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L.-F. Seet, L. Tong, R. S. M. Su, T. T. Wong; Upregulation of SPARC Expression in Pterygium. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2619.
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Pterygium is an ocular surface disease of unknown etiology. The secreted protein, acidic and rich in cysteine (SPARC) is a matrix protein involved in many systemic diseases such as cancers and fibrotic diseases. The aim of our study is to investigate the expression and potential involvement of SPARC in pterygium.
This study involved paired control or un-involved conjunctival and pterygium tissues from 6 patients. SPARC expression was determined by quantitative PCR (qPCR) and Western blotting. Immunofluorescence analysis was also carried out to examine the expression patterns of SPARC in conjunctival and pterygium tissue sections. In addition, the ability of SPARC to induce cell migration was tested on scratch wound assay using exogenous SPARC on human conjunctival epithelial cells. The ability of SPARC to induce cell proliferation was also measured using the xCELLigence system.
SPARC expression was strikingly upregulated in pterygium in comparison to normal conjunctival epithelium when assayed by both qPCR and Western blotting. This observation was corroborated by immunofluorescence analysis which showed strong staining for SPARC in the suprabasal and basal layers of the pterygium epithelium relative to the weaker staining pattern in the unaffected conjunctival epithelium. Scratch wound assay revealed that exogenous SPARC induces more rapid wound closure in human conjunctival epithelial cells. This is likely to be due to increase in cell migration rate induced by SPARC since the proliferation rate of the treated cells remained similar to untreated cells as determined by the xCELLigence system.
SPARC expression is present in normal conjunctiva epithelium and upregulated in pterygium. Increased SPARC expression may potentially result in more rapid cell migration in the conjunctival epithelial cells resulting in tissue invasion and matrix remodeling characteristic of pterygium. We therefore hypothesize that SPARC may be involved in the pathogenesis of pterygium.
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