Yassine J. Daoud

VEGF Secreted by Hypoxic Müller Cells Induces MMP-2 Expression and Activity in Endothelial Cells to Promote Retinal Neovascularization in Proliferative Diabetic Retinopathy

In proliferative diabetic retinopathy (PDR), retinal ischemia promotes neovascularization (NV), which can lead to profound vision loss in diabetic patients. Treatment for PDR, panretinal photocoagulation, is inherently destructive and has significant visual consequences. Therapies targeting vascular endothelial growth factor (VEGF) have transformed the treatment of diabetic eye disease but have proven inadequate for treating NV, prompting exploration for additional therapeutic options for PDR patients. In this regard, extracellular proteolysis is an early and sustained activity strictly required for NV. Extracellular proteolysis in NV is facilitated by the dysregulated activity of matrix metalloproteinases (MMPs). Here, we set out to better understand the regulation of MMPs by ischemia in PDR. We demonstrate that accumulation of hypoxia-inducible factor-1α in Müller cells induces the expression of VEGF, which, in turn, promotes increased MMP-2 expression and activity in neighboring endothelial cells (ECs). MMP-2 expression was detected in ECs in retinal NV tissue from PDR patients, whereas MMP-2 protein levels were elevated in the aqueous of PDR patients compared with controls. Our findings demonstrate a complex interplay among hypoxic Müller cells, secreted angiogenic factors, and neighboring ECs in the regulation of MMP-2 in retinal NV and identify MMP-2 as a target for the treatment of PDR.

Angiopoietin-like 4 is a potent angiogenic factor and a novel therapeutic target for patients with proliferative diabetic retinopathy.

Significance In proliferative diabetic retinopathy (PDR), the most vision-threatening sequela of diabetic eye disease, retinal ischemia leads to increased expression of angiogenic factors that promote neovascularization. Although therapies targeting the potent angiogenic mediator vascular endothelial growth factor have been remarkably successful for the treatment of diabetic macular edema, this approach has not proven sufficient to prevent the development of retinal neovascularization, implicating additional angiogenic factor(s) in PDR pathogenesis. We demonstrate here that angiopoietin-like 4 is a potent angiogenic mediator with markedly increased expression in the eyes of PDR patients. Our studies identify a novel therapeutic target for the treatment of ocular neovascular disease and may have broad implications for the treatment of other diseases dependent on pathologic angiogenesis. Diabetic eye disease is the most common cause of severe vision loss in the working-age population in the developed world, and proliferative diabetic retinopathy (PDR) is its most vision-threatening sequela. In PDR, retinal ischemia leads to the up-regulation of angiogenic factors that promote neovascularization. Therapies targeting vascular endothelial growth factor (VEGF) delay the development of neovascularization in some, but not all, diabetic patients, implicating additional factor(s) in PDR pathogenesis. Here we demonstrate that the angiogenic potential of aqueous fluid from PDR patients is independent of VEGF concentration, providing an opportunity to evaluate the contribution of other angiogenic factor(s) to PDR development. We identify angiopoietin-like 4 (ANGPTL4) as a potent angiogenic factor whose expression is up-regulated in hypoxic retinal Müller cells in vitro and the ischemic retina in vivo. Expression of ANGPTL4 was increased in the aqueous and vitreous of PDR patients, independent of VEGF levels, correlated with the presence of diabetic eye disease, and localized to areas of retinal neovascularization. Inhibition of ANGPTL4 expression reduced the angiogenic potential of hypoxic Müller cells; this effect was additive with inhibition of VEGF expression. An ANGPTL4 neutralizing antibody inhibited the angiogenic effect of aqueous fluid from PDR patients, including samples from patients with low VEGF levels or receiving anti-VEGF therapy. Collectively, our results suggest that targeting both ANGPTL4 and VEGF may be necessary for effective treatment or prevention of PDR and provide the foundation for studies evaluating aqueous ANGPTL4 as a biomarker to help guide individualized therapy for diabetic eye disease.

The intraoperative impression and postoperative outcomes of gamma-irradiated corneas in corneal and glaucoma patch surgery.

