A20 Rescues Failed Liver Regeneration in db/db Mice: Renewed Hope for Successful Use of Steatotic Liver Grafts.

Abstract

Increased incidence of obesity and consequently of extensive liver steatosis is a major contributor to scarcity of adequate liver grafts for transplantation. Livers with extensive macrosteatosis are susceptible to ischemia reperfusion injury and fail to properly regenerate. The aim of this study was to determine the impact of A20, an anti-inflammatory, anti-apoptotic and pro-regenerative protein in hepatocytes, and a regulator of lipid metabolism on outcome of partial hepatectomy (PH) in leptin receptor deficient db/db mice. These obese, hyperinsulinemic mice develop macrovesicular liver steatosis, causing defective liver regeneration and heightened death following PH. Methods. We overexpressed A20 in livers of 8-10 weeks old db/db and lean mice by i/v injection of recombinant adenovirus (rAd). Saline and rAd.β-galactosidase (rAd.β-gal) treated mice were used as controls. Five days after rAd. injection, we performed 2/3 PH. Surviving mice were sacrificed 48 hours later. Resected (0h) and remnant livers (48h) were recovered for histology, immunohistochemistry and RNA extraction. Morphometry was analyzed by hematoxylin and eosin staining and proliferation by immunostaining for the cell proliferation marker, Ki67. All animal experiments met the IACUC criteria for humane care. Results: Overexpression of A20 significantly reduced early lethality in db/db mice following PH. No lethality was observed in A20 treated db/db within 48 hours of PH, as compared to 33% incidence of death in saline and rAd.β-gal control groups. The survival advantage of A20-treated db/db correlated with high hepatocyte proliferation 48h post-PH, as evidenced by Ki67 immunostaining. This was in striking contrast with almost no proliferation noted at this time in control livers, predicting even more lethality in upcoming days. All lean mice, regardless of treatment survived PH and showed a significant increase in liver Ki67 immunostaining 48h after PH. Conclusion: This is the first demonstration that overexpression of A20 restores adequate liver regeneration and alleviates lethality of this procedure in mice with severe hepatic steatosis. Additional work is currently performed to uncover the molecular basis of this advantage. Regardless of mechanisms, these data support the hope of A20-based therapies to improve success of marginal liver grafts due to steatosis.