Cholangiocytes - Nicholas F. LaRusso

Pathobiology of Hepatic Epithelia

Current projects are related to NIH R01 24031.

Our recent data indicate that: (i) cholangiocyte cilia are mechano-, chemo- and osmo-sensors detecting changes in bile flow, composition and osmolarity; (ii) exosomes (vesicles in bile derived from cholangiocyte multivesicular bodies) interact with cilia triggering changes in cAMP that affect expression of selected  microRNAs (i.e., miR-15a); (iii) cystic cholangiocytes from the PCK rat, a model of ARPKD, have increased cAMP, decreased miR-15a,  overexpressed Cdc25A (a cell cycle protein whose mRNA is a target for miR-15a), and increased Hedgehog (Hh) components [ Patched (Ptc), Smoothened (Smo) and Gli-2] ; and (iv) pharmacologic reduction of cAMP and experimental upregulation of miR-15a with associated decrease of Cdc25A inhibits cell proliferation and cyst growth in vitro, and in PCK rats, octreotide reduces cholangiocyte cAMP and inhibits hepatic cystogenesis. Thus, we test the CENTRAL HYPOTHESIS that normal sensory/transducing activities of cholangiocyte cilia are disrupted in cystic liver disease leading to altered intracellular signaling and modified miRNA expression resulting in cholangiocyte hyperproliferation, ductal dysmorphogenesis, and hepatic cyst formation. Our three SPECIFIC AIMS test the hypotheses that:  (i) biliary exosomes bind to cholangiocyte cilia with involvement of polycystin 1 (mutated in ADPKD) and/or fibrocystin (mutated in ARPKD) affecting intracellular signaling (cAMP, Hh) and miRNA expression (miR-15a); (ii) in cystic cholangiocytes, elevated cAMP reduces expression of miR-15a via transcriptional activation of the CREB/ICER/CRE pathway causing miR-15a target proteins (Cdc25a, Ptc, Erk1) to increase leading to cholangiocyte hyperproliferation; and (iii) pharmacologic targeting of MEK, Smo and Cdc25a, components of the cAMP, Hh, and cell cycle machinery, respectively, inhibits cholangiocyte hyperproliferation in vitro and reduces hepatic cystogenesis in vivo in rodent models of ARPKD and ADPKD.