By Stuart P. Atkinson
The potential for cell replacement through the differentiation of embryonic stem cells (ESCs) or induced pluripotent stem cells (iPSCs) is a promising means of therapeutic intervention in many disease states, but may be limited by several problems, such as limited graft survival, restricted homing to the site of injury and host immune rejection. An alternative to this is the possibility of stimulating resident adult stem cells within the tissue to aid repair. It is generally assumed that the cells of the adult epicardium (the outer layer of heart tissue) are quiescent, incapable of migration or differentiation, while cells of the embryonic epicardium possess an innate ability to proliferate, migrate and differentiate into a number of mature cardiovascular cell types. However, data now suggests that resident stem/progenitor cells in the adult heart may produce de novo cardiomyocytes following injury.