cholangiocyte

Cholangiocytes are specialized epithelial cells that line the biliary tree of the liver, extending from the canals of Hering to the intrahepatic and extrahepatic bile ducts. They form a continuous monolayer around the bile ducts and play an active role in modifying bile as it flows toward the duodenum.

Morphologically, cholangiocytes vary along the ductal tree. Smaller intrahepatic ducts are lined by cuboidal cells, while larger ducts have tall columnar cells. The apical surface may bear cilia in larger ducts and microvilli in others, and the cells are connected by tight and adherens junctions that regulate paracellular transport.

Functionally, cholangiocytes actively modify bile by secreting bicarbonate and water, contributing to a protective, alkaline milieu known as the bicarbonate umbrella. This secretion is regulated by hormones and neurotransmitters; secretin stimulates bicarbonate-rich bile via cAMP and CFTR chloride channels, with contributing transporters such as the anion exchanger AE2. Other mediators, including acetylcholine and vasoactive intestinal peptide, influence cholangiocyte activity. Water transport occurs through aquaporins as bile proceeds through the ducts.

Developmentally, cholangiocytes arise from hepatic progenitor cells in the canals of Hering during liver organogenesis and can proliferate in response to injury, giving rise to ductular reactions that participate in regeneration.

Clinical relevance includes involvement in cholangiopathies. Diseases such as primary sclerosing cholangitis, biliary atresia, and cholangiocarcinoma originate from or involve cholangiocytes, highlighting their essential role in biliary physiology and pathology.