Munich, Germany -
It is known that when bone marrow stem cells are injected intravenously into a recipient, the injected cells home to the recipient bone marrow because the bone marrow stroma secretes various chemoattractant factors that cause migration of cells. Along these lines, induction of tissue injury is also known to cause chemoattraction of bone marrow stem cells to the area of injury, presumably as part of a physiological repair mechanism. It is, however, not clear to what extent disease conditions of tissue injury are associated with homing of stem cells to injured tissue.
In a recent paper (Theiss et al. Eur Heart J. 2007 Mar 29; Circulation of CD34+ progenitor cell populations in patients with idiopathic dilated and ischaemic cardiomyopathy) it was found that circulating CD34 cells are higher in patients with dilated cardiomyopathy as opposed to ischemic cardiomyopathy. Tissue analysis revealed that ischemic cardiomyopathy was associated with higher levels of stem cell chemoattractants such as SDF-1, and BNP as compared to dilated cardiomyopathy. These data are interpreted by the author to mean that "Reduced homing of stem cells might therefore explain the increased number of CD34 cells in DCM patients."
Whether this is the case or not remains to be resolved, however, the study does provide a nice description of upregulated stem cell chemoattractants in myocardial ischemia. Therapeutic utilization of the fact that injured myocardium is consitutively expressing chemoattractants should be performed. In fact it was already, in the trial by Osiris in which intravenously administered stem cells were capable of augmenting function of injured myocardium.