Adult vitreous structure and postnatal changes

Pharmacologic interventions for the prevention and treatment of retinopathy of prematurity

Retinopathy of Prematurity (ROP) is a preventable neovascular retinal disease with a lifetime impact on vision and ocular morbidities. Retinal vessel immaturity and oxygen therapy, influenced or modulated by several risk factors including oxidative stress, intermittent hypoxia and desaturations, inflammation, infection, malnutrition, retinal growth factor deficiencies or excesses, and others are determinant factors of pathologic retinal angiogenesis and ROP. These factors are pharmacologic targets for prevention and/or rescue therapy. These drugs, include intravitreal anti-vascular endothelial growth factor drugs, erythropoietin, ocular propranolol, caffeine, antioxidants, insulin-like growth factor-I, and omega 3 poly-unsaturated fatty acids, and are promising therapies to prevent ROP, but require further studies. Topical ocular non-steroidal anti-inflammatory drugs (NSAIDs) target inflammatory cascade but the best, safest, and most effective ocular NSAID and formulation remain to be developed. Timing of drug intervention appears critical. Moreover, the complex interactions of the various pathophysiologic mechanisms resulting in aberrant angiogenesis thence ROP strongly suggest that drug combinations and synergisms may be required for effective prevention of ROP and a lifetime of blindness.

Hydrodynamics of Intravitreal Injections into Liquid Vitreous Substitutes

Intravitreal injections have become the cornerstone of retinal care and one of the most commonly performed procedures across all medical specialties. The impact of hydrodynamic forces of intravitreal solutions when injected into vitreous or vitreous substitutes has not been well described. While computational models do exist, they tend to underestimate the starting surface area of an injected bolus of a drug. Here, we report the dispersion profile of a dye bolus (50 µL) injected into different vitreous substitutes of varying viscosities, surface tensions, and volumetric densities. A novel 3D printed in vitro model of the vitreous cavity of the eye was designed to visualize the dispersion profile of solutions when injected into the following vitreous substitutes-balanced salt solution (BSS), sodium hyaluronate (HA), and silicone oils (SO)-using a 30G needle with a Reynolds number (Re) for injection ranging from approximately 189 to 677. Larger bolus surface areas were associated with faster injection speeds, lower viscosity of vitreous substitutes, and smaller difference in interfacial surface tensions. Boluses exhibited buoyancy when injected into standard S1000. The hydrodynamic properties of liquid vitreous substitutes influence the initial injected bolus dispersion profile and should be taken into account when simulating drug dispersion following intravitreal injection at a preclinical stage of development, to better inform formulations and performance.

Conservative management of retinoblastoma: Challenging orthodoxy without compromising the state of metastatic grace. "Alive, with good vision and no comorbidity"

Retinoblastoma is lethal by metastasis if left untreated, so the primary goal of therapy is to preserve life, with ocular survival, visual preservation and quality of life as secondary aims. Historically, enucleation was the first successful therapeutic approach to decrease mortality, followed over 100 years ago by the first eye salvage attempts with radiotherapy. This led to the empiric delineation of a window for conservative management subject to a "state of metastatic grace" never to be violated. Over the last two decades, conservative management of retinoblastoma witnessed an impressive acceleration of improvements, culminating in two major paradigm shifts in therapeutic strategy. Firstly, the introduction of systemic chemotherapy and focal treatments in the late 1990s enabled radiotherapy to be progressively abandoned. Around 10 years later, the advent of chemotherapy in situ, with the capitalization of new routes of targeted drug delivery, namely intra-arterial, intravitreal and now intracameral injections, allowed significant increase in eye preservation rate, definitive eradication of radiotherapy and reduction of systemic chemotherapy. Here we intend to review the relevant knowledge susceptible to improve the conservative management of retinoblastoma in compliance with the "state of metastatic grace", with particular attention to (i) reviewing how new imaging modalities impact the frontiers of conservative management, (ii) dissecting retinoblastoma genesis, growth patterns, and intraocular routes of tumor propagation, (iii) assessing major therapeutic changes and trends, (iv) proposing a classification of relapsing retinoblastoma, (v) examining treatable/preventable disease-related or treatment-induced complications, and (vi) appraising new therapeutic targets and concepts, as well as liquid biopsy potentiality.

The obstacle course to the inner retina: Hyaluronic acid-coated lipoplexes cross the vitreous but fail to overcome the inner limiting membrane

Considerable research over the last few years has revealed dysregulation of growth factors in various retinal diseases, such as glaucoma, diabetic retinopathy and photoreceptor degenerations. The use of messengerRNA (mRNA) to transiently overexpress a specific factor could compensate for this imbalance. However, a critical challenge of this approach lies in the ability to efficiently deliver mRNA molecules to the retinal target cells. In this study we found that intravitreal (IVT) injection is an attractive approach to deliver mRNA to the retina, providing two critical barriers can be overcome: the vitreous and the inner limiting membrane (ILM). We demonstrated that the vitreous is indeed a major hurdle in the delivery of the cationic mRNA-complexes to retinal cells, both in terms of vitreal mobility and cellular uptake. To improve their intravitreal mobility and avoid unwanted extracellular interactions, we evaluated the use of hyaluronic acid (HA) as an electrostatic coating strategy. This HA-coating provided the complexes with a negative surface charge, markedly enhancing their mobility in the vitreous humor, without reducing their cellular internalization and transfection efficiency. However, although this coating strategy allows the mRNA-complexes to successfully overcome the vitreal barrier, the majority of the particles accumulated at the ILM. This study therefore underscores the crucial barrier function of the ILM toward non-viral retinal gene delivery and the need to smartly design mRNA-carriers able to surmount the vitreous as well as the ILM.

Bush-like integrin filament networks associated with hyaloid vasculature in murine neonate eyes

The vitreous of perinatal mice temporarily develops a unique vascular system, called the vasa hyaloidea propria (VHP). Observations showed the vessels possessed an extracellular matrix including the basement membrane in their entire length. Immunostaining of whole mount preparations of VHP with integrin β₁ antibody displayed a bush-like network consisting of long and straight fibers which were associated with the VHP but extended apart from the blood vessels. Electron microscopically, each fiber was composed of a bundle of thin filaments different from collagen fibrils. Macrophages associated with the VHP appeared to be arrested by the integrin bushes. The integrin bushes fragmented and disappeared by postnatal day 10, just before the regression of the VHP. Macrophages were involved in the digestion and clearance of integrin bushes. The vitreous integrin bushes appear to provide a scaffold for architectural maintenance of the hyaloid vessels and macrophages.

