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Jody A. Rada, Virginia R. Achen, Sudhir Penugonda, Robb W. Schmidt, Bobbie A. Mount; Proteoglycan Composition in the Human Sclera During Growth and Aging. Invest. Ophthalmol. Vis. Sci. 2000;41(7):1639-1648.
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purpose. Scleral proteoglycans were characterized from human donor eyes aged 2
months to 94 years to identify age-related changes in the synthesis
and/or accumulation of these extracellular matrix components.
methods. Newly synthesized proteoglycans (previously radiolabeled with 35SO4) and total accumulated scleral
proteoglycans were extracted with 4 M guanidine hydrochloride and
separated by molecular sieve chromatography on a Sepharose CL-4B
column. The elution positions of newly synthesized and total
accumulated proteoglycans were determined by assaying each fraction for
radioactivity and glycosaminoglycans, respectively. Regression analyses
were performed on the three major proteoglycan peaks to identify
age-related changes in scleral proteoglycan composition. Scleral
proteoglycans were further purified by anion-exchange chromatography
and characterized by sodium dodecyl sulfate–polyacrylamide gel
electrophoresis and Western blot analyses.
results. Human scleral proteoglycans were apparent as three major peaks after
chromatography on Sepharose CL-4B. The two faster eluting peaks
contained alternative forms of the cartilage proteoglycan, aggrecan,
whereas the third peak contained the small proteoglycans biglycan and
decorin. The relative percentage of newly synthesized and total
accumulated aggrecan increased approximately two- to sixfold from
infancy to 94 years. In contrast, the relative percentage of newly
synthesized and total accumulated biglycan and decorin decreased by
approximately 25%. Chromatography and Western blot results indicated
that the absolute amounts of all three proteoglycans significantly
increased in concentration within the sclera from birth to the fourth
decade. Beyond the fourth decade, decorin and biglycan decreased in all
scleral regions and were present in lowest concentrations by the ninth
decade. In contrast, aggrecan, which was present in highest
concentration in the posterior sclera, was not significantly reduced
with increasing age.
conclusions. The age-related changes in scleral proteoglycan composition observed in
the present study are likely to contribute to the regional alterations
in biomechanical properties of the sclera associated with growth and
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