Analysis of developmentally homogeneous neural crest cell populations in vitro. IV. Cell proliferation and synthesis of glycosaminoglycans

Glycosaminoglycans (GAG) have been implicated as regulators of morphogenesis and differentiation. We have cultured two different homogeneous populations of quail trunk neural crest cells with different predictable phenotypes after equivalent times in culture, and used these populations to distinguish changes in GAG synthesis before and after cell differentiation from changes that depend on time in culture, and that thus may reflect a non-specific response to in vitro culture conditions. Cells derived from the outgrowths surrounding explanted neural tubes remained mainly undifferentiated. These crest cells showed a decrease in [³H]glucosamine incorporation into total GAG with time in culture. A similar decrease in total GAG, and, in addition, a slight decrease in the proportion of hyaluronic acid (HA) was observed in cultures of cluster-derived cells that homogeneously differentiated into melanocytes. Putative mouse neural crest cells that did not form melanin under the present culture conditions showed, similarly to the quail neural crest cells, a high incorporation of [³H]glucosamine into HA relative to sulfated GAG. The proportion of HA did not decrease with time in culture in these mouse crest cells. When pigment granules appeared in avian crest cells, the proliferation rate decreased drastically, whereas the proliferation rate of cells that did not form pigment granules remained constant. The results indicate that time in culture rather than either a differentiation per se or a change in the rate of proliferation, is largely responsible for the observed changes in GAG synthesis.