Regulation of BMP8A expression during hepatic fibrogenesis process

Abstract

Introduction: Hepatocellular injury is the main triggering event of wound healing response that leads to liver fibrosis. Hepatic stellate cell (HSC) activation is crucial in the progression of fibrogenic process since they represent the major source of extracellular matrix components and contribute to the inflammatory response by secreting proinflammatory cytokines. Bone morphogenetic proteins (BMPs) are soluble growth factors which exert pleiotropic effects in various tissues regulating different physiological processes of cellular homeostasis. Regarding BMP8A, its implication in liver damage has been poorly investigated. Therefore, the aim of this study was to determine BMP8A expression in different fibrosis-mediated liver damage scenarios. Materials and methods: Histological study of livers was performed and hepatic BMP8A expression levels were determined by RT-qPCR in different experimental models of hepatic fibrosis: carbon tetrachloride injected mice, as a classic hepatic fibrosis model, mice subjected to bile duct ligation, as a model of cholestatic damage-derived hepatic fibrosis, and high fat diet fed mice, reproducing the progression of non-alcoholic fatty liver disease (NAFLD) which curses with variable states of concomitant fibrosis in advanced stages. Likewise, the same analysis was conducted in livers from 11 patients with biopsy proven NAFLD-derived fibrosis and 25 NAFLD patients without fibrosis. To reproduce the experimental conditions of the murine models, BMP8A levels were determined in hepatocytes stimulated with conditioned media derived from TGFbeta-stimulated hepatic stellate cells (LX2). Results: Firstly, murine models were validated through a histological examination of the liver and a molecular analysis of fibrotic specific markers. Next, hepatic BMP8A mRNA expression was significant increased in all studied models of hepatic fibrosis comparing with the respective controls. In fact, there is a positive correlation between hepatic BMP8A levels and fibrosis stage as well as with markers of fibrosis. Accordingly, the clinical study revealed an elevated BMP8A expression in fibrotic livers, in comparison with those without any fibrotic sign. Furthermore, in vitro experiments also showed an increased BMP8A expression in Huh7 cells treated with conditioned media derived from TGFbeta-activated LX2 cells. Conclusions: This study reveals for the first time an increased BMP8A hepatic expression in the context of hepatic fibrosis. Its detection in serum might be useful as a non-invasive tool for the diagnosis/prognosis of patients affected by this liver disease. Moreover, these results suggest that BMP8A is involved in hepatic fibrosis progression, being possibly relevant in its therapeutic manage.