Mesenchymal stem cell-derived extracellular vesicles and retinal ischemia-reperfusion

Retinal ischemia is a major cause of vision loss and impairment and a common underlying mechanism associated with diseases such as glaucoma, diabetic retinopathy, and central retinal artery occlusion. The regenerative capacity of the diseased human retina is limited. Our previous studies have shown the neuroprotective effects of intravitreal injection of mesenchymal stem cells (MSC) and MSC-conditioned medium in retinal ischemia in rats. Based upon the hypothesis that the neuroprotective effects of MSCs and conditioned medium are largely mediated by extracellular vesicles (EVs), MSC derived EVs were tested in an in-vitro oxygen-glucose deprivation (OGD) model of retinal ischemia. Treatment of R28 retinal cells with MSC-derived EVs significantly reduced cell death and attenuated loss of cell proliferation. Mechanistic studies on the mode of EV endocytosis by retinal cells were performed in vitro. EV endocytosis was dose- and temperature-dependent, saturable, and occurred via cell surface heparin sulfate proteoglycans mediated by the caveolar endocytic pathway. The administration of MSC-EVs into the vitreous humor 24 h after retinal ischemia in a rat model significantly enhanced functional recovery, and decreased neuro-inflammation and apoptosis. EVs were taken up by retinal neurons, retinal ganglion cells, and microglia. They were present in the vitreous humor for four weeks after intravitreal administration, with saturable binding to vitreous humor components. Overall, this study highlights the potential of MSC-EV as biomaterials for neuroprotective and regenerative therapy in retinal disorders.

Intact vitreous humor as a potential extracellular matrix hydrogel for cartilage tissue engineering applications

Decellularisation of tissues, utilising their biochemical cues, poses exciting tissue engineering (TE) opportunities. However, removing DNA from cartilage (dCart) requires harsh treatments due to its dense structure, causing loss of bioactivity and limiting its application as a cartilaginous extra cellular matrix (ECM). In this study, we demonstrate for the first time the successful application of vitreous humor (VH), a highly hydrated tissue closely resembling the glycosaminoglycan (GAG) and collagen composition of cartilage, as an ECM hydrogel to support chondrogenic differentiation. Equine VH was extracted followed by biochemical quantifications, histological examinations, cytotoxicity (human mesenchymal stromal cells, hMSCs and human articular chondrocytes, hACs) and U937 cell proliferation studies. VH was further seeded with hACs or hMSCs and cultured for 3-weeks to study chondrogenesis compared to scaffold-free micro-tissue pellet cultures and collagen-I hydrogels. Viability, metabolic activity, GAG and DNA content, chondrogenic gene expression (aggrecan, collagen I/II mRNA) and mechanical properties were quantified and matrix deposition was visualised using immunohistochemistry (Safranin-O, collagen I/II). VH was successfully extracted, exhibiting negligible amounts of DNA (0.4 ± 0.4 µg/mg dry-weight) and notable preservation of ECM components. VH displayed neither cytotoxic responses nor proliferation of macrophage-like U937 cells, instead enhancing both hMSC and hAC proliferation. Interestingly, encapsulated cells self-assembled the VH-hydrogel into spheroids, resulting in uniform distribution of both GAGs and collagen type II with increased compressive mechanical properties, rendering VH a permissive native ECM source to fabricate cartilaginous hydrogels for potential TE applications. STATEMENT OF SIGNIFICANCE: Fabricating bioactive and cell-instructive cartilage extracellular matrix (ECM) derived biomaterials and hydrogels has over recent years proven to be a challenging task, often limited by poor retention of inherent environmental cues post decellularisation due to the dense and avascular nature of native cartilage. In this study, we present an alternative route to fabricate highly permissive and bioactive ECM hydrogels from vitreous humor (VH) tissue. This paper specifically reports the discovery of optimal VH extraction protocols and cell seeding strategy enabling fabrication of cartilaginous matrix components into a hydrogel support material for promoting chondrogenic differentiation. The work showcases a naturally intact and unmodified hydrogel design that improves cellular responses and may help guide the development of cell instructive and stimuli responsive hybrid biomaterials in a number of TERM applications.

Ex vivo biophysical characterization of a hydrogel-based artificial vitreous substitute

Purpose

To characterize the biophysical properties of an artificial vitreous body substitute (VBS), which consists of a biocompatible, cross-linked, hyaluronic acid (HA)-based hydrogel, by analysing the VBS’s influence on intraocular pressure (IOP) and retinal integrity in distinct ex vivo eye models in order to evaluate the its potential for in vivo biocompatibility testing.

Methods

Pig eyes were obtained immediately postmortem, and VBS was injected after core-vitrectomy. IOP was followed for 24 h (n = 5). VBS influence on retinal integrity was investigated using isolated bovine retinas superfused with an oxygen saturated nutrient solution. An electroretinogram (ERG) was recorded on explanted bovine retinae using silver/silver chloride electrodes; after application of VBS for 2 min, a washout period of 70 min was employed. The percentage of a-and b-wave reduction at the end of the washout phase was compared to baseline values (n = 5). Data were calculated throughout as the mean and the standard deviation. qRT-PCR (Bax/Bcl–2-ratio, GFAP- and PGP9.5-levels) or western blot analysis was used to test for toxicity of Princess Volume after 24 h (and β-3 tubulin with GAPDH as a control gene). Significance was estimated by Student´s t-test; p ≤0.05 was considered to be statistically significant.

Results

The IOP increased non-significantly by 10% after 24 h. Short-term biocompatibility testing using isolated superfused bovine retinas showed neither significant reductions of the b-wave nor the a-wave amplitudes (b-wave reduction 14.2%, p>0.05; a-wave reduction 23.9%, p>0.05). qRT-PCR and western blot analysis did not reveal significant toxicity after 24 h.

Conclusions

The manufactured HA-based hydrogel showed highly favourable biophysical characteristics in the explored ex vivo models, justifying in vivo studies enabling the assessment of biocompatibility.

