Loss of Integrin αvβ8 in Murine Hepatocytes Accelerates Liver Regeneration

Stephen N Greenhalgh,Kylie P Matchett,Richard S Taylor,Katherine Huang,John T Li,Koy Saeteurn,Mhairi C Donnelly,Eilidh E.M Simpson,Joshua L Pollack,Amha Atakilit,Kenneth J Simpson,Jacquelyn J Maher,John P Iredale,Dean Sheppard,Neil C Henderson

doi:10.1016/j.ajpath.2018.10.007

Stephen N Greenhalgh, Kylie P Matchett + Show 13 more

Open Access

https://doi.org/10.1016/j.ajpath.2018.10.007

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Abstract

Recent fate-mapping studies in mice have provided substantial evidence that mature adult hepatocytes are a major source of new hepatocytes after liver injury. In other systems, integrin αvβ8 has a major role in activating transforming growth factor (TGF)-β, a potent inhibitor of hepatocyte proliferation. We hypothesized that depletion of hepatocyte integrin αvβ8 would increase hepatocyte proliferation and accelerate liver regeneration after injury. Using Itgb8flox/flox;Alb-Cre mice to deplete hepatocyte αvβ8, after partial hepatectomy, hepatocyte proliferation and liver-to-body weight ratio were significantly increased in Itgb8flox/flox;Alb-Cre mice compared with control mice. Antibody-mediated blockade of hepatocyte αvβ8 in vitro, with assessment of TGF-β signaling pathways by real-time quantitative PCR array, supported the hypothesis that integrin αvβ8 inhibition alters hepatocyte TGF-β signaling toward a pro-regenerative phenotype. A diethylnitrosamine-induced model of hepatocellular carcinoma, used to examine the possibility that this pro-proliferative phenotype might be oncogenic, revealed no difference in either tumor number or size between Itgb8flox/flox;Alb-Cre and control mice. Immunohistochemistry for integrin αvβ8 in healthy and injured human liver demonstrated that human hepatocytes express integrin αvβ8. Depletion of hepatocyte integrin αvβ8 results in increased hepatocyte proliferation and accelerated liver regeneration after partial hepatectomy in mice. These data demonstrate that targeting integrin αvβ8 may represent a promising therapeutic strategy to drive liver regeneration in patients with a broad range of liver diseases.

Highlights

Primary hepatocytes were isolated from Itgb8flox/flox;Alb-Cre mice and Cre-negative littermate controls. quantitative PCR (qPCR) for Itgb[8] confirmed expression in control hepatocytes and successful depletion in hepatocytes isolated from Itgb8flox/flox;Alb-Cre mice (Figure 1A)
Assessment of hepatocyte proliferation after two-thirds partial hepatectomy showed significantly increased proliferation in Itgb8flox/flox;Alb-Cre mice at 36, 48, and 72 hours after liver injury compared with control mice (Figure 1, B and C)
This increased hepatocyte proliferation was not followed by an increase in hepatocyte apoptosis at day 5 after partial hepatectomy, when liver regeneration was nearing completion in the Itgb8flox/flox;Alb-Cre mouse (Supplemental Figure S1)

Summary

Introduction

Depletion of hepatocyte integrin avb[8] results in increased hepatocyte proliferation and accelerated liver regeneration after partial hepatectomy in mice. These data demonstrate that targeting integrin avb[8] may represent a promising therapeutic strategy to drive liver regeneration in patients with a broad range of liver diseases. Recent fate-mapping studies in mice have provided strong evidence that, in most murine models of liver injury and regeneration, restoration of liver mass occurs predominantly through selfduplication of hepatocytes.[1,2] identifying targets that promote proliferation and expansion of the preexistent hepatocyte population represents an attractive therapeutic approach to drive liver regeneration.

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