HDAC inhibition ameliorates cone survival in retinitis pigmentosa mice

Cone photoreceptor cell death in inherited retinal diseases, such as Retinitis Pigmentosa (RP), leads to the loss of accurate and color vision and ultimately blindness. In RP, a vast number of mutations are affecting the structure and function of rod photoreceptors while cones remain mutation-free. Once majority of rods have degenerated cones are dying secondarily due to the increased oxidative stress, inflammation and loss of structural and nutritional support normally provided by rods. Here we demonstrated that secondary cone cell death in animal models for RP is governed by an increased activity of histone deacetylates (HDACs). A single intravitreal injection of an HDAC inhibitor at a late stage of the disease, when majority of rods have already degenerated, is sufficient to delay cone death and support long-term cone survival. Surviving cones are retaining functionality and are mediating light-driven ganglion cell responses. RNA-seq analysis of surviving cones demonstrated that HDAC inhibition affords multi-level protection trough regulation of different prosurvival pathways including MAPK, PI3K-AKT and autophagy. These study suggest a unique possibility for targeted pharmacological protection of both primary degenerating rods and mutation-free secondary dying cones and creates hope to maintain vision in RP patients independent of the disease stage. Overall design: 2000 to 5000 frozen sorted-cells were lysed in approximatively 10µl of lysis buffer and cDNA synthesis was performed using the SMART-Seq v4 Ultra Low Input RNA Kit (catalog 634888, Takara Bio). First-strand cDNA synthesis was performed using 20 to 50% of the input and was followed by full-length double-strand cDNA amplification using 17 PCR cycles. Quality of the resulting cDNA was validated using Bioanalyzer and High Sensitivity DNA Kit (Agilent) as well as Qubit dsDNA HS fluorometric quantification (ThermoFisher Scientific). NGS libraries were prepared using 150 pg of cDNA input and the Nextera XT DNA Library Preparation Kit (catalog FC-131-1024, Illumina) with 11 cycles of PCR.