Abstract 3126: Intercellular communication in the urothelium: Evidence for a switch in gap junction regulation during differentiation

Cells have a requirement for intercellular communication in order to maintain normal tissue polarity and homeostasis. Knowledge of the signaling molecules transferred through specific gap junctions is limited; however aberrant expression of connexins, the protein subunits of gap junctions, has been linked to many disorders including neoplastic transformation of brain and colorectal tissues. A number of reports have documented changes in connexin expression associated with bladder cancer. The aims of this study were 1) to define the connexins expressed by the epithelial lining of the human urinary tract (urothelium) in situ and in vitro; 2) to determine if expressed connexins assemble into functional gap junctions and 3) the contribution of specific connexins to urothelial tissue physiology. Established culture systems for normal human urothelial (NHU) cells were used to replicate proliferative (regenerative) or differentiated cell phenotypes. RT-PCR was used to screen normal urothelial tissue and NHU cell cultures for expression of connexin genes. Immunochemical techniques were employed to determine connexin expression and localization in situ and in vitro. Dye-transfer techniques were used on cultured cells to confirm that assembled gap junctions supported functional cell-cell communication. Of the 20 human connexin genes, six were expressed in situ and by differentiated cultures, whilst two were expressed only in proliferative culture conditions. NHU cells were capable of dye transfer in both proliferative and differentiated cultures, indicating the presence of functional gap junctions. Immunofluorescence microscopy demonstrated that the switch in medium from a low (0.09mM) to near physiological (2mM) calcium concentration resulted in increased assembly of gap junctions containing connexin-43. Connexin-32 was only expressed by differentiated cultures, as shown by RT-PCR and immunochemistry, where it was localized to intercellular borders indicating a functional role. This data represents the first systematic characterization of connexin family expression in the urothelium and provides evidence that urothelial cells alter their connexin expression upon differentiation to produce specific channels. Connexin-32 has been reported to be involved in terminal differentiation of human mammary gland and future work will focus on characterizing the role of connexins in defining the differentiated urothelial phenotype. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3126. doi:10.1158/1538-7445.AM2011-3126