Inhibition of conditioned media-mediated neuritogenesis of sensory ganglia by monoclonal antibodies to GM1 ganglioside

Abstract

The monosialoganglioside GM1 can potentiate the neuritogenic activity of media conditioned by several cell types: neonatal glia, C 6 glioma, embryonic chick heart or skeletal muscle and the rat myogenic line L 6. To probe further the neuritogenic activity of conditioned media (CM), 5 mouse monoclonal antibodies (mAbs) against GM1, designated B6, C3, C4h2, D1 and D3 were incorporated individually into nutrient medium (NM) supplemented with CM prior to incubation with sensory ganglia. Nine-day embryonic chick dorsal root ganglia were explanted onto collagen-coated coverslips and incubated at 35 °C for 5 h in NM supplemented with 150 μ/ml GM1. After washing with NM, the explants were re-fed with NM + CM containing 20% mAb and cultured for an additional 43 h. The resultant neuritogenesis was evaluated microscopically by determining mean neurite number and length of randomly mixed cultures. The 5 antibodies differed in their capacities to inhibit CM-mediated neuritogenesis of these primed target cells. D1 and D3 were most effective in reducing neurite length and number produced by all sources of the CM, while C3 and C4h2 were intermediate in their inhibition of neurite initiation (number). The effect of B6 on neurite initiation and elongation was the least. The ability of these mAbs to inhibit neuritogenic activity of CM derived from both glial and myogenic tissue suggests that gangliosides play a basic role in neuronal development. The differing responses elicited by the individual mAbs may reflect a relationship between the structural complexity of the GM1 molecule and the neuritogenic mechanisms. Since the various CMs may contain several specific growth factors, the potentiation of such factors by regions of the GM1 molecule may further regulate the character of the neuritogenic response.