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1 Chain Synthesis in the Mouse Developing Lung:
Requirement for Epithelial-Mesenchymal Contact and
Possible Role in Bronchial Smooth muscle Development

* Department of Pathology and Laboratory Medicine, Wayne State University School of Medicine, Detroit, Michigan 48201; Laminins, the main components of basement
membranes, are heterotrimers consisting of
Department of Laboratory Medicine and Pathology, University of Minnesota Medical School, Minneapolis, Minnesota 55455;
and § Connective Tissue Department, Institute for Experimental Medicine, Erlangen 91054, Germany
,
, and
polypeptide chains linked together by disulfide bonds.
Laminins-1 and -2 are both composed of
1 and
1
chains and differ from each other on their
chain, which is
1 and
2 for laminin-1 and -2, respectively.
The present study shows that whereas laminins-1 and -2 are synthesized in the mouse developing lung and in epithelial-mesenchymal cocultures derived from it, epithelial and mesenchymal monocultures lose their ability to synthesize the laminin
1 chain. Synthesis of laminin
1 chain however returns upon re-establishment of epithelial-mesenchymal contact. Cell-cell contact is critical, since laminin
1 chain is not detected in
monocultures exposed to coculture-conditioned medium or in epithelial-mesenchymal cocultures in which
heterotypic cell-cell contact is prevented by an interposing filter. Immunohistochemical studies on cocultures treated with brefeldin A, an inhibitor of protein
secretion, indicated both epithelial and mesenchymal
cells synthesize laminin
1 chain upon heterotypic cell-
cell contact. In a set of functional studies, embryonic
lung explants were cultured in the presence of monoclonal antibodies to laminin
1,
2, and
/
chains.
Lung explants exposed to monoclonal antibodies to laminin
1 chain exhibited alterations in peribronchial
cell shape and decreased smooth muscle development,
as indicated by low levels of smooth muscle
actin and
desmin. Taken together, our studies suggest that laminin
1 chain synthesis is regulated by epithelial-mesenchymal interaction and may play a role in airway
smooth muscle development.
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