Abstract
Purpose: :
Evaluation of animals models of human retinitis pigmentosa have been extensively documented. However, substantive documentation of human samples of retinitis pigmentosa have not been introduced into the literature. Our goal was to assess the state and condition of the late stage human retina with retinitis pigmentosa and evaluate the dependance of retinal remodeling on cone survival.
Methods: :
Samples from human subjects with retinitis pigmentosa were collected post-mortem through the Utah Lions Eye Bank and incubated with 1-amino-4-guanidobutane (AGB). Retinal fragments were incubated 10 minutes at 35 degrees C in oxygenated Ames-Hepes medium with 5mM AGB with and without iGluR agonists (KA 50uM, NMDA 1mM), followed by conventional fixation in buffered aldehydes and embedding in epoxy resins. Tissues were sectioned at 200nm followed by classification with computational molecular phenotyping (CMP) using an array of small and macromolecular signatures (aspartate, glutamate, glycine, glutamine, glutathione, GABA, taurine, CRALBP, GS, rhodopsin, LWS1 cone opsin, tyrosine hydroxylase).
Results: :
As in animal models of retinitis pigmentosa and most notably the P347L transgenic rabbit, progressive rod-specific degeneration leads to complete elimination of rods and rod signaling. There is extensive survival of substantially altered cones. However, the presence of cones prevents the onset of radical remodeling in the retina, also preserving iGluR mediated signaling to surviving horizontal and bipolar cells. Those surviving bipolar and horizontal cells demonstrate neurite sprouting and potential bipolar cell and retinal reprogramming through upregulation of iGluR expression.
Conclusions: :
Disease progression observed in the human condition shows that animal models of retinal degeneration recapitulate the human condition. Cone mediated preservation of bipolar cell signaling, retinal reprogramming and retinal remodeling seen in the human retinitis pigmentosa retina are all duplicated in animal models.
Keywords: retina • retina: distal (photoreceptors, horizontal cells, bipolar cells) • retina: proximal (bipolar, amacrine, and ganglion cells)