Adult stem cells: from new cell sources to changes in methodology.

Cardiovascular diseases constitute the first cause of mortality and morbidity worldwide. Alternative treatments like transplantation of (stem) cell populations derived from several adult tissue sources, like the bone marrow, skeletal muscle, or even adipose tissue, have been already employed in diverse clinical trials. Results from these studies and previous animal studies have reached to the conclusion that stem cells induce a benefit in the treated hearts, which is exerted mainly through paracrine mechanisms and not through direct differentiation as it was initially expected. However, a strong technical limitation for the stem cell therapy, which is the low level of cell survival and engraftment, diminishes their potential. Thus, new strategies like combination of the cells with bioengineering techniques have been developed and are being subject of intense research, suggesting that new strategies may improve the efficacy of these therapies. In this review, we will discuss the different therapeutic approaches, drawbacks, and future expectations of new regenerative therapies for cardiovascular diseases.