Cardiomyogenic Heterogeneity of Clonal Subpopulations of Human Bone Marrow Mesenchymal Stem Cells

We have evaluated the cardiomyogenic potential of clonal populations of human bone marrow mesenchymal stem cells (BM-MSC). Four rapidly proliferating clones of BM-MSC were obtained from the BM of a healthy donor which were then treated with 5-azacytidine and evaluated for the expression of GATA-4, NKx-2.5, FOG-2, TDGF-1, β-MHC, MEF2D and NPPA genes and cTnT, Desmin and β-MHC proteins. Of the four clones (i) Clone-1 had high expression of GATA-4 (1.89 fold (p<0.05), Nkx2.5 (2.29 fold; p<0.05), FOG2 (2.76 fold; p<0.05), TDGF1 (6.97 fold, p<0.005), βMHC (10.22 fold; p<0.005), MEF-2D (1.91 fold; p<0.005) and NPPA (1.65 fold; p<0.005); (ii) clone-2 had up-regulation of Nkx2.5 (1.98 fold; p<0.05) but down-regulation of rest of the genes; (iii) clone-3 had up-regulation of Nkx2.5 (2.11 fold; p<0.05), TDGF1 (1.88 fold; p<0.05), MEF-2D (1.30 fold; p<0.05) and NPPA (1.21 fold; p<0.05), down regulation of GATA-4 and Fog-2 but no change in βMHC gene; and (iv) clone-4 had up-regulation of MEF-2D (1.17 fold; p<0.05) and down regulation of GATA-4, Nkx2.5 but no change in other genes compared to untreated cells of the clones. At the protein level, clone-1 expressed cTnT, Desmin, and βMHC; clone-2 Desmin only while clones-3 and 4 each expressed cTnT, Desmin, and βMHC. Our data shows that BM-MSC are a heterogenous population of stem cells with sub-populations exhibiting a marked difference in the expression of cardiac markers both at gene and protein levels. This highlights that administering selected sub-populations of BM-MSC with a cardiomyogenic potential may be more efficacious than whole population of cells for cardiac regeneration.