Development of an Improved Animal Model of Overactive Bladder: Transperineal Ligation versus Transperitoneal Ligation in Male Rats

Is bladder outlet obstruction rat model to induce overactive bladder (OAB) has similarity to human OAB? Research on the events in smooth muscle, collagen, interstitial cell and telocyte distribution

BACKGROUND

Cellular and cytoskeletal events of overactive bladder (OAB) have not been sufficiently explored in human bladder due to different limitations. Bladder outlet obstruction (BOO) had been induced in different animal models with different methods to induce (OAB). Similarity of the animal models of BOO to the human OAB is postulated but has not been confirmed. The interstitial cells of Cajal (ICCs), and telocytes (TCs) are an important players in smooth muscles conductivity, they had not been well investigated in the previous BOO models. Objectives are to investigate the morphological pattern of cellular, cytoskeleton and telocytes distribution in BOO rat model and to match the events in two time periods and compare it to the findings in real-world human OAB.

METHODS

Female Sprague-Dawley rats (Rattus norvegicus) were randomly divided into: sham (n = 10), BOO 6 W (n = 10), BOO 8 W (n = 10). Operative procedure to Induce BOO was done under anesthesia with intraperitoneal Ketamine administration. The Effect of induction of BOO was evaluated after 6 and 8 weeks. The rats were anesthetized, and the urinary bladder was removed, while the rat was unconscious under anaesthesia it was transferred to the inhalation anaesthesia cage for euthanasia, rats were sacrificed under light anesthesia using isoflurane. Care of animals, surgical procedure, and euthanasia adhered to Guide for the Care and Use of Laboratory Animals, and AVMA Guidelines for the Euthanasia of Animals. The retrieved bladder was processed for examination with histopathology, immunohistochemistry (IHC), and transmission electron microscopy (EM).

RESULTS

Histological examination of the bladder shows thinner urothelium, condensation of collagen between muscle bundles. IHC with c-kit shows the excess distribution of ICCs between smooth muscle bundles. EM shows frequent distribution of TCs that were situated between collagen fibers. Finings in BOO 6 W group and BOO 8 W group were comparable.

CONCLUSION

The animal model study demonstrated increased collagen/ smooth muscle ratio, high intensity of ICCs and presence of TCs. Findings show that a minimally invasive procedure to induce BOO in rats had resulted in an OAB that has morphological changes that were stable in 6 & 8 weeks. We demonstrated the distribution of TCs and ICCs in the rat animal model and defined them. The population of TCs in the BOO rat model is described for the first time, suggests that the TCs and ICCs may contribute to the pathophysiology of OAB. Similarity of animal model to human events OAB was demonstrated. These findings warrant further study to define the role of TCs in OAB.

CLINICAL TRIAL REGISTRY

The study does not require a clinical trial registration; it is an experimental animal study in basic science and does not include human subjects.

Review of Animal Models to Study Urinary Bladder Function

Simple Summary

The treatment of urinary bladder dysfunction requires the knowledge of bladder function, which involves physiology, pathology, and even psychology. Several animal models are available to study a variety of bladder disorders. These models include animals from rodents, such as mice and rats, to nonhuman primates, such as rabbits, felines, canines, pigs, and mini pigs. This review adapted animal models to study bladder function according to facility, priority, and disease.

Abstract

The urinary bladder (UB) serves as a storage and elimination organ for urine. UB dysfunction can cause multiple symptoms of failure to store urine or empty the bladder, e.g., incontinence, frequent urination, and urinary retention. Treatment of these symptoms requires knowledge on bladder function, which involves physiology, pathology, and even psychology. There is no ideal animal model for the study of UB function to understand and treat associated disorders, as the complexity in humans differs from that of other species. However, several animal models are available to study a variety of other bladder disorders. Such models include animals from rodents to nonhuman primates, such as mice, rats, rabbits, felines, canines, pigs, and mini pigs. For incontinence, vaginal distention might mimic birth trauma and can be measured based on leak point pressure. Using peripheral and central models, inflammation, bladder outlet obstruction, and genetic models facilitated the study of overactive bladder. However, the larger the animal model, the more difficult the study is, due to the associated animal ethics issues, laboratory facility, and budget. This review aims at facilitating adapted animal models to study bladder function according to facility, priority, and disease.

The effects of oral administration of the novel muscarinic receptor antagonist DA-8010 on overactive bladder in rat with bladder outlet obstruction

Background

DA-8010 is a novel compound developed for the treatment of overactive bladder (OAB) and urinary incontinence. The aims of this study were to investigate the effects of DA-8010 on OAB in a rat model.

Methods

Study animals were divided into the following five groups of seven animals each: a sham-operated control group, a control group with partial bladder outlet obstruction (BOO) (OAB group), and three DA-8010 (doses of 0.3 mg/kg/day, 1 mg/kg/day, and 3 mg/kg/day, respectively) with partial BOO groups. Oral administration of the drugs was continued for 14 days after 2 weeks of partial BOO. After 4 weeks of partial BOO, cystometrography was performed in all groups. Additionally, pro-inflammatory cytokines, Rho-kinases, and histology of the bladder were analyzed.

