Análisis del perfil genómico y epigenómico de las células madre adultas multipotenciales humanas

Resum

We analyzed the genomic and epigenomic profile of adult stem cells and pluripotent stem cells to understand what mechanisms may establish or maintain a pluripotent state in stem cells. Firstly, stem cells from adult human bone marrow (mesenchymal stem cells, MSCs, and multipotent adult progenitor cells, MAPCs) and from human adipose tissue (adipose derived stem cells, ADSCs) were isolated and characterized. Different culture media for the clinical expansion of MSCs and ADSCs were also compared in order to find alternatives to fetal calf serum (FBS). The replacement of FBS by human serum (HS) or human platelet lysate (PL) did not alter the in vitro morphology, growth, phenotype, differentiation and immunoregulation capacities of human MSCs and ADSCs. Using well characterized populations of stem cells, we compared the transcriptome of pluripotent stem cells (NTERA-2) and adult stem cells (ASC), and examined the differences in the epigenetic profile that could explain their differentiation potential. We found distinct expression profiles between adult stem cells (ASCs) and pluripotent cells (NTERA-2), and between MAPCs and MSCs-ADSCs. Pluripotent cells and MAPCs shared a decrease in the expression of differentiation genes. The changes in expression could be explained by differences in the epigenetic regulation. The analysis of the Polycomb repressive marks, histone modifications and gene promoter methylation of differentiation and pluripotency genes demonstrated that cell populations with a wider stem cell potential (NTERA-2 and MAPC) showed more epigenetic repressive marks in differentiation genes. Our analysis of microRNAs established specific microRNA signatures involved in regulation of pluripotent and differentiation genes. Our study leads us to propose a stepwise model representing the different epigenetic stages from multipotent to pluripotent stem cells, which aids our understanding of the mechanism of pluripotency and cell reprogramming.