Genipin delays corneal stromal enzymatic digestion

Purpose: To evaluate the use of genipin in delaying enzymatic digestion of corneal stroma. Methods: Human corneal stromal tissue was treated with genipin, a known chemical crosslinker, and then along with control tissue was subjected to enzymatic digestion with collagenase. The effects of genipin treatment in retarding stromal digestion were analyzed with phase contrast microscopy, a protein quantification assay, second harmonic generation imaging, and transmission electron microscopy. Results: Genipin increased stromal resistance to enzymatic digestion when compared with untreated stroma. A morphologic analysis and protein quantification showed increased stromal resistance to enzymatic digestion once stromal tissue was treated with genipin. Second harmonic generation imaging revealed persistent fibrillar collagen signaling in genipin-treated tissue in contrast with untreated tissue suggesting that genipin retards collagenolysis. Conclusions: Genipin increases stromal resistance to enzymatic digestion in controlled experiments as demonstrated by protein quantification studies and through morphologic imaging. Translational Relevance: This study explores the novel use of genipin in delaying enzymatic stromal digestion. Delaying stromal melting in the setting of corneal infectious or autoimmune keratitis can potentially decrease clinical morbidity

Multiple Optical Elastography Techniques Reveal the Regulation of Corneal Stiffness by Collagen XII

9 pags., 5 figs., 1 tab.PURPOSE. Collagen XII plays a role in regulating the structure and mechanical properties of the cornea. In this work, several optical elastography techniques were used to investigate the effect of collagen XII deficiency on the stiffness of the murine cornea. METHODS. A three-prong optical elastography approach was used to investigate the mechanical properties of the cornea. Brillouin microscopy, air-coupled ultrasonic optical coherence elastography (OCE) and heartbeat OCE were used to assess the mechanical properties of wild type (WT) and collagen XII¿deficient (Col12a1¿/¿) murine corneas. The Brillouin frequency shift, elastic wave speed, and compressive strain were all measured as a function of intraocular pressure (IOP). RESULTS. All three optical elastography modalities measured a significantly decreased stiffness in the Col12a1¿/¿ compared to the WT (P < 0.01 for all three modalities). The optical coherence elastography techniques showed that mean stiffness increased as a function of IOP; however, Brillouin microscopy showed no discernable trend in Brillouin frequency shift as a function of IOP. CONCLUSIONS. Our approach suggests that the absence of collagen XII significantly softens the cornea. Although both optical coherence elastography techniques showed an expected increase in corneal stiffness as a function of IOP, Brillouin microscopy did not show such a relationship, suggesting that the Brillouin longitudinal modulus may not be affected by changes in IOP. Future work will focus on multimodal biomechanical models, evaluating the effects of other collagen types on corneal stiffness, and in vivo measurements.Supported by the National Institutes of Health, grant numbers R01EY022362, R01EY030063, R01EY029395, R01EY028666, and P30EY007551

Modulation transfer function and optical quality after bilateral implantation of a+3.00 D versus a+4.00 D multifocal intraocular lens

PURPOSE: To determine whether the improvement in intermediate vision after bilateral implantation of an aspheric multifocal intraocular lens (IOL) with a +3.00 diopter (D) addition (add) occurs at the expense of optical quality compared with the previous model with a +4.00 D add. SETTING: Department of Ophthalmology, University of Sao Paulo, Sao Paulo, Brazil. DESIGN: Prospective randomized double-masked comparative clinical trial. METHODS: One year after bilateral implantation of Acrysof Restor SN6AD1 +3.00 D IOLs or Acrysof Restor SN6AD3 +4.00 D IOLs, optical quality was evaluated by analyzing the in vivo modulation transfer function (MTF) and point-spread function (expressed as Strehl ratio). The Strehl ratio and MTF curve with a 4.0 pupil and a 6.0 mm pupil were measured by dynamic retinoscopy aberrometry. The uncorrected and corrected distance visual acuities at 4 m, uncorrected and distance-corrected near visual acuities at 40 cm, and uncorrected and distance-corrected intermediate visual acuities at 50 cm, 60 cm, and 70 cm were measured. RESULTS: Both IOL groups comprised 40 eyes of 20 patients. One year postoperatively, there were no statistically significant between-group differences in the MTF or Strehl ratio with either pupil size. There were no statistically significant between-group differences in distance or near visual acuity. Intermediate visual acuity was significantly better in the +3.00 D IOL group. CONCLUSION: Results indicate that the improvement in intermediate vision in eyes with the aspheric multifocal +3.00 D add IOL occurred without decreasing optical quality over that with the previous version IOL with a +4.00 D add

Amniotic membrane induces apoptosis of interferon-γ activated macrophages in vitro

