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

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.

Synapse and Receptor Alterations in Two Different S100B-Induced Glaucoma-Like Models

“…Though in DBA/2J mice no functional impairments could be observed in cells with normal morphology [ 94 ], rats with intraocular S100B injection showed a reduction in their electroretinogram amplitudes regarding the a- and b-wave after 14 days [ 29 ]. Although no electroretinogram data for systemic S100B immunization are available, rats that received a systemic ONA immunization showed a reduction in their a- and b-wave after 6 weeks [ 95 ], and S100B is a component of ONA [ 96 ]. The a-wave amplitude represents the electrical activity of the photoreceptors, and the b-wave amplitude reflects the electrical output of the inner nuclear layer.…”

Complement-Mediated Microglial Phagocytosis and Pathological Changes in the Development and Degeneration of the Visual System

“…AAV-mediated intravitreal delivery of a CR2-Crry construct, which inhibits all complement pathways at C3 activation, provides neuroprotection to RGCs in murine models of glaucoma (10) and MS (8). Finally, intravitreal injection of a monoclonal antibody against mouse C5 also protected RGCs in a glaucoma model (11). These preclinical studies highlight the potential of targeted and/or localized delivery of complement inhibition with multiple modes of administration in reducing RGC death and visual loss in models of retinal and neurological disease.…”

“…AAV-mediated expression of soluble C3d-targeted CR2-Crry by retinal ganglion cells reduces neuronal loss in a glaucoma model ( 10 ), in part by inhibiting phagocytosis of opsonized RGC synapses. Inhibition of C5 via intravitreal injection of an anti-C5 monoclonal antibody also reduced neuronal loss ( 11 ), indicating that both C3 activation products and terminal pathway products (C5a and/or MAC) may contribute to RGC loss.…”

“…However, aberrant overactivation of the complement system in retinal disease can result in damage to RGCs with degradation and loss of synaptic connections on the retinal or thalamic side (4). The role of complement-mediated inflammation in retinal disease in general and anterograde degeneration of RGCs in particular is quite well explored, and several preclinical and clinical studies show that inhibiting specific complement pathways is protective (9)(10)(11)(12).…”

Glaukom im Fokus

“…Außerdem wurden die retinalen Ganglienzellen vor einem Verlust geschützt (Abb. 2 a, b) [13]. Auch die Auswirkung der C5-Therapie auf die Sehnerven wurde analysiert.…”