Kavirach Tantiwongse

Brain‐Derived Neurotrophic Factor (BDNF) Acts Primarily via the JAK/STAT Pathway to Promote Neurite Growth in the Major Pelvic Ganglion of the Rat: Part 2

INTRODUCTION Identification of the molecular mechanism of cavernous nerve regeneration is essential for future development of neuroprotective and regenerative strategies. AIM To identify specific signal transduction pathway(s) associated with brain-derived neurotrophic factor (BDNF) enhanced cavernous nerve regeneration in an in vitro model. MATERIALS AND METHODS Using 6-month-old male Fisher rats, inhibitors of four candidate signaling pathways were added to BDNF-treated explant cultures of major pelvic ganglia with attached cavernous nerve fragments. Study groups comprised of controls, BDNF alone at 50 ng/mL, or BDNF 50 ng/mL and inhibitors against MEK, PI3-K, PKA, and JAK/STAT pathways at increasing concentrations. MAIN OUTCOME MEASURE The maximal neurite length for each tissue culture was measured and the mean maximal length +/- standard deviation was determined for all groups at 24, 36, and 48 hours. RESULTS The JAK/STAT specific inhibitor AG490 significantly reduced BDNF-enhanced neurite growth. Maximum neurite lengths at 24, 36, and 48 hours for BDNF 50 ng/mL treated groups were 182.3, 348.1, and 528.1 microm, compared with AG490 at 25 microM (86.4, 165.1, 278.3 microm), 50 microM (78.8, 151.7, 235.3 microm), and 100 microM (71.83, 107.0, 219.6 microm) (P < 0.05). Neurite measures for BDNF with 25 and 50 microM U0126 (MEK pathway) were reduced to 402.0 and 424.3 microm at 48 hours, respectively (P < 0.05), likely reflecting an accessory molecular pathway. A similar observation was made for 100 uM LY294002 (PI3-K). No difference was observed for PKA inhibition. CONCLUSION The JAK/STAT pathway is the major signal-transduction pathway of BDNF-enhanced cavernous nerve growth in an in vitro rat model.

Intracavernous Growth Differentiation Factor‐5 Therapy Enhances the Recovery of Erectile Function in a Rat Model of Cavernous Nerve Injury

INTRODUCTION Neurogenic erectile dysfunction remains a serious complication in the postprostatectomy population. Effective protective and regenerative neuromodulatory strategies are needed. AIM To determine the effect of growth differentiation factor-5 (GDF-5) on erectile function and its mechanism in a rat model of cavernous nerve (CN) injury. MAIN OUTCOME MEASURES Erectile function was assessed by CN electrostimulation at 4 weeks. Penile tissues were examined by real-time polymerase chain reaction (PCR) and immunohistochemical analyses. METHODS Forty-eight male Sprague-Dawley rats were randomly divided into six equal groups: one group underwent sham operation (uninjured controls), while five groups underwent bilateral CN crush. Crush-injury groups were treated at the time of injury with intracavernous injection of a slow-release suspension of liquid microparticles containing no GDF-5 (vehicle), 0.4 microg (low concentration), 2 microg (intermediate concentration), or 10 microg GDF-5 (high concentration). One untreated group served as injured controls. RESULTS GDF-5 enhanced erectile recovery and significantly increased intracavernous pressure in the low and intermediate-concentration groups vs. injured controls. Low-concentration GDF-5 demonstrated the best functional preservation, as the intracavernous pressure increase in this group did not differ significantly from uninjured controls. A dose-response relationship was confirmed for the effects of GDF-5 in penile tissue. Low-concentration GDF-5 showed better preservation of the penile dorsal nerves and antiapoptotic effects in the corpus cavernosum (P < 0.05 vs. injured controls). Although high concentration GDF-5 did not confer meaningful erectile recovery, this dose was more effective at decreasing transforming growth factor-beta than low-concentration GDF-5. CONCLUSIONS Intracavernous injection of low (0.4 microg) or intermediate-concentration GDF-5 (2 microg) was effective in preserving erectile function in a rat model of neurogenic erectile dysfunction. The underlying mechanism appears to involve neuron preservation and antiapoptosis.

Neurturin enhances the recovery of erectile function following bilateral cavernous nerve crush injury in the rat

Background The molecular mechanisms responsible for the survival and preservation of function for adult parasympathetic ganglion neurons following injury remain incompletely understood. However, advances in the neurobiology of growth factors, neural development, and prevention of cell death have led to a surge of clinical interest for protective and regenerative neuromodulatory strategies, as surgical therapies for prostate, bladder, and colorectal cancers often result in neuronal axotomy and debilitating loss of sexual function or continence. In vitro studies have identified neurturin, a glial cell line-derived neurotrophic factor, as a neuromodulator for pelvic cholinergic neurons. We present the first in vivo report of the effects of neurturin upon the recovery of erectile function following bilateral cavernous nerve crush injury in the rat. Methods In these experiments, groups (n = 8 each) consisted of uninjured controls and animals treated with injection of albumin (blinded crush control group), extended release neurotrophin-4 or neurturin to the site of cavernous nerve crush injury (100 μg per animal). After 5 weeks, recovery of erectile function (treatment effect) was assessed by cavernous nerve electrostimulation and peak aortic pressures were measured. Investigators were unblinded to specific treatments after statistical analyses were completed. Results Erectile dysfunction was not observed in the sham group (mean maximal intracavernous pressure [ICP] increase of 117.5 ± 7.3 cmH2O), whereas nerve injury and albumin treatment (control) produced a significant reduction in ICP elevation of 40.0 ± 6.3 cmH2O. Neurturin facilitated the preservation of erectile function, with an ICP increase of 55% at 62.0 ± 9.2 cmH2O (p < 0.05 vs control). Extended release neurotrophin-4 did not significantly enhance recovery of erectile function with an ICP change of 46.9 ± 9.6. Peak aortic blood pressures did not differ between groups. No significant pre- and post-treatment weight differences were observed between control, neurotrophin-4 and neurturin cohorts. All animals tolerated the five-week treatment course. Conclusion Treatment with neurturin at the site of cavernous nerve crush injury facilitates recovery of erectile function. Results support further investigation of neurturin as a neuroprotective and/or neuroregenerative agent facilitating functional recovery after cavernous or other pelvic autonomic nerve injuries.

The effect of intracavernosal growth differentiation factor‐5 therapy in a rat model of cavernosal nerve injury

To determine whether the intracavernosal application of growth differentiation factor‐5 (GDF‐5) influences nerve regeneration and erectile function after cavernosal nerve injury in a rat model.

The potential of hormones and selective oestrogen receptor modulators in preventing voiding dysfunction in rats.

To investigate whether oestrogen, selective oestrogen receptor modulators (SERMs), and growth hormone (GH) can prevent the development of voiding dysfunction in a postpartum postmenopausal rat model of voiding dysfunction.