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J.W. McAvoy, L. Taliana, M.D. M. Evans, S.L. Ang, B. Bojarski; A Role for Vitronectin in the Lens? . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2875.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Lens capsule forms during lens morphogenesis. Its primary extracellular matrix (ECM) constituents include type IV collagen, laminin, heparan sulphate proteoglycan, fibronectin and entactin/nidigen. Recent studies have shown that vitronectin (Vn) is one of the ECM molecules that accumulates during posterior capsule opacification. There is no information on Vn in the normal lens, so we set out to determine if it is expressed during normal lens development and to study how a vitronectin substratum influences lens cell behaviour. Methods:For immunohistochemistry, a primary mouse monoclonal antibody (CSIRO A62) to Vn was used to localise this ECM protein in sections of embryonic and postnatal rodent lenses. For SDS PAGE and western analysis, protein lysate from P21 rat lens capsules (with adherent epithelial cells) was separated by SDS–PAGE and probed for Vn using A62. In situ hybridisation for Vn was also carried out on paraffin sections of rodent lenses. Lens epithelial explants from P21 rats were cultured on dishes precoated with either Vn (1ug/ml), fibronectin (Fn, 10ug/ml), laminin (Ln, 10ug/ml), or left uncoated. Explants were immuno–stained using primary antibodies to alpha–smooth muscle actin. Results:Vn was identified in the cytoplasm of lens epithelial cells at all embryonic and postnatal stages examined. Vn was also localised in lens capsule at some later embryonic and postnatal stages. SDS PAGE of P21 capsule lysates showed a band at 70kD, matching the positive control (purified Vn). This band was confirmed to be Vn by western analysis. In situs showed that Vn mRNA was expressed in the epithelium and was strongest in the equatorial region at all stages of lens development. Under serum–free conditions, lens epithelial cells migrated onto the Vn, Fn and Ln coated surfaces. Most cells on Vn and Fn expressed alpha–smooth muscle actin and appeared fibroblastic/myofibroblastic. Cells that migrated on Ln maintained a predominantly epithelial–like morphology. Conclusions:Vn is expressed by lens epithelial cells and is present in lens capsule during development. Lens epithelial cells can attach and migrate on Vn in vitro; however, on this substratum (and on Fn), the cells undergo an epithelial–mesenchymal transition that is characteristic of some forms of cataract. This result raises questions as to how, or if, lens cells interact with Vn and Fn in normal development and how this relationship may be disrupted during cataract formation.
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