Increased expression of Protein S in eyes with diabetic retinopathy and diabetic macular edema

Protein S (PS) is a multifunctional glycoprotein that ameliorates the detrimental effects of diabetes mellitus (DM). The aim of this study was to evaluate the distribution of PS in diabetic retinopathy (DR) and diabetic macular edema (DME). This was a study of 50 eyes with DM (37 with DME, 6 with proliferative DR, and 7 with no DR) and 19 eyes without DM. The level of PS was measured by enzyme immunoassay and was compared between eyes with or without DM, with or without DME, and with severe DME (>= 350 mu m) or mild DME (<350 m). We also performed immunohistopathologic evaluations of post-mortem eyes and the cystoid lesions excised during surgery. The aqueous free PS was significantly higher with DM (7.9 +/- 1.2 ng/ml, P<0.01) than without DM (6.10.7). The aqueous free PS was significantly elevated with DME (8.2 +/- 1.2, P<0.05) compared to proliferative DR (7.01.0) and no DR (7.0 +/- 0.7). Eyes with severe DME had significantly higher aqueous free PS than mild DME (8.5 +/- 1.3 vs. 7.7 +/- 1.0, P<0.05). Immunohistochemistry showed PS in the outer plexiform layer of the retina and cystoid lesion. The higher expression of PS with DR and DME suggests that PS is involved in their pathogenesis.

Automated summary

This study evaluated the distribution of Protein S in diabetic retinopathy and diabetic macular edema, suggesting its involvement in the pathogenesis of these conditions. The higher expression of Protein S in eyes with DR and DME indicates its potential role in these complications of diabetes.