Rod-cone interactions: Developmental and clinical significance

During the last decade, numerous research reports have considerably improve d our knowledge about the physiopathology of retinal degenerations. Three n on-mutually exclusive general areas dealing with therapeutic approaches hav e been proposed; gene therapy, pharmacology and retinal transplantations. T he first approach involving correction of the initial mutation, will need a great deal of time and further development before becoming a therapeutic t ool in human clinical practice. The observation that cone photoreceptors, e ven those seemingly unaffected by any described anomaly, die secondarily to rod disappearance related to mutations expressed specifically in the latte r, led us to study the interactions between these two photoreceptor populat ions to search for possible causal links between rod degeneration and cone death. These in vivo and in vitro studies suggest that paracrine interactio ns between both cell types exist and that rods are necessary for continued cone survival. Since the role of cones in visual perception is essential, p ending the identification of the factors mediating these interactions under way, rod replacement by transplantation and/or neuroprotection by trophic f actors or alternative pharmacological means appear as promising approaches for limiting secondary cone loss in currently untreatable blinding conditio ns. (C) 2001 Elsevier Science Ltd. All rights reserved.