Inhibitory effects of neurocan and phosphacan on neurite outgrowth from retinal ganglion cells in culture

PURPOSE. Neurocan and phosphacan are nervous tissue-spe cific chondroitin s ulfate proteoglycans (CSPGs) that are highly expressed in postnatal rat ret ina. To elucidate potential roles of neurocan and phosphacan on neurite out growth from retinal ganglion cells (RGCs), in vitro experiments were conduc ted with purified RGCs. METHODS. Neurocan and phosphacan were purified from postnatal rat brain by DEAE-column chromatography and subsequent gel chromatography. RGCs were obt ained from postnatal rat retinas by a two-step immunopanning procedure usin g an anti-Thy 1,1 antibody and an anti-macrophage antibody. Neurite outgrow th from RGCs was examined on poly-L-lysine (PLL)-conditioned plates, and PL L-conditioned plates treated with neurocan or phosphacan. RESULTS. Compared with PLL-conditioned plates, neurocan and phosphacan inhi bited neurite outgrowth from RGCs at 48 and 72 hours after seeding. When ch ondroitin sulfate side chains linked to the core proteins were digested by chondroitinase ABC, the inhibitory effect remained, indicating that the cor e proteins are related to the effect. Furthermore, the digestion of chondro itin sulfate side chains linked to phosphacan core protein significantly pr omoted the inhibitory effect of phosphacan on neurite outgrowth from RGCs. CONCLUSIONS. Neurocan and phosphacan, which are highly expressed in postnat al rat retina, inhibit neurite outgrowth from postnatal rat RGCs, indicatin g that these proteoglycans may be inhibitory factors against neurite outgro wth from RGCs during retinal development.