Are we closer to cardiac regeneration?
Heart disease remains one of the leading causes of mortality. In contrast to adult teleost fish and amphibians, in adult mammals the resident cardiac cells are not able to regenerate heart tissue and restore efficiently the cardiac function after heart failure, being hypertrophy the most relevant compensation for the loss of cardiomyocytes. Since there are not enough heart donors available for transplantation, in recent years, new approaches have been explored, and a number of groups have been focused on the use of the stem cells. Although adipose tissue-derived cells or cardiac-derived stem cells are being explored (1,2), the largest clinical experience has been acquired with intracoronary delivery of bone marrow stem cells (BMSC) to treat acute myocardial infarction and chronic ischemic heart failure. However, the published data in the last 10 years do not show a substantial long-term benefit (3). The reasons that could explain BMSC inefficacy for cardiac repair could be: (I) only a very small fraction of the injected cells remain in the targeted area, and (II) BMSC are not able to differentiate into cardiac muscle. Actually, the current consensus is that any improvement in cardiac function after BMSC transplantation is likely to be the result of a paracrine action. Thus, success of cardiac cell therapy will be determined by the development of methods to improve engraftment and generation of cells capable to regenerate the damaged tissue (4).