Intraocular and plasma levels of cellular fibronectin in patients with uveitis and diabetes mellitus

Role of fibronectin and IOL surface modification in IOL: Lens capsule interactions

Posterior Capsule Opacification (PCO) is one of the most common complications of cataract surgery. While studies have shown that IOL material properties and fibronectin adsorption may affect IOL-induced PCO in the clinical setting, the mechanism governing such interactions is not totally understood. Since strong adhesion forces between IOLs and posterior capsules (PCs) have been shown to impede cell infiltration and thus reduce PCO formation, this study was designed to assess whether fibronectin adsorption and IOL material properties would impact the IOL:PC adhesion force and cell infiltration using a PCO predictive in vitro model and a macromolecular dye imaging model, respectively. Our results showed that fibronectin adsorption significantly increased the adhesion forces and reduced simulated cell infiltration between acrylic foldable IOLs and the PC at physiological temperature in comparison to fibronectin-free controls. This fibronectin-mediated strong IOL: PC bond may be contributing to low PCO rates in the clinic for acrylic foldable IOLs. In addition, acrylic foldable IOLs coated with Di(ethylene glycol) (Diglyme), a hydrophilic coating known to reduce protein adsorption, was tested for its ability to alter adhesion force and cell infiltration. We observed that IOLs coated with Diglyme coating greatly reduced surface hydrophobicity and fibronectin adsorption of acrylic foldable IOLs. Furthermore, Diglyme coated IOLs showed significantly reduced adhesion force and increased simulated cell infiltration at the IOL:PC interface. The overall results support the hypothesis that IOL surface properties and their ability to adsorb fibronectin may have great impact on the IOL:PC adhesion force. A tight binding between IOLs and PC may contribute to the reduction of cell infiltration and thus the PCO incidence rate in the clinic.

Damage-Associated Molecular Patterns (DAMPs) in Retinal Disorders

Damage-associated molecular patterns (DAMPs) are endogenous danger molecules released from the extracellular and intracellular space of damaged tissue or dead cells. Recent evidence indicates that DAMPs are associated with the sterile inflammation caused by aging, increased ocular pressure, high glucose, oxidative stress, ischemia, mechanical trauma, stress, or environmental conditions, in retinal diseases. DAMPs activate the innate immune system, suggesting their role to be protective, but may promote pathological inflammation and angiogenesis in response to the chronic insult or injury. DAMPs are recognized by specialized innate immune receptors, such as receptors for advanced glycation end products (RAGE), toll-like receptors (TLRs) and the NOD-like receptor family (NLRs), and purine receptor 7 (P2X7), in systemic diseases. However, studies describing the role of DAMPs in retinal disorders are meager. Here, we extensively reviewed the role of DAMPs in retinal disorders, including endophthalmitis, uveitis, glaucoma, ocular cancer, ischemic retinopathies, diabetic retinopathy, age-related macular degeneration, rhegmatogenous retinal detachment, proliferative vitreoretinopathy, and inherited retinal disorders. Finally, we discussed DAMPs as biomarkers, therapeutic targets, and therapeutic agents for retinal disorders.

Mesenchymal marker expression is elevated in Müller cells exposed to high glucose and in animal models of diabetic retinopathy

Müller cells are retinal glial cells and exhibit a fibroblast-like phenotype and ability to migrate in diabetic retinopathy (DR). However, expression of mesenchymal markers, which promote fibrosis in various organs, has not been characterized in the diabetic retina. We examined changes in the expression of these markers in Müller cells exposed to high glucose and in animal models of diabetic retinopathy. High glucose conditions increased mesenchymal maker expression and migration in Müller cells. Snail, N-cadherin, Vimentin, β-catenin, and α-smooth muscle actin (α-SMA) levels were all dramatically increased in retinas from humans with diabetic retinopathy (DR) and from DR mouse models. In addition, Snail overexpression increased the expression of connective tissue growth factor (CTGF) and fibronectin, while Snail knockdown attenuated high glucose-induced increases in fibronectin and CTGF expression. These results demonstrate for the first time that mesenchymal markers are upregulated in retinas from a diabetic mouse model, and that Snail and N-cadherin levels are also increased in Müller cells exposed to high glucose. This suggests mesenchymal proteins may play a crucial role in the development of DR.

