AB303. SPR-30 Neurotrophin dysregulation after dual injury childbirth model is corrected via electrical stimulation of the pudendal nerve in a rat model

Objective: Stress urinary incontinence (SUI), the leakage of urine due to an increase in abdominal pressure, affects 30% of women over the age of 40. Childbirth is the primary risk factor for SUI since the child’s head passing through the birth canal can injure the EUS and the nerve that innervates it, the pudendal nerve (PN). Animal models with combined EUS [vaginal distension (VD)] and PN crush (PNC) injuries have shown that the nerve does not recover as well as with PNC alone and the animals have delayed return of function. Typically after a nerve injury, the neuron upregulates neurotrophin factors [i.e., brain derived neurotrophin factor (BDNF)] and their receptors [i.e., tyrosine kinase B (Trk B) and p75], and Schwann cells also upregulate neurotrophin factors [i.e., glial derived neurotrophin factor (GDNF) and NT4] as part of the regeneration process. The impaired nerve regeneration in the dual injury model was shown to be due to a dysregulation of BDNF in the PN motoneuron, so any potential treatment would need to upregulate BDNF. Electrical stimulation (ES) has been shown to upregulate BDNF and Trk B in neurons and GDNF in Schwann cells. Our previous work has shown daily and 4 times per week stimulation for 2 weeks accelerates functional recovery after PNC + VD. The aim of the study was to determine if daily stimulation causes an upregulation of neurotrophin factor and their receptors in motoneurons of the PN after injury. We hypothesize that the accelerated recovery from ES is mediated by an upregulation of BDNF and NT4 and their receptor Trk B, as well as GFRα1, the receptor of GDNF.

Methods: Animals were divided into five groups: Sham PNC, PNC, PNC + VD, PNC + VD with sham stimulation (SS) or PNC + VD + ES. ES (20 Hz, 0.3 mA, 0.1 ms) was conducted daily for 1 or 2 weeks after injury, when the spinal cord was harvested from L4–S3. The spinal cord was sectioned and Onuf’s nucleus, the motoneuron nucleus for the PN, was harvested via laser capture microscopy. RNA was then isolated and preamplified before running PCR and compared to GAPDH expression. A one way Anova was used to determine statistically significant differences between groups.

Results: One week after PNC + VD, BDNF was not upregulated as previously shown. Neither were p75 or GFRα1, as expected. NT4 was not downregulated after PNC + VD, as expected. P75 was significantly increased in the PNC + VD + ES group compared to the PNC + VD group 2 weeks after injury. BDNF was also upregulated 2 weeks after PNC + VD + ES compared to PNC + VD.

Conclusions: P75, NT4 and GFRα1 expression data suggest that PNC + VD causes dysregulation of other regenerative proteins other than BDNF. BDNF was upregulated 2 weeks after PNC + VD with ES. Future research will be designed to investigate the mechanism of this effect.

Funding Source(s): VA Merit A1262-R and the RR&D Service of the VA

Keywords: Neurotrophic factors; neuromodulation; gene expression; stress urinary incontinence (SUI); childbirth injury model