Urinary bladder hypertrophy characteristic of male ROMK Bartter's mice does not occur in female mice

A comparison of urinary bladder weight in male and female mice across five models of diabetes and obesity

Introduction: Diabetes often leads to lower urinary tract dysfunction. The most frequently assessed parameter of urinary bladder dysfunction in animal models of diabetes is an enlargement of the bladder, which is consistently observed in type 1 and less consistently in type 2 diabetes. The vast majority of studies on bladder weight in animal models of diabetes and obesity has been performed in males, and no studies have directly compared this outcome parameter between sexes. Methods: Therefore, we have compared bladder weight and bladder/body weight ratio in five mouse models of obesity and diabetes (RIP-LCMV, db/db, ob/ob (two studies), insulin receptor substrate 2 (IRS2) knock-out mice and mice on a high-fat diet; pre-specified secondary analysis of a previously reported study). Results: In a pooled analysis of the control groups of all studies, females exhibited slightly lower glucose levels, lower body weight, and lower bladder weight, but bladder/body weight ratio was similar in both sexes (0.957 vs. 0.986 mg/g, mean difference 0.029 [-0.06; 0.118]). Among the six diabetic/obese groups, bladder/body weight ratio was similar in both sexes in three but smaller in female mice in three other groups. The mRNA expression of a panel of genes implied in the pathophysiology of bladder enlargement and/or fibrosis and inflammation did not differ systematically between sexes. Conclusions: We conclude that sex differences in diabetes/obesity-associated bladder enlargement may be model dependent.

Sex and Gender Differences in the Pharmacology of the Overactive Urinary Bladder

Dysfunction of the lower urinary tract in general and the overactive bladder syndrome (OAB) in particular are prevalent and have major impact on the quality of life of the afflicted patients and their partners. We concisely review sex and gender differences in patients and animal models in physiological bladder function, its alterations in disease (mostly OAB), and its responses to treatment. Women appear to have a smaller functional bladder capacity and, therefore, must void more often than men. On the other hand, men have a greater bladder outlet resistance, which is partly attributed to a longer urethra and partly to the presence of the prostate. Sex and gender differences in bladder contractility appear small and were not found consistently. The ability of bladder smooth muscle to relax may be somewhat smaller in females. However, females are heavily underrepresented in experimental studies on bladder function. Stress urinary incontinence is found predominantly in women (particularly those after childbirth). OAB is similarly prevalent in men and women. Females seek treatment much more often and are overrepresented in clinical trials. Treatment responses in OAB patients are similar in both genders for oral medications, but improvements upon injections of onabotulinum toxin type A appear smaller in men. We conclude that there is no evidence for major sex and gender differences in bladder dysfunction as related to OAB and its treatment responses, but female animals are heavily underrepresented in experimental studies.

Biomarkers in the diagnosis and symptom assessment of patients with bladder pain syndrome: a systematic review

INTRODUCTION AND HYPOTHESIS

Bladder pain syndrome (BPS) is a disease of unknown etiology defined as an unpleasant sensation related to the bladder, associated with lower urinary tract symptoms of more than 6 weeks' duration, in the absence of any identifiable causes. Despite its impact on quality of life (QoL) and socioeconomic burden, there are no objective methods for the diagnosis or assessment of therapeutic response. We systematically reviewed biomarkers associated with BPS to update the current knowledge on this issue.

METHODS

A systematic review of the Cochrane Library, Embase, PubMed/MEDLINE, LILACS, SCOPUS, and ClinicalTrials.gov databases was conducted following the PRISMA statement. Original articles investigating biomarkers for the diagnosis or symptom assessment of patients with BPS were assessed; no language restrictions were applied. Animal or post-mortem studies were excluded.

RESULTS

Of the 478 records retrieved, 11 articles were included. MIF, NGF, Etio-S, APF, and a combined methylhistamine/Il-6 model were increased in BPS urine samples versus controls. Also increased were glyceraldehyde in stool, in addition to the expression of some genes (ARID1A, ARF, CHAT, eNOS, GLI-1, iNOS, MCP-1, NGF, WNT-8A, WNT-10A), nerve density, IL-16, VCAM-1, and ICAM-1 in bladder tissue specimens. In contrast, some fecal bacteria, expression of other genes (CHT, HB-EGF, OCT-1, SMRT-1, WNT11) in the bladder urothelium, and urinary DNA methylation in CpG-sites, MCP-3, G5P1, and HB-EGF were decreased in BPS. As none of the biomarkers was studied more than once, a Forest plot could not be constructed. Only 4 articles reported the relation of biomarkers to symptom scores.

CONCLUSIONS

Potential biomarkers for BPS in urine, stool, and bladder biopsy specimens are described. Further research is needed before their use in clinical practice.

Lipopolysaccharide stimulates BK channel activity in bladder umbrella cells

Bladder urothelium plays an active role in response to bacterial infection. There is little known about the electrophysiological activity in urothelial cells in this process. We used a nonenzymatic method to isolate bladder urothelial tissue and to patch clamp umbrella cells in situ. A 200 pS conductance potassium (K⁺) channel was detected from female C57BL6 mice. Of 58 total patches, 17.2% patches displayed the 200 pS K⁺ conductance channel. This K⁺ conductance channel showed Ca²⁺ sensitivity and voltage dependence. Specific big-conductance potassium channel (BK) inhibitors (paxilline, iberiotoxin) blocked the 200 pS K⁺ conductance channel activity. RT-PCR and immunoblot confirmed BK channel pore-forming α-subunit (BK-α) mRNA and protein in urothelium. Immunohistochemistry also showed the BK-α located in urothelium. The above data provided evidence that the 200 pS K⁺ conductance channel was a BK channel. Lipopolysaccharide (LPS), a component of uropathogenic Escherichia coli, was used to investigate the role of BK channel in the pathogenesis of urinary tract infection. BK channel activity as NP_o increased threefold within 30 min of exposure to LPS. mRNAs for LPS receptors (TLR4, CD14, MD-2) were expressed in the urothelium but not in lamina propria or detrusor. Blockade of the receptors by an antagonist (polymyxin B) abrogated LPS's effect on BK channel. The involvement of protein kinase A (PKA) on BK channel activity was demonstrated by applying PKA blockers (H89 and PKI). Both PKA inhibitors abolished the BK channel activity induced by LPS. In conclusion, BK channel was identified in bladder umbrella cells, and its activity was significantly increased by LPS.