This result effectively
ruled out the possibility that LDPCs could have originated from the initial nonhepatocyte cell population in culture. Next, we wanted to substantiate our PKH staining results by documenting the phenotypic changes taking place during the transformation of hepatocytes into LDPCs. To that end, we performed RT-PCR and IF analyses of hepatocyte- and LDPC-specific markers at predetermined time points during the culture period. On days 0, 4, 8, and 12, cultures were examined for expression of albumin, HNF-1α (hepatocyte specific), selleckchem CD45, and LMO2 (LDPC specific). RT-PCR studies showed that in the beginning, cells expressed albumin and HNF-1α and no identifiable CD45 and LMO2. By day 4, there was a rapid decline
in hepatocyte-specific markers, and LDPC-specific markers became detectable at low levels. Subsequently, on days 8 and 12, hepatocyte markers became undetectable, and LDPC markers were expressed ZD1839 manufacturer at increasingly higher levels (Fig. 3A). IF studies revealed a similar pattern of marker expression, further confirming our RT-PCR data (Fig. 3B). In addition to these four markers, we examined the expression pattern of several other highly relevant hepatic genes during the culture period to better characterize the transformation process. We looked at the expression of mature hepatocyte markers HepPar1 and HNF-4α, immature hepatocyte marker Liv2,24 biliary ductal/oval cell
marker CK19, and liver progenitor/embryonic liver marker Sall425 in a time-dependent manner. IF staining and quantitative analysis of the images revealed a pattern (Supporting Fig. 2A,B), which was consistent with rapid transformation of mature hepatocytes into cells with liver progenitor phenotype, thus supporting our findings shown in Fig. 3. Both the RT-PCR and IF studies correlated well with the morphological changes that took place in the cultures, including temporal appearance of LDPCs. Taken together, the rat studies Carnitine palmitoyltransferase II strongly suggested that LDPCs originated from mature hepatocytes by direct dedifferentiation. To gain further insight into the process of dedifferentiation of hepatocytes to LDPCs and to establish a stem/progenitor cell hierarchy, we examined the expression of several oval cell markers during the culture period. We considered the possibility that hepatocytes could be transitioning through an oval cell-like stage en route to becoming LDPCs. This was based on the phenotypic similarities between oval cells and LDPCs, suggesting a potential lineage relationship. Therefore, we studied the expression of OV-6, CK7, and GGT during the dedifferentiation of hepatocytes into LDPCs.