Myocardial regeneration of the failing heart

Human heart failure (HF) is one of the leading causes of morbidity and mortality worldwide. Currently, heart transplantation and implantation of mechanical devices represent the only available treatments for advanced HF. Two alternative strategies have emerged to treat patients with HF. One approach relies on transplantation of exogenous stem cells (SCs) of non-cardiac or cardiac origin to induce cardiac regeneration and improve ventricular function. Another complementary strategy relies on stimulation of the endogenous regenerative capacity of uninjured cardiac progenitor cells to rebuild cardiac muscle and restore ventricular function. Various SC types and delivery strategies have been examined in the experimental and clinical settings; however, neither the ideal cell type nor the cell delivery method for cardiac cell therapy has yet emerged. Although the use of bone marrow (BM)-derived cells, most frequently exploited in clinical trials, appears to be safe, the results are controversial. Two recent randomized trials have failed to document any beneficial effects of intracardiac delivery of autologous BM mononuclear cells on cardiac function of patients with HF. The remarkable discovery that various populations of cardiac progenitor cells (CPCs) are present in the adult human heart and that it possesses limited regeneration capacity has opened a new era in cardiac repair. Importantly, unlike BM-derived SCs, autologous CPCs from myocardial biopsies cultured and subsequently delivered by coronary injection to patients have given positive results. Although these data are promising, a better understanding of how to control proliferation and differentiation of CPCs, to enhance their recruitment and survival, is required before CPCs become clinically applicable therapeutics.