Transforming growth factor-beta1 regulates basement membrane formation by alveolar epithelial cells in vitro.
Immortalized alveolar type II epithelial (SV40-T2) cells formed a continuous, thin lamina densa when they were cultured on collagen fibrils with the supplement of 1.0 ng/ml TGF-beta1. Corresponding to lamina densa formation, immunohistochemical analysis of laminin, type IV collagen, perlecan, and entactin (nidogen) indicated integration of these components in a linear array beneath the SV40-T2 cells. Synthesis of these basement membrane constituents was significantly enhanced by TGF-beta1 in a dose-dependent manner. On the other hand, TGF-beta1 did not affect the synthesis of extracellular matrix-regulatory enzymes and their inhibitors, such as type II transglutaminase, matrix metalloproteinase-2, plasminogen activator inhibitor-1, or tissue inhibitor of matrix metalloproteinase-1. These results indicate that basement membrane formation in the presence of 1.0 ng/ml TGF-beta1 is attributable to enhanced synthesis of basement membrane constituents. However, formation of a continuous basement membrane was inhibited at a TGF-beta1 concentration of 5.0 ng/ml. Synthesis of the basement membrane constituents was further enhanced at this concentration and the extracellular matrix-regulatory enzymes remained unchanged. The deposits of cellular fibronectin and type I collagen beneath SV40-T2 cells were significantly augmented. Thus excessive production of interstitial extracellular matrix components appears to obstruct the integration of basement membrane constituents into a continuous architecture. These results indicate that the basement membrane formation by SV40-T2 cells is achieved at the optimal TGF-beta1 concentration.
Furuyama
A
A
Environmental Health Sciences Division, National Institute for Environmental Studies, Tsukuba, Ibaraki, Japan. kawagoe@nies.go.jp
Iwata
M
M
Hayashi
T
T
Mochitate
K
K
D000818:Animals; D001485:Basement Membrane / Q000502:physiology / Q000648:ultrastructure*; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000502:physiology / Q000648:ultrastructure*; D008168:Lung / Q000166:cytology; D008854:Microscopy, Electron; D051381:Rats; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D016212:Transforming Growth Factor beta