Significance of cell-to-cell contacts for the directional movement of neural crest cells within a hydrated collagen lattice

Neural tubes whose neural crest had just begun migration were isolated from stage-14 chick embryos, cleaned with 0.1% trypsin, and cultured in transparent hydrated collagen lattices (HCL) in an effect to stimulate in part the three-dimensional environment through which neural crest cells migrate in situ, in the embryo. The concentration of collagen in the lattices varied from 50 microgram/ml to 390 microgram/ml. The mode of movement and contact behaviour of neural crest cells migrating from the neural tube under these conditions were recorded directly with time-lapse cinemicrography. Both their shape and their rate of translocation were dependent on the concentration of collagen in the HCL. In low concentrations (50 microgram/ml to 105 microgram/ml), neural crest cells have elongate spindle shapes and translocate at an average rate of 1 micrometer/min, whereas in high concentrations (190 microgram/ml to 390 microgram/ml), their shape is rounded, and they translocate at an average rate of only 0-5 micrometer/min. Neural crest cells migrate from neural tubes in these preparations principally in loose clusters, with a few single cells in the lead. The cells in these groups display leading-to-trailing edge adhesions and form tongues or streams of cells directed away from the neural tube. The paths of migration of both individual cells and groups of cells are aligned with the collagen fibrils of the HCL, which radiate from the neural tube. The classical visible characteristic of contact inhibition of movement, change in direction of cell movement after contact with other cells, was not observed; neither the rate of translocation nor the time spent migrating away from the tube is dependent on the number of contacts between cells. It is concluded that the directional movement of neural crest cells in HCL cultures does not depend on contact inhibition of movement.