Palate cell motility and substrate interaction

To elucidate the mechanism by which palate shelves reorient during embryogenesis, migration of palate mesenchymal cells has been studied employing various substrates. When palate explants were cultured in a hydrated collagen lattice, it was observed that bipolar spindle-shaped cells migrated out of each explant toward the other. These cells were aligned parallel to each other and to the fibrous tracks that formed. The cells appeared to move along and through the fibrous tracks. Cell migration was dependent on the presence of serum and fibronectin. The fibrous tracks viewed by phase microscopy were sensitive to collagenase. Scanning electron microscopy revealed that the collagen fibers of the hydrated lattice had coalesced into larger bundles. Pretreatment of explants with serotonin stimulated cell migration out of the explant into the hydrated collagen lattice. This effect was specific, since the antagonist methysergide blocked the stimulation produced by serotonin. Employing other substrates, it was noted that palate cells migrating out of double explants toward each other produced large wrinkles in a polysiloxane substratum. Similarly, cultured monolayer cells also produced wrinkles that disappeared as cells rounded up after trypsin treatment. Finally, monolayer cells pulled on and distorted collagen films when cultured on the substrate. It is concluded that migrating palate cells can interact with their substrate producing tractional forces. Serotonin-induced modulation of cell motility and its relationship to palate reorientation are discussed.