Cholangiocyte Cilia and Basal Bodies

Primary cilia are nonmotile, tubular organelles extending from the cell plasma membrane. They are important in maintaining normal cell physiology and in many clinical disorders (i.e., cilia-related diseases or ciliopathies) associated with abnormalities in ciliary structure and/or function. In the intrahepatic bile ducts, primary cilia extend from the cholangiocyte apical plasma membrane into the ductal lumen. Cholangiocyte cilia are sensory organelles that recognize the current state of bile, i.e., its flow, chemical composition, and osmolality, and transmit the related information into intracellular signaling, i.e., function as mechano-, chemo-, and osmosensors. In contrast, in ciliopathies, the structural and/or functional abnormalities of these organelles in cholangiocytes lining liver cysts are associated with activation or down-regulation of several intracellular signaling pathways, in particular, cAMP and [Ca2+]i, leading to hepatic cystogenesis.