Early posterior vitreous detachment is associated with LAMA5 dominant mutation

BACKGROUND

Extracellular matrix molecular components, previously linked to multisystem syndromes include collagens, fibrillins and laminins. Recently, we described a novel multisystem syndrome caused by the c.9418G>A p.(V3140M) mutation in the laminin alpha-5 (LAMA5) gene, which affects connective tissues of all organs and apparatus in a three generation family. In the same family, we have also reported a myopic trait, which, however, was linked to the Prolyl 4-hydroxylase subunit alpha-2 (P4HA2) gene. Results of investigation on vitreous changes and their pathogenesis are reported in the present study.

MATERIALS AND METHODS

Nineteen family individuals underwent complete ophthalmic examination including best-corrected visual acuity (BCVA), fundus examination, fundus photography, intraocular pressure measurement, axial length measurement using ocular biometry, Goldmann visual field examination, standard electroretinogram, SD-OCT. Segregation analysis of LAMA5 and P4HA2 mutations was performed in enrolled members.

RESULTS

The vitreous alterations fully segregated with LAMA5 mutation in both young and adult family members. Slight reduction of retinal thickness and peripheral retinal degeneration in only two patients were reported.

CONCLUSIONS

In this work we showed that PVD is a common trait of LAMA5 multisystem syndrome, therefore occurring as an age-unrelated trait. We hypothesize that the p.(V3140M) mutation results in a reduction of retinal inner limiting membrane (ILM) stability, leading to a derangement in the macromolecular structure of the vitreous gel, and PVD. Further investigations will be necessary to elucidate the role of wild type and mutated LAMA5 in the pathogenesis of PVD.

Rheological Properties and Age-Related Changes of the Human Vitreous Humor

The vitreous humor is a fragile, transparent hydrogel situated between the lens and the retina, occupying 80% of the eye's volume. Due to its viscoelastic behavior, the vitreous serves as a mechanical damper for the eye, absorbing impacts, and protecting the lens and retina. The vitreous liquefies with age, which compromises its function as a shock absorber and causes complications including retinal detachment, macular holes, and vitreous hemorrhage. Studies on the viscoelastic properties of the vitreous have been limited. Rheological testing of the vitreous has commonly been done on non-primate mammalian species. Human vitreous rheological properties have been previously reported; however, various measurement techniques were used, resulting in data that differed by orders of magnitude. Shear rheometry is commonly used to characterize soft tissues and hydrogels such as the vitreous humor. However, no human vitreous rheological data have been reported using this technique, preventing direct comparison to other published work. Additionally, no age-related changes in the mechanical properties of the human vitreous humor have been reported. Human vitreous samples (n = 39, aged 62 ± 15 years) were tested using a shear rheometer. Small amplitude oscillatory shear and creep experiments were performed. The linear viscoelastic region of the human vitreous was found to be below 1% strain. The solid phase of the old human vitreous was found to be stiffer than the young human vitreous and the porcine vitreous. The stiffness of the human vitreous gel also appeared to be positively correlated with age. Vitreous dehydration due to a decrease in hyaluronic acid concentration with age was proposed to cause the stiffening of the solid phase of the vitreous gel. Vitreous liquefaction, therefore, might be characterized as a simultaneous increase in liquid volume and localized stiffening of the vitreous gel. The phase separation of the vitreous humor with age has been hypothesized as the cause of many vitreous-related complications. This study provides viscoelastic properties and age-related changes of the human vitreous humor, which will aid in the design of biomimetic vitreous substitutes, enhancement in analyzing intravitreal transport of therapeutics, and understanding the pathological conditions of the vitreous humor.

Identification of unique proteins in vitreous fluid of patients with noninfectious uveitis

PURPOSE

Uveitis is a cause for concern in the developing countries like India. Its poor diagnosis and lack of proper therapeutics often cause blindness in children and young adults. Moreover, the exact mechanism of pathogenesis of different types of uveitis is still elusive. Modern proteomic techniques are found to be advantageous for an in-depth understanding of the ocular physiology using proteomic diversity. Our aim was to identify unique proteins involved in the pathogenesis of autoimmune or noninfectious uveitis.

METHODS

Vitreous fluid samples (n = 90) were obtained from infectious (N = 34) and noninfectious (N = 56) uveitis patients, and their protein profiles were compared by analysing sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and 2D electrophoresis. Unique proteins were identified through matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS) and further studied for pathway analysis.

RESULTS

Protein spots having different molecular weights were observed in noninfectious vitreous fluid samples. Enzymatic digestion of these spots after MALDI-TOF MS analysis revealed different proteins. We identified 25 different proteins through SDS-PAGE and 22 through 2D electrophoresis. 50% of the proteins from SDS-PAGE were associated with heterotrimeric G-protein signalling pathway-rod outer segment phototransduction. 50% proteins from SDS-PAGE and 20% from 2D electrophoresis revealed association with de novo purine biosynthesis. Carbonic anhydrase 1 and serpin B3 were found to be common in both analyses.

CONCLUSION

High-throughput proteomic and pathway analyses have exposed the potential association of these proteins with autoimmune pathogenesis in uveitis. The exact role of most of the proteins in autoimmune uveitis is yet to be unfurled.

Personalized Proteomics for Precision Health: Identifying Biomarkers of Vitreoretinal Disease

Proteomic analysis is an attractive and powerful tool for characterizing the molecular profiles of diseased tissues, such as the vitreous. The complexity of data available for analysis ranges from single (e.g., enzyme-linked immunosorbent assay [ELISA]) to thousands (e.g., mass spectrometry) of proteins, and unlike genomic analysis, which is limited to denoting risk, proteomic methods take snapshots of a diseased vitreous to evaluate ongoing molecular processes in real time. The proteome of diseased ocular tissues was recently characterized, uncovering numerous biomarkers for vitreoretinal diseases and identifying protein targets for approved drugs, allowing for drug repositioning. These biomarkers merit more attention regarding their therapeutic potential and prospective validation, as well as their value as reproducible, sensitive, and specific diagnostic markers.

TRANSLATIONAL RELEVANCE

Personalized proteomics offers many advantages over alternative precision-health platforms for the diagnosis and treatment of vitreoretinal diseases, including identification of molecular constituents in the diseased tissue that can be targeted by available drugs.

