Complement C3-targeted gene therapy restricts onset and progression of neurodegeneration in chronic mouse glaucoma

Abstract

Dysregulation of the complement system is implicated in neurodegeneration, including human and animal glaucoma. Optic nerve and retinal damage in glaucoma is preceded by local complement upregulation and activation, but whether targeting this early innate immune response could have therapeutic benefit remains undefined. Because complement signals through three pathways that intersect at complement C3 activation, here we targeted this step to restore complement balance in the glaucomatous retina, and to determine its contribution to degeneration onset and/or progression. To achieve this, we combined adeno-associated viral retinal gene therapy with the targeted C3 inhibitor CR2-Crry. We show that intravitreal injection of AAV2.CR2-Crry produced sustained Crry overexpression in the retina, and reduced deposition of the activation product complement C3d on retinal ganglion cells and the inner retina of DBA/2J mice.This resulted in neuroprotection of retinal ganglion cell axons and somata despite continued intraocular pressure elevation, suggesting a direct restriction of neurodegeneration onset and progression, and significant delay to terminal disease stages. Our study uncovers a damaging effect of complement C3 or downstream complement activation in glaucoma and establishes AAV2.CR2-Crry as a viable therapeutic strategy to target pathogenic C3-mediated complement activation in the glaucomatous retina.

Developmental roles of microglia: A window into mechanisms of disease

“…C1q is localized to RGC compartments (Stevens et al, ), and KO in the DBA/2J mouse is neuroprotective (Howell et al, ), while paradoxically KO of C3 worsens pathology (Harder et al, ), suggesting that the roles of complement are complex. Targeted inhibition of the C3 activation step by retinal gene therapy restricts the progression of neurodegeneration (Bosco et al ). AMD is associated with mutations in several complement proteins and the pathogenic role of complement system has received great attention (Anderson et al, ; Warwick et al, ; Bora et al, ; McHarg et al, ).…”

Ocular hypertension suppresses homeostatic gene expression in optic nerve head microglia of DBA/2 J mice

“…Notably these data pointed to major neuroinflammatory changes at a pre-degenerative stage of disease, including changes in the complement system, endothelin system, and cell-adhesion pathways. Our group and others have experimentally validated molecules in these pathways to demonstrate their importance and role in glaucoma (from mouse to human [2,12,[23][24][25][26][27][28][29];). In addition, these pathways have been independently identified in other models of glaucomatous insult and retinal ganglion cell death (ocular hypertension, optic nerve crush, optic nerve transection / axotomy [30][31][32]) supporting the utility of DBA/2 J retina and optic nerve head tissue for modelling glaucoma.…”

GLP-1 Receptor Agonist NLY01 Reduces Retinal Inflammation and Neuron Death Secondary to Ocular Hypertension

“…A1 astrocytes upregulate C3 , and C3 inhibitors were shown to reduce RGC cell death in the DBA/2J mouse model of glaucoma (Bosco et al, 2018). We demonstrate elevated C3 production following A1 activation and decreased C3 production following NLY01 inhibition in our glaucoma model.…”