A comparison of secondary palate development with different in vitro techniques.

Palatal processes from 14-day fetal C57BL mice were cultured under varying conditions for 48 hours and prepared for light and electron microscopy. Disruption of the epithelium along the medial border occurred when single palatal processes were explanted onto Millipore filters, plasma clots, or lens paper in subjacent contact with nutrient medium. Paired processes under the same culture conditions demonstrated typical midline epithelial disruption and mesenchymal fusion. Regions of mesenchymal necrosis occurred in processes grown on nutrient agar in a dish or submerged in nutrient medium. In similar cultures medial epithelial disruption did not occur in single processes and mesenchymal fusion of paired processes was either delayed or did not occur. Disruption of the epithelium along the medial border in single palatal processes, and mesenchymal fusion in paired palatal processes, occurred when palates were grown on nutrient agar supported above but in contact with nutrient medium. The results indicated that responses of palatal epithelium and mesenchyme may be altered by different in vitro procedures. These observations emphasize that many factors must be considered in interpreting developmental changes in palatal processes grown in vitro.