Changes of neuregulin-1 (NRG-1) expression in a rat model of overactive bladder induced by partial urethral obstruction: is NRG-1 a new biomarker of overactive bladder?

Hyperpolarization-activated cation currents in medium-size dorsal root ganglion cells are involved in overactive bladder syndrome in rats

BACKGROUND

To investigate the functions of the hyperpolarization-activated cation currents in medium-size dorsal root ganglion cells in a rat model of overactive bladder syndrome.

METHODS

Rats with OAB were screened using a urodynamic testing device. The whole-cell patch clamp technique was used to investigate changes in excitability and hyperpolarization-activated cation current (I_h) of medium-size cells in the L6 dorsal root ganglia (DRG) of the OAB rats. Intrathecal injection of the specific I_h inhibitor ZD7288 was used to investigate changes of voiding function and I_h of medium-size cells in the L6 DRG.

RESULTS

The urinary bladder weight of the OAB rats was significantly increased (p < 0.01); However, 7 days after intrathecally administration of ZD7288 (2 μM), the weight of rat bladder was significantly reduced (p < 0.01). The excitability of the medium-size cells in the L6 DRG of the OAB rats was significantly increased, and the number of action potentials elicited by a 500 pA stimulus was also markedly increased. Furthermore, ZD7288 significantly reduced the excitability of the medium-size DRG cells. The medium-size cells in the DRG of the OAB rats had a significantly increased I_h current density, which was blocked by ZD7288.

CONCLUSIONS

The I_h current density significantly increased in medium-size cells of the L6 DRG in the OAB model. A decrease of the I_h current was able to significantly improve the voiding function of the OAB rats, in addition to lowering their urinary bladder weight. Our finding suggested that the observed increase of I_h current in the medium-size DRG neurons might play an important role in the pathological processes of OAB.

Urethral orifice hyaluronic acid injections: a novel animal model of bladder outlet obstruction

Background

We produced a novel model of bladder outlet obstruction (BOO) by periurethral injection of hyaluronic acid and compared the cystometric features, postoperative complications, and histopathological changes of that model with that of traditional open surgery.

Methods

Forty female Sprague-Dawley rats were divided into three groups. Fifteen rats were subcutaneously injected with 0.2 ml hyaluronic acid at 5, 7, and 12 o’clock around the urethral orifice. Another fifteen rats underwent traditional open partial proximal urethral obstruction surgery, and 10 normal rats used as controls. After 4 weeks, filling cystometry, postoperative complications, and histopathological features were evaluated in each group. Three rats were also observed for 12 weeks after hyaluronic acid injection to evaluate the long-term effect.

Results

Hyaluronic acid periurethral injection caused increased maximum cystometric capacity, maximum bladder pressure, micturition interval, and post-void residual urine volume compared with control (p < 0.01). The injection group had significantly shorter operative time, less incidence of incision infection and bladder stone formation compared with the surgery group (p < 0.01). Hematoxylin and eosin (HE) staining showed suburothelial and interstitial hyperemia edema and smooth muscle hypertrophy in both injection and surgery bladders; these were not observed in the control group. Bladder weight and thickness of smooth muscle in the injection and surgery groups were significantly greater than those in the control group (p < 0.01). Urethral epithelial hyperplasia and lamina propria inflammation were observed in the surgery group but not in the injection or control groups. Rats periurethrally injected hyaluronic acid were stable the compound was not fully absorbed in any rat after 12 weeks.

Conclusions

Hyaluronic acid periurethral injection generates a simple, effective, and persistent animal model of BOO with lower complications, compared with traditional surgery.