Results

There was a significant increase in the contraction interval and a decrease in contraction pressure in the 3 mg/kg/day DA-8010 group versus those in the OAB group. Rho kinase was also significantly decreased in the DA-8010 3 mg/kg/day dosage treatment group. The increased ratio of collagen to smooth muscle after partial BOO was significantly attenuated in the DA-8010 3 mg/kg/day dosage group.

Conclusions

Oral administration of DA-8010 at 3 mg/kg/day improved findings in an OAB rat model induced by partial BOO. Our results suggest that the novel muscarinic receptor antagonist DA-8010 may be a promising drug for treating patients with OAB.

Proteomic Analysis of Urothelium of Rats with Detrusor Overactivity Induced by Bladder Outlet Obstruction

Overactive bladder (OAB) syndrome is a condition that has four symptoms: urgency, urinary frequency, nocturia, and urge incontinence and negatively affects a patient's life. Recently, it is considered that the urinary bladder urothelium is closely linked to pathogenesis of OAB. However, the mechanisms of pathogenesis of OAB at the molecular level remain poorly understood, mainly because of lack of modern molecular analysis. The goal of this study is to identify a potential target protein that could act as a predictive factor for effective diagnosis and aid in the development of therapeutic strategies for the treatment of OAB syndrome. We produced OAB in a rat model and performed the first proteomic analysis on the mucosal layer (urothelium) of the bladders of sham control and OAB rats. The resulting data revealed the differential expression of 355 proteins in the bladder urothelium of OAB rats compared with sham subjects. Signaling pathway analysis revealed that the differentially expressed proteins were mainly involved in the inflammatory response and apoptosis. Our findings suggest a new target for accurate diagnosis of OAB that can provide essential information for the development of drug treatment strategies as well as establish criteria for screening patients in the clinical environment.

Near-Normalized Gene Expression Profiles in Bladder With Detrusor Overactivity in Rats With Bladder Outlet Obstruction After Deobstruction

PURPOSE

The pathophysiological role of detrusor overactivity (DO) in the bladder, which is commonly observed in various bladder diseases, is not well understood. DO appears in bladder outlet obstruction (BOO), and may continue even after subsequent deobstruction. DO therefore provides an excellent opportunity to observe molecular biological changes.

METHODS

In this study, to understand the molecular effects of persistent DO after BOO induction and deobstruction, we performed awake cystometry on female Sprague-Dawley rats divided into 4 groups: a sham group, a BOO group, a deobstructed group with DO after BOO (DDO), and a deobstructed group without DO after BOO (non-DDO). Total RNA was extracted from the bladder samples, and gene expression profiles were compared between the sham and model groups.

RESULTS

DO was observed in 5 of the 6 rats (83%) in the BOO group, and in 6 of the 13 rats (46%) in the deobstructed group. The non-DDO group showed a significantly greater residual volume than the DDO group. Through a clustering analysis of gene expression profiles, we identified 7,532 common upregulated and downregulated genes, the expression of which changed by more than 2 fold. In the BOO group, 898 upregulated and 2,911 downregulated genes were identified. The non-DDO group showed 3,472 upregulated and 4,025 downregulated genes, whereas in the DDO group, only 145 and 72 genes were upregulated and downregulated, respectively.

CONCLUSIONS

Abnormal function and gene expression profiles in bladders after BOO were normalized in the BOO rats with DO after deobstruction, whereas in those without DO, abnormal function persisted and the gene expression profile became more abnormal. DO may play a protective role against the stress to the bladder induced by BOO and deobstruction as a form of adaptive neuroplasticity.

Benefits and limitations of animal models in partial bladder outlet obstruction for translational research

The functions of the lower urinary tract have been investigated for more than a century. Lower urinary tract symptoms, such as incomplete bladder emptying, weak urine stream, daytime urinary frequency, urgency, urge incontinence and nocturia after partial bladder outlet obstruction, is a frequent cause of benign prostatic hyperplasia in aging men. However, the pathophysiological mechanisms have not been fully elucidated. The use of animal models is absolutely imperative for understanding the pathophysiological processes involved in bladder dysfunction. Surgical induction has been used to study lower urinary tract functions of numerous animal species, such as pig, dog, rabbit, guinea pig, rat and mouse, of both sexes. Several morphological and functional modifications under partial bladder outlet obstruction have not only been observed in the bladder, but also in the central nervous system. Understanding the changes of the lower urinary tract functions induced by partial bladder outlet obstruction would also contribute to appropriate drug development for treating these pathophysiological conditions. In the present review, we discuss techniques for creating partial bladder outlet obstruction, the characteristics of several species, as well as issues of each model, and their translational value.