Ramazan Yagci

Heparin Mimetic Peptide Nanofibers Promote Angiogenesis

New blood vessel formation (angiogenesis) is one of the most important processes required for functional tissue formation. Induction of angiogenesis is usually triggered by growth factors released by cells. Glycosaminoglycans (e.g., heparan sulphates) in the extracellular matrix aid in proper functioning of these growth factors. Therefore, exogeneous heparin or growth factors were required for promoting angiogenesis in previous regenerative medicine studies. Here we report for the first time induction of angiogenesis by a synthetic nanofibrous peptide scaffold without the addition of any exogenous growth factors or heparin. We designed and synthesized a self-assembling peptide amphiphile molecule that is functionalized with biologically active groups to mimic heparin. Like heparin, this molecule has the ability to interact with growth factors and effectively enhance their bioactivity. The nanofibers formed by these molecules were shown to form a 3D network mimicking the structural proteins in the extracellular matrix. Because of heparin mimicking capabilities of the peptide nanofibers, angiogenesis was induced without the addition of exogenous growth factors in vitro. Bioactive interactions between the nanofibers and the growth factors enabled robust vascularization in vivo as well. Heparin mimetic peptide nanofibers presented here provide new opportunities for angiogenesis and tissue regeneration by avoiding the use of heparin and exogenous growth factors. The synthetic peptide nanofiber scaffolds enriched with proper chemical functional groups shown in this study can be used to induce various desired physiological responses for tissue regeneration.

Antioxidant Status and Oxidative Stress in Primary Open Angle Glaucoma and Pseudoexfoliative Glaucoma

Purpose: The aim of this study was to establish the antioxidant status and oxidative stress in patients with primary open-angle glaucoma (POAG) and pseudoexfoliative glaucoma (PEG). Methods: Serum levels of total antioxidant capacity (TAC) and superoxide dismutase (SOD) as indicators of antioxidant status; and total oxidant status (TOS), nitric oxide (NO), protein carbonyl (PC), and malondialdehyde (MDA) as indicators of oxidative stress were measured from the blood samples of patients with POAG (n = 23), PEG (n = 24) and healthy control subjects (n = 19) by spectrophotometry. Results: Mean TAC level was 0.6 ± 0.1 mmol/L in the POAG group; 0.5 ± 0.1 mmol/L in the PEG group and 1.2 ± 0.3 mmol/L in the control group (p = 0.001). Mean SOD level was 13 ± 0.5 mg/L in the POAG group, 11.6 ± 0.2 mg/L in the PEG group and 9.4 ± 0.6 mg/L in the control group (p = 0.001). Mean TOS level was 19.6 ± 2.6 μmol/L in the POAG group, 21.2 ± 4.2 μmol/L in the PEG group and 15.1 ± 7 μmol/L in the control group (p = 0.001). Mean NO level was 74.3 ± 14.4 µmol/L in the POAG group, 66.1 ± 8.1 µmol/L in the PEG group and 62.3 ± 13.5 µmol/L in the control group (p = 0.005). Mean PC level was 641.5 ± 102.5 nmol/mg in the POAG group, 988.3 ± 214.7 nmol/mg in the PEG group and 654.4 ± 150.7 nmol/mg in the control group (p = 0.001). Mean MDA level was 1.9 ± 0.2 µmol/L in the POAG group, 1.7 ± 0.4 µmol/L in the PEG group and 1.1 ± 0.2 µmol/L in the control group (p = 0.001). Conclusion: The findings of the present study are potentially of significance and add to the growing body of evidence for oxidative stress in POAG and PEG. Decreased antioxidant defense and increased oxidative stress system may play an important role in the pathogenesis of POAG and PEG.

Use of melatonin to prevent selenite-induced cataract formation in rat eyes.

