Nerve Growth Factor (NGF) is essential in the development and survival of cells of the nervous system. In a cohort of female aging patients diagnosed with overactive bladder (OAB), its urinary levels are low compared to healthy controls. High activity of the enzyme matrix metalloproteinase-9 (MMP-9), the main protease that degrades NGF into inactive peptides was oberved in the same samples. Murine diabetic models with bladder dysfunction also display low NGF content in bladder tissue with elevated MMP-9. Chronic treatment of these mice with THX-B, an antagonist of the pro-inflammatory receptor p75NTR, restored NGF levels in bladder and improved detrusor contractile activity. MMP-9 levels were decreased by THX-B only in female. We aim here to understand the differences in NGF synthesis between male and female bladder cells.

Smooth muscle (SMC) and urothelial (URO) cells were isolated from male and female sprague-Dawley rat bladders after collagenase IV digestion. Cells were incubated for 24 hours with THX-B (5 microg/mL) or the nitric oxide generator sodium nitroprusside (SNP, 300 microM). Cell extracts and culture medium were analyzed using Elisa kits (NGF and proNGF), enzyme activity (MMP-9, furin, plasmin) by enzymatic kits, RTqPCR and immunoblotting for cell proteins.

THX-B led to an increase in NGF secretion from male and female urothelial cells while proNGF was increased in male only. No changes by THX-B was observed in SMC in both gender. SNP decreased NGF secretion in URO and SMC in female cells only. On the other hand, THX-B and SNP respectively decreased and increased MMP-9 activity in female cells while male cells were unaffected by both treatment. NGF mRNA levels were unaffected in both gender. Proteolytic enzymes converting proNGF into NGF, namely plasmin, MMP-7, MMP-3 and furin, were increased by SNP and THX-B in female cells while the same enzymes were decreased in male cells, suggesting other post-translational point of controls of mature NGF synthesis in the latter.

Sex-specific processing of neurotrophins has been observed in other pathologies such as Alzheimer's disease. Interestingly, the same proteases appear to be involved in LUTS.

These data confirmed that the mechanisms regulating the secretion of NGF and proNGF in rats is sex-specific and relies on different pathways of synthesis. These data should be taken into account when considering OAB in male and female patients.