To investigate the level of nerve growth factor (NGF) mRNA in bladder tissue and the effect of botulinum toxin A (BTX-A) treatment in patients with interstitial cystitis (IC).

A total of 19 patients with IC were treated with 100 U or 200 U of intravesical BTX-A injections followed by cystoscopic hydrodistension 2 weeks later. Bladder mucosa biopsies were performed before BTX-A injection and immediately after hydrodilation and in 12 controls. The NGF mRNA and protein levels in bladder tissues were assessed by real-time polymerase chain reaction and immunohistochemistry studies to determine differences in NGF expression between patients with IC before and after BTX-A treatment and compare with controls.

At 3 months, 14 patients had symptomatic improvement (responders) and 5 did not (nonresponders). The NGF mRNA levels at baseline in the overall IC patient group were significantly greater than those in the controls (0.65 ± 0.33 versus 0.42 ± 0.25, P = 0.046). At 2 weeks after BTX-A treatment, the NGF mRNA levels had decreased to 0.47 ± 0.23 (P = 0.002, compared with baseline) and were no longer significantly different from those of the controls. The NGF mRNA levels decreased significantly in responders and were significantly decreased after BTX-A in 11 patients with a visual analog pain scale reduction of 2 or more. The immunoreactivity study of bladder tissue from patients with IC showed greater NGF density at baseline compared with controls, but the difference was no longer significant after successful BTX-A treatment.

Intravesical BTX-A injections plus hydrodistension reduce bladder pain in patients with IC. The NGF levels in the bladder tissue were significantly increased in patients with IC and decreased to normal level after treatment in responders.