Intravitreal Therapy Against the Complement Factor C5 Prevents Retinal Degeneration in an Experimental Autoimmune Glaucoma Model.

Sabrina Reinehr,Stephanie C Joachim,Marc Schargus,H Burkhard Dick,M Ali Asaad,Sara C Gomes,Caroline J Gassel,Gesa Stute

doi:10.3389/fphar.2019.01381

Abstract

In glaucoma, studies revealed an involvement of the complement system. In an experimental autoimmune glaucoma model, immunization with an optic nerve homogenate antigen (ONA) led to retinal ganglion cell (RGC) loss, while intraocular pressure (IOP) remained unchanged. Here, we investigated the therapeutic effect of a complement system inhibition in this model. Hence, rats were immunized with ONA and compared to controls. In one eye of the ONA animals, an antibody against complement factor C5 was intravitreally injected (15 μmol: ONA+C5-I or 25 μmol: ONA+C5-II) before immunization and then every two weeks. IOP was measured weekly. After 6 weeks, spectral-domain optical coherence tomographies (SD-OCT), electroretinograms (ERG), immunohistochemistry, and quantitative real-time PCR analyses were performed. IOP and retinal thickness remained unchanged within all groups. The a-wave amplitudes were not altered in the ONA and ONA+C5-I groups, whereas a decrease was noted in ONA+C5-II animals (p < 0.05). ONA immunization provoked a significant decrease of the b-wave amplitude (p < 0.05), which could be preserved in ONA+C5-I, but not in ONA+C5-II animals. ONA animals showed a loss of RGCs (p = 0.001), while ONA+C5-I and ONA+C5-II retinae had similar cell counts as controls. A significant downregulation of apoptotic Bax/Bcl2 mRNA was noted in ONA+C5-I retinae (p = 0.02). Significantly more C3+ and MAC+ cells were observed in ONA animals (p < 0.001). The amount of C3+ cells in both treatment groups was significantly increased (p < 0.01), while the number of MAC+ cells in the treated retinas did not differ from controls. The number of activated microglia cells remained unchanged in ONA animals, but was increased in the treatment groups (p < 0.05). Recoverin+ cells were diminished in ONA animals (p = 0.049), but not in treated ones. Rho mRNA was downregulated in ONA and in ONA+C5-II retinas (both p = 0.014). Less opsin+ cones were observed in ONA animals (p = 0.009), but not in the treated groups. Our results indicate that the C5 antibody inhibits activation of the complement system, preventing the loss of retinal function as well as RGC, cone bipolar, and photoreceptor loss. Therefore, this approach might be a suitable new treatment for glaucoma patients, in which immune dysregulation plays an important factor for the development and progression of glaucoma.

Highlights

Glaucoma is a group of diseases of various causes with progressive optic nerve degeneration and loss of retinal ganglion cells (RGCs) with advancing visual field loss (Weinreb et al, 2014)
A dysregulation of the complement system seems to contribute to glaucoma damage
The results presented here depicted RGC loss after ONA immunization, which could be preserved by administration of the C5 antibody

Summary

Introduction

Glaucoma is a group of diseases of various causes with progressive optic nerve degeneration and loss of retinal ganglion cells (RGCs) with advancing visual field loss (Weinreb et al, 2014). It is the second most common cause of blindness worldwide (Quigley and Broman, 2006). One-sixth to one-third of patients with openangle glaucoma show normal IOP levels This form of glaucoma is called normal-pressure glaucoma (EGS, 2017). Disease-specific changes in complex autoantibody profiles were found in sera from glaucoma patients (Joachim et al, 2008; Reichelt et al, 2008). Differences in the profiles of IgG autoantibodies between patients with normalpressure glaucoma and patients with high pressure glaucoma were described (Tezel et al, 1998; Grus et al, 2004; Grus et al, 2006)

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