Cocultured Schwann Cells Rescue Irradiated Pelvic Neuron Outgrowth and Increase Survival

Abstract

ABSTRACTBackgroundProstatic radiation therapy (RT) leads to erectile dysfunction by damaging peri-prostatic pro-erectile nerves of the pelvic ganglion. Schwann cells (SC) facilitate neuronal repair after mechanical injury, however, their role in repair of pelvic neurons post-radiation hasn’t been explored.AimTo determine if SCs cocultured with primary pelvic neurons can rescue neuronal survival and growth after ex vivo RT.MethodsMajor pelvic ganglia (MPG) were collected from adult male Sprague-Dawley rats (n = 12) to isolate SCs. SCs received RT (0 or 8 Gy), were plated on coated coverslips and grown to confluence before the addition of neurons. Additional MPGs were irradiated (0 or 8 Gy) and digested to isolate pelvic neurons. Dissociated neurons were plated alone or atop SC-coated coverslips to create 6 experimental groups (n = 3/grp): (i) Control (CON) MPG, (ii) RT MPG, (iii) CON SC + CON MPG, (iv) CONSC + RT MPG, (v) RT SC + CON MPG, and (iv) RT SC + RT MPG. After 72 hours, coverslips were fixed and stained for beta-tubulin (neuron marker), S100 (SC marker), neuronal nitric oxide synthase (nitrergic marker), tyrosine hydroxylase (sympathetic marker), and terminal deoxynucleotidyl transferase dUTP nick-end labeling.OutcomesWe measured neurite length, branching, specific neuron populations and apoptosis.ResultsEx vivo RT decreased MPG neuron length, increased apoptosis and decreased nitrergic neurons in monoculture. Compared to all other groups, CON SC + RT MPG cocultures demonstrated increased neurite outgrowth (P < .001). Neurite branching was decreased in the RT MPG + RT SC coculture, but unchanged in other cocultures. Groups containing RT MPG neurons exhibited increased apoptosis, but coculture with CON SC reduced the degree of RT-induced apoptosis (P < .01). The number of tyrosine hydroxylase positive neurons was unchanged while nitrergic neurons were significantly lower in RT neurons and coculture with CON SCs was unable to prevent nitrergic loss.Clinical TranslationThese findings suggest that SCs may be an important target in prostate cancer patients with radiation-induced pelvic neuropathy to promote MPG neuron survival and neuronal repair after RT.Strengths and LimitationsThis is the first study to characterize the ex vivo ability of SCs to rescue pelvic nerve growth and survival. The study is limited by little supporting mechanistic molecular data and the need to confirm the ability of healthy SCs to promote pelvic neuron survival and repair following prostatic RT in vivo.ConclusionUnirradiated SCs partially mitigated RT-induced MPG apoptosis but did not affect the loss of nitrergic neuron populations suggesting that SCs promote irradiated MPG neuron survival and facilitate intrinsic repair functions.