Isolation of functional polarized bile duct units from mouse liver

The development of genetically altered murine animals has generated a need for in vitro systems in the mouse. We have now characterized a novel isolat ed bile duct unit (IBDU) preparation from the mouse to facilitate such stud ies. The mouse IBDU is isolated by portal perfusion of collagenase, blunt d issection, further enzymatic digestions, filtering through sized mesh, and culturing on Matrigel for 16-72 h. This mouse IBDU forms a central, enclose d lumen lined by polarized cytokeratin-19-positive cholangiocytes with nume rous microvilli on the apical membrane. The IBDU responds to secretory stim uli, including secretin, vasoactive intestinal peptide, IBMX, and forskolin , resulting in expansion of the central lumen from secretion as quantified by videomicroscopy. The secretory response to secretin is dependent on Cl- and HCO3- in the perfusate. These findings indicate that mouse IBDUs are in tact, polarized, functional bile duct secretory units that permit quantitat ive measurements of fluid secretion from mouse bile duct epithelium for the first time. This method should facilitate studies of cholangiocyte secreti on in genetically altered murine animal models.