Purpose: To evaluate effects of melatonin on sodium selenite-induced cataract formation. Methods: Twenty-three Sprague-Dawley rat pups were randomized into three groups. Group 1(n = 9), injected with selenite (s.c.) on postpartum day 10; group 2 (n = 7), injected with selenite (s.c.) on day 10 plus melatonin (i.p.) on days 8–15; group 3 (n = 7), saline-injected controls. Development of cataract was assessed weekly under a dissection microscope. Rat lenses and serums were analyzed for antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT); oxidative stress indicators xanthine oxidase (XO) and malondialdehyde (MDA), a marker of lipid peroxidation; and protein carbonyl (PC), a marker of protein oxidation. Results: Significant differences (p < 0.05) were seen in cataract development by the three groups. All rats developed dense nuclear cataract in group 1. Dense nuclear cataract was not observed in group 2: five of seven rats developed minor cataracts, while the other two had clear lenses. In control rats (group 3), all lenses remained clear. In selenite group (group 1), lens and serum levels of MDA, PC, and XO were significantly higher and levels of SOD and CAT were significantly lower than those in control group (p < 0.001). In selenite+melatonin group (group 2), lens and serum levels of MDA, PC, and XO significantly decreased and levels of SOD and CAT significantly increased when compared with selenite group. Conclusions: Studies with the rat selenite cataract model strongly support the activity of melatonin as an endogenous antioxidant and anticataract agent.

Oxidative Macromolecular Damage in Age-Related Macular Degeneration

Purpose: To evaluate oxidative damage to the macromolecules, including protein, lipid, and DNA, in association with total oxidation status (TOS), total antioxidant capacity (TAC) in patients with exudative age-related macular degeneration (AMD). Materials and Methods: Serum levels of malondialdehyde (MDA) as an index of lipid peroxidation, protein carbonyl (PC) as a marker of protein oxidation, 8-hydroxy-29-deoxyguanosine (8-OHdG) as an indicator of oxidative DNA damage along with TOS, TAC were measured by specific methods in 47 patients with exudative AMD and 25 age- and sex-matched healthy subjects. Results: Significantly higher MDA, PC, 8-OHdG, TOS, and lower TAC levels were detected in the serum of patients with exudative AMD compared with their controls (p < 0.001). Conclusion: The results indicate that an imbalance between TOS and TAC leads to not only increased lipid damage, but also protein and DNA damage. These first reported results suggest that protein and DNA damage might also play a role in the pathogenesis of AMD.

Oxidative Stress and Protein Oxidation in Pseudoexfoliation Syndrome

Purpose: To investigate the oxidant/antioxidant status and protein oxidation in pseudoexfoliation syndrome. Methods: The activity of serum superoxide dismutase (SOD) and the levels of serum malondialdehyde (MDA) and protein carbonyl (PC) were measured in 50 patients with pseudoexfoliation (PEX) and in 55 healthy controls. Results: There was significant difference in the SOD activity in PEX group compared with the control group (p < 0.001). In addition, MDA and PC levels were significantly higher in patients than in the controls (p < 0.001). Conclusions: Decrease in SOD activity and the higher levels of MDA and PC indicate increased oxidative stress. Our results suggest a possible role of oxidative stress in pathology of PEX syndrome.

Prevention of Selenite-Induced Cataractogenesis by N-Acetylcysteine in Rats

Purpose: To evaluate the effect of N-acetylcysteine on selenite-induced cataract formation in a rat model. Materials and Methods: Thirty-four Sprague-Dawley rat pups were divided into three groups. Eight pups received only selenite on postpartum day 10 (group 1), 14 pups received selenite on day 10 and additional acetylcysteine on postnatal days 9 to 15 (group 2), and 12 pups received only saline (group 3, control). All pups were daily examined for the presence of cataract under the microscope, starting from the day their eyes opened. Glutathione and malondialdehyde levels were evaluated in both serum and lenticular samples while protein carbonyl level was studied only in lenticular samples. Results: In group 1, 50% of the rats developed dense nuclear opacities and 50% developed slight nuclear opacities, while in group 2 only 14.3% developed dense nuclear opacities and 21.4% developed slight nuclear opacities (p < 0.05). None of the rats in group 3 developed any lens opacity. In lenticular samples, mean glutathione level was statistically lower in group 1 compared to groups 2 and 3 (p < 0.05), while malondialdehyde and protein carbonyl levels were both statistically higher in group 1 compared to groups 2 and 3 (p < 0.05). Serum level of glutathione was statistically lower in group 1 compared to groups 2 and 3 (p < 0.05), while serum malondialdehyde level was statistically lower in group 3 compared to groups 1 and 2. Conclusions: N-acetylcysteine appears to inhibit selenite-induced cataractogenesis in the rat model, and this seems to be caused by the prevention of oxidative damage.

Inhibitory effects of topical thymoquinone on corneal neovascularization.

