Expression and role of SerpinE2 in cardiac fibrosis

Abstract

Cardiac fibrosis is a common histological feature of a broad spectrum of cardiovascular diseases including myocardial infarction. Proteases and their inhibitors are known to be involved in the regulation of extracellular matrix deposition and remodeling. SerpinE2 is a serine protease inhibitor expressed within the myocardium, which targets thrombin and the proteases of the plasminergic system. This inhibitor has been shown to be involved in lung fibrosis and could be an actor of cardiac remodeling. To study SerpinE2 expression in human left ventricle biopsies, from organ donors (control) and recipient explanted patients. To evaluate SerpinE2 role in cardiac remodeling and fibrosis in the mouse TAC (transverse aortic constriction) model. LV biopsies from organ donors and recipient explanted patients were characterized by histology and classified. SerpinE2 mRNA and protein expression in human samples were assessed by RT-qPCR and Western-Blot after pulverization in liquid nitrogen. Immunofluorescence was used to characterize SerpinE2 expression within paraffin embedded biopsies sections. Wild-type (WT) and SerpinE2-deficient (KO) mice were subjected to 27G TAC model and cardiac function was followed weekly by echocardiography Doppler. After 4 weeks, mice were sacrificed, hearts were harvested and frozen in liquid nitrogen. Heart cryosections were then used for histological fibrosis analysis (Sirius red) or for RNA extraction and RT-qPCR. We found that SerpinE2 expression (mRNA and protein) was significantly increased (×2.5) in the infarcted zone of the biopsies from the LV of explanted patients, compared with non-infarcted area and control donors. SerpinE2 mRNA expression in these samples was also strongly correlated with the expression on type I and III collagens, and TGF-ß. Immunofluorescence assays showed that SerpinE2 protein was mainly detected within the fibrotic areas of the explanted donors. Echocardiography Doppler of 27G mice showed significant decrease in KO animals LV mass and thickness compared with WT counterparts. A significant 2.3 times decrease in type I collagen mRNA expression was observed in KO mice but this was not confirmed by Sirius red staining in heart sections. These data suggest that SerpinE2 could be an actor and/or a biomarker or cardiac fibrosis.