A micellized bone morphogenetic protein-7 prodrug ameliorates liver fibrosis by suppressing transforming growth factor- β signaling

Abstract

Bone morphogenetic protein-7 (BMP-7) antagonizes transforming growth factor-β (TGF-β), which is critically involved in liver fibrogenesis. Here, we designed a micelle formulation consisting of a protein transduction domain (PTD) fused BMP-7 polypeptide (mPTD-BMP-7) to enhance endocytic delivery, and investigated its ability to ameliorate liver fibrosis. The mPTD-BMP-7 formulation was efficiently delivered into cells via endocytosis, where it inhibited TGF-β mediated epithelial-mesenchymal transition. After successfully demonstrating delivery of fluorescently labeled mPTD-BMP-7 into the murine liver in vivo, we tested the mPTD-BMP-7 formulation in a murine liver fibrosis model, developed by repeated intraperitoneal injection of hepatotoxic carbon tetrachloride, twice weekly from 4 to 16 weeks. mPTD-BMP-7 effects were tested by injecting the mPTD-BMP-7 formulation (or vehicle control) into the lateral tail at a dose of 50 (n=8) or 500 μg/kg (n=10), also twice per week from 4 to 16 weeks. Vehicle-treated control mice developed fibrous septa surrounding the liver parenchyma and marked portal-to-portal bridging with occasional nodules, whereas mice treated with mPTD-BMP-7 showed only fibrous expansion of some portal areas, with or without short fibrous septa. Using the Ishak scoring system, we found that the fibrotic burden was significantly lower in mPTD-BMP-7 treated mice than in control mice (all P<0.001). Treatment with mPTD-BMP-7 protected tight junctions between hepatocytes and reduced extracellular matrix protein levels. It also significantly decreased mRNA levels of collagen 1A, smooth muscle α-actin, and connective tissue growth factor compared with that in control mice (all P<0.001). Collectively, out results indicate that mPTD-BMP-7, a prodrug formulation of BMP-7, ameliorates liver fibrosis by suppressing the TGF-β signaling pathway in a murine liver fibrosis model.