Shock waves treatment induces differentiation of cardiac primitive cells in vitro.

The identification of resident stem cells and progenitors of cardiomyocytes, endothelial and smooth muscle cells in the adult human heart has triggered the studies of new treatment options influencing their proliferation, migration and differentiation. It has been recently made known that shock waves (SW) therapy enhances the expression of VEGF and its receptor Flt-1 in human umbilical vein endothelial cells in vitro and proves beneficial in patients with coronary artery disease. We assessed the hypothesis that shock waves can have positive effects on precursors of all cardiac cell populations, namely cardiomyocytes, endothelial, smooth muscle cells and fibroblasts. We used bioptic pieces from normal adult hearts (n=10) and from human hearts explanted due to the ischemic cardiomyopathy (n=14) to obtain the outgrowth of cardiac cells in vitro. The precursors and progenitors of cells of cardiac lineages were identified and quantified by immunocytochemistry. The cell proliferation and expression of differentiation markers were then examined by immunocytochemistry and western blot, both without and after exposition to 800 shots of SW at 0,1mJ/mm2. The growth rate of cardiac cells was slowed down by the SW treatment due to the decrease of fibroblast relative number in the cell culture (83% vs. 56%, p < 0.05). The expression of Flk-1 increased significantly in the primitive cells from both normal and diseased hearts after SWtreatment (4-fold and 2-fold, respectively). Similarly, the SW treatment increased nearly 2-fold the expression of smooth muscle actin, while the increase of α-sarcomeric actin and MHC expression was not significant. The expression of MLC-1 decreased significantly after SW treatment of normal cells and increased in the cells from pathological hearts, while MLC-2 decreased in both cell types. Importantly, the number of primitive cells and expression of differentiation markers were always significantly higher in the control cells from pathological hearts when compared with the normal hearts. The results indicate that differentiation of primitive cells in the myocardium is markedly enhanced in chronic pathological conditions. The SW treatment influences positively differentiation and maturation of cardiomyocytes, endothelial and smooth muscle cells, reducing the relative number of fibroblasts in vitro, possibly due to the influence on growth factor production and release, enhancing their auto- and paracrine action. The effects of SW therapy were markedly more prominent in the cells from normal hearts, therefore its use may be recommended in the early stages of heart failure.