The vitreopapillary interface in healthy and glaucoma: posterior vitreous detachment in the vitreopapillary interface study

PURPOSE

To investigate the vitreopapillary interface (VPI) in health and glaucoma according to the different stages of posterior vitreous detachment (PVD) formation.

METHODS

Prospective single centre study including healthy subjects and glaucoma patients. PVD staging was performed with spectral domain optical coherence tomography. Gender, age, lens status and refractive error were assessed in both groups. Glaucoma patients additionally had a comprehensive ophthalmological investigation including intraocular pressure measurement, visual field testing and confocal imaging of the optic nerve head.

RESULTS

Data on 523 subjects (993 eyes) were included from the VPI study (clinicaltrials.gov NCT02290795) database (493 eyes of 258 healthy subjects and 500 eyes of 265 glaucoma patients). Healthy subjects were significantly younger than primary open angle glaucoma patients (59.7 ± 14.81 versus 70.0 ± 10.78 years, p < 0.001), but were otherwise matched for refractive error and gender. Significantly more glaucomatous eyes were pseudophakic (26.6% versus 5.1%). Including only phakic nonoperated eyes from subjects between 50 and 80 years old decreased the age difference between healthy and open angle glaucoma (64.1 ± 8.0 versus 65.9 ± 6.7 years, p = 0.051). Comparing these subgroups rendered similar average ages for PVD stages 0 and 4, in contrast to the significant older age for the glaucoma subgroup in stage 1 (64.1 ± 6.01 versus 61.4 ± 8.38 years, p < 0.001) and a trend towards significance in stage 3 (70.8 ± 69.8 versus 67.5 ± 5.92 years, p = 0.051).

CONCLUSION

The VPI study is a large clinical trial investigating the VPI in health and glaucoma. A subset of glaucoma patients seems to experience stages 1-3 of PVD formation at older age compared to healthy subjects.

Binding of Small Molecule Drugs to Porcine Vitreous Humor

Pharmacokinetics in the posterior eye segment has therapeutic implications due to the importance of retinal diseases in ophthalmology. In principle, drug binding to the components of the vitreous, such as proteins, collagen, or glycosaminoglycans, could prolong ocular drug retention and modify levels of pharmacologically active free drug in the posterior eye segment. Since drug binding in the vitreous has been investigated only sparsely, we studied vitreal drug binding of 35 clinical small molecule drugs. Isolated homogenized porcine vitreous and the drugs were placed in a two-compartment dialysis system that was used to separate the bound and unbound drug. Free drug concentrations and binding percentages were quantitated using LC-MS/MS. Drug binding levels varied between 21 and 74% in the fresh vitreous and 0 and 64% in the frozen vitreous. The vitreal binding percentages did not correlate with those in plasma. Our data-based pharmacokinetic simulations suggest that vitreal binding of small molecule drugs has only a modest influence on the AUC of free drug or drug half-life in the vitreous. Therefore, it is likely that vitreal binding is not a major reason for interindividual variability in ocular drug responses or drug-drug interactions.

Exploiting Advanced Hydrogel Technologies to Address Key Challenges in Regenerative Medicine

Regenerative medicine aims to tackle a panoply of challenges from repairing focal damage to articular cartilage to preventing pathological tissue remodeling after myocardial infarction. Hydrogels are water-swollen networks formed from synthetic or naturally derived polymers and are emerging as important tools to address these challenges. Recent advances in hydrogel chemistries are enabling researchers to create hydrogels that can act as 3D ex vivo tissue models, allowing them to explore fundamental questions in cell biology by replicating tissues' dynamic and nonlinear physical properties. Enabled by cutting edge techniques such as 3D bioprinting, cell-laden hydrogels are also being developed with highly controlled tissue-specific architectures, vasculature, and biological functions that together can direct tissue repair. Moreover, advanced in situ forming and acellular hydrogels are increasingly finding use as delivery vehicles for bioactive compounds and in mediating host cell response. Here, advances in the design and fabrication of hydrogels for regenerative medicine are reviewed. It is also addressed how controlled chemistries are allowing for precise engineering of spatial and time-dependent properties in hydrogels with a look to how these materials will eventually translate to clinical applications.

In vitro and ex vivo models to study drug delivery barriers in the posterior segment of the eye

Many ocular disorders leading to blindness could benefit from efficient delivery of therapeutics to the retina. However, despite extensive research into drug delivery vehicles and administration techniques, efficacy remains limited because of the many static and dynamic barriers present in the eye. Comprehension of the various barriers and especially how to overcome them can improve our ability to estimate the potential of existent drug delivery vectors and support the design of new ones. To this end, this review gives an overview of the most important ocular barriers for each administration route to the back of the eye. For each barrier, its biological composition and its role as an obstacle towards macromolecules, nanoparticles and viral vectors will be discussed; special attention will be paid to the influence of size, charge and lipophilicity of drug(s) (carrier) on their ability to overcome each barrier. Finally, the most significant available in vitro and ex vivo methods and models to test the potential of a therapeutic to cross each barrier are listed.

Preventing Obstructions of Nanosized Drug Delivery Systems by the Extracellular Matrix

Although nanosized drug delivery systems are promising tools for the treatment of severe diseases, the extracellular matrix (ECM) constitutes a major obstacle that endangers therapeutic success. Mobility of diffusing species is restricted not only by small pore size (down to as low as 3 nm) but also by electrostatic interactions with the network. This article evaluates commonly used in vitro models of ECM, analytical methods, and particle types with respect to their similarity to native conditions in the target tissue. In this cross-study evaluation, results from a wide variety of mobility studies are analyzed to discern general principles of particle-ECM interactions. For instance, cross-linked networks and a negative network charge are essential to reliably recapitulate key features of the native ECM. Commonly used ECM mimics comprised of one or two components can lead to mobility calculations which have low fidelity to in vivo results. In addition, analytical methods must be tailored to the properties of both the matrix and the diffusing species to deliver accurate results. Finally, nanoparticles must be sufficiently small to penetrate the matrix pores (ideally R_d/p < 0.5; d = particle diameter, p = pore size) and carry a neutral surface charge to avoid obstructions. Larger (R_d/p >> 1) or positively charged particles are trapped.

