Gap junctions and connexin expression in human suburothelial interstitial cells

Abstract

Objective To determine whether suburothelial interstitial cells of the human bladder express gap junctions, and if so, to establish their extent and composition, using immunocytochemistry, confocal microscopy and electron microscopy. Materials and methods Bladder tissue was obtained at cystectomy; the tissue was: (i) frozen for cryosectioning and Northern blot analysis; (ii) fixed and embedded for standard thin‐section electron microscopy; and (iii) processed using low‐denaturation conditions in Lowicryl for immunogold‐label electron microscopy. Cryosections were immunofluorescently labelled using antibodies against connexins 43, 40 and 45, vimentin, desmin and c‐Kit ligand, and examined by confocal microscopy. Double labelling was used to determine the spatial relationship of labelling for connexin43 with that of vimentin and desmin. Thin‐section electron microscopy was used to investigate interstitial cell ultrastructure and permit unequivocal identification of gap junctions, and immunogold labelling of Lowicryl sections was applied to localize connexin43. Results Immunoconfocal microscopy showed prominent labelling for the gap junction protein, connexin43, in a suburothelial band of cells that was also strongly positive for vimentin. The connexin43/vimentin‐positive cells showed only weak labelling for desmin and c‐Kit ligand, and were immunonegative for connexins 40 and 45. Northern blotting showed a corresponding abundance of connexin43 transcript in the mucosal layer but not the detrusor layer of the bladder wall. Electron microscopy revealed abundant gap junctions, recognized by their pentalaminar structure, between the cell processes of interstitial cells in the suburothelial zone. That these interstitial cell gap junctions were the source of the connexin43 immunolabelling observed by immunoconfocal microscopy was confirmed by immunogold labelling in sections of Lowicryl‐embedded tissue examined by electron microscopy. Conclusion A network of interstitial cells, extensively linked by connexin43‐containing gap junctions, is located beneath the urothelium in human bladder. As gap junctions provide pathways for direct cell‐to‐cell communication, the interstitial cellular network may operate as a functional syncytium, integrating signals and responses in the bladder wall.

Discs-large homolog 1 regulates smooth muscle orientation in the mouse ureter

“…Furthermore, the apparently smooth and regular contractions and lack of obvious twitching movements suggest that the mutant SMCs are organized and do communicate with each other to propagate a coordinated contraction. Consistent with this, expression and localization of connexin 45, a component of ureteric smooth muscle gap junctions (21,22), were comparable in wild-type and Dlgh1 Ϫ/Ϫ ureter (Fig. 5 C and D).…”

Control of Urinary Drainage and Voiding

“…Alterations to BICC function have also been reported in OAB and obstructed bladder in both humans and animal models (79,92,(94)(95)(96)(97). Increased expression of connexin 43 has been reported in patients with OAB, suggesting increased signal transduction between BICCs and BSM cells, potentially leading to motility problems (98,99). This cell is just beginning to attract attention as a possible contributor to bladder motility disorders but it is not currently known whether alterations in BICCs are primary or secondary to disease processes.…”

Expression and distribution of key enzymes of the cyclic GMP signaling in the human clitoris: relation to phosphodiesterase type 5 (PDE5)

“…In some of the cells, PDE2 was found co-localized with vimentin, a specific feature of ICs and neurons, thereby confirming earlier findings describing immunolabeling for ICs in cardiac tissue and the urogenital tract (Figure 3c). [13][14][15][16][17] Staining specific for PDE11A (dual-substrate PDE) was observed in single nerve trunks located in the clitoral stroma (Figure 1f). In contrast, no labeling indicating PDE2 or PDE5 was observed in nerve fibers or nerve endings (Table 1).…”

“…28 It has been suggested that ICs may have a pivotal role as so-called pacemakers and mediators of neurotransmission in the bladder, urethra and penile erectile tissue. [14][15][16][17]29 The role of ICs in the clitoris remains to be established. Some hypotheses have been proposed: adult mesenchymal cells, which might participate in (a) intercellular signaling or (b) chemo-mechanical transducing or act as (c) players in pace-making through direct cell-to-cell communication.…”