Development of Diurnal Micturition Pattern in Mice After Weaning

Establishment of an overactive bladder model in mice

BACKGROUND

Overactive bladder (OAB) is a syndrome characterized by symptoms of urinary urgency, often accompanied by frequent urination and nocturia or urge incontinence.

METHODS

Twenty female ICR mice were randomly divided into pBOO (partial bladder outlet obstruction) and control groups. The mouse OAB model was constructed by ligating the bladder outlet. Eight weeks after the operation, the methods of voiding spot on paper (VSOP), isolated detrusor muscle, and HE staining were used for analysis and research.

RESULTS

After the operation, two mice in the experimental and one in control died, and one in the control groups had an abnormal bladder size, so it was excluded from the statistical analysis. Eight weeks after the operation, there was an insignificant difference (P = 0.15) in the body weight of mice in the pBOO (26.54 ± 2.62 g) and the control group (24.84 ± 1.76 g). The number of urinations in 12 h was significantly higher (P < 0.001) in the pBOO (7.63 ± 1.19) than in the control group (4.13 ± 0.99). Also, the 12-h urine volume of pBOO (1491.23 ± 94.72 μL) was significantly greater (P = 0.006) than that of the control group (1344.86 ± 88.17 μL). The isolated bladder of the pBOO mice was significantly heavier than that in the control group (53.16 ± 1.79 mg vs. 24.54 ± 1.80 mg, P < 0.001), the horizontal and vertical length of the bladder in pBOO group were larger than those in the control group (P < 0.001). The detrusor thickness of pBOO group (357.50 ± 11.88 µm) was significantly thicker than that of control group (258.52 ± 17.22 µm, P < 0.001), and the isolated muscle strip was more sensitive to carbachol stimulation. According to HE staining, the bladder wall of the pBOO mice was significantly thickened.

CONCLUSIONS

A pBOO-mediated mouse OAB model was successfully established by ligating the bladder outlet.

Animal Model for Lower Urinary Tract Dysfunction in Parkinson's Disease

Although Parkinson's disease (PD) is characterized by the loss of dopaminergic neurons in the substantia nigra and subsequent motor symptoms, various non-motor symptoms often precede these other symptoms. While motor symptoms are certainly burdensome, a wide range of non-motor symptoms have emerged as the key determinant of the quality of life in PD patients. The prevalence of lower urinary tract symptoms differs according to the study, with ranges between 27% and 63.9%. These can be influenced by the stage of disease, the presence of lower urinary tract-related comorbidities, and parallels with other manifestations of autonomic dysfunction. Animal models can provide a platform for investigating the mechanisms of PD-related dysfunction and for the assessment of novel treatment strategies. Animal research efforts have been primarily focused on PD motor signs and symptoms. However, the etiology of lower urinary tract dysfunction in PD has yet to be definitively clarified. Several animal PD models are available, each of which has a different effect on the autonomic nervous system. In this article, we review the various lower urinary tract dysfunction animal PD models. We additionally discuss techniques for determining the appropriate model for evaluating the development of lower urinary tract dysfunction treatments.

Bladder outlet obstruction disrupts circadian bladder function in mice

The circadian clock programs daily rhythms and coordinates multiple behavioural processes, including micturition. Partial bladder outlet obstruction (pBOO) in mice produces hyperactive voiding. However, long-term effects of pBOO on bladder function have not been clarified. In this study, we investigated micturition under conditions of impaired circadian bladder function by inducing long-term pBOO by tying the proximal urethra. Micturition behavior was evaluated at 1, 3, 6 and 12 months after surgery. We used automated voided stain on paper method for a precise micturition recording for mice. And quantitative assessment of gene expression was performed at 24 months after pBOO surgery using qRT-PCR procedure. The micturition frequencies in the pBOO group were significantly decreased at 3, 6, and 12 months compared to those at 1 month after operation in the same group (p < 0.05). Body weight of pBOO mice was significantly increased compared to sham operated mice at 12 months. The expression level of mRNA was exhibited a 3.4-fold nominal increased for a 5-HT2B receptor in the pBOO group compared to the sham group. The current study found that long-term pBOO led to disruption of the circadian bladder function (the day/night cycle) in mice, similar to those observed in human as nocturia. This disruption is possible involvement of the gain of body weight and/or serotonergic alteration after pBOO.