Purpose: To report the short-term outcome of gamma-irradiated sterile cornea in corneal and glaucoma patch graft surgeries when viable endothelium is not necessary. Methods: Surgeons who have used the irradiated corneas were asked to rate their impression from 1 (fair) to 4 (very good). Specific intraoperative questions included availability, ease of use, clarity, thickness, tensile strength, and suturing. Postoperative outcomes included epithelialization, biological incorporation, and clarity of tissue, as well as any adverse outcomes. Results: Irradiated sterile cornea has been used in more than 150 surgeries so far. The major uses for irradiated cornea were as glaucoma patch graft (65.3%), as corneal patch graft (14%), in anterior lamellar keratoplasty (10.7%), and in keratoprosthesis (10%). The mean score for packaging of tissue was 3.75 (SD, 0.45), ease of use 3.83 (SD, 0.39), clarity 3.62 (SD, 0.51), thickness 3.67 (SD, 0.49), tensile strength 3.64 (SD, 0.50), and suturing 3.62 (SD, 0.65). Postoperative outcomes were also favorable, including epithelialization (mean ± SD, 3.46 ± 0.69), biological incorporation (mean ± SD, 3.46 ± 0.69), and clarity (mean ± SD, 3.43 ± 0.85). There were 4 episodes of corneal melt (all occurred in patients with previous corneal melt). There were no reported cases of tissue rejection or infection. Conclusions: Gamma-irradiated sterile cornea is a promising new development that may help increase the supply of donor cornea tissue. It virtually eliminates the risk of infection while providing a long shelf life. It is particularly helpful in emergency situations or in remote areas. However, longer follow-up and a prospective study comparing the outcomes of the irradiated corneas with those of the optisol-stored corneas are needed.

Transforming growth factor β and insulin signal changes in stromal fibroblasts of individual keratoconus patients.

Keratoconus (KC) is a complex thinning disease of the cornea that often requires transplantation. The underlying pathogenic molecular changes in this disease are poorly understood. Earlier studies reported oxidative stress, metabolic dysfunctions and accelerated death of stromal keratocytes in keratoconus (KC) patients. Utilizing mass spectrometry we found reduced stromal extracellular matrix (ECM) proteins in KC, suggesting ECM-regulatory changes that may be due to altered TGFβ signals. Here we investigated properties of stromal cells from donor (DN) and KC corneas grown as fibroblasts in serum containing DMEM: F12 or in serum-free medium containing insulin, transferrin, selenium (ITS). Phosphorylation of SMAD2/3 of the canonical TGFβ pathway, was high in serum-starved DN and KC fibroblast protein extracts, but pSMAD1/5/8 low at base line, was induced within 30 minutes of TGFβ1 stimulation, more so in KC than DN, suggesting a novel TGFβ1-SMAD1/5/8 axis in the cornea, that may be altered in KC. The serine/threonine kinases AKT, known to regulate proliferation, survival and biosynthetic activities of cells, were poorly activated in KC fibroblasts in high glucose media. Concordantly, alcohol dehydrogenase 1 (ADH1), an indicator of increased glucose uptake and metabolism, was reduced in KC compared to DN fibroblasts. By contrast, in low glucose (5.5 mM, normoglycemic) serum-free DMEM and ITS, cell survival and pAKT levels were comparable in KC and DN cells. Therefore, high glucose combined with serum-deprivation presents some cellular stress difficult to overcome by the KC stromal cells. Our study provides molecular insights into AKT and TGFβ signal changes in KC, and a mechanism for functional studies of stromal cells from KC corneas.

What is central toxic keratopathy syndrome if it is not diffuse lamellar keratitis grade IV

The Central Toxic Keratopathy (CTK) syndrome describes a rare, acute, self-limited, non-inflammatory process that yields central corneal opacification and significant hyperopic shift after refractive surgery. Despite being exceedingly rare, certain clinical features of CTK give the condition a striking resemblance to other more serious inflammatory conditions, including diffuse lamellar keratitis (DLK). As the authors demonstrate in this article, despite the overlapping clinical features, CTK is a disease process that is distinct from DLK and, therefore, in need of distinct management interventions.

Inhibition of Corneal Neovascularization by Subconjunctival Injection of Fc-Endostatin, a Novel Inhibitor of Angiogenesis.

We assessed the antiangiogenic effects of subconjunctival injection of Fc-endostatin (FcE) using a human vascular endothelial growth factor-induced rabbit corneal neovascularization model. Angiogenesis was induced in rabbit corneas through intrastromal implantations of VEGF polymer implanted 2 mm from the limbus. NZW rabbits were separated into groups receiving twice weekly subconjunctival injections of either saline; 25 mg/mL bevacizumab; 2 mg/mL FcE; or 20 mg/mL FcE. Corneas were digitally imaged at 5 time points. An angiogenesis index (AI) was calculated (vessel length (mm) × vessel number score) for each observation. All treatment groups showed a significant decrease in the vessel length and AI compared to saline on all observation days (P < 0.001). By day 15, FcE 2 inhibited angiogenesis significantly better than FcE 20 (P < 0.01). There was no significant difference between FcE 2 and BV, although the values trended towards significantly increased inhibition by BV. BV was a significantly better inhibitor than FcE 20 by day 8 (P < 0.01). FcE was safe and significantly inhibited new vessel growth in a rabbit corneal neovascularization model. Lower concentration FcE 2 exhibited better inhibition than FcE 20, consistent with previous FcE studies referencing a biphasic dose-response curve. Additional studies are necessary to further elucidate the efficacy and clinical potential of this novel angiogenesis inhibitor.