Posterior Vitreous Detachment and the Posterior Hyaloid Membrane

PURPOSE

Despite posterior vitreous detachment being a common ocular event affecting most individuals in an aging population, there is little consensus regarding its precise anatomic definition. We investigated the morphologic appearance and molecular composition of the posterior hyaloid membrane to determine whether the structure clinically observed enveloping the posterior vitreous surface after posterior vitreous detachment is a true basement membrane and to postulate its origin. Understanding the relationship between the vitreous (in both its attached and detached state) and the internal limiting membrane of the retina is essential to understanding the cause of rhegmatogenous retinal detachment and vitreoretinal interface disorders, as well as potential future prophylactic and treatment strategies.

DESIGN

Clinicohistologic correlation study.

PARTICIPANTS

Thirty-six human donor globes.

METHODS

Vitreous bodies identified to have posterior vitreous detachment were examined with phase-contrast microscopy and confocal microscopy after immunohistochemically staining for collagen IV basement membrane markers, in addition to extracellular proteins that characterize the vitreoretinal junction (fibronectin, laminin) and vitreous gel (opticin) markers. The posterior retina similarly was stained to evaluate the internal limiting membrane. Findings were correlated to the clinical appearance of the posterior hyaloid membrane observed during slit-lamp biomicroscopy after posterior vitreous detachment and compared with previously published studies.

MAIN OUTCOME MEASURES

Morphologic appearance and molecular composition of the posterior hyaloid membrane.

RESULTS

Phase-contrast microscopy consistently identified a creased and distinct glassy membranous sheet enveloping the posterior vitreous surface, correlating closely with the posterior hyaloid membrane observed during slit-lamp biomicroscopy in patients with posterior vitreous detachment. Immunofluorescent confocal micrographs demonstrated the enveloping membranous structure identified on phase-contrast microscopy to show positive stain results for type IV collagen. Immunofluorescence of the residual intact internal limiting membrane on the retinal surface also showed positive stain results for type IV collagen.

CONCLUSIONS

The results of this study provide immunohistochemical evidence that the posterior hyaloid membrane is a true basement membrane enveloping the posterior hyaloid surface. Because this membranous structure is observed only after posterior vitreous detachment, the results of this study indicate that it forms part of the internal limiting membrane when the vitreous is in its attached state.

Human retinal endothelial cells and astrocytes cultured on 3-D scaffolds for ocular drug discovery and development

Topical ocular ketorolac improves the outcomes of severe retinopathy of prematurity and when administered with systemic caffeine, decreases the severity of oxygen-induced retinopathy. We tested the hypothesis that co-cultures of human retinal endothelial cells (HRECs) and human retinal astrocytes (HRAs) on 3-dimensional (3-D) hydrogel scaffolds is a more representative biomimetic paradigm of the blood-retinal-barrier (BRB) than 2-D cultures, and should be utilized for preclinical drug discovery and development. Mono- and co-cultures of HRECs and HRAs were treated with standard doses of ketorolac, ibuprofen, and/or caffeine, and exposed to hyperoxia, intermittent hypoxia (IH), or normoxia on 2-D surfaces or 3-D biodegradable hydrogel scaffolds (AlgiMatrix or Geltrex). Media and cells were collected at 72h post treatment for arachidonic acid metabolites. Cells cultured on 3-D scaffolds exhibited less oxidative stress and variability in drug responses. HRAs enhanced the responses of HRECs to drugs and changes in oxygen environment. PGE2 and PGI2 were the predominant prostanoids produced in response to IH, reflecting COX-2 immunoreactivity. We conclude that HRECs and HRAs co-cultured on 3-D scaffolds may recapitulate drug responses of the dynamic BRB and therefore should be implemented for preclinical ocular drug discovery and development.

Toward smart design of retinal drug carriers: a novel bovine retinal explant model to study the barrier role of the vitreoretinal interface

Retinal gene delivery via intravitreal injection is hampered by various physiological barriers present in the eye of which the vitreoretinal (VR) interface represents the most serious hurdle. In this study, we present a retinal explant model especially designed to study the role of this interface as a barrier for the penetration of vectors into the retina. In contrast to all existing explant models, the developed model is bovine-derived and more importantly, keeps the vitreous attached to the retina at all times to guarantee an intact VR interface. After ex vivo intravitreal injection into the living retinal explant, the route of fluorescent carriers across the VR interface can be tracked. By applying two different imaging methods on this model, we discovered that the transfer through the VR barrier is size-dependent since 40 nm polystyrene particles are more easily taken up in the retina than 100 and 200 nm sized particles. In addition, we found that removing the vitreous, as commonly done for culture of conventional explants, leads to an overestimation of particle uptake, and conclude that the ultimate barrier to overcome for retinal uptake is undoubtedly the inner limiting membrane. Damaging this matrix resulted in a massive increase in particle transfer into the retina. In conclusion, we have developed a highly relevant ex vivo model that maximally mimics the human in vivo physiology which can be applied as a representative test set-up to assess the potential of promising drug delivery carriers to cross the VR interface.

Therapeutic effects of a novel siRNA-based anti-VEGF (siVEGF) nanoball for the treatment of choroidal neovascularization

Age-related macular degeneration (AMD) is the leading cause of blindness in developed countries and is characterized by the development of choroidal neovascularization (CNV). Therapies for AMD have focused on suppressing angiogenic factors, such as vascular endothelial growth factor (VEGF), mainly via conventional anti-VEGF antibody agents. However, additional efforts have been made to develop effective small-interfering RNA (siRNA)-based intracellular therapeutic agents. In this study, we have manufactured a novel siRNA-based anti-VEGF nanoball (siVEGF NB). The siVEGF NB was composed of a siRNA hydrogel with a core of anti-VEGF sequence siRNA coated with branched PEI (bPEI) and hyaluronic acid (HA) in order by applying an electrical force. The novel siVEGF NBs, which were employed in a laser-induced CNV mouse model, were optimized as a retinal and choroidal delivery system through the vitreous humor to the sub-retinal space via CD44 receptor endocytosis on the inner limiting membrane, and showed therapeutic effects via pathways bypassing the TLR3-induced siRNA-class effect. The therapeutic effects of siVEGF NBs lasted for 2 weeks after intravitreal injection showing high targeting efficiency to the sub-retinal space. Thus, the newly developed siVEGF NB may have great potential for the delivery of RNAi-based therapeutics for ocular diseases, including AMD.

