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Long‐Term Persistence of Fetal Hepatocyte Gene Signature Following Transplantation to Adult Liver

Hepatic cell transplantation (HCT) offers a potential treatment for end‐stage liver disease which mitigates the issues of organ supply for whole‐liver orthotopic transplantation, but HCT is limited by the short duration of efficacy of transplanted adult cells. Fetal hepatocytes have shown durable long‐term posttransplant potency in clinical trials, but ethical concerns hinder their routine procurement. By comparing the transcriptome of posttransplant fetal colonies to pretransplant fetal cells, and contrasting them with adult hepatocytes, we hope to characterize the gene expression differences between fetal and adult hepatocytes that are retained in fetal cells following HCT. We aim to identify mechanisms among these responsible for the durable fetal proliferative phenotype, and potentially elucidate new strategies to improve HCT for clinical use. Methods: Using the Dipeptidyl Peptidase IV rat model, we performed Laser Capture Microdissection (LCM) on sections of liver 10 months after fetal HCT. We collected paired fetal‐ and adult‐origin hepatocytes from multiple biological replicates. Isolated total RNA from these samples were submitted for RNA‐Seq by GENEWIZ. To investigate pretransplant cells, adult and fetal hepatocytes were prepared from digested whole liver. Fetal hepatocytes were immunopurified by using the hepatic marker LAP, as well the putative bipotential marker OC.2. Isolated RNA was run on Affymetrix microarrays. The results from these studies were analyzed together in R. Results: Our posttransplant RNA‐Seq results when analyzed by 3D PCA showed a distinct clustering effect by tissue type. We observed over 700 significantly (FDR<0.05) differentially expressed genes between the fetal colonies and surrounding adult host hepatocytes. Gene Ontology (GO) analysis of these sets shows that the genes expressed in fetal colonies play a role in membrane transport processes, while those expressed in adult host correspond to lipid metabolism activity. We demonstrate here that the fetal hepatocyte transcriptome is partially maintained 10 months posttransplant. This likely reflects the durably‐retained differences in regulatory histone post‐translational modifications (hPTMs) we have previously identified in this same population. Future studies will explore the regulatory mechanisms linked to critical growth‐regulating genes.