Interaction of alpha-6 integrin with laminin-1 is essential for cardiac regeneration mediated by cardiac primitive cells

According to the recent findings, CD117(+) cells reside in the subepicardium and epicardially-derived cells may represent a population of cardiac primitive cells. We have previously shown the presence of laminin-1, typical of developing heart, in the subepicardium of human adult heart with chronic ischemic cardiomyopathy. Hence, the hypothesis arises that laminin-1 may influence cardiac primitive cells biology. CD117(+) cells from adult human heart were cultured on laminin-1, laminin-2 or albumin. Specific human alpha6 integrin small interfering RNA (siRNA) was used to examine the contribution of alpha6 integrin and laminin interactions to the cell proliferation, apoptosis and migration in vitro. Both laminin-1 and laminin-2 increased the proliferation of cells, as evaluated with BrdU incorporation. In the presence of laminin-2 the proliferation rate reached 7.9±0.4% (n=4), whereas during the culture of cardiac primitive cells on laminin-1 the incorporation of BrdU was over 4-fold higher (n=4, p