Micturition video thermography in awake, behaving mice

BACKGROUND

Our understanding of the neural circuits controlling micturition and continence is constrained by a paucity of techniques for measuring voiding in awake, behaving mice.

NEW METHOD

To facilitate progress in this area, we developed a new, non-invasive assay, micturition video thermography (MVT), using a down-facing thermal camera above mice on a filter paper floor.

RESULTS

Most C57B6/J mice void infrequently, with a stereotyped behavioral sequence, and usually in a corner. The timing of each void is indicated by the warm thermal contrast of freshly voided urine. Over the following 10-15 min, urine cools to ∼3 °C below the ambient temperature and spreads radially in the filter paper. By measuring the area of cool contrast comprising this "thermal void spot," we can derive the initially voided volume. Thermal videos also reveal mouse behaviors including a home-corner preference apart from void spots, and a stereotyped, seconds-long pause while voiding.

COMPARISON WITH EXISTING METHODS AND CONCLUSIONS

MVT is a robust, non-invasive method for measuring the timing, volume, and location of voiding. It improves on an existing technique, the void spot assay, by adding timing information, and unlike the cystometrogram preparation, MVT does not require surgical catheterization. Combining MVT with current neuroscience techniques will improve our understanding of the neural circuits that control continence, which is important for addressing the growing number of patients with urinary incontinence as the population ages.

Changes in excitability and ion channel expression in neurons of the major pelvic ganglion in female type II diabetic mice

Bladder cystopathy and autonomic dysfunction are common complications of diabetes, and have been associated with changes in ganglionic transmission and some measures of neuronal excitability in male mice. To determine whether type II diabetes also impacts excitability of ganglionic neurons in females, we investigated neuronal excitability and firing properties, as well as underlying ion channel expression, in major pelvic ganglion (MPG) neurons in control, 10-week, and 21-week Lepr^db/db mice. Type II diabetes in Lepr^db/db animals caused a non-linear change in excitability and firing properties of MPG neurons. At 10 weeks, cells exhibited increased excitability as demonstrated by an increased likelihood of firing multiple spikes upon depolarization, decreased rebound spike latency, and overall narrower action potential half-widths as a result of increased depolarization and repolarization slopes. Conversely, at 21 weeks MPG neurons of Lepr^db/db mice reversed these changes, with spiking patterns and action-potential properties largely returning to control levels. These changes are associated with numerous time-specific changes in calcium, sodium, and potassium channel subunit mRNA levels. However, Principal Components Analysis of channel expression patterns revealed that rectification of excitability is not simply a return to control levels, but rather a distinct ion channel expression profile in 21-week Lepr^db/db neurons. These data indicate that type II diabetes can impact the excitability of post-ganglionic, autonomic neurons of female mice, and suggest that the non-linear progression of these properties with diabetes may be the result of compensatory changes in channel expression that act to rectify disrupted firing patterns of Lepr^db/db MPG neurons.

Non-invasive voiding assessment in conscious mice

OBJECTIVE

To review available options of assessing murine bladder function and to evaluate a non-invasive technique suitable for long-term recording.

METHODS

We reviewed previously described methods to record rodent bladder function. We used modified metabolic cages to capture novel recording tracings of mouse micturition. We evaluated our method in a pilot study with female mice undergoing partial bladder outlet obstruction or sham operation, respectively; half of the partial obstruction and sham group received treatment with an S6K-inhibitor, targeting the mTOR pathway, which is known to be implicated in bladder response to obstruction.

RESULTS

Our non-invasive method using continuous urine weight recording reliably detected changes in murine bladder function resulting from partial bladder outlet obstruction or treatment with S6K-inhibitor. We found obstruction as well as treatment with S6K-inhibitor to correlate with a hyperactive voiding pattern.

CONCLUSIONS

While invasive methods to assess murine bladder function largely disturb bladder histology and intrinsically render post-cystometry gene expression analysis of questionable value, continuous urine weight recording is a reliable, inexpensive, and critically non-invasive method to assess murine bladder function, suitable for a long-term application.

Involvement of interstitial cells of Cajal in bladder dysfunction in mice with experimental autoimmune encephalomyelitis

BACKGROUND

Bladder dysfunction is an important symptom of experimental autoimmune encephalomyelitis (EAE). Our previous study showed that EAE-induced upregulation of the E-prostanoid receptor 3 (EP3) and E-prostanoid receptor 4 (EP4) in the bladder was accompanied by bladder dysfunction. Although many other studies have evaluated the lower urinary tract symptoms in multiple sclerosis, the mechanism remains unclear.

