Ciliary ganglia and spinal cord explants release an ascorbate-like compound which stimulates proline hydroxylation and collagen formation in muscle cultures

A low-molecular-weight factor from embryonic rat brain stimulates collagen production in rat muscle cultures. This effect is associated with increased hydroxylation of proline residues in collagenous proteins produced by the cells. Here, we show that increased hydroxylation (22- and 7.5-fold) was also observed with extracts of rat embryonic spinal cord and extracts of the rat pheochromocytoma cell line PC12. A 5-25-fold stimulation in proline hydroxylation was obtained when muscle cells were cocultured with chick ciliary ganglia or with embryonic rat spinal cord explants. Medium conditioned by rat spinal cord explants also increased prolyl hydroxylation. Incubation of the muscle-nerve cocultures with ascorbate oxidase markedly reduced the observed increase in proline hydroxylation. These results show that the cultured explants release a factor which promotes proline hydroxylation and collagen production by muscle. This factor seems to be ascorbic acid or an ascorbate-like compound.