Nerve Injury-Induced Protein 1 (Ninjurin-1) Is a Novel Therapeutic Target for Cavernous Nerve Injury-Induced Erectile Dysfunction in Mice

IntroductionRadical prostatectomy for prostate cancer can not only induce cavernous nerve injury (CNI) but also result in structural changes in the cavernous tissues. Nerve injuryinduced protein 1, Ninjurin1 (Ninj1), is known to be involved in neuroinflammatory processes and to be related to vascular regression during the embryonic period.AimThe study aims to determine whether and how Ninj1 neutralizing antibody (Ninj1Ab) restores erectile function in mice with CNI.MethodsTwelveweekold C57BL/6J mice were used and distributed into four groups: sham operation group and CNI groups receiving a single intracavernous injection of immunoglobulin G (IgG) control antibody, lowdose Ninj1Ab (1.0 μg/20 μL), or highdose Ninj1Ab (2.5 μg/20 μL).Main Outcome MeasuresOne week after bilateral cavernous nerve crush, erectile function was measured by electrical stimulation of the cavernous nerve. The penis was harvested for histologic examinations and Western blot analysis.ResultsThe cavernous expression of Ninj1 protein was upregulated up to 7 days after CNI and returned to baseline levels thereafter. Local delivery of Ninj1Ab significantly increased penile neuronal nitric oxide synthase and neurofilament contents, induced cavernous endothelial proliferation and phosphorylation of Akt and endothelial nitric oxide synthase, and decreased endothelial cell apoptosis in the CNI mice by upregulating angiopoietin1 and downregulating angiopoietin2. Highdose Ninj1Ab induced profound restoration of erectile function in the CNI mice (91% of sham control values), whereas lowdose Ninj1Ab elicited partial improvement.ConclusionThe dual neurotrophic and angiogenic effects of Ninj1 blockade may provide a good opportunity for treating erectile dysfunction resulting from radical prostatectomy.