptoethanol overnight for 3 hours in complete and serum-free Dulbecco's Modified Eagle's Medium, respectively. Following overnight treatment, neuron-like cells with axonal and dendritic-like projections originating from the cell body toward the neighboring cells were observed in the culture. The mRNA expression of neuronal-specific markers, Map2, Nefl, Tau, and Nestin, was significantly higher, indicating that the treated cells differentiated into neuronal-like cells. Immunostaining showed that differentiated cells were positive for the neuronal markers Flk, Nef, Nestin, and β-tubulin.

A tumor deconstruction platform identifies definitive end points in the evaluation of drug responses

Tumor heterogeneity and the presence of drug-sensitive and refractory populations within the same tumor are almost never assessed in the drug discovery pipeline. Such incomplete assessment of drugs arising from spatial and temporal tumor cell heterogeneity reflects on their failure in the clinic and considerable wasted costs in the drug discovery pipeline. Here we report the derivation of a flow cytometry-based tumor deconstruction platform for resolution of at least 18 discrete tumor cell fractions. This is achieved through concurrent identification, quantification and analysis of components of cancer stem cell hierarchies, genetically instable clones and differentially cycling populations within a tumor. We also demonstrate such resolution of the tumor cytotype to be a potential value addition in drug screening through definitive cell target identification. Additionally, this real-time definition of intra-tumor heterogeneity provides a convenient, incisive and analytical tool for predicting drug efficacies through profiling perturbations within discrete tumor cell subsets in response to different drugs and candidates. Consequently, possible applications in informed therapeutic monitoring and drug repositioning in personalized cancer therapy would complement rational design of new candidates besides achieving a re-evaluation of existing drugs to derive non-obvious combinations that hold better chances of achieving remission.

Proteomics approaches in the identification of molecular signatures of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are undifferentiated, multi-potent stem cells with the ability to renew. They can differentiate into many types of terminal cells, such as osteoblasts, chondrocytes, adipocytes, myocytes, and neurons. These cells have been applied in tissue engineering as the main cell type to regenerate new tissues. However, a number of issues remain concerning the use of MSCs, such as cell surface markers, the determining factors responsible for their differentiation to terminal cells, and the mechanisms whereby growth factors stimulate MSCs. In this chapter, we will discuss how proteomic techniques have contributed to our current knowledge and how they can be used to address issues currently facing MSC research. The application of proteomics has led to the identification of a special pattern of cell surface protein expression of MSCs. The technique has also contributed to the study of a regulatory network of MSC differentiation to terminal differentiated cells, including osteocytes, chondrocytes, adipocytes, neurons, cardiomyocytes, hepatocytes, and pancreatic islet cells. It has also helped elucidate mechanisms for growth factor-stimulated differentiation of MSCs. Proteomics can, however, not reveal the accurate role of a special pathway and must therefore be combined with other approaches for this purpose. A new generation of proteomic techniques have recently been developed, which will enable a more comprehensive study of MSCs.

Immortalization of bone marrow-derived porcine mesenchymal stem cells and their differentiation into cells expressing cardiac phenotypic markers

Mesenchymal stem cells (MSCs) may be among the first stem cell types to be utilized in the clinic for cell therapy, because of their ease of isolation and extensive differentiation potential. Using a porcine model, we have established several cell lines from MSCs to facilitate in vitro and in vivo studies of their potential use for cellular therapy. Bone marrow-derived primary MSCs were immortalized using the pRNS-1 plasmid. We obtained four stable immortalized cell lines that exhibited higher proliferative capacities than the parental cells. All four cell lines displayed a common phenotype similar to that of primary mesenchymal cells, characterized by constitutively high expressions of CD90, CD29, CD44, SLA I and CD46, while CD172a, CD106 and CD56 were less expressed. Remarkably, treatment with 5-azacytidine-stimulated porcine MSCs lines to differentiate into cells that were positive for cardiac phenotypic markers, such as α-actin, connexin-43, sarcomeric actin, serca-2 and, to a lesser extent, desmin and troponin-T. These porcine MSC lines will be valuable biological tools for developing strategies for ex vivo expansion and differentiation of MSCs into a specific lineage.

