Osteopontin is a proximal effector of leptin-mediated non-alcoholic steatohepatitis (NASH) fibrosis

Abstract

Introduction Liver fibrosis develops when hepatic stellate cells (HSC) are activated into collagen-producing myofibroblasts. In non-alcoholic steatohepatitis (NASH), the adipokine leptin is upregulated, and promotes liver fibrosis by directly activating HSC via the hedgehog pathway. We reported that hedgehog-regulated osteopontin (OPN) plays a key role in promoting liver fibrosis. Herein, we evaluated if OPN mediates leptin-profibrogenic effects in NASH. Methods Leptin-deficient (ob/ob) and wild-type (WT) mice were fed control or methionine-choline deficient (MCD) diet. Liver tissues were assessed by Sirius-red, OPN and αSMA IHC, and qRT-PCR for fibrogenic genes. In vitro, HSC with stable OPN (or control) knockdown were treated with recombinant (r)leptin and OPN-neutralizing or sham-aptamers. HSC response to OPN loss was assessed by wound healing assay. OPN-aptamers were also added to precision-cut liver slices (PCLS), and administered to MCD-fed WT (leptin-intact) mice to determine if OPN neutralization abrogated fibrogenesis. Results MCD-fed WT mice developed NASH-fibrosis, upregulated OPN, and accumulated αSMA+ cells. Conversely, MCD-fed ob/ob mice developed less fibrosis and accumulated fewer αSMA+ and OPN+ cells. In vitro, leptin-treated HSC upregulated OPN, αSMA, collagen 1α1 and TGFβ mRNA by nearly 3-fold, but this effect was blunted by OPN loss. Inhibition of PI3K and transduction of dominant negative-Akt abrogated leptin-mediated OPN induction, while constitutive active-Akt upregulated OPN. Finally, OPN neutralization reduced leptin-mediated fibrogenesis in both PCLS and MCD-fed mice. Conclusion OPN overexpression in NASH enhances leptin-mediated fibrogenesis via PI3K/Akt. OPN neutralization significantly reduces NASH fibrosis, reinforcing the potential utility of targeting OPN in the treatment of patients with advanced NASH.

Epigallocatechin-3-Gallate Upregulates miR-221 to Inhibit Osteopontin-Dependent Hepatic Fibrosis

“…Multiple studies have shown that OPN is involved in hepatic fibrosis and that neutralization of OPN is effective in abrogating fibrosis [4,5, 12–15]. Our previous work demonstrated that EGCG can decrease OPN expression through OPN mRNA degradation.…”

“…Hepatic fibrosis develops when chronic liver injury activates progenitor cells to repair tissue, but these multipotent cells often become dysfunctional with sustained injury and induce fibrogenic repair and excess cell growth [4, 5]. The hallmark of liver fibrosis is the accumulation of extracellular matrix proteins.…”

“…This alters the hepatic cytoarchitecture, leading to an obstruction of function [1]. Multiple growth factors and cytokines are associated with driving progenitor cell activation and subsequent hepatic fibrosis [1, 4, 5]. Osteopontin (OPN), a secreted phosphoprotein, is one such cell signaling molecules associated with cell injury and fibrosis [4–7].…”

“…Multiple growth factors and cytokines are associated with driving progenitor cell activation and subsequent hepatic fibrosis [1, 4, 5]. Osteopontin (OPN), a secreted phosphoprotein, is one such cell signaling molecules associated with cell injury and fibrosis [4–7]. Studies have shown that measuring OPN in the plasma of liver disease patients is an effective biomarker for assessing the severity of liver fibrosis [8–11].…”

“…Furthermore, it has been demonstrated that hepatocytes act as a major source of OPN, and act in a paracrine role in activating HSCs and increasing collagen-I production [12]. Multiples studies have found that neutralizing OPN abrogates the development of fibrosis [4, 5, 12–15]. In a murine model of thioacetamide (TAA)-induced hepatic fibrosis, OPN-knockout mice demonstrated less hepatic damage and a faster resolution of fibrosis [15].…”