Neither laminin nor prior optic nerve section are essential for the regeneration of adult mammalian retinal ganglion cell axons in vitro.

Abstract

Retinal explants obtained from normal adult rats and from operated animals in which the optic nerve had been sectioned 10 days previously were cultured in either serum-containing or serum-free medium on poly-L-lysine and laminin substrata. Regenerating ganglion cell axons growing from these explants have been identified using monoclonal antibodies against Thy-1.1 cell surface glycoprotein and the 200-kDa subunit neurofilament protein. Irrespective of substratum or medium composition, axons regenerated from 28-49% of normal rat retinal explants. This percentage increased to 60-84% of explants from operated rats. There were no significant differences in percentages of explants from normal or operated rats showing neurite outgrowth when substrata of either poly-L-lysine or laminin were compared in serum-free medium. In serum-containing medium the results were less easily interpreted due to the presence of an outgrowth of non-neuronal (glia and mesenchymal) 'flat cells', which served as a preferred axonal substratum in many cases. Thus we show that adult rat retinal ganglion cell axons will regrow in vitro, and that a 'priming' optic nerve section will increase this response. In neither case is the response laminin-dependent.