Background: Retinitis pigmentosa is characterized by the sequential loss of rod and cone photoreceptors. The\r\npreservation of cones would prevent blindness due to their essential role in human vision. Rod-derived Cone\r\nViability Factor is a thioredoxin-like protein that is secreted by rods and is involved in cone survival. To validate the\r\nactivity of Rod-derived Cone Viability Factors (RdCVFs) as therapeutic agents for treating retinitis Pigmentosa, we\r\nhave developed e-conome, an automated cell counting platform for retinal flat mounts of rodent models of cone\r\ndegeneration. This automated quantification method allows for faster data analysis thereby accelerating\r\ntranslational research.\r\nMethods: An inverted fluorescent microscope, motorized and coupled to a CCD camera records images of cones\r\nlabeled with fluorescent peanut agglutinin lectin on flat-mounted retinas. In an average of 300 fields per retina,\r\nnine Z-planes at magnification X40 are acquired after two-stage autofocus individually for each field. The projection\r\nof the stack of 9 images is subject to a threshold, filtered to exclude aberrant images based on preset variables.\r\nThe cones are identified by treating the resulting image using 13 variables empirically determined. The cone\r\ndensity is calculated over the 300 fields.\r\nResults: The method was validated by comparison to the conventional stereological counting. The decrease in\r\ncone density in rd1 mouse was found to be equivalent to the decrease determined by stereological counting. We\r\nalso studied the spatiotemporal pattern of the degeneration of cones in the rd1 mouse and show that while the\r\nreduction in cone density starts in the central part of the retina, cone degeneration progresses at the same speed\r\nover the whole retinal surface. We finally show that for mice with an inactivation of the Nucleoredoxin-like genes\r\nNxnl1 or Nxnl2 encoding RdCVFs, the loss of cones is more pronounced in the ventral retina.\r\nConclusion: The automated platform e-conome used here for retinal disease is a tool that can broadly accelerate\r\ntranslational research for neurodegenerative diseases.
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