Liver Wound Healing Is Associated with An Increase in Mfge8 Expression in Hepatocytes

Abstract

Being recognized as a typical pathological feature of liver diseases, apoptosis-induced hepatocyte injury leading to sterile inflammation drives a wound-healing path in vivo. We and other researchers reported that Milk fat globule-EGF factor 8 (MFGE8) preserves tissue homeostasis, protects against tissue injury and inflammation, and attenuates nonalcoholic fatty liver disease and fibrosis. However, it is unclear whether and how MFGE8 is involved in liver regeneration from hepatocyte-apoptosis-induced injury. Our aim is to study current knowledge to this extent, we created a novel triple-transgenic mouse model, an inducible hepatocyte-specific apoptosis phenotype (namely, 3XTg-iHAP), in which the inducible hepatocyte-specific FasL expression is under control of the combined LoxP-Albumin-Cre system and rtTA Tet-On regulatory element. The liver tissues from 3XTg-iHAP and their littermates were collected at 8 h, 24 h, 48 h, 72 h, and 5 D after doxycycline (Dox, 5mg/kg, s.c., single dose) treatment and subjected to histological examination, RNAScope in situ hybridization (ISH) and qRT-PCR analysis. We first confirmed that the 3XTg-iHAP mice developed normal, viable, and fertile. Upon Dox treatment, qRT-PCR confirmed FasL expression was specifically induced in the liver tissues of 3XTg-iHAP mice (male, 7 weeks) but not in their littermates. H&E sections show the induction of hepatocyte apoptosis as early as 24 h followed by apoptosis-induced sterile inflammation and injury, hepatocyte mitosis, and regeneration in the liver parenchyma of 3XTg-iHAP mice. In the ISH assay, we found that (1) In littermate control mice, Mfge8 transcripts were localized in the intrahepatic bile duct epithelial cells (i.e., cholangiocytes) within the portal area. (2) In Dox-treated 3XTg-iHAP mice, we observed a profound increase of Mfge8 gene expression in parenchymal hepatocytes of the liver featured with apoptosis-associated sterile injury. In summary, we validated a novel 3XTg-iHAP mouse liver wound-healing model. The Mfge8 gene is constitutively expressed in the bile duct epithelial cells under the normal physiological condition, while upregulated in hepatocytes in response to the apoptosis-induced injury and repair. Our results suggest that liver wound healing is associated with an increase in Mfge8 expression in hepatocytes. The underlying mechanisms of whether and how MFG-E8 promotes the liver wound healing process need to be further studied. Grants are supported by NIH and the U.S. Department of Veterans Affairs. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.