Preferential expression of connexin37 and connexin40 in the endothelium of the portal veins during mouse liver development

Hepatic blood vessels consist of the hepatic artery and three types of venous channels (the portal veins, the sinusoids, and the hepatic veins). This study was undertaken to analyze, by immunohistochemistry, connexin expression throughout the vascular development of the fetal mouse liver with special attention being given to portal vein development. In the adult liver, connexin37 and connexin40 were expressed in the endothelium of the portal vein and hepatic artery, but not in those of the hepatic vein and sinusoids. Connexin43 was expressed in mesothelial cells and smooth muscle cells of the portal veins. The preferential expression of connexin37 and connexin40 in portal veins was seen throughout liver development, including its primordium formation stage (10.5-day or 11.5-day stage), although connexin37 expression was transiently seen in free nonparenchymal cells in fetal stages. The differentiation of each blood vessel in the hepatic vascular system may occur in early developmental stages, soon after hepatic primordium formation.