2 The cells can be clonogenically expanded ex vivo in a serum-free medium tailored for endodermal progenitors [Kubota's medium (KM)]9 and have the potential to differentiate

into mature functional hepatocytes and cholangiocytes in vivo. The microenvironment of stem cell niches modulates stem cell proliferation, influences symmetric division versus asymmetric division, controls differentiation, protects cells from physiological stresses, and helps them to contribute to tissue formation in development and in regeneration in adult life.7 The components of the stem cell microenvironment regulating these processes include distinct cell-cell interactions and paracrine signals, which comprise both soluble and extracellular Small molecule library matrix factors, as well as the three-dimensional Everolimus solubility dmso (3D) architecture, which shapes and dictates the delivery of these cues. The studies reported here are focused on mesenchymal companion cells and their provision of critical paracrine signals regulating the parenchymal lineage stages. Paracrine signals were identified with purified subpopulations of mesenchymal cells cultured under serum-free conditions. A set of these signals was then used to regulate precisely the growth and/or fates of hHpSCs under feeder-free conditions. In a separate report, we are focusing on studies of lineage-dependent

soluble signals (J. Uronis and L. Reid, unpublished data, 2010). 3D, three-dimensional; AFP, α-fetoprotein; ALB, albumin; ASMA, α-smooth muscle actin; BC, bile canaliculus; C1A1, ADAMTS5 collagen 1A1; C3A1, collagen

3A1, C4A5, collagen 4A5; C5A2, collagen 5A2; CK, cytokeratin; CS-PG, chondroitin sulfate proteoglycan; DAPI, 4′,6-diamidino-2-phenylindole; ELS, elastin; EpCAM, epithelial cell adhesion molecule; ER, endoplasmic reticulum; FN, fibronectin; GFAP, glial fibrillar acidic protein; GAG, glycosaminoglycan; GPYC, glypican; HA, hyaluronan; HDM, hormonally defined medium; hHB, human hepatoblast; hHpSC, human hepatic stem cell; hHpSTC, human hepatic stellate cell; hMSC, human mesenchymal stem cell; HP-PG, heparin proteoglycan; HS-PG, heparan sulfate proteoglycan; HUVEC, human umbilical cord vein endothelial cell; ICAM, intercellular cell adhesion molecule; ICG, indocyanine green; IF, intermediate filament; KDR, kinase insert domain receptor; KM, Kubota’s medium; LA4, laminin A4; LB2, laminin B2; LB3, laminin B3; MCM, mesenchymal cell medium; MKM, modified Kubota’s medium; MKM-C, modified Kubota’s medium for cholangiocytes; MKM-H, modified Kubota’s medium for hepatocytes; mRNA, messenger RNA; NCAM, neural cell adhesion molecule; NPC, nonparenchymal cell; qRT-PCR, quantitative reverse transcription polymerase chain reaction; SDC2, syndecan 2; SR, secretin receptor; TEM, transmission electron microscopy; VEGF, vascular endothelial growth factor; vWF, von Willebrand factor.