Haematopoietic stem cells and repair of the ischaemic heart.

HSCs (haematopoietic stem cells) are multipotent stem cells that give rise to all cells of the blood cell lineage. In recent years, it has been proposed that bone marrow serves as a reservoir for cardiomyogenic precursors and that, following cardiac injury, these stem cells circulate to the site of injury where they contribute to myocardial repair and regeneration. This concept of stem cell plasticity has been controversial and, in fact, several key studies on the cardiomyogenic potential of HSCs have not been reproducible in the hands of independent investigators. Despite this controversy, the clinical community has pushed forward with clinical trials of bone marrow transplantation for the treatment of ischaemic heart disease. The following review summarizes the mechanistic underpinnings of bone marrow transplantation into ischaemic myocardium, focusing on the basic science that forms the foundation of this field, and highlights the controversies and new avenues for research that have emerged. It also describes the current state of the art in clinical trials of bone marrow transplantation for heart failure.