Rat-derived amniotic epithelial cells differentiate into mature hepatocytes in vivo with no evidence of cell fusion

Amniotic epithelial cells (AEC) derived from human placenta represent a useful and noncontroversial source for liver-based regenerative medicine. Previous studies suggested that human-and rat-derived AEC differentiate into hepatocyte-like cells upon transplantation. In the retrorsine (RS) model of liver repopulation, clusters of donor-derived cells engrafted in the recipient liver and, importantly, showed characteristics of mature hepatocytes. The aim of the current study was to investigate the possible involvement of cell fusion in the emergence of hepatocyte clusters displaying a donor-specific phenotype. To this end, 4-week-old GFP+/DPP-IV- rats were treated with RS and then transplanted with undifferentiated AEC isolated from the placenta of DPP-IV+ pregnant rats at 16-19 days of gestational age. Results indicated that clusters of donor-derived cells were dipeptidyl peptidase type IV (DPP-IV) positive, but did not express the green fluorescent protein (GFP), suggesting that rat amniotic epithelial cells (rAEC) did not fuse within the host parenchyma, as no colocalization of the two tags was observed. Moreover, rAEC-derived clusters expressed markers of mature hepatocytes (eg, albumin, cytochrome P450), but were negative for the expression of biliary/progenitor markers (eg, epithelial cell adhesion molecule [EpCAM]) and did not express the marker of preneoplastic hepatic nodules glutathione S-transferase P (GST-P). These results extend our previous findings on the potential of AEC to differentiate into mature hepatocytes and suggest that this process can occur in the absence of cell fusion with host-derived cells. These studies support the hypothesis that amnion-derived epithelial cells can be an effective cell source for the correction of liver disease.