High expression of VEGF is associated with immature angiogenesis within the urinary bladder wall and bladder afferent nerve sensitization, leading to visceral hyperalgesia and pelvic pain. Research suggests a shift in VEGF alternative splice variant (VEGF-Axxxa and VEGF-Axxxb) expression with several pathologies (e.g., neuropathic pain and inflammation) as well as differing effects on pain. Translational studies have also demonstrated increased total VEGF expression in the bladders of women with interstitial cystitis/bladder pain syndrome. In the present study, we quantified VEGF alternative splice variant expression in lower urinary tract tissues under control conditions and with cyclophosphamide (CYP)-induced cystitis. Using conscious cystometry and intravesical instillation of a potent and selective VEGF receptor 2 (VEGFR2) tyrosine kinase inhibitor (Ki-8751, 1 mg/kg) in Wistar rats (male and female) with acute and chronic CYP-induced cystitis and control (no CYP) rats, we further determined the functional effects of VEGFR2 blockade on bladder function. With VEGFR2 blockade, bladder capacity increased (P ≤ 0.01) in male and female control rats as well as in male and female rats with acute (P ≤ 0.05) or chronic (P ≤ 0.01 or P ≤ 0.05, respectively) CYP-induced cystitis. Void volume also increased in female control rats (P ≤ 0.01) and female rats with acute (P ≤ 0.05) or chronic (P ≤ 0.05) CYP-induced cystitis as well as in male control rats (P ≤ 0.05) and male rats with chronic CYP-induced cystitis (P ≤ 0.01). These data suggest that VEGF may be a biomarker for interstitial cystitis/bladder pain syndrome and that targeting VEGF/VEGFR2 signaling may be an effective treatment.
Keywords: growth factors; inflammation; interstitial cystitis; micturition; pelvic pain; vascular endothelial growth factor.