Sustaining Intravitreal Residence With L-Arginine Peptide-Conjugated Nanocarriers

Purpose

Intravitreal injection of antiangiogenic agents is becoming a standard treatment for neovascular retinal diseases. Sustained release of therapeutics by injecting colloidal carriers is a promising approach to reduce the injection frequency, which reduces treatment burdens and the risk of complications on patients. Such sustained release often requires carriers to have micrometer-scale dimension that, however, can potentially promote glaucoma and inflammation. Small, polycationic particles can be immobilized in vitreous through multiple cooperative ionic interactions with hyaluronic acid of the vitreous interior, but such particles are generally toxic. Here, we synthesized and examined a biocompatible dextran-based nanocarrier (<50 nm in diameter) conjugated with cationic peptides containing L-arginine with minimal toxicity, aiming to provide sustained release of therapeutic drugs in vitreous.

Methods

We synthesized the nanocarriers with condensed cholesteryl dextran (CDEX) as core material. Cationic peptides containing 1 to 4 arginine groups, along with fluorescence tags, were conjugated to the CDEX surface. We monitored the carrier diffusion rate ex vivo and half-lives in vivo in rodent vitreous using fluorescence imaging. We evaluated the toxicity by histological examinations at the second, third, eighth, and thirty-sixth week.

Results

The diffusion rate of nanocarriers was inversely related to zeta potential values in freshly isolated vitreous humor. We observed increased half-lives in vivo with increasing zeta potential (up to 240 days). Histological examinations confirmed no adverse effects on ocular morphology and organization.

Conclusions

We demonstrated the potential of L-arginine peptide-conjugated nanocarriers toward safe and sustained therapeutic release system for posterior eye diseases.

Isotope-coded protein label based quantitative proteomic analysis reveals significant up-regulation of apolipoprotein A1 and ovotransferrin in the myopic chick vitreous

This study used isotope-coded protein label (ICPL) quantitative proteomics and bioinformatics analysis to examine changes in vitreous protein content and associated pathways during lens-induced eye growth. First, the vitreous protein profile of normal 7-day old chicks was characterized by nano-liquid chromatography electrospray ionization tandem mass spectrometry. A total of 341 unique proteins were identified. Next, myopia and hyperopia were induced in the same chick by attaching -10D lenses to the right eye and +10D lenses to the left eye, for 3 and 7 days. Protein expression in lens-induced ametropic eyes was analyzed using the ICPL approach coupled to LCMS. Four proteins (cystatin, apolipoprotein A1, ovotransferrin, and purpurin) were significantly up-regulated in the vitreous after 3 days of wearing -10D lenses relative to +10D lens contralateral eyes. The differences in protein expression were less pronounced after 7 days when the eyes approached full compensation. In a different group of chicks, western blot confirmed the up-regulation of apolipoprotein A1 and ovotransferrin in the myopic vitreous relative to both contralateral lens-free eyes and hyperopic eyes in separate animals wearing +10D lenses. Bioinformatics analysis suggested oxidative stress and lipid metabolism as pathways involved in compensated ocular elongation.

ULTRASONOGRAPHIC FINDINGS IN THE VITREOUS OF PATIENTS WITH AGE-RELATED MACULAR DEGENERATION TREATED WITH INTRAVITREAL ANTI-VASCULAR ENDOTHELIAL GROWTH FACTOR INJECTIONS

PURPOSE

We aimed to assess the relationship of repeated intravitreal injection of anti-vascular endothelial growth factor, the main treatment for exudative age-related macular degeneration, with changes in vitreous ultrasonographic findings in patients with age-related macular degeneration.

METHODS

We retrospectively collected data from 41 patients (41 age-related macular degeneration eyes, 41 control eyes) on age, sex, number of injections, and type of anti-vascular endothelial growth factor (ranibizumab, aflibercept). Ocular ultrasonography was performed with open eyelids, under topical anesthesia, and using carbomers as ultrasonographic gel. Topographic, quantitative, and kinetic ultrasonography was performed in all eye quadrants using a 10-MHz posterior pole probe, and vitreous reflectivity was assessed.

RESULTS

The mean age of patients was 79 (range: 59-94) years, with a mean of five intravitreal anti-vascular endothelial growth factor injections (range: 1-13). No significant ultrasonographic differences were found relative to the incidence of partial or complete posterior vitreous detachment. Vitreous hyperechogenicity increased in the treated eye (P < 0.001), and the vitreous reflectivity range increased with the number of injections (P = 0.041, R = 0.214). However, the type of anti-vascular endothelial growth factor used and the time elapsed since the last intravitreal injection was not significant (P > 0.05).

CONCLUSION

These preliminary results indicate a proportional increase in ultrasonographic reflectivity of vitreous gel with the number of injections.

pH of anti-VEGF agents in the human vitreous: low impact of very different formulations

Background

The aim of the study was to measure pH changes of the human vitreous caused by the intravitreal drugs bevacizumab, ranibizumab, aflibercept, and ziv-aflibercept.

Methods

Fresh human vitreous samples were obtained during core vitrectomy (23-gauge) from patients with epiretinal gliosis. Aliquots of bevacizumab, ranibizumab, aflibercept or ziv-aflibercept (2 µl) were added consecutively to 200 µl of vitreous samples or 0.9% NaCl saline. The pH was measured using a pH-sensitive microelectrode. Rituximab, in off-label use against intraocular lymphoma, was tested as an IgG1 antibody.

Results

The pH of the administered drugs was 5.91 for bevacizumab (95% CI 5.63–6.19), 5.32 for ranibizumab (95% CI 5.0–5.63), 6.05 for aflibercept (95% CI 5.78–6.31), ziv-aflibercept 6.1 (95% CI 6.05–6.15), and 6.29 for rituximab (95% CI 5.97–6.61). While the fresh and undiluted vitreous fluid showed pH values of 7.0–7.4, pH values increased if saline or rituximab were added. In contrast, the pH decreased slightly if aflibercept, bevacizumab, ranibizumab or ziv-aflibercept were supplemented. The observed pH decreases were not significant after ranibizumab was added. Significant changes were only notable with higher-than-normal amounts of bevacizumab (26–40 µl). The vitreous showed the most robust buffering capacity towards ranibizumab and rituximab.

