Long-Term Persistence of Fetal Hepatocyte Gene Expression and Histone Modification Signatures Following Transplantation to Adult Liver

Introduction: Hepatic cell transplantation offers an alternative to orthotopic liver transplantation for chronic liver disease. We previously demonstrated that fetal rat hepatocytes durably persist and proliferate when transplanted to an injured adult liver. To identify mechanisms underlying fetal hepatocyte repopulation, we profiled gene expression and histone post-translational modifications (hPTM) of post-transplantation fetal colonies and surrounding liver, as well as those of primary fetal and adult hepatocytes. Methods: Using the DPPIV rat model, we transplanted and traced fetal hepatocytes into adult hosts. At 10 months after transplantation, we used laser capture microscopy to isolate fetal-derived colonies and surrounding adult host tissue. RNA and histones were extracted from laser captured tissue and isolated hepatocytes for RNA-seq and quantitation of hPTM. Results: Principal component analysis of RNA-seq results discriminated between fetal-derived colonies and surrounding adult host tissue. We identified 953 differentially expressed genes, many of which were significantly overexpressed in pre-transplant fetal hepatocytes relative to adult hepatocytes. This gene set included a disproportionate number of genes encoding ion transmembrane transporters. Proteomic analyses identified 13 distinct marks on Histone H3 whose relative abundance differed significantly between fetal-derived colonies and adult host tissue. Of these 13 marks, 11 had abundance profiles similar to those of fetal hepatocytes. Conclusions: A distinct gene expression and epigenetic profile seen in pre-transplant fetal cells is retained for at least 10 months following transplantation. Ontological and pathway analysis indicates activation of ion transporters, which may relate to the growth advantage of transplanted fetal cells. Comparative gene expression profiling analysis of RNA-seq data for pre-transplant sorted fetal and adult hepatocytes, as well as post-transplant fetal-derived colony tissue and surrounding adult host tissue.