The influence of neural tube-derived factors on differentiation of neural crest cells in vitro. I. Histochemical study on the appearance of adrenergic cells.

The neural crest gives rise to numerous derivatives including adrenergic and cholinergic neurons, supportive cells of the nervous system, and melanocytes. In tissue culture, neural crest cells explanted from both cranial and trunk regions were found to differentiate into adrenergic neuroblasts or into pigmented cells when grown in medium containing 10% chick embryo extract. When the embryo extract concentration was lowered to 2%, no catecholamine-containing cells (as assayed by formaldehyde-induced fluorescence) were detected, although pigment cells were observed. These results suggest the presence of a factor(s) in embryo extract that promotes or supports adrenergic differentiation. To examine the possible tissue sources of this factor(s), neural tube, notochord, or somite cells were used to condition medium containing 2% embryo extract. When neural crest cells were grown in medium conditioned by neural tube cells, adrenergic neuroblasts were observed in all cultures. However, somite- and notochord conditioned medium did not support adrenergic differentiation. In addition, medium supplemented with extracts derived from central nervous system components did support adrenergic expression, whereas medium supplemented with embryo extract from which the neural tissue was removed did not. Direct contact with neural tube cell ghost membranes was unable to substitute for high embryo extract concentrations or for neural tube-conditioned medium. These results suggest that the neural tube makes a diffusible factor(s) that will support adrenergic differentiation of neural crest cells.