Epigenetic Dysregulation in Mesenchymal Stem Cell Aging and Spontaneous Differentiation

BACKGROUND: Mesenchymal stem cells (MSCs) hold great promise for the treatment of difficult diseases. As MSCs represent a rare cell population, ex vivo expansion of MSCs is indispensable to obtain sufficient amounts of cells for therapies and tissue engineering. However, spontaneous differentiation and aging of MSCs occur during expansion and the molecular mechanisms involved have been poorly understood. METHODOLOGY/PRINCIPAL FINDINGS: Human MSCs in early and late passages were examined for their expression of genes involved in osteogenesis to determine their spontaneous differentiation towards osteoblasts in vitro, and of genes involved in self-renewal and proliferation for multipotent differentiation potential. In parallel, promoter DNA methylation and hostone H3 acetylation levels were determined. We found that MSCs underwent aging and spontaneous osteogenic differentiation upon regular culture expansion, with progressive downregulation of TERT and upregulation of osteogenic genes such as Runx2 and ALP. Meanwhile, the expression of genes associated with stem cell self-renewal such as Oct4 and Sox2 declined markedly. Notably, the altered expression of these genes were closely associated with epigenetic dysregulation of histone H3 acetylation in K9 and K14, but not with methylation of CpG islands in the promoter regions of most of these genes. bFGF promoted MSC proliferation and suppressed its spontaneous osteogenic differentiation, with corresponding changes in histone H3 acetylation in TERT, Oct4, Sox2, Runx2 and ALP genes. CONCLUSIONS/SIGNIFICANCE: Our results indicate that histone H3 acetylation, which can be modulated by extrinsic signals, plays a key role in regulating MSC aging and differentiation

Cardiovascular surgery for realization of regenerative medicine.

Regenerative medicine is emerging as a new approach to the treatment of severe cardiovascular diseases that are resistant to conventional therapies. Although the type of cell transplanted (e.g., pluripotent stem cells, bone marrow-derived stem cells, skeletal myoblasts, or cardiac stem cells) influences the outcome of stem cell transplantation, the method of transplantation is also important, as the efficiency of engraftment after simple needle injection is poor. Scaffold-free cell sheet transplantation technology is one of the most promising methods in this regard. Although the results of clinical trials of stem cell therapy have been marginal to date, further elucidation of the actual mechanisms of cardiac repair following cell therapy would enhance the potential for full-scale implementation of stem cell therapy. In addition to stem cell therapy, the field of cardiovascular regenerative medicine includes interspecific chimera technology, drug delivery systems using biodegradable materials, and gene therapy. Integration of these new modalities with conventional therapies will be important to realize the goal of cardiovascular regenerative medicine tailored to the condition of each individual patient. Cardiovascular surgery would be an excellent means of carrying out this strategy and could potentially resolve the health problems of the increasing number of advanced cardiovascular patients. Herein, we review the recent basic and clinical research associated with the realization of regenerative medicine in the field of cardiovascular surgery

The role of PKCε-dependent signaling for cardiac differentiation

Protein kinase Cepsilon (PKCε) exerts a well-known cardio-protective activity in ischemia–reperfusion injury and plays a pivotal role in stem cell proliferation and differentiation. Although many studies have been performed on physiological and morphological effects of PKCε mis-expression in cardiomyocytes, molecular information on the role of PKCε on early cardiac gene expression are still lacking. We addressed the molecular role of PKCε in cardiac cells using mouse cardiomyocytes and rat bone marrow mesenchymal stem cells. We show that PKCε is modulated in cardiac differentiation producing an opposite regulation of the cardiac genes NK2 transcription factor related, locus 5 (nkx2.5) and GATA binding protein 4 (gata4) both in vivo and in vitro. Phospho-extracellular regulated mitogen-activated protein kinase 1/2 (p-ERK1/2) levels increase in PKCε over-expressing cells, while pkcε siRNAs produce a decrease in p-ERK1/2. Indeed, pharmacological inhibition of ERK1/2 rescues the expression levels of both nkx2.5 and gata4, suggesting that a reinforced (mitogen-activated protein kinase) MAPK signaling is at the basis of the observed inhibition of cardiac gene expression in the PKCε over-expressing hearts. We demonstrate that PKCε is critical for cardiac cell early gene expression evidencing that this protein is a regulator that has to be fine tuned in precursor cardiac cells