Human apolipoprotein(a) kringle V inhibits ischemia-induced retinal neovascularization via suppression of fibronectin-mediated angiogenesis

Retinal neovascularization is observed in progression of diabetic retinopathy. New vessels grow into the vitreous cavity in proliferative diabetic retinopathy, resulting in traction retinal detachment and vitreous hemorrhage. To overcome the catastrophic visual loss due to these complications, efforts have been focused on the treatment of retinal neovascularization. In this study, we demonstrated the inhibitory effect of recombinant human apolipoprotein(a) kringle V (rhLK8) in an animal model of ischemia-induced retinal neovascularization. rhLK8 induced no definite toxicity on endothelial cells and retinal tissues at the therapeutic dosage. Interestingly, rhLK8 showed antiangiogenic effect, particularly on fibronectin-mediated migration of endothelial cells. Further experiments demonstrated high binding affinity of rhLK8 to α3β1 integrin, and suppression of it might be the mechanism of antiangiogenic effect of rhLK8. Furthermore, rhLK8 inhibited phosphorylation of focal adhesion kinase, resulting in suppression of activation of consequent p130CAS-Jun NH(2)-terminal kinase. Taken together, our data suggested the possible application of rhLK8 in the treatment of retinal neovascularization by suppression of fibronectin-mediated angiogenesis.

Clinical features of patients with diabetes mellitus presenting with their first episode of uveitis

PURPOSE

Little is known about uveitis in patients with diabetes mellitus (DM). The authors studied diabetic patients with their first episode of uveitis.

METHODS

Cross-sectional, case note study documenting the uveitis, underlying cause/syndrome, treatment, type of DM and treatment, and any diabetic retinopathy.

RESULTS

There were 34 patients (M/F: 17/17, 48 eyes) with their first uveitis episode (33 had type 2 DM). Mean age of onset of DM 49 years and uveitis 56 years. Uveitis was bilateral in 14 (45%), with most having idiopathic anterior uveitis. Visual acuity 6/18-6/60 in 15 eyes, and worse than 6/60 in 11 eyes. There was 3-4+ flare in 16 eyes, 3-4+ anterior chamber cells in 13 eyes. Diabetic retinopathy was seen in 20 (42%) eyes, and mean blood glucose was 13.64 mmol/L in 11 patients.

CONCLUSIONS

Diabetic patients presenting with uveitis, whatever the aetiology, may have severe inflammation, reduced vision, and poor glycaemic control.

Impact of fibronectin on surface properties of intraocular lenses

PURPOSE

Physical properties of intraocular lens (IOL) surfaces determine biocompatibility. IOL hydrophobicity of commercially available IOLs with and without fibronectin (FN) coating can be determined by surface contact angle (SCA) measurements. SCA data of IOLs may allow for a rational selection of an IOL type as a function of underlying eye disease.

SETTING

University Hospital of Saarland, Homburg (Saar), Germany

METHODS

Thirteen IOL types were tested. IOLs were made of poly(methyl methacrylate)(PMMA), acrylate, or silicone. Select IOLs were surface modified by the manufacturer with heparin or a polysaccharide coating. SCA values of IOLs, either uncoated or precoated with FN, were determined using the sessile water drop method.

RESULTS

SCA values ranged from 61.3 to 116.1 degrees for unmodified IOLs, with PMMA IOLs being more hydrophilic (median SCA, 74.1 degrees ), silicone IOLs more hydrophobic (median SCA, 113.3 degrees ), and acrylate IOLs intermediate (median SCA, 86.6 degrees ). Upon FN coating, all genuine acrylate lenses became significantly more hydrophilic while this effect was either nonsignificant or opposite on some PMMA and silicon IOLs. Heparin or polysaccharide surface modification resulted in significantly reduced SCA values. On acrylate IOLs, SCA values did not correlate with the aqueous content of the material.

