Abstract 14924: SM22-Cre-Mediated SOCS3 Deficient Mice Exhibit Pericardial Fibrosis, Diastolic Dysfunction, and Increased Mortality Rates Due to Augmented Activation of STAT3 in Fibroblasts

Abstract

Background: Suppressor of cytokine signaling-3 (SOCS3) is a cytokine-inducible potent negative regulator of STAT3 signaling pathway. Here, we aimed to determine whether SOCS3 in non-cardiomyocytes would play a role in cardiovascular pathophysiology. Methods and Results: To investigate the role of SOCS3 in non-cardiomyocytes, we generated conditional knockout mice by crossing SOCS3-flox mice with SM22-α-Cre mice (SM22-SOCS3-KO mice). Mortality rates in the SM22-SOCS3-KO mice was significantly higher than that in the wild-type mice (WT). Heart weight to body weight ratio was significantly increased in SM22-SOCS3-KO mice compared with WT at 12 months of age. Echocardiographic analyses revealed that SM22-SOCS3-KO mice showed significantly increased left ventricular diastolic dysfunction compared with WT from 12 months of age. Sirius-red staining revealed that thickness of pericardium and cardiac interstitial fibrosis in SM22-SOCS3-KO mice were markedly greater compared with WT mice at 12 months of age. Western blot analyses showed that phosphorylated STAT3 was significantly increased in SM22-SOCS3-KO hearts compared with WT mice at 12 months of age. PCR array analysis revealed that the expression of pro-fibrotic ctgf , pdgf , and TGF-beta family genes including tgf-beta1 , tgf-beta2 , and tgf-beta3 , were significantly higher in SM22-SOCS3-KO hearts than those in WT at 6 months of age. We also found that circulating interleukin-6 concentration was significantly higher in SM22-SOCS3-KO mice compared with WT mice at 12 months of age. After interleukin-6 administration, in the heart tissue from SM22-SOCS3-KO mice, coimmunostaining of phosphorylated STAT3 and ER-TR7 revealed that STAT3 activation occurred in fibroblasts in the coronary arterial adventitia and pericardium. Conclusion: Thus, SM22-Cre-mediated SOCS3 deletion induces higher mortality rates, increased pericardial fibrosis, cardiac interstitial fibrosis, and increased diastolic dysfunction in aging mice, possibly through the increased activation of STAT3 in fibroblasts.