ausblenden:
Schlagwörter:
SERUM RESPONSE FACTOR; ACTIN DYNAMICS; HIBERNATING MYOCARDIUM;
TRANSCRIPTION FACTORS; DEPENDENT REGULATION; VASCULAR-DISEASE; CHRONIC
ISCHEMIA; NITRIC-OXIDE; SRF ACTIVITY; GENE
Zusammenfassung:
Gradual occlusion of coronary arteries may result in reversible loss of cardiomyocyte function (hibernating myocardium), which is amenable to therapeutic neovascularization. The role of myocardin-related transcription factors (MRTFs) co-activating serum response factor (SRF) in this process is largely unknown. Here we show that forced MRTF-A expression induces CCN1 and CCN2 to promote capillary proliferation and pericyte recruitment, respectively. We demonstrate that, upon G-actin binding, thymosin beta 4 (T beta 4), induces MRTF translocation to the nucleus, SRF-activation and CCN1/2 transcription. In a murine ischaemic hindlimb model, MRTF-A or T beta 4 promotes neovascularization, whereas loss of MRTF-A/B or CCN1-function abrogates the T beta 4 effect. We further show that, in ischaemic rabbit hindlimbs, MRTF-A as well as T beta 4 induce functional neovascularization, and that this process is inhibited by angiopoietin-2, which antagonizes pericyte recruitment. Moreover, MRTF-A improves contractile function of chronic hibernating myocardium of pigs to a level comparable to that of transgenic pigs overexpressing T beta 4 (T beta 4tg). We conclude that MRTF-A promotes microvessel growth (via CCN1) and maturation (via CCN2), thereby enabling functional improvement of ischaemic muscle tissue.
