Gene Therapy into Photoreceptors and Müller Glial Cells Restores Retinal Structure and Function in Crb1 Retinitis Pigmentosa Mouse Models

Abstract

Purpose: Mutations in the CRB1 gene lead to severe recessive inherited retinal dystrophies. Gene transfer therapy is the most promising cure for retinal dystrophies and has primarily been applied for recessive null conditions via a viral gene expression vector transferring a cDNA encoding an enzyme or channel protein, and targeting expression to one cell type. Therapy for the human CRB1 disease will be more complex, as CRB1 is a structural and signaling transmembrane protein present in three cell classes: Müller glia, cone and rod photoreceptors. In this study, we applied CRB1 and CRB2 gene therapy vectors in Crb1-retinitis pigmentosa mouse models at mid-stage disease.

Methods: We used subretinal injection of AAV viral CRB1 or CRB2 gene therapy vectors into mouse eyes lacking Crb1 and/or Crb2 proteins, and analysed the eyes by electroretinography, histology, immunohistochemistry, and immunoelectron microscopy.

Results: We tested if CRB expression restricted to Müller glial cells or photoreceptors or co-expression in both is required to recover retinal function. We show that targeting both Müller glial cells and photoreceptors with the CRB2 gene therapy vector ameliorated retinal function and structure in Crb1 mouse models. Surprisingly, targeting a single cell type or all cell types with the CRB1 gene therapy vector reduced retinal function.

Conclusions: We show the first pre-clinical studies for CRB1-related eye disorders using CRB2 gene therapy vectors and initial elucidation of the cellular mechanisms underlying CRB1 function.