Cardiac shock wave therapy: assessment of safety and new insights into mechanisms of tissue regeneration

Abstract

Although low-energy extracorporeal cardiac shock wave (ECSW) therapy represents an attractive non-invasive treatment option for ischaemic heart disease, the precise mechanisms of its action and influence on the cardiac tissue remain obscure. The goal of this study was to evaluate the effects of SW application on cardiac function and structure. Four-month-old Fisher 344 rats were subjected to ECSW therapy. Echocardiographic measurements of cardiac function were performed at baseline and at 1 and 3 months after treatment. Signs of inflammation, apoptosis and fibrosis were evaluated by immunohistochemistry in the control and treated hearts. ECSW application did not provoke arrhythmia or increase the troponin-I level. At all time points, the left ventricular ejection fraction and fractional shortening remained stable. Histological analysis revealed neither differences in the extracellular matrix collagen content nor the presence of fibrosis; similarly, there were no signs of inflammation. Moreover, a population of cardiac cells that responded eagerly to ECSW application in the adult heart was identified; c-kit-positive, Ki67-positive, orthochromatic cells, corresponding to cardiac primitive cells, were 2.65-fold more numerous in the treated myocardium. In conclusion, non-invasive ECSW therapy is a safe and effective way of activating cardiac stem cells and myocardial regeneration. Because many factors influence cellular turnover in the ischaemic myocardium during the course of ischaemic heart disease, cardiac remodelling, and heart failure progression, studies to identify the optimal treatment time are warranted.

© 2011 The Authors Journal of Cellular and Molecular Medicine © 2011 Foundation for Cellular and Molecular Medicine/Blackwell Publishing Ltd.

Figures

Fig 1

Application of ECSW does not induce myocardial necrosis. High-sensitivity ELISA was used to determine the actual concentration of cTnI in plasma collected from rodents at baseline and at 1 hr after the application of 100 shots of SW at 0.25 mJ/mm2. The cTnI levels remained stable after the treatment (n = 4, P = 0.45).

Fig 2

ECSW application does not induce structural damage to the heart. Histochemistry and immunohistochemistry methods were used to evaluate the morphology of cardiac tissue in control and treated animals at 3 months after ECSW application. Haematoxylin and eosin staining revealed no signs of inflammatory infiltration in control (A) or SW-treated hearts (B). Masson’s trichrome (collagen in blue; C, D) and Picrosirius stainings (collagen in red; E, F) revealed no signs of fibrosis in control (C, E) or SW-treated hearts (D, F). Scale bar: 100 μm.

Fig 3

ECSW therapy did not provoke apoptosis of the cardiac cells. The percentage of apoptotic cells, as evaluated by the TUNEL assay, was similar at 5 weeks (n = 4, P = 0.35) and 13 weeks (n = 4, P = 0.28) in control and treated rats.

Fig 4

ECSW application increases the number of cardiac primitive cells. Clusters of c-kit-positive, Ki67-positive and Flk-1-positive cells were observed in the myocardium of ECSW-treated animals only. Representative images of the serial sections of cardiac tissue stained by immunohistochemistry for c-kit (A), Flk-1 (B) and Ki67 (C) are shown. Scale bar: 50 μm.

Fig 5

Toluidine blue staining excludes the presence of mastocytes in the activated cell clusters. Representative images with a mastocyte (A) demonstrating typical metachromatic granules in the cytoplasm and a cluster of orthochromatic c-kit-positive cells (B). Scale bar: 100 μm.