Mesenchymal stem cells (MSCs) are an adult stem cell population that share some phenotypic characteristics with embryonic stem cells but lack the ethical or safety concerns associated with such undifferentiated cells. MSCs are located primarily in the bone marrow and to a lesser extent other tissues and can be positively selected, ex vivo culture expanded and are able to differentiate into the mesenchymal tissue lineage of osteocytes, chondrocytes and adipocytes. A precursor of MSCs termed mesenchymal progenitor cells (MPCs) can be further isolated from bone marrow resulting in a homogenous product containing a significantly purer population of MSCs without the high number of contaminating cells inherent toMSC isolation techniques. Additionally, MSCs lack certain co-stimulatory receptors such as HLA class II and locally secrete factors downregulating T cell responses allowing for allogeneic usage as an off-the-shelf product. MSCs increase neovascularization and cardiomyocyte regeneration in a number of animal models resulting in improvement in cardiac functional outcome and limitation of the progression to heart failure. The mechanism(s) of improvement remains a matter of debate. Alternatives include direct differentiation of the MSCs vs. paracrine secretion of factors that indirectly effect endogenous tissue and local progenitor cells. While the exact mechanism of cardiac improvement continues to be explored, it is clear that allogeneic MSCs offer a reproducible, inexpensive, regulatory-friendly cellular therapy treatment for cardiovascular disease that will need to be investigated in larger safety and efficacy clinical trials.
Stem cells; Tissue therapy; Myocardial ischemia; Myocardium
