Permissive effect of fibronectin on collagen gel contraction mediated by bovine trabecular meshwork cells.
OBJECTIVE
The effect of fibronectin on the contractility of trabecular meshwork (TM) cells was investigated.


METHODS
The contractility of bovine TM cells was evaluated by culture of the cells in a collagen gel and measurement of the change in the diameter of the gel under various conditions. The formation of stress fibers and the localization of integrin alpha5 and beta1 chains (which together form a fibronectin receptor) in bovine TM cells were investigated by laser confocal microscopy of cells stained with phalloidin and antibodies to the integrin subunits.


RESULTS
The addition of fibronectin to collagen gels containing bovine TM cells induced marked gel contraction in a time- and concentration-dependent manner. Cytochalasin D (an inhibitor of microfilament formation) and the peptide GRGDSP (Gly-Arg-Gly-Asp-Ser-Pro), a fibronectin receptor antagonist, each inhibited this effect of fibronectin, whereas nocodazole (an inhibitor of microtubule polymerization) and the control peptide GRGESP (Gly-Arg-Gly-Glu-Ser-Pro) did not. Furthermore, fibronectin induced the spreading of cells, the formation of actin stress fibers, and the expression of integrin alpha5 in the collagen gel-embedded TM cells.


CONCLUSIONS
Fibronectin promotes collagen gel contraction mediated by bovine TM cells. Moreover, the formation of actin stress fibers and upregulation of integrin alpha5 appear to contribute to this permissive effect of fibronectin. The interaction of fibronectin with TM cells may thus be a determinant of the contractility of TM tissue.
D000199:Actins / Q000378:metabolism; D000818:Animals; D002417:Cattle; D003094:Collagen / Q000378:metabolism*; D003286:Contracture / Q000378:metabolism*; D015638:Cytochalasin D / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005353:Fibronectins / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D019084:Fluorescent Antibody Technique, Indirect; D005782:Gels; D039081:Integrin alpha5beta1 / Q000378:metabolism; D018613:Microscopy, Confocal; D015739:Nocodazole / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D022502:Stress Fibers / Q000378:metabolism; D013997:Time Factors; D014129:Trabecular Meshwork / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
D000199:Actins; D005353:Fibronectins; D005782:Gels; D039081:Integrin alpha5beta1; D009842:Oligopeptides; D015638:Cytochalasin D; D003094:Collagen; C058161:glycyl-arginyl-glycyl-aspartyl-seryl-proline; D015739:Nocodazole