OBJECTIVES

To investigate the effects of interstitial cells of Cajal (ICC) on bladder dysfunction in a novel neurogenic bladder model induced by experimental autoimmune encephalomyelitis.

MATERIALS AND METHODS

The EAE model was induced by a previously established method, and bladder functions in mice were evaluated. Bladders were harvested for the analysis of ICCs and the genes associated with bladder mechanosensation including pannexin 1 (Panx1) and Gja1 (encoding connexin43) by immunofluorescence and western blotting. The stem cell factor cytokine (SCF) was intraperitoneally injected at the beginning of EAE onset.

RESULTS

EAE mice developed profound bladder dysfunction characterized by significant urine retention, increased micturition and decreased urine output per micturition. EAE induced a significant decrease in c-Kit expression and ICCs number. EAE also induced a significant increase in pannexin 1 and connexin43. SCF treatment could ameliorate all of these pathological changes.

CONCLUSIONS

ICCs and stem cell factor play an important role in EAE-induced bladder dysfunction, which may be used as therapeutic options in treating patients with multiple sclerosis-related bladder dysfunction.

Nocturia: The circadian voiding disorder

Nocturia is a prevalent condition of waking to void during the night. The concept of nocturia has evolved from being a symptomatic aspect of disease associated with the prostate or bladder to a form of lower urinary tract disorder. However, recent advances in circadian biology and sleep science suggest that it might be important to consider nocturia as a form of circadian dysfunction. In the current review, nocturia is reexamined with an introduction to sleep disorders and recent findings in circadian biology in an attempt to highlight the importance of rediscovering nocturia as a problem of chronobiology.

Influence of animal husbandry practices on void spot assay outcomes in C57BL/6J male mice

AIMS

Mice are increasingly being used as models to investigate aspects of urinary dysfunction that humans with lower urinary tract symptoms (LUTS) experience. One method used to examine voiding function is the spontaneous void spot assay. The purpose of this study was to characterize and identify animal husbandry conditions that might confound results of the spontaneous void spot assay in male C57Bl/6J mice.

METHODS

Mice were placed in cages lined with filter paper for 4 hr and urine was visualized with UV transillumination. Voiding parameters including urine spot number, spot size, total urine area, primary void area, corner and center voiding were quantified.

RESULTS

Adult male mice void more frequently with advancing age and a subpopulation (5-10%) display a frequent spotting pattern at 6-9 weeks of age. Voiding was not significantly different in male mice weaned to group housing (4-6 per cage) versus single housing, and was not altered when they were used as breeders. Voiding was changed upon transferring group housed adult males to single density cages, which decreased total urine area. Repeated assays of male voiding behavior over three consecutive days increased primary void area by the third day of monitoring and revealed that voiding behavior is impacted by routine cage changes and time of day.

CONCLUSIONS

Together these results identify housing and husbandry practices that influence male voiding behaviors in the spontaneous void spot assay and will inform voiding behavior analyses conducted with male C57Bl/6J mice.

Pannexin 1 involvement in bladder dysfunction in a multiple sclerosis model

Bladder dysfunction is common in Multiple Sclerosis (MS) but little is known of its pathophysiology. We show that mice with experimental autoimmune encephalomyelitis (EAE), a MS model, have micturition dysfunction and altered expression of genes associated with bladder mechanosensory, transduction and signaling systems including pannexin 1 (Panx1) and Gja1 (encoding connexin43, referred to here as Cx43). EAE mice with Panx1 depletion (Panx1^−/−) displayed similar neurological deficits but lesser micturition dysfunction compared to Panx1^+/+ EAE. Cx43 and IL-1β upregulation in Panx1^+/+ EAE bladder mucosa was not observed in Panx1^−/− EAE. In urothelial cells, IL-1β stimulation increased Cx43 expression, dye-coupling, and p38 MAPK phosphorylation but not ERK1/2 phosphorylation. SB203580 (p38 MAPK inhibitor) prevented IL-1β-induced Cx43 upregulation. IL-1β also increased IL-1β, IL-1R-1, PANX1 and CASP1 expression. Mefloquine (Panx1 blocker) reduced these IL-1β responses. We propose that Panx1 signaling provides a positive feedback loop for inflammatory responses involved in bladder dysfunction in MS.