EPITHELIAL MORPHOGENESIS IN MOUSE EMBRYONIC SUBMANDIBULAR-GLAND - ITSRELATIONSHIPS TO THE TISSUE ORGANIZATION OF EPITHELIUM AND MESENCHYME

Epithelial tissues in various organ rudiments undergo extensive shape changes during their development. The processes of epithelial shape ch ange are controlled by tissue interactions with the surrounding mesenc hyme which is kept in direct contact with the epithelium. One of the o rgans which has been extensively studied is the mouse embryonic subman dibular gland, whose epithelium shows the characteristic branching mor phogenesis beginning with the formation of narrow and deep clefts as w ell as changes in tissue organization. Various molecules in the mesenc hyme, including growth factors and extracellular matrix components, af fect changes of epithelial shape and tissue organization. Also, mesenc hymal tissue exhibits dynamic properties such as directional movements in groups and rearrangement of collagen fibers coupled with force-gen eration by mesenchymal cells. The epithelium, during early branching m orphogenesis, makes a cell mass where cell-cell adhesion systems are l ess developed. Such properties of both the mesenchyme and epithelium a re significant for considering how clefts, which first appear as unsta ble tiny indentations on epithelial surfaces, are formed and stabilize d.