ADULT STEM CELL TRIAL AT BARTS and THE LONDON NHS TRUST

The heart is an organ of limited regenerative capacity and as such has insufficient potential to repair itself. The response to injury comprises adaptive mechanisms such as the opening up of collateral vessels, the hypertrophy of pre-existing cardiomyocytes and the scar formation by stimulation of fibroblasts (remodelling). Recent work that has analysed atrial tissue from sex mismatched heart transplant recipients has demonstrated that primitive cells can migrate into the transplanted heart from the recipient in small numbers . Histological examination has shown that these cells express surface markers demonstrating differentiation into various cell types (cardiomyocytes, endothelial cells and vascular smooth muscle cells) had taken place. This important observation implies that there may be a background level of cellular renewal by engraftment and differentiation of primitive cells that is insufficient to deal with significant levels of myocyte damage. The most likely source of these primitive cells is the bone marrow. Experiments in mice have demonstrated homing and engraftment of labelled bone marrow derived progenitor cells to the site of myocardial infarction. As before, histological examination demonstrated that these labelled cells had undergone a process of differentiation and expressed cardiomyocyte surface markers.