EXPRESSION OF TENASCIN IN FETAL AND ADULT SALIVARY-GLANDS COMPARED WITH THE EXPRESSION OF TYPE-IV COLLAGEN AND LAMININ-HISTOMORPHOLOGICAL ROLES

To elucidate the role of extracellular matrix and basement membrane as sociated proteins at the ectodermal-ectomesenchymal interface of devel oping salivary glands, human fetal submandibular glands (n=100), gesta tional age varying from 10 to 40 weeks, were evaluated for expression of tenascin, type IV collagen and laminin by using immunohistochemical methods and the results were compared with their expression in adult glands (n=20). Immunoreactive tenascin was present in the epithelial-m esenchymal interface of developing salivary ducts beginning from 10 we eks of gestational age during the early developing stages. In the late developmental stages, the intensity of immunoreaction was reduced aro und the proximal striated ducts and no immunoreaction was seen around the intercalated duct and acinar cells. Adult submandibular glands had immunoreactive tenascin confined to the periductal connective tissue of distal segment of striated and excretory ducts. Type IV collagen an d laminin were observed in the basement membrane of salivary ducts and acini beginning from 16-18 weeks, and the intensity of reaction was m ore prominent during intermediate developing stages (19-32 weeks). The intensity of reaction was, however, less prominent in late developmen tal stages (33-40 weeks) which was similar to that in the adult glands . The present study suggests that tenascin forms an epithelial-ectomes enchymal interface before the organization of collagen IV and laminin in the basement membrane of salivary ducts and acini in developing hum an submandibular glands. The accumulation of the basement membrane pro teins, however, are associated with stages of more active cytodifferen tiation and morphodifferentiation of the glands.