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L. T. Ho, B. Caterson, A. J. Quantock, K. M. Meek; The Variation in Sulphation Patterns of Keratan Sulphate in Central versus Peripheral Regions of the Cornea. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4526.
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© ARVO (1962-2015); The Authors (2016-present)
To discover how sulphated glycosaminoglycans (sGAGs) and sulphation patterns of keratan sulphate (KS) change from the centre of the cornea, peripherally.
Full thickness biopsies of adult bovine corneas, 3mm x 3mm in size, were taken horizontally from the centre of the cornea outwards to the 12mm position. Total sGAG was calculated from DMMB assays of papain digests, whilst the amount of sulphated KS was quantified by a series of ELISAs of the digests in which the monoclonal antibodies, 5D4 and 1B4 were used. Respectively, these recognise high-sulphated (i.e. minimally pentasulphated) and lower-sulphated epitopes on KS GAG chains. Data are presented as the average of four corneas.
Total sGAG remains unchanged between the central 0-6mm of the cornea and the 6-12mm peripheral zone (inner = 0.046±0.006 mg/mg dry weight; outer = 0.050±0.012 mg/mg dry weight: p=0.421). The amount of high-sulphated, 5D4-recognizible, KS GAG is also constant between the centre of the cornea and the periphery (0.532±0.474 ng/mg dry weight versus 0.502±0.152 ng/mg dry weight: p=0.870). The amount of lesser sulphated 1B4-recognizible, KS GAG, however, increases by over 60% between the central 6mm and the 6-12mm zone (0.216±0.064 ng/mg dry weight versus 0.342±0.112 ng/mg dry weight: p=0.015).
High sulphated KS chains are relatively more abundant in central regions of the cornea when compared to lesser sulphated chains, with proportionally elevated levels of lesser sulphated KS found peripherally. The changing sulphation patterns of KS GAGs across the cornea could have potential implications for stromal water binding capacity, differential substitution either on lumican or keratocan, and/or extracellular matrix architecture.
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