Stimulation of collagen production in vitro by ascorbic acid released from explants of migrating avian neural crest

Embryonic neuronal tissues contain a collagen-stimulating factor, shown to enhance the hydroxylation and secretion of proline-containing macromolecules by cultured muscle cells. Here we report on a similar activity found during avian embryonic development in explants of migrating mesencephalic neural crest. The degree of proline hydroxylation of proteins secreted into the medium was stimulated 2.5-6-fold in neural crest-muscle and neural crest-somite cocultures, as compared with control cultures devoid of crest explants. No such stimulation occurred when cocultures were treated with the enzyme ascorbate oxidase (EC 1.10.3.3), suggesting that the active factor in neural crest explants was ascorbic acid or an ascorbate-like molecule. Further characterization of this molecule was performed in crest explants and other embryonic tissues by using HPLC with amperometric detection: this study revealed that migrating cephalic neural crest contains 1.5 micrograms ascorbic acid per mg protein. Our results suggest that ascorbic acid and/or related molecule(s) could act during development of the nervous system as a trigger for collagen production and subsequent assembly of an extracellular matrix.