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Laminin alpha1 chain synthesis in the mouse developing lung: requirement for epithelial-mesenchymal contact and possible role in bronchial smooth muscle development.

Schuger L, Skubitz AP, Zhang J, Sorokin L, He L - J. Cell Biol. (1997)

Bottom Line: In a set of functional studies, embryonic lung explants were cultured in the presence of monoclonal antibodies to laminin alpha1, alpha2, and beta/gamma chains.Lung explants exposed to monoclonal antibodies to laminin alpha1 chain exhibited alterations in peribronchial cell shape and decreased smooth muscle development, as indicated by low levels of smooth muscle alpha actin and desmin.Taken together, our studies suggest that laminin alpha1 chain synthesis is regulated by epithelial-mesenchymal interaction and may play a role in airway smooth muscle development.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology and Laboratory Medicine, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.

ABSTRACT
Laminins, the main components of basement membranes, are heterotrimers consisting of alpha, beta, and gamma polypeptide chains linked together by disulfide bonds. Laminins-1 and -2 are both composed of beta1 and gamma1 chains and differ from each other on their alpha chain, which is alpha1 and alpha2 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 alpha1 chain. Synthesis of laminin alpha1 chain however returns upon re-establishment of epithelial-mesenchymal contact. Cell-cell contact is critical, since laminin alpha1 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 alpha1 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 alpha1, alpha2, and beta/gamma chains. Lung explants exposed to monoclonal antibodies to laminin alpha1 chain exhibited alterations in peribronchial cell shape and decreased smooth muscle development, as indicated by low levels of smooth muscle alpha actin and desmin. Taken together, our studies suggest that laminin alpha1 chain synthesis is regulated by epithelial-mesenchymal interaction and may play a role in airway smooth muscle development.

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Photomicrographs  of a main bronchus including  peribronchial mesenchymal  cells in lung explants cultured for 3 d in the presence  of 100 μg/ml of normal  mouse IgG (a), anti-LM α1  chain antibody (b), anti-LM  α1 chain antibody preincubated with 200 μg/ml of LM-1  (c), anti-LM α2 antibody  (d), and anti-LM β1/γ1 antibody (e). Note that in the  control (a) the peribronchial  mesenchymal cells (m) are  polarized (elongated and oriented concentrically to the  bronchus), whereas the peribronchial mesenchymal cells  in explants exposed to anti-LM α1 chain antibody (b)  are round. This effect was  corrected by preincubation  of the antibody with LM-1  (c) and was not observed in  explants exposed to the other  antibodies (d and e). The epithelial cells (e) showed no  morphological alterations. Bar,  20 μm.
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Figure 9: Photomicrographs of a main bronchus including peribronchial mesenchymal cells in lung explants cultured for 3 d in the presence of 100 μg/ml of normal mouse IgG (a), anti-LM α1 chain antibody (b), anti-LM α1 chain antibody preincubated with 200 μg/ml of LM-1 (c), anti-LM α2 antibody (d), and anti-LM β1/γ1 antibody (e). Note that in the control (a) the peribronchial mesenchymal cells (m) are polarized (elongated and oriented concentrically to the bronchus), whereas the peribronchial mesenchymal cells in explants exposed to anti-LM α1 chain antibody (b) are round. This effect was corrected by preincubation of the antibody with LM-1 (c) and was not observed in explants exposed to the other antibodies (d and e). The epithelial cells (e) showed no morphological alterations. Bar, 20 μm.

Mentions: Microscopic evaluation of hematoxylin- and eosin-stained sections showed well preserved epithelial and mesenchymal cellular architecture with scattered mitotic figures in both tissue compartments. A normal histological pattern was seen in the mesenchyme of lung explants exposed to antibodies against LM α2 or LM β1/γ1 chains or to normal mouse IgG. In these explants the peribronchial mesenchymal cells were elongated in shape (polarized) and arranged concentrically to the airway (Fig. 9, a, d, and e), whereas the rest of the mesenchymal cells were round in shape (unpolarized). However, in the lung explants exposed to 50 or 100 μg/ml of monoclonal antibody to LM α1 chain, the mesenchymal cells were uniformly round (unpolarized), regardless of their proximity to the bronchial tree (Fig. 9 b). The effect that mAb AL-4 had on mesenchymal cell morphology was corrected by preincubation of AL-4 with LM-1 (Fig. 9 c).


