BDNF and cAMP promote retinal ganglion cell survival and function in a porcine model of traumatic optic neuropathy

Abstract

Purpose : Neurotrophic factors play a key role in neuroprotection and regeneration of retinal ganglion cells (RGCs) as shown in rodent models of optic neuropathies. However, advancement towards clinical application has been limited by lack of data from large animal models. Here we tested the hypothesis that brain-derived neurotrophic factor (BDNF) and 8-(4-chlorophenylthio) (CPT)-cAMP together promote RGC survival in a porcine model of traumatic optic neuropathy.

Methods : Optic nerve crush (ONC) was surgically performed in Yucatan minipigs (5.5-6 months old) under general anesthesia. The contralateral optic nerves served as uncrushed controls. At the end of surgery, BDNF and CPT-cAMP (or 0.9% NaCl for vehicle control) were intravitreally injected into both eyes. Fundus exams, intraocular pressure measurements, and flash visual evoked potential (fVEP) recordings were performed prior to and 2 and 4 weeks after ONC. At week 3, eyes were injected with cholera toxin B subunit (CTB) to anterogradely label RGC axons in the optic nerve. At week 4, eyes and optic nerves were harvested and fixed. Retinas were dissected and immunostained for RBPMS (RGC marker), mounted, imaged by confocal microscopy, and quantified for RGC survival. Optic nerves were cryosectioned, imaged by fluorescent microscopy, and analyzed for RGC axon survival and regeneration.

Results : Fundus exam revealed edema of optic nerve head in the crushed eye and bilateral vascular attenuation after unilateral ONC. No change was observed in intraocular pressure. fVEP after ONC exhibited lower peak amplitude compared to uncrushed controls, and BDNF plus CPT-cAMP-treated eyes had decreased variation in peak latency compared to vehicle control. RBPMS immunofluorescence revealed increased RGC survival in retinal flatmounts treated with BDNF plus CPT-cAMP, and increased axon survival was observed in optic nerve sections from treated animals.

Conclusions : BDNF and CPT-cAMP treatment resulted in improved functional and histological outcomes for RGCs in a large animal injury model. This combination of neurotrophic factors has therapeutic potential for neuroprotection after optic nerve injury.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

BDNF and CPT-cAMP treatment promotes RGC survival in Yucatan minipigs. (A) Longitudinal sections of CTB-labeled optic nerves and (B) RBPMS-immunostained retinal flatmounts from animals 4 weeks after ONC. *, ONC site.