Role Of Gut Microbiota In Liver Regeneration: Analysis Of Hepatic Structural Changes And Extracellular Matrix Component After Partial Hepatectomy In Mice

Abstract

Gut microbiota is involved in liver regeneration. Absence of gut microbiota in sterile, germ-free (GF) mice and in antibiotic-treated mice causes reduced liver regeneration. The involvement of gut microbiota in liver regeneration with regards to structural changes and extracellular matrix (ECM) expression has not been elucidated. Furthermore, evaluation of liver regeneration in GF mice that have been reintroduced with normal gut microbiota (ex-germ-free/XGF mice) has not been done. We aim to investigate the role of gut microbiota in liver regeneration by utilising models of GF and XGF mice. The use of XGF mice in liver regeneration study has not been previously utilised and is therefore novel to our study. Structural remodelling which includes structural changes and matrisome gene expression was observed following partial hepatectomy (PHx) in GF, XGF, and wild-type (WT) mice. At 72-hr post PHx, GF mice demonstrated reduced liver mass, hepatocyte proliferation, and cytokine and growth factor responses compared to WT mice, indicating reduced liver regeneration. Structural changes in the form of hepatocyte hypertrophy, hepatocyte clusters, loss of normal radiating pattern of the hepatic cords, mitotic figures, and cytoplasmic vacuoles, were more prominent in GF mice compared to WT mice. This, in addition to lower expression of matrisome and collagen genes indicate delayed hepatic remodelling in GF mice. Ex-germ-free mice demonstrated normal liver mass, hepatocyte proliferation, and improved cytokine and growth factor responses at 72-hr post PHx, indicating improved liver regeneration. Ex-germ-free mice also demonstrated improved structural changes and higher matrisome and collagen gene expression compared to GF mice, indicating improved hepatic remodelling. Commonly expressed ECM regulators were ADAMTS, MMP, TIMP, and Serpin, and LOX proteins at 3- and 72-hr post PHx respectively. Certain differences in liver regeneration of XGF and WT mice persists, which may be due to the differences in gut microbiota composition between the groups, in addition to ongoing inflammatory changes of the XGF liver in response to reconstitution procedure. In conclusion, the study further confirmed the role of gut microbiota in liver regeneration by demonstrating reduced liver regeneration in GF mice, and improved liver regeneration in sterile mice reintroduced with normal gut microbiota. Gut microbiota may also be essential for structural remodelling and ECM expression during liver regeneration. Also giving insight to the importance of the matrisome in liver regeneration and demonstrating changes in matrisome expression throughout the regenerative process may indicate the possible direct involvement of the matrisome proteins in regulating liver regeneration.