CONCLUSIONS

This study associates IOL materials, surface modifications, and the role of FN preadsorption with SCA values reflecting surface hydrophobicity versus hydrophilicity. It provides a rationale for specific IOL selection as a function of the clinical setting, and a basis for IOL development using tailored surface physicochemistry to enhance biocompatibility and to reduce susceptibility to implant infection.

Proteomics of the aqueous humor in healthy New Zealand rabbits

There are several physiological roles postulated for aqueous humor, a liquid located in the anterior and posterior chamber of the eye, such as maintenance of the intraocular pressure, provision of nutrients, and removal of metabolic waste from neighboring tissues and provision of an immune response and protection during inflammation and infection. To link these function to specific or classes of proteins, identification of the aqueous humor proteome is essential. Aqueous humor obtained from healthy New Zealand white rabbits was analyzed using three synergistic protein separation methods: 1-D gel electrophoresis, 2-DE, and 1-DLC (RPLC) prior to protein identification by MS. As each of these separation methods separates intact proteins based on different physical properties (pIs, molecular weights, hydrophobicity, solubility, etc.) the proteome coverage is expanded. This was confirmed, since overlap between all three separation technologies was only about 8.2% with many proteins found uniquely by a single method. Although the most dominant protein presented in normal aqueous humor is albumin, by using this extensive separation/MS strategy, additional proteins were identified in total amount of 98 nonredundant proteins (plus an additional ten proteins for consideration). This expands the current protein identifications by approximately 65%. The aqueous humor proteome comprises a specific selection of cellular and plasma based proteins and can almost exclusively be divided into four functional groups: cell-cell interactions/wound healing, proteases and protease inhibitors, antioxidant protection, and antibacterial/anti-inflammatory proteins.

Elevated levels and fragmented nature of cellular fibronectin in the plasma of gastrointestinal and head and neck cancer patients

BACKGROUND

Tumor invasion occurs following enzymatic degradation of components of the extracellular matrix. The proteolysis-resistant domains of matrix components are likely to appear in the blood plasma during invasion, and could be used as markers of malignancy. Cellular fibronectin (cFN), a major ECM component, possesses 3 alternately spliced principal protease resistant domains; two of which, extra domain A (EDA) and III connecting segment (IIICS), were selected for this study of the nature of the plasma cFN molecules and its levels in normal subjects (n=51), and patients with gastrointestinal (G-I, n=145) or head and neck (H-N, n=127) cancers.

METHODS

ELISA was used to measure the cFN levels in plasma and Western blotting to analyze its fragmented nature in plasma samples from normal individuals and patients with G-I or H-N cancers.

RESULTS

cFN in blood plasma, as probed by anti-EDA and anti-IIICS antibodies on Western blots, is found to exist entirely in a fragmented form in normal subjects and G-I and H-N cancer patients. The cFN polypeptides in plasma have Mr of 160 and 100. The levels of plasma cFN, determined by ELISA using the 2 antibodies, are found to be increased in G-I and H-N cancers. In a significant number of stomach (43%), gall bladder (35%) and colon (17%) cancer cases an additional anti-EDA-reactive 30 kD peptide is seen in the plasma.

CONCLUSIONS

The mean rise for all sites is statistically significant, and 65% of all patients show cFN levels >80th percentile of normal values. The characterization of the 30 kD peptide showed that it does not contain the IIICS domain and also lacks the central cell- and heparin-binding sites.

Characterization of semenogelin proteins in the human retina

Semenogelin I and II are the major proteins present in semen coagulum. In the present study, semenogelin I and II were detected in human RPE lysates by proteomic analysis. We further analyzed the expression of these proteins in the retinal cells in vivo and in vitro. Western blots detected semenogelin I and II in both RPE and neural retina while the vitreous contained only SgII. Cryo and paraffin sections of human retina were processed for both immunofluorescence and DAB reaction with an antibody that recognizes both forms of semenogelin proteins. Retina and RPE total lysates were evaluated for the presence of these proteins and in a human RPE cell line (D407). Both proteins were detected by western blot in human RPE and in D407 cell lysates. Immunoreactivity was detected in the ganglion cell and photoreceptor layer of the retina. Our data support the expression of semenogelin I and II in the human retina in several different compartments. Further studies towards addressing the function of these proteins in the retina are in progress.