Histochemical study of retinal photoreceptors development during pre- and postnatal period and their association with retinal pigment epithelium

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Objective(s):The aim of this study was to evaluate distribution and changes of glycoconjugates of retinal photoreceptors during both pre- and postnatal development. Materials and Methods: Tissue sections from days 15 to 20 of Wistar rat embryos and 1 to 12 postnatal days of rat newborns including developing eye were prepared for lectinhistochemistry technique. Horseradish peroxidase (HRP)-labeled lectins including Vicia villosa (VVA), peanut agglutinin (PNA), Maclura pomifera (MPA) and wheat germ agglutinin (WGA-ІІ) were used. Alcian blue (pH 2.5) was used for counterstaining. Results: Interphotoreceptor matrix (IPM) plays a crucial role in photoreceptors differentiation and acts as a mediator in interactions between photoreceptors and retinal pigment epithelium (RPE). Specific cell surface glycoconjugates secreted from cone cells could help us to distinguish these cells from rod photoreceptors. Our results for the first time revealed the strong reaction of cone photoreceptors with the cone-specific lectin (PNA) at postnatal day 12 (P12).  Postnatal day 12 can be determined as the final differentiation of cone photoreceptors. Conclusion: According to our findings, we suggest that the generation of the eye photoreceptors begins from pre- natal period and their final differentiations will continue to postnatal period. Glycoconjugates including (β-D-Gal [1–3]-D-GalNac) and (β-D-Gal) terminal sugars play a critical role in the pre- and postnatal development and differentiation of retinal photoreceptors.