Neurogenic and cardiomyogenic differentiation of mesenchymal stem cells isolated from minipig bone marrow

The present study investigated the potential of minipig bone marrow-mesenchymal stem cells (BM-MSCs) to differentiate in vitro into neuron- and cardiomyocyte-like cells. Isolated BM-MSCs exhibited a fibroblast-like morphology, expressed CD29, CD44 and CD90, and differentiated into osteocytes, adipocytes and chondrocytes. Upon induction in two different neuronal specific media, most of BM-MSCs acquired the distinctive morphological features and positively stained for nestin, neurofilament-M (NF-M), neuronal nuclei (NeuN), β-tubulin, galactocerebroside (Gal-C) and glial fibrillary acidic protein (GFAP). Expression of nestin, GFAP and NF-M was further demonstrated by RT-PCR and RT-qPCR. Following cardiomyogenic induction, MSCs exhibited a stick-like morphology with extended cytoplasmic processes, and formed cluster-like structures. The expression of cardiac specific markers α-smooth muscle actin, cardiac troponin T, desmin and α-cardiac actin was positive for immunofluorescence staining, and further confirmed by RT-PCR and RT-qPCR. In conclusion, our results showed the in vitro differentiation ability of porcine BM-MSCs into neuron-like and cardiomyocyte-like cells.

Human BM stem cells initiate angiogenesis in human islets in vitro

BM stem cells may have regenerative effects on islet function through angiogenesis. Human islets (100islet equivalent/mL) were cultured alone (control) or co-cultured (experimental group) with whole human BM (1 × 10(6) cells/mL) for 210 days. A protein array measuring angiogenesis factors found upregulated (experimental vs control, day 210) proteins levels of VEGF-a (535 vs 2 pg/mL), PDGF (280.79 vs 0 pg/mL), KGF (939 vs 8 pg/mL), TIMP-1 (4592 vs 4332 pg/mL) and angiogenin (506 vs 97 pg/mL). Lower protein levels of angiopoietin-2 (5 vs 709 pg/mL) were observed. Depletion of pro-angiogenesis factors in co-culture decreased the effects of BM-induced islet vascularization. Depletion of VEGF-a, eKGF and PDGF significantly reduced islet vascularization but individual depletion of KGF and PDGF had less effects overall on vessel formation. BM-induced vascularization showed significant endothelial cell distribution. Islet vascularization was linked to islet growth. A decrease in islet size indicated poor vascularization. Insulin release was evident in the tissues generated from human islet-BM co-culture throughout the entire culture period. Significant increase in insulin (28.66-fold vs control) and glucagon (24.4-fold vs control) gene expression suggest BM can induce endocrine cell regeneration. In conclusion, BM promotes human islet tissue regeneration via regulation of angiogenesis factors.

Gene expression profiles following intracoronary injection of mesenchymal stromal cells using a porcine model of chronic myocardial infarction

BACKGROUND AIMS

We evaluated the therapeutic potential of injection of in vitro differentiated bone marrow mesenchymal stromal cells (MSC) using a swine model.

METHODS AND RESULTS

Myocardial infarction was induced by coronary occlusion. Three groups (n = 5 each) were analyzed: one group received an injection of 17.8 ± 9.3 × 10(6) 5-azacytidine-treated allogeneic MSC 1 month after infarction; a placebo group received an injection of medium; and controls were kept untreated. After 4 weeks, heart samples were taken from three infarcted areas, interventricular septa, ventricles and atria. Gene expression profiles of genes related to contractility (Serca2a), fibrosis (Col1a1), cardiomyogenesis (Mef2c, Gata4 and Nkx2.5) and mobilization of stem cells (Sdf1, Cxcr4 and c-kit) were compared by quantitative real-time PCR (qRT-PCR). Gene expression profiles varied in different heart areas. Thus Serca2a expression was reduced in infarcted groups in all heart regions except for the left ventricles, where Col1a1 was overexpressed. The expression of genes related to cardiomyogenesis decreased in the infarcted zones and left atria compared with healthy hearts. Interestingly, increased expression of Cxcr4 was detected in infarcted regions of MSC-treated pigs compared with the placebo group.

CONCLUSIONS

Infarction induced changes in expression of genes involved in various biologic processes. Genes involved in cardiomyogenesis were downregulated in the left atrium. The intracoronary injection of MSC resulted in localized changes in the expression of Cxcr4.

