Isolation and Characterization of Cardiac MSCs from Rat Foetal Hearts

Foetal heart derived mesenchymal stem cells (MSCs) are envisaged as a suitable cell type for cardiac regeneration because of their pre‐natal origin and cardiac commitment. However, there is very little data as to their identity or characterization. We have isolated a population of stem cells from rat foetal hearts (n=20), which is similar to typical MSCs. These stem cells proliferated in cultures as plastic adherent cells with a trigonal/spindle shaped morphology, and were positive for CD29, CD44, CD73, CD90 and CD105 markers and negative for CD31, CD45 and HLA‐DR. Moreover, they differentiated into adipogenic and osteogenic cells, as evidenced by Oil red‐O and Alizarin red staining, respectively. In addition, they expressed the embryonal markers Oct‐4, Nanog, Sox‐2, SSEA‐1, SSEA‐3 and SSEA‐ 4 and the cardiovascular genes Isl‐1, flk‐1, Nkx2.5 and GATA‐4 at the gene or protein level and exhibited induced differentiation into cardiac troponin‐T and β‐ MHC‐expressing cardiomyocytes, CD31‐expressing endothelial cells and SM‐MHC‐expressing smooth muscle cells. They were expandable to up to more than 120 population doublings and up to the observation period of the 21st passage. They continuously expressed telomerase reverse transcriptase and maintained a normal karyotype and a similar profile of embryonal and cardiovascular markers and cardiovascular tri‐lineage differentiation potential. These findings together suggest that the foetal heart contains a population of primitive MSCs that is pre‐ committed to the cardiovascular lineage and that they could be extensively expanded in an undifferentiated state, thereby indicating their potential therapeutic value in cardiovascular regenerative medicine.