cGMP‐generating cells in the bladder wall: identification of distinct networks of interstitial cells

Abstract

OBJECTIVE To identify cells which might contribute to the complex physiological responses of the guinea‐pig bladder, and specifically to describe the distribution and types of cell in the bladder wall of the guinea pig which respond to nitric oxide (NO) with an increase in intracellular cGMP, i.e. putative interstitial cells (ICs). MATERIALS AND METHODS The whole bladder was removed from 11 male guinea pigs killed by cervical dislocation. Sections of the bladder wall, from the dome lateral wall and base, were isolated and incubated separately in Krebs’ solution at 36 °C, gassed with 95% O2 and 5% CO2, and containing 1 mmol/L of the nonspecific phosphodiesterase inhibitor isobutyl‐methyl‐xanthene. Individual pieces of tissue were then exposed to 100 µmol/L of the NO donor NONOate for 10 min; control tissues remained in Krebs’ solution. Tissues were then fixed in 4% paraformaldehyde and processed for immunohistochemistry. cGMP and neuronal NO synthase (nNOS) were subsequently visualized using appropriate primary and secondary antibodies. RESULTS Cells responding to NO with an increase in cGMP were detected in the dome, lateral wall and base, with positive cells in the thin outer surface of the wall (muscle coat), associated with muscle bundles in an outer layer of muscle, and in a region immediately beneath the urothelium. These cells (not urothelium, smooth muscle or vascular) are described as interstitial cells. Superficial urothelial umbrella cells were apparent and were strongly cGMP‐positive. A high density of interstitial cells was associated with muscle bundles on the outer aspects of the wall, while few cells were detected on inner bundles. Thus there appeared to be two distinct types of muscle, inner and outer, with no obvious orientation of the fibres in each layer. Both muscle groups contained fibres expressing nNOS. In the outer muscle layer most of these fibres co‐localized with cGMP, suggesting that different populations of nerves innervate each layer. There were more nNOS‐positive fibres in the base of the bladder than in the dome. Three populations of cGMP‐positive interstitial cells were associated with the outer muscle layer; cells in the outer surface (muscle coat interstitial cells, MC‐ICs), cells on the surface of the bundles (superficial, SM‐ICs) and cells within the muscle bundles (intramuscular, IM‐ICs). The IM‐ICs form a network in close apposition to the smooth muscle cells while the SM‐ICs may connect adjacent muscle bundles and connect to the MC‐ICs. Thus, there is a network linking potentially the muscle cells in the outer muscle bundles. cGMP‐positive cells were also detected in the suburothelial layer (suburothelial, SU‐ICs) which had a different structure to the cells associated with muscle, had a oval cell bodies with bifurcating processes and appeared to form a complex network; they were prevalent in the base and virtually absent in the dome. CONCLUSIONS There are structures within the bladder wall that can be identified and categorized by the ability of the constituent cells to in...

Detrusor myocyte activity and afferent signaling

“…3 and 4) and might be controlled by several factors, including a peripheral myovesical plexus consisting of intramural ganglia and ICC. 6,52 As described previously, intercellular connections may contribute to module control, but also to locally generated mediators (see below). Kinder and Mundy 63 found that spontaneous contractile activity developed more often in muscle strips from overactive rather than from normal bladders, a finding underlined by Brading 25 and confirmed by Mills et al 64 Brading 25 discussed the occurrence of ''patchy denervation'' in cases of DO, with subsequent changes of the smooth muscle cells, for example, supersensitivity to ACh (Fig.…”

“…65 The frequency of spontaneous rhythmic contractions of isolated detrusor smooth muscle preparations seems to vary between species, and is probably also dependent on experimental factors. 4,52 Characteristically, these contractions are resistant to the Na-channel blocker tetrodotoxin (TTX) and cannot be blocked by hexamethonium, atropine, a-adrenergic (a-AR) blockers, b-AR blockers, or suramin, apparently excluding direct involvement of nerves and nerve-released transmitters. 4 As mentioned previously, contractions can be effectively inhibited by L-type Ca 2þ channel blockers and K þ channel openers and agents that decrease K þ permeability.…”

“…54,55 ICCs are c-kit positive in the guinea-pig bladder 51 and are also highly immunoreactive for cGMP. 50,52 Kubota et al 56 assessed the possible role of these c-kit positive cells in the bladder, and investigated the effects of the c-kit tyrosine kinase inhibitor, imatinib mesylate (Glivec 1 ), on spontaneous excitation and ion channel activity in detrusor smooth muscle using intracellular microelectrodes, isometric muscle tension recordings, and patch-clamp techniques. Glivec converted AP bursts into continuous firing without affecting their shape, but at high concentrations of the drug, spontaneous APs were abolished.…”

Novel type of interstitial cell (Cajal-like) in human fallopian tube

“…In a series of recent papers, ICC-like cells have been claimed to occur in other organs: vas deferens [25], urethra [26][27][28], bladder [29][30][31][32][33], ureter [34,35], uterus [36,37], blood vessels [38][39][40], lymphatics [41], prostate [42,43], penis [44], mammary gland [45] and pancreas [46].…”

PDE5 inhibitors for LUTS

“…Gillespie et al [42][43][44] found subepithelial neurogenic NOS containing nerves present in bladder interstitial cells. These nerves produce cGMP, facilitating relaxation.…”