Conclusions

The pH changes in vitreous samples elicited by the usual intravitreal anti-VEGF drugs differed clearly, but only by much higher concentrations than used in the clinical routine. Although the ingredient solution of ranibizumab showed the lowest pH, it caused only moderate changes of vitreal pH compared to bevacizumab, aflibercept or ziv-aflibercept.

Vitreous Humor Changes Expression of Iron-Handling Proteins in Lens Epithelial Cells

Purpose

In humans, vitrectomy is associated with development of nuclear cataracts. Iron catalyzes free radical formation causing oxidative damage, which is implicated in cataract formation. This study was designed to determine if vitreous humor, which can initiate differentiation of lens epithelial cells, would have an effect on iron-handling proteins.

Methods

Cultured canine lens epithelial cells were treated with collected canine vitreous humor. Lysates of treated and control cells were separated by SDS-PAGE. Ferritin H- and L-chains, transferrin receptor 1, and aquaporin 0 were immunodetected and quantitated with specific antibodies. Morphologic changes in treated cells were assessed.

Results

Treatment of lens epithelial cells with a 33% (vol/vol) solution of vitreous humor changed the morphology of lens cells and induced expression of aquaporin 0, a marker of fiber cell differentiation that was undetectable in control cells. Treatment did not modify the size of iron-handling proteins but significantly increased content of ferritin from 2.9- to 8.8-fold over control and decreased levels of transferrin receptor by 37% to 59%.

Conclusions

Vitreous humor may significantly limit iron uptake by transferrin/transferrin receptor pathway, and by increasing ferritin levels could profoundly increase the iron-storage capacity of ferritin in lens cells. Vitreous humor may play a significant protective role against iron-catalyzed oxidative damage of lens epithelial cells and therefore in the formation of cataracts.

Regional distribution of phospholipids in porcine vitreous humor

This project explores the regional phospholipid distribution in porcine vitreous humor, retina, and lens. Matrix-assisted laser desorption mass spectrometry has been used previously to image lipids, proteins, and other metabolites in retinas and lenses. However, the regional composition of phospholipids in vitreous humors is not known. To address this issue, we have applied this mass spectral method to explore the regional phospholipid distribution in porcine vitreous humor both ex-situ and in-vitro. To establish the possible source(s) of phospholipids in the vitreous humor, compositional studies of the lens and retina were also pursued. Due to the overall low levels of phospholipids in vitreous humor, it was necessary to optimize the experimental approaches for ex-situ and in-vitro studies. The sensitivity observed in the spectra of methanol extracts from the lens and retina was higher than that for methanol:chloroform extracts, but the compositional trends were the same. A fourfold improvement in sensitivity was observed in the analysis of vitreous humor extracts obtained with the Bligh and Dyer protocol relative to the other two extraction methods. For ex-situ studies, the 'stamp method' with para-nitroaniline as the matrix was chosen. Throughout the vitreous humor, phosphatidylcholines were the most abundant phospholipids. In-vitro results showed higher relative levels of phospholipids compared to the 'stamp' method. However, more details in the regional phospholipid distribution were provided by the ex-situ approach. Both in-vitro and ex-situ results indicated higher levels of phospholipids in the posterior vitreous region, followed by the anterior and central regions. The posterior region contained more unsaturated species whereas more saturated phospholipids were detected in the anterior region. The observed trends suggest that the phospholipids detected in the posterior vitreous humor migrate from the retina and associated vasculature while those present in the anterior regions are likely to derive from the lens. Not all species found in the lens were observed in the vitreous humor. For example, whereas cholesterol was present in lens extracts, it was not detected in the vitreous humor. Overall, the higher relative abundance of unsaturated species in the posterior vitreous humor and also present in the retina suggests that these species may be able to disrupt the water-collagen-hyaluronan network and contribute to vitreous liquefaction.

Prevalence of posterior vitreous detachment in glaucoma patients and controls

PURPOSE

To evaluate the impact of oxidative stress - present in glaucoma - on the vitreous. We therefore compare the presence of early and late stages of posterior vitreous detachment (PVD) between patients with glaucoma and controls.

METHODS

The vitreous state was evaluated by the combination of optical coherence tomography and ultrasound. The main outcome was the vitreous state classified into 'no PVD', 'initial PVD' and 'advanced PVD'.

RESULTS

We evaluated the vitreous state in 48 patients with glaucoma (age: mean 66.5 ± 11.9 years; visual field deviation: mean 10.4 ± 6.8 dB) and compared the results with 101 previously investigated controls (age: mean 73.6 ± 9.3 years). After one-to-one matching on age and sex, ordinal logistic regression revealed that patients with glaucoma were significantly more likely to exhibit advanced PVD stages compared to non-glaucoma patients (OR 2.60, 95% confidence interval: 1.06-6.36, p = 0.037).

CONCLUSION

Our results suggest that the presence or absence of PVD might be a valuable hint for diagnosing glaucoma - however, further research is needed to determine whether PVD can be used to supplement current glaucoma screening guidelines.

The diffusion dynamics of PEGylated liposomes in the intact vitreous of the ex vivo porcine eye: A fluorescence correlation spectroscopy and biodistribution study

The diffusion dynamics of nanocarriers in the vitreous and the influence of nanocarrier physicochemical properties on these dynamics is an important aspect of the efficacy of intravitreal administered nanomedicines for the treatment of posterior segment eye diseases. Here we use fluorescence correlation spectroscopy (FCS) to determine liposome diffusion coefficients in the intact vitreous (D_Vit) of ex vivo porcine eyes using a modified Miyake-Apple technique to minimize the disruption of the vitreous fine structure. We chose to investigate whether the zeta potential of polyethylene glycol functionalized (i.e. PEGylated) liposomes altered liposome in situ diffusion dynamics in the vitreous. Non-PEGylated cationic nanocarriers have previously shown little to no diffusion in the vitreous, whilst neutral and anionic have shown diffusion. The liposomes investigated had diameters below 150nm and zeta potentials ranging from -20 to +12mV. We observed that PEGylated cationic liposomes had significantly lower D_Vit values (1.14μm²s^-1) than PEGylated neutral and anionic liposomes (2.78 and 2.87μm²s^-1). However, PEGylated cationic liposomes had a similar biodistribution profile across the vitreous to the other systems. These results show that PEGylated cationic liposomes with limited cationic charge can diffuse across the vitreous and indicate that the vitreous as a barrier to nanocarriers (Ø<500nm) is more complicated than simply an electrostatic barrier as previously suggested.

