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P. Hiscott, C. Howard, M. García-Fiñana, Q. Yan; Expression of the Matricellular Protein SPARC in the Human Retinal Pigment Epithelium Changes With Age. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3012.
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The expression of the matricellular protein SPARC (Secreted Protein, Acidic and Rich in Cysteine) in retinal pigment epithelial cells (RPEc) of human eyes was analyzed to determine whether SPARC expression changes between young and old ages and/or retinal regions (peripheral versus posterior) of the donors. The findings were also correlated with Bruch’s membrane thickness.
SPARC protein level in the RPEc was detected in 36 human donor eyes (16 aged ≤65 years; 20 aged >65 years) by immunohistochemical staining in an age-masked study. Sections incorporating both posterior and peripheral retina of each eye were stained with mouse anti-human SPARC IgG by an immunoperoxidase technique using a red chromogen (fast red). Controls were done with non-immune serum. The staining intensity in the RPE cells of each eye was assessed by Aequitas Image Analysis and the results were subjected to statistical analysis (2-way analysis of variance). Profile analysis was used to ascertain Bruch’s membrane thickness.
Intensity of SPARC staining was significantly lower in the donors aged >65 years group than in the younger age group, both for posterior and for peripheral RPEc (p=0.05 and p=0.009, respectively). Intensity of staining was less in posterior than peripheral retinal RPEc of both groups (combined p=0.042). Bruch’s membrane thickness increased with age in both macular and peripheral regions (p=0.036 and p=0.002, respectively). No correlation was found between the decrease in SPARC level and increase in Bruch’s thickness, in either macular or peripheral regions (p=0.627 and p=0.62, respectively).
SPARC level is significantly lower in RPEc of older eyes than in that of the younger eyes; and lower in posterior than in peripheral RPEc. This disparity is independent of Bruch’s membrane thickness. Given the putative roles of SPARC in cell-matrix interactions and cellular differentiation, reduction of the protein in RPEc with age may impinge upon common pathologies that involve the ageing chorioretinal interface such as age-related macular degeneration.
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