Abstract
Abstract: :
Purpose: We have shown previously that osteopontin (OPN) is a novel neurite outgrowth–promoting extracellular matrix protein in the mouse retina (Hikita et al, MCN 2003, 23: 427–430). Experiments were performed to further characterize OPN’s outgrowth promoting activity and to determine temporal and spatial expression of OPN in the developing mouse optic tract. Methods:OPN expression and localization in embryonic C57BL/6 mouse optic tract were determined via immunohistochemistry. In vitro adhesion, explant, and neurite outgrowth assays of embryonic day–15 (E15) mouse retinal cells were performed, using various forms of purified OPN. Results: OPN immunoreactivity was detected in developing mouse retina in proximity to retinal ganglion cells (RGC), in the fiber layer, in the optic nervehead, and the optic tract at the time of RGC axon extension. Purified OPN supported adhesion and neurite outgrowth of dissociated embryonic mouse retinal cells and axon outgrowth from E15 retinal explants. Conclusions: We have demonstrated novel adhesion and axon promoting activities of osteopontin for retinal ganglion cells. Also, we have shown that it is expressed in pathways followed by RGC axons. Our findings suggest that OPN may be involved in RGC axon extension during retinal development. Further studies of retinal development in OPN null mice are currently underway.
Keywords: retinal development • retinal adhesion • extracellular matrix