7 Similarly, small amounts selleck products of albumin are synthesized and are not packaged as in later lineage stages, implicating lineage-dependent

distinctions in posttranscriptional and translational protein processing. The hHpSCs are isolated by dual immunoselection for EpCAM+/NCAM+ cells from livers of all donor ages. In adult livers, which have scarce hepatoblast populations, EpCAM+ selection alone results in isolation of predominantly hHpSCs.7, 16 In culture, the hHpSCs form colonies capable of self-replication17 and of differentiation to mature cells in culture and in vivo.7, 18 Cells expand ex vivo if cultured in Kubota’s medium, a serum-free medium containing only insulin, transferrin/fe,

lipids, no copper, and low calcium19, 20 and if cocultured with angioblasts. These feeders are replaceable with purified type III collagen substrates, embedding into weakly crosslinked hyaluronan hydrogels, or a mixture of both.13, 21 If transplanted in vivo, they yield mature liver tissue. If cultured under distinct conditions (see below) they lineage-restrict into hepatoblasts.13 Hepatoblasts (hHBs) are diploid bipotent cells giving rise to hepatocytic and cholangiocytic lineages, associated with precursors of both endothelia and hepatic stellate cells, and the liver’s probable transit amplifying cells.13 They reside throughout parenchyma of fetal and neonatal FK228 livers or as single cells and small cell aggregates tethered to the ends of canals of Hering in adult livers.8 With donor age, hHBs decline to <0.01% of the parenchymal cells in postnatal livers.7, 8 They expand during regenerative processes associated with certain diseases such as cirrhosis. Previously, hHBs were referred to as “intermediate hepatobiliary cells of the ductular reactions”22; extensive characterization enabled us to refer to them, as hepatoblasts.8

They can be isolated by dual immunoselection for EpCAM+/ICAM-1+. They have enormous expansion potential cultured in Kubota’s medium, especially if supplemented with epidermal growth factor (EGF) and hepatocyte growth factor (HGF), or on feeders of stellate cell precursors Acyl CoA dehydrogenase replaceable by substrata of type IV collagen, laminin, hyaluronans, or mixtures of these expansion is without proven self-replication.13, 23, 24 The hHBs, larger (10-12 μm) and with higher amounts of cytoplasm than hHpSCs, have an antigenic profile that overlaps with hHpSCs.6, 7, 15 Shared phenotypic traits include CXCR4, CD133, SOX17, MDR1, cytokeratins (CK) 8/18 and 19, Hedgehog proteins (Sonic and Indian), and null expression of late P450s (e.g., P450-3A) or markers for hemopoietic, endothelia, or mesenchymal cells (as for hHpSCs).