ASTROCYTES FROM ADULT-RAT OPTIC NERVES ARE NONPERMISSIVE FOR REGENERATING RETINAL GANGLION-CELL AXONS

We have directly compared the abilities of astrocytes from newborn and adult rats to support or inhibit the growth of regenerating axons in vitro. Astrocytes prepared from newborn rats were able to promote reti nal ganglion cell (RGC) axon growth from embryonic and adult rat and f rom adult fish retinal explants. Retinal axons from E16 rat retinae gr ew significantly faster on astrocytes from neonatal rats than those fr om E18 or adult rat retinae with growth rates comparable to RGC axons from adult fish retinae. RGC regeneration from adult rat retinae was a lmost completely inhibited on adult rat optic nerve astrocytes. Only a xons from adult fish retinae were able to extend onto monolayers from these reactive astrocytes, although their growth rates were significan tly reduced. We conclude that the failure of mammalian RGC axons to re grow within the lesioned optic nerve environment is, at least in part, due to nonpermissive aspects of adult ''reactive'' optic nerve astroc ytes. However, the cell intrinsic growth potential of RGCs also appear s to influence their ability to extend axons on cellular substrates. ( C) 1995 Academic Press, Inc.