TECHNICAL ADVANCE Open Access ℮-conome: an automated tissue counting platform of cone photoreceptors for rodent models of retinitis pigmentosa Emmanuelle Clérin 1,2,3 , Nicolas Wicker 4 , Saddek Mohand-Saïd 1,2,3 , Olivier Poch 4 , José-Alain Sahel 1,2,3 and Thierry Léveillard 1,2,3* Abstract Background: Retinitis pigmentosa is characterized by the sequential loss of rod and cone photoreceptors. The preservation of cones would prevent blindness due to their essential role in human vision. Rod-derived Cone Viability Factor is a thioredoxin-like protein that is secreted by rods and is involved in cone survival. To validate the activity of Rod-derived Cone Viability Factors (RdCVFs) as therapeutic agents for treating retinitis Pigmentosa, we have developed e-conome, an automated cell counting platform for retinal flat mounts of rodent models of cone degeneration. This automated quantification method allows for faster data analysis thereby accelerating translational research. Methods: An inverted fluorescent microscope, motorized and coupled to a CCD camera records images of cones labeled with fluorescent peanut agglutinin lectin on flat-mounted retinas. In an average of 300 fields per retina, nine Z-planes at magnification X40 are acquired after two-stage autofocus individually for each field. The projection of the stack of 9 images is subject to a threshold, filtered to exclude aberrant images based on preset variables. The cones are identified by treating the resulting image using 13 variables empirically determined. The cone density is calculated over the 300 fields. Results: The method was validated by comparison to the conventional stereological counting. The decrease in cone density in rd1 mouse was found to be equivalent to the decrease determined by stereological counting. We also studied the spatiotemporal pattern of the degeneration of cones in the rd1 mouse and show that while the reduction in cone density starts in the central part of the retina, cone degeneration progresses at the same speed over the whole retinal surface. We finally show that for mice with an inactivation of the Nucleoredoxin-like genes Nxnl1 or Nxnl2 encoding RdCVFs, the loss of cones is more pronounced in the ventral retina. Conclusion: The automated platform ℮-conome used here for retinal disease is a tool that can broadly accelerate translational research for neurodegenerative diseases. Background Retinitis pigmentosa (RP) is characterized clinically by an initial loss of night vision resulting from the degeneration of rod photoreceptors directly due to a genetic deficit, fol- lowed irreparably over a period of several years by the loss of central vision that results from the non-cell autono- mous death of cone photoreceptors [1]. Because cones dominate the centre of the retina and are responsible for the high-acuity and color vision, their preservation would be medically relevant as a therapy aimed at preventing blindness [2]. We have studied the mechanisms involved in the secondary degeneration of cone photoreceptors in the rd1 mouse model of recessive RP, which carries a mutation in the rod photoreceptor-specific cGMP phos- phodiesterase b-subunit gene [3]. Initially, we showed that grafting normal photoreceptors (97% of rods) into the eyes of this rod-less model, before the degeneration of cones, exerts a protective effect on cones [4]. We subsequently demonstrated that the neuroprotective activity was * Correspondence: thierry.leveillard@inserm.fr 1 INSERM, U968, Paris, F-75012, France Full list of author information is available at the end of the article Clérin et al. BMC Ophthalmology 2011, 11:38 http://www.biomedcentral.com/1471-2415/11/38 © 2011 Clérin et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.