Proteome analysis of rat bone marrow mesenchymal stem cell differentiation

Bone marrow multipotent stromal cells (or mesenchymal stem cells; MSCs) have the capacity for renewal and the potential to differentiate in culture into several cell types including osteoblasts, chondrocytes, adipocytes, cardiomyocytes, and neurons. This study was designed to investigate the protein expression profiles of rat bone marrow MSCs during differentiation into adipogenic (by dexamethasone, isobutylmethylxanthine, insulin, and indomethacin), cardiomyogenic (by 5-azacytidine), chondrogenic (by ascorbic acid, insulin-transferrin-selenous acid, and transforming growth factor-β1), and osteogenic (by dexamethasone, β-glycerophosphate, and ascorbic acid) lineages by well-known differentiation inducers. Proteins extracted from differentiated MSCs were separated using two-dimensional gel electrophoresis (2-DE) and protein spots were detected using Sypro Ruby dye. Protein spots that were determined to be up- or down-regulated when the expression of corresponding spots (between weeks 1 and 2, 1 and 3, 1 and 4) showed an increase (≥2-fold) or decrease (≤0.5-fold) were successfully identified by MALDI-TOF-MS. In summary, 23 new proteins were identified either up- or down-regulated during differentiation experiments.

Comparative proteomics research on rat MSCs differentiation induced by Shuanglong Formula

ETHNOPHARMACOLOGICAL RELEVANCE

Shuanglong Formula (SLF) is a classic formula for treating heart disease in traditional Chinese medicine (TCM). And it has been reported that the combinational treatment of SLF with autologous mesenchymal stem cells (MSCs) transplantation could be of benefit to people with acute myocardial infarction. However, their underlying mechanisms are not clear.

AIM OF THE STUDY

The effects of whole formula and its herbal main ingredients on rat MSCs differentiation towards cardiomyocytes were investigated and the distinct protein expression profile in MSC-derived cardiomyocytes studied.

MATERIALS AND METHODS

The protein expression profiles of rat MSCs and cardiomyocyte-like cells were determined with two-dimensional gel electrophoresis (2-DE).

RESULTS

Our data demonstrated that SLF can induce MSCs into cardiomyocyte-like cells and around 36 proteins mainly involved in cytoskeleton, cell tissue energy metabolism and signal transduction have been shown to be regulated distinctly by SLF treatment.

CONCLUSIONS

Data presented in this study suggest that large rearrangement of the proteome occur during the differentiation process of the MSCs to terminally differentiated cardiomyocyte-like cells and offer the possibility for further characterization of specific targets driving the stem cell differentiation.

Proteome of mesenchymal stem cells

Proteomics has evolved, in recent years, into effective tools for basic and applied stem cell research, and has been extensively used to facilitate the identification of changes in signal transduction components, especially with regard to plasticity, proliferation, and differentiation. Several recent reports have also employed proteomic strategies to characterize human mesenchymal stem cells (hMSC) and their differentiated derivatives. Although these approaches have yielded valuable data, the results highlight the fact that only the limited numbers of proteins are characterized at the protein level in these cells, thus necessitating expandable MSC proteome dataset. This review presents, for the first time, an expandable list of MSC proteins, which will function as a starting point for the generation of a comprehensive reference map of their proteome. Also, the better way to bridge current gap between genomics and proteomics study such as integrated proteomic and transcriptomic analyses is discussed.

Concise review: trends in stem cell proteomics

Gene expression analyses of stem cells (SCs) will help to uncover or further define signaling pathways and molecular mechanisms involved in the maintenance of self-renewal, pluripotency, and/or multipotency. In recent years, proteomic approaches have produced a wealth of data identifying proteins and mechanisms involved in SC proliferation and differentiation. Although many proteomics techniques have been developed and improved in peptide and protein separation, as well as mass spectrometry, several important issues, including sample heterogeneity, post-translational modifications, protein-protein interaction, and high-throughput quantification of hydrophobic and low-abundance proteins, still remain to be addressed and require further technical optimization. This review summarizes the methodologies used and the information gathered with proteome analyses of SCs, and it discusses biological and technical challenges for proteomic study of SCs. Disclosure of potential conflicts of interest is found at the end of this article.