Effects of nonenzymatic glycosylation of extracellular matrix components on cell survival and sensory neurite extension in cell culture.

Diabetic sensory polyneuropathy is characterized by a distal axonopathy of dying-back type. It is accompanied by a failure of axonal regeneration, in which nonenzymatic glycosylation (glycation) of the extracellular matrix may be involved. In the present study, the effects of glycation of collagen IV and laminin, major components of basal lamina, on neuron survival and neurite extension were investigated in tissue culture. Fast glycation of laminin was achieved by incubation with glycolaldehyde and glycation of collagen IV by incubation with glucose. The degree of glycation was estimated by fluorescence analysis. Glycated or nonglycated laminin or collagen IV were used as substrates for culture of dorsal root ganglion (DRG) neurons from neonatal rats. Cultures were assessed for the proportion of cells attaching to the substrate, surviving and bearing neurites. Cell attachment and the proportion bearing neurites were significantly reduced on collagen IV glycated for 2 weeks, but survival was only affected by glycation for 4 or 5 weeks. All 3 parameters were significantly reduced on glycated compared with unglycated laminin. Glycation of both laminin and collagen IV produced considerable morphological differences in the cultured neurons on scanning electron microscopy. Dissociated DRG neurons from adult animals with streptozotocin-induced diabetes cultured on nonglycated substrates survived less well and produced fewer neurites. Glycation of collagen IV and laminin thus affects neuronal survival, neurite production and cell morphology, and diabetes affects both the survival of sensory neurons in culture and their ability to extend neurites.