EXPRESSION AND IMMUNOHISTOCHEMICAL LOCALIZATION OF LAMININ AND TYPE-IV COLLAGEN IN DEVELOPING HUMAN FETAL TRACHEAL GLANDS

The expression and distribution of laminin and type IV collagen, two m ajor components of the basement membrane, were investigated at the epi thelio-mesenchymal interface of the human developing tracheal glands f rom 10 to 37 weeks of gestation. The localization of these molecules w as assessed by indirect immunoperoxidase and indirect immunofluorescen ce staining and correlated to morphogenesis and epithelial cell differ entiation. Laminin and type IV collagen were detected as early as 10 w eeks of gestation in a continuous, linear pattern in the basement memb rane surrounding the epithelial tracheal tube. By 12 weeks of gestatio n the basement membrane developed large openings at the tips of the bu dding glands beneath poorly differentiated cells, concomitant with the onset of morphogenetic movements. The remodeling of the basement memb rane led to branching epithelial morphogenesis. The maturation and the functional differentiation of the secretory cells appeared later in t he epithelium, when the basement membrane was strongly labeled with bo th anti-laminin and anti-type IV collagen antibodies, after 24 weeks o f gestation. At this time the basement membrane became regular and thi ck and the maturation of serous cells increased progressively. These r esults suggest that the remodeling of the basement membrane takes plac e very early during gestation and that the morphogenesis and the matur ation of the tracheal glands are rapidly achieved in humans.