Erythropoietin Slows Photoreceptor Cell Death in a Mouse Model of Autosomal Dominant Retinitis Pigmentosa.

PURPOSE:To test the efficacy of systemic gene delivery of a mutant form of erythropoietin (EPO-R76E) that has attenuated erythropoietic activity, in a mouse model of autosomal dominant retinitis pigmentosa. METHODS:Ten-day old mice carrying one copy of human rhodopsin with the P23H mutation and both copies of wild-type mouse rhodopsin (hP23H RHO+/-,mRHO+/+) were injected into the quadriceps with recombinant adeno-associated virus (rAAV) carrying either enhanced green fluorescent protein (eGFP) or EpoR76E. Visual function (electroretinogram) and retina structure (optical coherence tomography, histology, and immunohistochemistry) were assessed at 7 and 12 months of age. RESULTS:The outer nuclear layer thickness decreased over time at a slower rate in rAAV.EpoR76E treated as compared to the rAAV.eGFP injected mice. There was a statistically significant preservation of the electroretinogram at 7, but not 12 months of age. CONCLUSIONS:Systemic EPO-R76E slows death of the photoreceptors and vision loss in hP23H RHO+/-,mRHO+/+ mice. Treatment with EPO-R76E may widen the therapeutic window for retinal degeneration patients by increasing the number of viable cells. Future studies might investigate if co-treatment with EPO-R76E and gene replacement therapy is more effective than gene replacement therapy alone

Systemic rAAV.EpoR76E preserves ONL thickness.

<p>A-C) OCT images (A, B) and quantification (C) in 7-month old hP23H <i>RHO</i>^+/-,m<i>RHO</i>^+/+ mice. D-F) OCT images (D,E) and quantification (F) in 12-month old hP23H <i>RHO</i>^+/-,m<i>RHO</i>^+/+ mice. Bars in images indicate ONL thickness. ***p<0.001.</p

Systemic rAAV.EpoR76E has no effect on opsin localization or glial reactivity.

<p>Representative fluorescence micrographs near the optic nerve of 12-month old hP23H <i>RHO</i>^+/-,m<i>RHO</i>^+/+ mice treated with rAAV.eGFP (A, C, E), or rAAV.EpoR76E (B, D, F) labeled with DAPI (blue) and anti-rhodopsin (red; A, B), anti-M/L and anti-S-cone opsins (green; C,D), or anti-GFAP (red; E,F). Scale bar represents 50μm. Examples of microglial infiltration into the ONL in 12-month old hP23H <i>RHO</i>^+/-,m<i>RHO</i>^+/+ mice treated with rAAV.eGFP (G), or rAAV.EpoR76E (H), DAPI (blue), anti-IBA1 (red). Scale bar represents 25 μm.</p

Systemic rAAV.EpoR76E preserves scotopic ERG amax.

<p>A) Representative waveforms from 7 month old hP23H <i>RHO</i>^+/-,m<i>RHO</i>^+/+ mice at 2.88 cd•s/m². B) Quantification of the ERG amax at 0, 1, and 2.88 cd•s/m² in wild-type and 7- month old hP23H <i>RHO</i>^+/-,m<i>RHO</i>^+/+ mice. ***p<0.001. C) Quantification of the scotopic ERG bmax in wild-type and 7-month old hP23H <i>RHO</i>^+/-,m<i>RHO</i>^+/+ mice. D) Quantification of photopic bmax in wild-type and 12-month old hP23H <i>RHO</i>^+/-,m<i>RHO</i>^+/+ mice.</p