Purpose: Thymoquinone, one of the biologically active components of black seed oil, has anti-inflammatory and antioxidant properties. We aimed to study the effect of thymoquinone on corneal neovascularization in rats and to compare its efficacy with that of triamcinolone acetonide. Methods: Chemical cauterization of the cornea was performed with silver nitrate/potassium nitrate sticks in 40 eyes in 40 rats. An examiner blinded to the experiments scored the intensity of the cauterization. Topical instillation of thymoquinone 0.1%, thymoquinone 0.4%, and triamcinolone acetonide was continued for 7 days. The inhibitory effects of the drugs on corneal neovascularization were tested and compared with each other and with controls with a computer program that evaluates percent areas of cornea covered by neovascularization. Results: The means of percent area of corneal neovascularization in the thymoquinone 0.1%, thymoquinone 0.4%, triamcinolone acetonide, and control groups were 60.1%, 45%, 46%, and 72%, respectively. The inhibitory effect of thymoquinone 0.4% was found to be equal to that of triamcinolone acetonide (P = 0.87). The thymoquinone 0.4% and triamcinolone groups were different from the thymoquinone 0.1% and control groups (P < 0.05). There was also a significant difference between the percent area of corneal neovascularization in the thymoquinone 0.1% group and that of the controls (P < 0.05). The mean burn stimulus intensities were not different among the groups (P = 0.54). Conclusions: Thymoquinone was shown to have an inhibitory effect, comparable with that of triamcinolone, on corneal neovascularization in this rat model. However, thymoquinone decreased corneal neovascularization in a dose-dependent manner.

Cyclosporin effectively inhibits posterior capsule opacification after phacoemulsification in rabbits: a preliminary study

Purpose:  To evaluate whether cyclosporin A prevents or reduce posterior capsule opacification after phacoemulsification surgery in rabbit eyes.

Comparison of Corneal Layers and Anterior Sclera in Emmetropic and Myopic Eyes.

Purpose: The aim of this study was to compare the thickness of preocular tear film, corneal layers, and anterior sclera in patients with moderate to high myopia and emmetropia with anterior segment spectral domain optical coherence tomography. Methods: This cross-sectional comparative study included 31 patients with high myopia and 31 emmetropic healthy controls. Patients with myopia had axial lengths ranging from 24 to 29 mm, whereas age-matched controls had axial lengths from 21 to 23.9 mm. Patients with myopia had refractive errors from −4.00 to −11.00 diopters spherical equivalent. Preocular tear film, corneal epithelium, Bowman layer, stroma, and Descemet membrane–endothelium complex were measured in the central cornea. Anterior scleral measurements were made at distances of 1, 3, and 5 mm from the limbus. Corneal–scleral thickness was measured with the anterior segment module of spectral domain optical coherence tomography. Results: No statistically significant differences (P > 0.05) between patients with myopia and controls emerged regarding the thickness of preocular tear film, corneal epithelium, Bowman layer, corneal stroma, and Descemet membrane–endothelium complex. The anterior scleral thickness values of 1, 3, and 5 mm from the limbus were similar in both patients with myopia and control participants (P > 0.05). There were no significant correlations between central cornea stromal thickness and anterior scleral thickness in myopic participants (P > 0.05). Conclusions: The thickness of anterior wall structures and preocular tear film of patients with moderate to high myopia are not statistically different compared with those of healthy controls.

Molecular identification of adenoviral conjunctivitis in Turkey.

Purpose. The aim of the study was isolation of adenoviruses by cell culture and identification using polymerase chain reaction (PCR) and phylogenetic analyses in patients clinically diagnosed with viral conjunctivitis in Ankara, Turkey. Methods. Conjunctival swabs from 34 patients with acute conjunctivitis were tested using cell culture isolation and PCR for adenovirus detection. PCR-positive samples were sequenced and typed. Results. The positive results of adenovirus were 26.5% (9 of 34) by the PCR method and 20.6% by culture isolation. Nine samples positive at PCR were identified by phylogenetic analyses as human adenovirus 8 (HAdV-8) (4 of 9), HAdV-3 (3 of 9), HAdV-4 (1 of 9), and HAdV-B (1 of 9). Conclusions. Our study showed types of adenoviruses in patients with ocular infection that occurred in this region of Turkey for the first time. Furthermore, sequence-based typing method is an efficient, accurate, and rapid means of diagnosis and typing of the adenovirus and has significant clinical and epidemiologic implications. HAdV-8 was major type for acute conjunctivitis in Ankara, Turkey. Further studies are required to reveal the major types of HAdVs that cause ocular diseases in this region of the world.