Diabetes-induced morphological, biomechanical, and compositional changes in ocular basement membranes.

The current study investigates the structural and compositional changes of ocular basement membranes (BMs) during long-term diabetes. By comparing retinal vascular BMs and the inner limiting membrane (ILM) from diabetic and non-diabetic human eyes by light and transmission electron microscopy (TEM), a massive, diabetes-related increase in the thickness of these BMs was detected. The increase in ILM thickness was confirmed by atomic force microscopy (AFM) on native ILM flat-mount preparations. AFM also detected a diabetes-induced increase in ILM stiffness. The changes in BM morphology and biophysical properties were accompanied by partial changes in the biochemical composition as shown by immunocytochemistry and western blots: agrin, fibronectin and tenascin underwent relative increases in concentration in diabetic BMs as compared to non-diabetic BMs. Fibronectin and tenascin were particularly high in the BMs of outlining microvascular aneurisms. The present data showed that retinal vascular BMs and the ILM undergo morphological, biomechanical and compositional changes during long-term diabetes. The increase in BM thickness not only resulted from an up-regulation of the standard BM proteins, but also from the expression of diabetes-specific extracellular matrix proteins that are not normally found in retinal BMs.

Pneumatic Retinopexy for Rhegmatogenous Retinal Detachment in Pseudophakia.

PURPOSE: To identify the characteristics predictive of unfavorable outcomes for pneumatic retinopexy (PR) in the repair of pseudophakic rhegmatogenous retinal detachments (RD). METHODS: A retrospective chart review was performed at a single institution to identify patients who underwent PR in pseudophakic eyes. Pre- and postoperative data were reviewed and analyzed to evaluate predictive factors of failure. RESULTS: Forty-four patients met the study criteria. PR was successful in 23 (52.3%) patients. The failed cases underwent scleral buckles, vitrectomies, or both. A retinal tear located outside the superior four clock hours was a significant predictor of PR failure. At six months post-intervention, the failure and success groups were statistically similar for vision and rate of reattachment. CONCLUSIONS: Modified criteria for PR in pseudophakia may include cases with retinal breaks within the superior four clock hours. If further surgery is required, the final vision and anatomic reattachment are not disadvantaged by the initial PR procedure.

The bi-functional organization of human basement membranes.

The current basement membrane (BM) model proposes a single-layered extracellular matrix (ECM) sheet that is predominantly composed of laminins, collagen IVs and proteoglycans. The present data show that BM proteins and their domains are asymmetrically organized providing human BMs with side-specific properties: A) isolated human BMs roll up in a side-specific pattern, with the epithelial side facing outward and the stromal side inward. The rolling is independent of the curvature of the tissue from which the BMs were isolated. B) The epithelial side of BMs is twice as stiff as the stromal side, and C) epithelial cells adhere to the epithelial side of BMs only. Side-selective cell adhesion was also confirmed for BMs from mice and from chick embryos. We propose that the bi-functional organization of BMs is an inherent property of BMs and helps build the basic tissue architecture of metazoans with alternating epithelial and connective tissue layers.