Amniotic membrane (AM) used as a temporary or permanent graft for ocular surface reconstruction has a potent anti-inflammatory effect. We would like to investigate the mechanism whereby AM induces macrophage apoptosis in vitro. Mouse macrophages, Raw 264.7 cells, were cultured on plastic, type I collagen, corneal stromal slice or AM stromal matrix in serum-free medium with or without interferon-γ (IFN-γ). Cells were stained by LIVE/DEAD assay, Hoechst-33342, and TUNEL assay for cell death and apoptosis. Cell lysates and conditioned media were analysed by Cell Death Detection ELISA assay for quantitation of apoptosis. Conditioned media were also analysed by Griess assay for the nitrite concentration and ELISA assay for tumour necrosis factor alpha (TNF-α) concentration. Lysates of cells were subjected to Western blot analyses of IKK-α, IKK-β, p65 (RelA) subunit of nuclear factor κB (NF-κB), total Akt, phospho-Akt (Ser473), and phospho-FKHR (Thr24)/phosphor-FKHRL1 (Thr32). At 48 hr after cultivation, cells showed a low level of apoptosis when cultured on plastic, type I collagen and corneal stromal slice with or without IFN-γ and on AM without IFN-γ. Nevertheless, cells showed a significant increase of apoptosis when cultured on AM with IFN-γ activation, and this phenomenon became apparent only after 48 hr. IFN-γ-activated macrophages on plastic continuously produced nitric oxide (NO) and TNF-α during 72 hr culturing. In contrast, there was no NO and TNF-α production after 48 hr culture on AM. NO inhibitors, L-NMMA and L-NIL, attenuated NO production of IFN-γ-activated macrophages on AM, while apoptosis was not decreased accordingly. Expression of IKK-α, IKK-β, p65 (RelA) subunit of NF-κB total Akt, phosopho-Akt (Ser473), and phospho-FKHR (Thr24)/FKHRL1 (Thr32) was all down-regulated in IFN-γ-activated macrophages cultured on AM. In conclusion, AM stromal matrix induces apoptosis of IFN-γ activated, but not non-activated macrophages, not through the generation of NO, but instead by down-regulating anti-apoptotic NF-κB and Akt-FKHR signalling pathways

Collagen V insufficiency in a mouse model for Ehlers Danlos-syndrome affects viscoelastic biomechanical properties explaining thin and brittle corneas

Ehlers–Danlos syndrome (EDS) is a genetic disease leading to abnormalities in mechanical properties of different tissues. Here we quantify corneal biomechanical properties in an adult classic EDS mouse model using two different measurement approaches suited for murine corneal mechanical characterization and relate differences to stromal structure using Second Harmonic Generation (SHG) microscopy. Quasi-static Optical Coherence Elastography (OCE) was conducted non-invasively during ambient pressure modulation by − 3 mmHg. 2D-extensometry measurements was conducted invasively consisting of a pre-conditioning cycle, a stress-relaxation test and a rupture test. In a total of 28 eyes from a Col5a1+/− mouse model and wild-type C57BL/6 littermates (wt), Col5a1+/− corneas were thinner when compared to wt, (125 ± 11 vs 148 ± 10 μm, respectively, p < 0.001). Short-term elastic modulus was significantly increased in OCE (506 ± 88 vs 430 ± 103 kPa, p = 0.023), and the same trend was observed in 2D-extensometry (30.7 ± 12.1 kPa vs 21.5 ± 5.7, p = 0.057). In contrast, in stress relaxation tests, Col5a1+/− corneas experienced a stronger relaxation (55% vs 50%, p = 0.01). SHG microscopy showed differences in forward and backward scattered signal indicating abnormal collagen fibrils in Col5a1+/− corneas. We propose that disturbed collagen fibril structure in Col5a1+/− corneas affects the viscoelastic properties. Results presented here support clinical findings, in which thin corneas with global ultrastructural alterations maintain a normal corneal shape.ISSN:2045-232

Collagen XII Regulates Corneal Stromal Structure by Modulating Transforming Growth Factor-beta Activity

Collagen XII is a regulator of corneal stroma structure and function. The current study examined the role of collagen XII in regulating corneal stromal transforming growth factor (TGF)-beta activation and latency. Specifically, with the use of conventional collagen XII null mouse model, the role of collagen XII in the regulation of TGF-beta latency and activity in vivo was investigated. Functional quantification of latent TGF-beta in stromal matrix was performed by using transformed mink lung reporter cells that produce luciferase as a function of active TGF-beta. Col12a1 knockdown with shRNA was used to test the role of collagen XII in TGF-beta activation. Col12a1(-/-) hypertrophic stromata were observed with keratocyte hyperplasia. Increased collagen fibril forward signal was found by second harmonic generation microscopy in the absence of collagen XII. Collagen XII regulated mRNA synthesis of Serpine1, Col1a1, and Col5a1 and deposition of collagens in the extracellular matrix. A functional plasminogen activator inhibitor luciferase assay showed that collagen XII is necessary for latent TGF-beta storage in the extra cellular matrix and that collagen XII down-regulates active TGF-beta. Collagen XII dictates stromal structure and function by regulating TGF-beta activity. A hypertrophic phenotype in Col12a1(-/-) corneal tissue can be explained by abnormal up-regulation of TGF-beta activation and decreased latent storage