Abstract

Endogenous cardiac progenitor cells (CPC) have the potential to regenerate damaged tissue following myocardial infarction and restore contractility; however, their insufficient numbers hinders the replacement of the massive loss of cardiomyocytes. In vitro expansion of various CPC populations has been proposed, based on surface markers' expression and isolation techniques, but doubt remains as to which is the optimal population for regenerative therapy. Here we compare expression of stem cell and early cardiac genes in CPC populations to that in differentiating embryonic stem cells (ESCs).

CPCs were isolated from adult mouse atria and expanded in adherent culture as CDCs[A] (via explant-derived cells, cardiosphere formation for 3 days); CDCs[B] (as CDCs[A] with cardiospheres kept for 5 days); Coll[C] (after collagenase & trypsin digestion); Coll[D] (as Coll[C] with a 5 day cardiosphere step). Gene-expression was assessed using RT-PCR and compared to ESCs at day 4 or day 7 of cardiac differentiation for cardiac and stem cell genes or to CDCs[A] for mesenchymal/fibroblast markers.

All populations had lower expression of Oct4 and Sox2 than the differentiating ESCs. CDCs[A] also expressed lower levels of early cardiac genes, whereas expression of early cardiac genes in CDCs[B] and Coll[C] was comparable to day 4 ESCs. c-Kit expression was significantly higher in Coll[C] than in CDCs[A] or CDCs[B] and was further increased after cardiosphere formation in Coll[D], however expression of Sca1 and CD105 was increased in CDCs[B]. Thus these progenitors resemble ESCs before day 7 of differentiation but expression of c-kit or Sca-1 can be manipulated during expansion.