Immunomagnetic exclusion of PECAM-1-positive endothelial cells in fetal mouse liver cell cultures causes impaired growth and gene expression of hepatoblasts and stellate cells

Abstract

Previous studies using mice having defective VEGF signaling have demonstrated that vascular development is indispensable for early hepatic organogenesis. However, not only whether its action lasts during later hepatic development, but also what molecules are involved in that action remains to be determined. The present study was undertaken to examine the effects of primitive sinusoidal endothelial cells on hepatic growth and maturation in primary culture of fetal mouse liver cells, and to determine their molecular mechanisms. When endothelial cells were excluded from E12.5 liver cell cultures by using PECAM-1-antibody-coated magnetic beads, the growth of hepatoblasts and stellate cells was conspicuously reduced and hepatic maturation was also suppressed. Conditioned medium prepared from fetal liver cell cultures containing almost all hepatic cell types stimulated the growth and gene expression of hepatoblasts and stellate cells similarly to the cultures in the presence of endothelial cells. HGF mRNA expression was downregulated in endothelial cellfree cultures of fetal liver cells, and the addition of HGF to the culture medium rescued the cells from the effects of endothelial cell depletion. These data suggest that humoral factors, including HGF, which are produced by endothelial cells or stellate cells, are involved in fetal hepatocyte growth and maturation.