Refractive surgery in systemic and autoimmune disease.

Patients with underlying systemic disease represent challenging treatment dilemma to the refractive surgeon. The refractive error in this patient population is accompanied by a systemic disease that may have an ocular or even a corneal component. The literature is rather sparse about the use of laser refractive surgery (LRS) and such procedure is not approved by the United States Food and Drug Administration (FDA) in this patient population. Patients with collagen vascular disease, diabetes mellitus (DM), allergic and atopic disease, or human immunodeficiency virus (HIV) are never ideal for LRS. Patients with uncontrolled systemic disease or ocular involvement of the disease should not undergo LRS. However, a patient with well-controlled and mild disease, no ocular involvement, and not on multidrug regimen may be a suitable candidate if they meet stringent criteria. There is a need for a large, multicenter, controlled trial to address the safety and efficacy of LRS in patients with systemic disease before such technology can be widely adopted by the refractive surgery community.

Iris Suture Fixation of Subluxated Intraocular Lenses

PURPOSE To assess the results of iris suture fixation of subluxated intraocular lenses. DESIGN Retrospective study. METHODS This was a nonrandomized chart review of eyes with subluxated intraocular lenses that underwent iris suture fixation at an academic institutional care center. Seventy-two eyes of 67 consecutive patients were included. The following cases were excluded: posterior dislocations necessitating pars plana vitrectomy; secondary implantations for aphakia; and iris suture fixation at primary cataract extraction. Main outcome measures included visual acuity improvement, surgically induced astigmatism, and postsurgical complications. RESULTS The mean follow-up duration was 16.64 ± 24.37 months (median = 4.03 months). All patients had preoperative monocular diplopia or unstable vision attributable to the subluxated intraocular lenses, and 40.3% of them required aphakic correction. There was an overall improvement in best-corrected visual acuity from a mean preoperative logMAR 0.35 ± 0.32 (Snellen equivalent∼20/45) to logMAR 0.21 ± 0.25 (20/32, P = .001). There was no significant change in astigmatism secondary to the surgery. The mean difference in preoperative keratometry readings was 1.6 ± 1.07 diopter (D), whereas the mean postoperative manifest refraction astigmatic error (vertexed to the corneal surface) was 1.29 ± 0.92 D (P < .02). Re-subluxations occurred in 7 eyes during follow-up; the majority of these eyes underwent repeat fixation. Most (93.55%) intraocular lenses were stable and centered at the final follow-up. Glaucoma developed in 2 eyes postoperatively. CONCLUSIONS Iris suture fixation of subluxated intraocular lenses was efficacious for the eyes included in this study, and it led to long-term stability of the intraocular lenses in 93.55% of cases.

A comprehensive guide to managing astigmatism in the cataract patient

Improvements in cataract surgery and ophthalmic lens technology have turned cataract surgery into a refractive procedure. Patients are expecting that they will no longer require contact lens or glasses for excellent vision. In order to meet the patient’s expectations, the surgeon must be meticulous with preoperative measurements and precise with the intraoperative alignment of the implanted toric lens. Technological advances in intraoperative aberrometry and image guidance software will improve intraoperative alignment of astigmatism correcting lens. Despite the improvements in measurements, unforeseen refractive outcomes will occur and it is critical that the cataract surgeon is equipped to correct any problems. A systematic evaluation should be undertaken to find the source of the error. Complete ocular exam with lens axis measurement, manifest refraction and repeat corneal measurements should be done. Treatment options to correct residual refractive error include toric lens rotation, laser vision correction with photorefractive keratectomy or laser in-situ keratomileusis, piggyback lens placement or intraocular lens (IOL) exchange. Prior to selecting a treatment option, it is important to compare pre- and post-operative calculations. If preoperative calculations are correct, a vector analysis can be performed to determine suggested IOL adjustment to correct the refractive error. If toric lens rotation does not provide a satisfactory refractive outcome, laser vision correction is recommended as a first option. If the patient is not a good refractive candidate, an IOL exchange with a monofocal lens or with the appropriate toric lens, if the loops can be safely placed in the bag, is advocated.

Ophthalmic features of systemic diseases.

Abstract The eye is intricately integrated with the functions of the body. Ocular changes may precede or run concurrently with various systemic conditions and often represent important prognostic indicators of disease progression. In addition to a thorough diagnostic evaluation and treatment of underlying processes, individuals with systemic diseases and concurrent ocular changes may need comprehensive ophthalmic examination to reduce the risk of visual impairment and morbidity. In this review the authors highlight the clinically relevant ocular signs that occur parallel with systemic conditions. In particular, the study focuses on the varied clinical presentations that can lead to rapid diagnosis to improve management of eye disorders that accompany systemic diseases.