Degradation of chondroitin sulfate proteoglycan enhances the neurite-promoting potential of spinal cord tissue

The contribution of chondroitin sulfate proteoglycan (CSPG) in the suppress ion of axonal growth in rat spinal cord has been examined by means of an in vitro bioassay in which regenerating neurons are grown on tissue section s ubstrate. Dissociated embryonic chick dorsal root ganglionic neurons were g rown on normal and injured adult spinal cord tissue sections treated with c hondroitinases. Neuritic growth on normal spinal cord tissue was meager. Ho wever, both the percentage of neurons with neurites and the average neurite length were substantially greater on sections treated with chondroitinase ABC. Enzymes that specifically degraded dermatan sulfate or hyaluronan were ineffective. Neuritic growth was significantly greater on injured (compare d to normal) spinal cord and a further dramatic increase resulted from chon droitinase ABC treatment. Neurites grew equally within white and gray matte r regions after chondroitinase treatment. Observed increases in neurite out growth on chondroitinase-treated tissues were largely inhibited in the pres ence of function-blocking laminin antibodies. These findings indicate that inhibitory CSPG is widely distributed and predominant in both normal and in jured spinal cord tissues. Additionally, inhibitory CSPG is implicated in n egating the potential stimulatory effects of laminin that might otherwise s upport spinal cord regeneration. (C) 1998 Academic Press.