Morphology and behavior of quail neural crest cells in artificial three-dimensional extracellular matrices.

Neural crest cells migrate extensively through a complex extracellular matrix (ECM) to sites of terminal differentiation. To determine what role the various components of the ECM may play in crest morphogenesis, quail (Coturnix coturnix japonica) neural crest cells have been cultured in three-dimensional hydrated collagen lattices containing various combinations of macromolecules known to be present in the crest migratory pathways. Neural crest cells migrate readily in native collagen gels whereas the cells are unable to use denatured collagen as a migratory substratum. The speed of movement decreases linearly as the concentration of collagen in the gel increases. Speed of movement of crest cells is stimulated in gels containing 10% fetal calf serum and chick embryo extract, 33 micrograms/ml fibronectin cell-binding fragments, 3 mg/ml chondroitin sulfate, or 3 mg/ml chondroitin sulfate proteoglycan when compared to rates of movement through collagen lattices alone. Low concentrations of hyaluronate (250-500 micrograms/ml) in a 750 micrograms/ml collagen gel do not alter rates of movement over collagen alone, but higher concentrations (4 mg/ml) greatly inhibit migration. Conversely, hyaluronate (250 micrograms/ml) significantly increases speed of movement if the crest cells are cultured in high concentration collagen gels (2.5 mg/ml), suggesting that hyaluronate is expanding spaces and consequently enhancing migration. The morphology and mode of movement of neural crest cells vary with the matrix in which they are grown and can be correlated with their speed of movement. Light and scanning electron microscopy reveal rounded, blebbing cells in matrices associated with slower translocation, whereas rounded cells with branching filopodia or lamellipodia are associated with rapid translocation. Bipolar cells with long processes are observed in cultures of rapidly moving cells that appear to be adhering strongly, as well as in cultures of cells that are stationary for long periods. These data, considered with the known distribution of macromolecules in the early embryo, suggest the following: (1) Both collagen and fibronectin can act as preferred substrata for migration. (2) Chondroitin sulfate and chondroitin sulfate proteoglycan increase speed of movement, but probably do so by decreasing adhesiveness and thereby producing more frequent detachment. In the embryo, crest cells would most likely avoid regions containing high concentrations of chondroitin sulfate. (3) Hyaluronate cannot act as a substratum for migration, but in low concentrations it can open spaces in the matrix and consequently may stimulate movement. The complex interactions of combined matr