Protective role of Gremlin‐1 in myocardial function
Iris Müller, Martina Schneider, Karin Müller, Oleg Lunov, Oliver Borst, Thomas Simmet, Meinrad Gawaz
Abstract
Abstract Background Gremlin‐1 is a cystine knot protein and is expressed in organs developing fibrosis. Transient ischaemia leads to myocardial fibrosis, a major determinant of impaired myocardial function. Materials and methods Expression of Gremlin‐1 was investigated in infarcted myocardium by real‐time PCR, Western blot analysis, histological and immunohistochemistry staining. We further elaborated the colocalization of Gremlin‐1 and TGF‐β proteins by confocal microscopy and co‐immunoprecipitation experiments. The interaction between Gremlin‐1 and TGF‐β was analysed by photon correlation spectroscopy. Gremlin‐1 modulation of the TGF‐β‐dependent collagen I synthesis in fibroblasts was investigated using ELISA and immunohistochemistry experiments. The effect of prolonged administration of recombinant Gremlin‐1 on myocardial function following ischaemia/reperfusion was accessed by echocardiography and immunohistochemistry. Results Gremlin‐1 is expressed in myocardial tissue and infiltrating cells after transient myocardial ischaemia ( P < .05). Gremlin‐1 colocalizes with the pro‐fibrotic cytokine transforming growth factor‐β (TGF‐β) expressed in fibroblasts and inflammatory cell infiltrates ( P < .05). Gremlin‐1 reduces TGF‐β‐induced collagen production of myocardial fibroblasts by approximately 20% ( P < .05). We found that Gremlin‐1 binds with high affinity to TGF‐β ( K D = 54 nmol/L) as evidenced by photon correlation spectroscopy and co‐immunoprecipitation. intravenous administration of m Gremlin‐1‐Fc, but not of equivalent amount of Fc control, significantly reduced infarct size by approximately 20%. In the m Gremlin‐1‐Fc group, infarct area was reduced by up to 30% in comparison with mice treated with Fc control (I/LV: 4.8 ± 1.2% vs 6.0 ± 1.2% P < .05; I/AaR: 15.2 ± 1.5% vs 21.1 ± 5%, P < .05). Conclusions The present data disclose Gremlin‐1 as an antagonist of TGF‐β and presume a role for Gremlin‐1/TGF‐β interaction in myocardial remodelling following myocardial ischaemia.