P. Van Kerrebroeck

Alterations to network of NO/cGMP-responsive interstitial cells induced by outlet obstruction in guinea-pig bladder

Interstitial cells (ICs) play a role in regulating normal bladder activity. This study explores the possibility that the sub-urothelial and muscle networks of NO/cGMP-responsive ICs are altered in animals with surgically induced outflow obstruction. In sham-operated animals, the urothelium comprised NO-stimulated cGMP-positive (cGMP+) umbrella cells, an intermediate layer and a basal layer that stained for nNOS. cGMP+ sub-urothelial interstitial cells (su-ICs) were found below the urothelium. cGMP+ cells were also associated with the outer muscle layers: on the serosal surface, on the surface of the muscle bundles and within the muscle bundles. Several differences were noted in tissues from obstructed animals: (1) the number of cGMP+ umbrella cells and intensity of staining was reduced; (2) the intermediate layer of the urothelium consisted of multiple cell layers; (3) the su-IC layer was increased, with cells dispersed being throughout the lamina propria; (4) cGMP+ cells were found within the inner muscle layer forming nodes between the muscle bundles; (5) the number of cells forming the muscle coat (serosa) was increased; (6) an extensive network of cGMP+ cells penetrated the muscle bundles; (7) cGMP+ cells surrounded the muscle bundles and nodes of ICs were apparent, these nodes being associated with nerve fibres; (8) nerves were found in the lamina propria but rarely associated with the urothelium. Thus, changes occur in the networks of ICs following bladder outflow obstruction. These changes must have functional consequences, some of which are discussed.

The localization of cyclo-oxygenase immuno-reactivity (COX I-IR) to the urothelium and to interstitial cells in the bladder wall.

Localized phasic contractions in the bladder wall (autonomous activity) have been hypothesized to be an integral part of a motor/sensory system contributing to bladder sensation. The sites responsible for generating this activity, the mechanisms involved in its propagation and modulation remain unknown. This phasic motor activity is modulated by exogenous prostaglandins. Therefore, analysis of the sites of prostaglandin production and action within the bladder wall may shed light on the mechanisms of generation and modulation of this phasic activity. In this paper we report the localization of immuno‐reactivity indicative of the expression of cyclo‐oxygenase enzyme type I (COX I‐IR) within the bladder wall. Basically, three types of COX I‐IR cell were identified: epithelial cells in the basal and intermediate layers of the urothelium, complex vimentin‐positive and COX I‐IR cells in the lamina propria and vimentin‐negative COX I‐IR cells in the lamina propria and on the surface of the inner muscle bundles. These vimentin‐negative/COX I‐IR cells appear to be in close apposition to a continuous network of vimentin‐positive cells, which extends from the lamina propria into the inner muscle layers and subsequently into the outer muscle layers. However, the interstitial cells in this region might form a distinctly different sub‐type. First, the interstitial cells in this region differ from those in the inner layer by their responsiveness to NO with a rise in cGMP. Two subtypes have been identified: cells on the surface of the muscle bundles and within the muscle bundles. Second, COX I‐IR cells are not associated with the interstitial cells in the outer layers. The physiological significance for these apparent differences in the interstitial cell network is not clear. However, such differences are likely to reflect differences in the processes involved in their activation, modulation and control.

Do patients with OAB experience bladder sensations in the same way as healthy volunteers? A focus group investigation†‡

To describe the terminology and pattern of bladder sensations experienced during non‐invasive rapid bladder filling in a controlled setting in patients with OAB and to compare these results with a previous study conducted in healthy volunteers.

Relaxant Effects of Estradiol through Non-Genomic Pathways in Male and Female Pig Bladder Smooth Muscle

The precise effect of low estrogen levels on urinary bladder contractility remains controversial. The present study was designed to analyze the effect of 17β-estradiol in bladder smooth muscle contractility and the involvement of specific estrogen receptor stimulation in this effect. Castrated male and female pig detrusor strips were mounted for tension recording in an organ bath, superfused with Krebs solution at 37°C and stimulated electrically and pharmacologically. In order to verify the acute effect of 17β-estradiol on muscle contractility, the strips were incubated with different concentrations of the hormone. Muscle contractions were induced by potassium chloride, acetylcholine chloride and electrical field stimulation. The involvement of the estrogen receptor in the effects of 17β-estradiol was assessed by incubation of some strips with the selective estrogen receptor antagonist ICI 182.780 before estradiol was applied. Estradiol at a dose of 30 µmol/l elicited a lower amplitude of contractions induced by EFS, Ach and KCl in female as well as in castrated male pig bladder smooth muscle strips. The effects of 17β-estradiol were stronger in contractions induced by potassium chloride than those induced by other forms of stimulation. Pre-treatment with the pure estrogen receptor antagonist had no effect on 17β-estradiol-induced inhibition of muscle contractility. These observations suggest that 17β-estradiol induces lower amplitude of contraction of female as well as castrated male pig detrusor which is not mediated by the classic estrogen receptor. Furthermore, we can conclude that estradiol has a stronger inhibitory effect on the depolarization of muscle cell membrane compared to a muscarinic receptor-induced contraction.

Changes in bladder innervation in a mouse model of Alzheimer's disease

AIMnThe aims of this study were to compare the structure of bladders from a transgenic mouse model of Alzheimers disease with age matched control animals and to explore the idea that any structural differences might be related to functional bladder changes associated with the condition.nnnMATERIALS AND METHODSnTwo groups of mice were used. Transgenic animals in which the murine Amyloid Precursor Protein (APP) gene has been partly replaced by the human APP including both the Swedish and London mutations and that overexpress a mutant of the human Presenilin 1 gene (PS1M146L) driven by the PDGF promoter. The transgenic mice (App(SL)/PS1(M146L)) aged 24+/-3 months were used. The second group was an age matched control group of C57 black mice. The bladders from each group were isolated, fixed in 4% paraformaldehyde and prepared for immunohistochemistry. Antibodies to the vesicular acetylcholine transporter (VAChT) and neuronal nitric oxide synthase (nNOS) were used to identify neural structures.nnnRESULTSnCholinergic nerves (VAChT(+)) were observed in the inner and outer muscle bundles of App(SL)/PS1(M146L) and control mice. No major differences were noted in the distribution of these fibres. In contrast, there was a distinct difference in the innervation of the sub-urothelial layer. In App1(SL)/PS1(M146L) mice there were numerous VAChT and nNOS positive fibres in sharp contrast to the paucity of similar nerves in control animals. VAChT and nNOS did not appear to co-localise in the same nerve fibres within the lamina propria. Pairs of nerve fibres, nNOS(+) and VAChT(+), were observed to be intertwined and run in close proximity. A particularly unusual feature of the App(SL)/PS1(M146L) mouse bladder was the presence of neurones within the bladder wall. These nerve cell bodies were seen in all App(SL)/PS1(M146L) mouse bladders. The neurones could be found singly or in small ganglion like groups of cells and were located in all layers of the bladder wall (sub-urothelium, in the lamina propria adjacent to the inner muscle and within the inner muscle and outer muscle layers). No nerve cells or small ganglia were noted in any of the control bladders studied.nnnCONCLUSIONSnThere are structural differences in the bladders of App(SL)/PS1(M146L) mice compared to control animals. These differences are associated with sub-urothelial nerves which, because of their location, are likely to be sensory fibres. This may lead to a changed sensory processing from the App(SL)/PS1(M146L) bladders. The physiological role of the intra-mural neurones and ganglia is not known. It is speculated that they may be associated with peripheral motor/sensory mechanisms linked to the generation and modulation of sensation.