Laminin alpha1 chain synthesis in the mouse developing lung: requirement for epithelial-mesenchymal contact and possible role in bronchial smooth muscle development.

Schuger L, Skubitz AP, Zhang J, Sorokin L, He L - J. Cell Biol. (1997)

Photomicrographs  of a main bronchus including  peribronchial mesenchymal  cells in lung explants cultured for 3 d in the presence  of 100 μg/ml of normal  mouse IgG (a), anti-LM α1  chain antibody (b), anti-LM  α1 chain antibody preincubated with 200 μg/ml of LM-1  (c), anti-LM α2 antibody  (d), and anti-LM β1/γ1 antibody (e). Note that in the  control (a) the peribronchial  mesenchymal cells (m) are  polarized (elongated and oriented concentrically to the  bronchus), whereas the peribronchial mesenchymal cells  in explants exposed to anti-LM α1 chain antibody (b)  are round. This effect was  corrected by preincubation  of the antibody with LM-1  (c) and was not observed in  explants exposed to the other  antibodies (d and e). The epithelial cells (e) showed no  morphological alterations. Bar,  20 μm.
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Related In: Results  -  Collection

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Figure 9: Photomicrographs of a main bronchus including peribronchial mesenchymal cells in lung explants cultured for 3 d in the presence of 100 μg/ml of normal mouse IgG (a), anti-LM α1 chain antibody (b), anti-LM α1 chain antibody preincubated with 200 μg/ml of LM-1 (c), anti-LM α2 antibody (d), and anti-LM β1/γ1 antibody (e). Note that in the control (a) the peribronchial mesenchymal cells (m) are polarized (elongated and oriented concentrically to the bronchus), whereas the peribronchial mesenchymal cells in explants exposed to anti-LM α1 chain antibody (b) are round. This effect was corrected by preincubation of the antibody with LM-1 (c) and was not observed in explants exposed to the other antibodies (d and e). The epithelial cells (e) showed no morphological alterations. Bar, 20 μm.
Mentions: Microscopic evaluation of hematoxylin- and eosin-stained sections showed well preserved epithelial and mesenchymal cellular architecture with scattered mitotic figures in both tissue compartments. A normal histological pattern was seen in the mesenchyme of lung explants exposed to antibodies against LM α2 or LM β1/γ1 chains or to normal mouse IgG. In these explants the peribronchial mesenchymal cells were elongated in shape (polarized) and arranged concentrically to the airway (Fig. 9, a, d, and e), whereas the rest of the mesenchymal cells were round in shape (unpolarized). However, in the lung explants exposed to 50 or 100 μg/ml of monoclonal antibody to LM α1 chain, the mesenchymal cells were uniformly round (unpolarized), regardless of their proximity to the bronchial tree (Fig. 9 b). The effect that mAb AL-4 had on mesenchymal cell morphology was corrected by preincubation of AL-4 with LM-1 (Fig. 9 c).

Bottom Line: In a set of functional studies, embryonic lung explants were cultured in the presence of monoclonal antibodies to laminin alpha1, alpha2, and beta/gamma chains.Lung explants exposed to monoclonal antibodies to laminin alpha1 chain exhibited alterations in peribronchial cell shape and decreased smooth muscle development, as indicated by low levels of smooth muscle alpha actin and desmin.Taken together, our studies suggest that laminin alpha1 chain synthesis is regulated by epithelial-mesenchymal interaction and may play a role in airway smooth muscle development.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology and Laboratory Medicine, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.

ABSTRACT
Laminins, the main components of basement membranes, are heterotrimers consisting of alpha, beta, and gamma polypeptide chains linked together by disulfide bonds. Laminins-1 and -2 are both composed of beta1 and gamma1 chains and differ from each other on their alpha chain, which is alpha1 and alpha2 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 alpha1 chain. Synthesis of laminin alpha1 chain however returns upon re-establishment of epithelial-mesenchymal contact. Cell-cell contact is critical, since laminin alpha1 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 alpha1 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 alpha1, alpha2, and beta/gamma chains. Lung explants exposed to monoclonal antibodies to laminin alpha1 chain exhibited alterations in peribronchial cell shape and decreased smooth muscle development, as indicated by low levels of smooth muscle alpha actin and desmin. Taken together, our studies suggest that laminin alpha1 chain synthesis is regulated by epithelial-mesenchymal interaction and may play a role in airway smooth muscle development.

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