Morphological changes in HepG2 cells cocultured with mouse embryonic hepatocytes. (A) Mouse primary embryonic hepatocytes were identified by detecting albumin. (B) After coculturing with mouse embryonic hepatocytes at 12.5-, 13.5-, 14.5- and 15.5-d gestation, HepG2 cells were observed. No proliferation was observed, and most HepG2 cells became round and shrunken in shape and detached and drifted in the 13.5-d and 14.5-d groups. Moreover, only a few cells were observed, and they appeared mononuclear and hexagonal, similar to hepatocytes. However, in 12.5-d and 15.5-d groups, apparent proliferation was observed with no obvious morphological changes. Scale bar = 20 μm.