Spontaneous Contractile Activity of the Detrusor Muscle and Its Role in the Pathogenesis of Overactive Bladder Syndrome

Acute radiation impacts contractility of guinea-pig bladder strips affecting mucosal-detrusor interactions

Radiation-induced bladder toxicity is associated with radiation therapy for pelvic malignancies, arising from unavoidable irradiation of neighbouring normal bladder tissue. This study aimed to investigate the acute impact of ionizing radiation on the contractility of bladder strips and identify the radiation-sensitivity of the mucosa vs the detrusor. Guinea-pig bladder strips (intact or mucosa-free) received ex vivo sham or 20Gy irradiation and were studied with in vitro myography, electrical field stimulation and Ca2+-fluorescence imaging. Frequency-dependent, neurogenic contractions in intact strips were reduced by irradiation across the force-frequency graph. The radiation-difference persisted in atropine (1μM); subsequent addition of PPADs (100μM) blocked the radiation effect at higher stimulation frequencies and decreased the force-frequency plot. Conversely, neurogenic contractions in mucosa-free strips were radiation-insensitive. Radiation did not affect agonist-evoked contractions (1μM carbachol, 5mM ATP) in intact or mucosa-free strips. Interestingly, agonist-evoked contractions were larger in irradiated mucosa-free strips vs irradiated intact strips suggesting that radiation may have unmasked an inhibitory mucosal element. Spontaneous activity was larger in control intact vs mucosa-free preparations; this difference was absent in irradiated strips. Spontaneous Ca2+-transients in smooth muscle cells within tissue preparations were reduced by radiation. Radiation affected neurogenic and agonist-evoked bladder contractions and also reduced Ca2+-signalling events in smooth muscle cells when the mucosal layer was present. Radiation eliminated a positive modulatory effect on spontaneous activity by the mucosa layer. Overall, the findings suggest that radiation impairs contractility via mucosal regulatory mechanisms independent of the development of radiation cystitis.

Urinary Urgency in Working Women: What Factors Are Associated with Urinary Urgency Progression?

BACKGROUND

Urinary urgency is the primary symptom of overactive bladder (OAB). This study aimed to identify targets for effective intervention to delay progression of urinary urgency.

MATERIAL AND METHODS

Secondary analyses of data from a study conducted with female employees of a large academic medical center were conducted. Women were ≥18 years and nonpregnant at the time of the survey. An online questionnaire obtained demographic information, presence of lower urinary tract symptoms, and toileting behaviors. Bivariate analyses and multivariate logistic regression were applied to explore factors related to different stages of urinary urgency.

RESULTS

Four stages of urinary urgency were constructed: (1) Stage 1: no urinary symptoms (n = 20), (2) Stage 2: continent but urinary urgency reported (n = 19), (3) Stage 3: nonsevere urgency urinary incontinence (UUI) (incontinent but leakage ≤1/day, n = 74); and (4) Stage 4: severe UUI (leakage ≥1/day, n = 26). In multivariate analyses, older women were more likely to be in Stage 3 than in Stage 2 (aOR 1.053, 95% CI 1.012-1.096). Women who lost urine with defecation were more likely to be in Stage 4 than Stage 3 (aOR 3.828, 95% CI 1.921-7.629). Women who habitually strained to empty the bladder faster were more likely to be in Stage 4 than in Stage 3 (aOR 6.588, 95% CI 1.317-32.971).

CONCLUSIONS

Losing urine with defecation and making the bladder empty faster by pushing down should be explored as intervention targets to prevent women from progressing from Stage 3 to Stage 4.

Structural and functional changes in gap junctional intercellular communication in a rat model of overactive bladder syndrome induced by partial bladder outlet obstruction

The aim of the present study was to investigate the association between connexin (Cx)43 levels and alterations in gap junctional mediation of intercellular communication in overactive bladder syndrome (OAB), and to examine the effects of connexin inhibitor on this condition. Adult female Wistar rats with OAB following partial bladder outlet obstruction (PBBO) (OAB group, n=37) and sham-operated rats (control group, n=17) were studied. The ultrastructure of the rat detrusor was observed by transmission electron microscopy and the protein expression levels of Cx43 were analyzed using western blot analysis. Furthermore, bladder detrusor cells in both groups were cultured and cells in the OAB group were randomly divided into ten groups. In nine of these groups, 18-β glycyrrhetinic acid (18β-GA) was administered at various doses and durations. All groups were compared using fluorescence redistribution after photobleaching and a laser scanning confocal microscope. Cystometry demonstrated that gap junctions were an abundant mechanism among adjacent cells, and Cx43 protein expression levels were increased in the OAB group following 6 weeks of obstruction, as compared with the control group. Mean fluorescence recovery rates in the OAB group were significantly increased, as compared with the control group (P<0.01). Mean fluorescence recovery rates were noted following 18β-GA administration. These results suggested that upregulation of Cx43 induces structural and functional alterations in gap junctional intercellular communication following PBOO, and connexin inhibitors may be a novel therapeutic strategy for the clinical treatment of OAB.