Increased axon regeneration in astrocytes grown in the presence of proteoglycan synthesis inhibitors

Abstract

ABSTRACT We have recently reported that the critical difference between astrocytic cell lines that are good or poor promoters of axon growth lies in the extracellular matrix. We demonstrated that much of this difference between matrix produced by permissive and non-permissive cell lines could be ascribed to one or more dermatan/keratan sulphate proteoglycans and that these proteoglycans are able to block the neurite-promoting effect of laminin. These proteoglycans are also produced by cultures of primary astrocytes. In the present study, we have demonstrated that treatment of both astrocytic cell lines and primary astro-cytes with inhibitors of proteoglycan synthesis, β-D-xylosides and sodium chlorate, can strongly influence the axon growth promoting properties of both matrix and whole cells. Dorsal root ganglia grown on matrix or in con-ditioned medium from cultures treated with β-D-xylosides or sodium chlorate had twice as many axons and the axons grew to twice the length as in control cultures. Following treatment of Neu7 cells with proteoglycan synthesis inhibitors there was also a significant reduction in the ability of Neu7 conditioned medium to block the neurite-promoting effect of laminin. Dorsal root ganglia grown on Neu7 cells treated with sodium chlorate extended 2 to 3 times the number of axons for approximately 300 mm longer distance than on control cultures. Treatment of Neu7 cells with β-D-xylosides, however, did not make the cells less inhibitory to axon growth. We have also examined the effects of proteoglycan synthesis inhibitors on three-dimensional primary astrocyte cultures, which closely mimic the in vivo effects of astrocytes on axon growth. Here again, dorsal root ganglia extended many more axons for a longer distance than in control cultures. We conclude from these results that interfering with astrocyte proteo-glycan synthesis makes them better able to support axon regeneration.