Abstract
Abstract: :
Purpose: Previous work has shown that osteopontin (OPN), a multi-functional, secreted extracellular matrix protein, has been localized to the retinal ganglion cell layer of adult rat retina (Ju et al. Brain Research 2000, v 852, pp. 217-220). OPN has been shown to bind a number of integrins, in a variety of tissues. Experiments were performed to determine if OPN is present in the developing mouse retina and if it is capable of supporting neurite outgrowth. Methods: OPN expression and localization in embryonic C57/BL6 mouse retina of multiple developmental time points were determined via immunohistochemistry and Western blot. In vitro neurite outgrowth assays of embryonic day 15 mouse retinal cells were performed, using OPN as a substrate and various antibodies against integrin receptors to determine the role of OPN in process extension, as well as the integrin(s) involved. Results: OPN expression was widespread in E10 mouse retina and became more localized to the inner retina as development proceeded (E12, E15, E17, P1). Western blots of retinal extracts indicated the presence of OPN protein. Results of neurite outgrowth assays showed that process extension on OPN is inhibited by antibodies to mouse OPN and ß1 integrin and is partially inhibited by antibody to α4 integrin. Conclusions: Our findings suggest that OPN is present in the embryonic mouse retina and may be involved in the axon extension of retinal ganglion cells via a ß1 integrin.
Keywords: 564 retinal development • 403 extracellular matrix • 560 retinal culture