Efficacy of two different thiol-modified crosslinked hyaluronate formulations as vitreous replacement compared to silicone oil in a model of retinal detachment

The efficacy of two novel artificial vitreous body substitutes (VBS) consisting of highly biocompatible thiolated cross-linked hyaluronic acid (HA)-based hydrogels in comparison to silicone oil in a model of retinal detachment was investigated. Pars plana vitrectomy (23G) was performed in the right eye of 24 pigmented rabbits. Retinal detachment of two quadrants was induced by creating a small retinotomy near the vascular arcade and injecting balanced salt solution (BSS) subretinally. The retina was reattached by injecting air, which was followed by increasing the infusion pressure, and the retinal tear was treated by endolaser photocoagulation. At the end of the procedure, the eye was filled either with 5000-cs silicone oil (after fluid air exchange) or the respective hydrogel (with two different viscosities). Follow-up examination included slit lamp examination, funduscopy, intraocular pressure measurements (IOP), optical coherence tomography (OCT) and electroretinogram (ERG) measurements. After a maximum follow-up of four weeks both eyes were removed, examined macroscopically, photographed, and prepared for histology. Of the eight rabbits that received silicone oil, seven (87.5%) developed a recurrent retinal detachment with pronounced proliferative vitreoretinopathy within the first two weeks after surgery. In contrast, in the hydrogel treated eyes, the retina stayed attached in the majority of the cases (73.3%). IOP and retinal morphology were normal as long as the retina remained re-attached. In conclusions, this model of retinal detachment, both thiolated crosslinked hyaluronate hydrogels showed superior efficacy when compared to silicone oil. These hydrogels have a promising potential as novel vitreous body substitutes.

Pharmacokinetic aspects of retinal drug delivery

Drug delivery to the posterior eye segment is an important challenge in ophthalmology, because many diseases affect the retina and choroid leading to impaired vision or blindness. Currently, intravitreal injections are the method of choice to administer drugs to the retina, but this approach is applicable only in selected cases (e.g. anti-VEGF antibodies and soluble receptors). There are two basic approaches that can be adopted to improve retinal drug delivery: prolonged and/or retina targeted delivery of intravitreal drugs and use of other routes of drug administration, such as periocular, suprachoroidal, sub-retinal, systemic, or topical. Properties of the administration route, drug and delivery system determine the efficacy and safety of these approaches. Pharmacokinetic and pharmacodynamic factors determine the required dosing rates and doses that are needed for drug action. In addition, tolerability factors limit the use of many materials in ocular drug delivery. This review article provides a critical discussion of retinal drug delivery, particularly from the pharmacokinetic point of view. This article does not include an extensive review of drug delivery technologies, because they have already been reviewed several times recently. Instead, we aim to provide a systematic and quantitative view on the pharmacokinetic factors in drug delivery to the posterior eye segment. This review is based on the literature and unpublished data from the authors' laboratory.

Prediction of intraocular antibody drug stability using ex-vivo ocular model

Following intravitreal (IVT) injection, therapeutic proteins get exposed to physiological pH, temperature and components in the vitreous humor (VH) for a significantly long time. Therefore, it is of interest to study the stability of the proteins in the VH. However, the challenge posed by the isolated VH (such as pH shift upon isolation and incubation due to the formation of smaller molecular weight (M_W) degradation products) can result in artefacts when investigating protein stability in relevance for the actual in vivo situation. In this current study, an ex-vivo intravitreal horizontal stability model (ExVit-HS) has been successfully developed and an assessment of long-term stability of a bi-specific monoclonal antibody (mAb) drug in the isolated VH for 3months at physiological conditions has been conducted. The stability assessment was performed using various analytical techniques such as microscopy, UV visible for protein content, target binding ELISA, Differential Scanning Calorimetry (DSC), Capillary-electrophoresis-SDS, Size Exclusion (SEC) and Ion-exchange chromatography (IEC) and SPR-Biacore. The results show that the ExVit-HS model was successful in maintaining the VH at physiological conditions and retained a majority of protein in the VH-compartment throughout the study period. The mAb exhibited significantly less fragmentation in the VH relative to the PBS control; however, chemical stability of the mAb was equally compromised in VH and PBS. Interestingly, in the PBS control, mAb showed a rapid linear loss in the binding affinity. The loss in binding was almost 20% higher compared to that in VH after 3months. The results clearly suggest that the mAb has different degradation kinetics in the VH compared to PBS. These results suggest that it is beneficial to investigate the stability in the VH for drugs intended for IVT injection and that are expected longer residence times in the VH. The studies show that the ExVit-HS model may become a valuable tool for evaluating stability of protein drugs and other molecules following IVT injection.

The Effect of Age on Dexamethasone Intravitreal Implant (Ozurdex®) Response in Macular Edema Secondary to Branch Retinal Vein Occlusion

PURPOSE

To investigate the effect of age on dexamethasone intravitreal implant (Ozurdex®) response in macular edema secondary to branch retinal vein occlusion (BRVO).

METHODS

Seventy-three eyes of 73 patients with macular edema secondary to BRVO were recruited in the study. The patients in the study were divided into the following four groups according to their ages: group 1 (<60 years), group 2 (60-69 years), group 3 (70-79 years), and group 4 (≥80 years). Single-dose Ozurdex injection was applied to all patients. The effectiveness of Ozurdex treatment on macular edema is evaluated via optical coherence tomography (OCT) according to the age groups.

RESULTS

Two months after Ozurdex injection, mean reduction of central retinal thickness in groups 1, 2, 3, and 4 were -466.4 ± 149.6, -379.7 ± 238.7, -280.1 ± 233.0, and -180.5 ± 81.4 µm, respectively. This reduction of central retinal thickness decreased with aging (p = 0.001). Also, ages of patients were negatively correlated with the mean reduction of central retinal thickness for the whole study group (r = -0.439, p < 0.001).

CONCLUSION

Our study revealed that the effectiveness of Ozurdex treatment decreases with aging.

From the analysis of pharmacologic vitreolysis to the comprehension of ocriplasmin safety

INTRODUCTION

Pharmacologic vitreolysis is a strategy used to treat anomalous posterior vitreous detachment, by weakening vitreoretinal adhesion with an intravitreal drug. Pharmacologic vitreolysis facilitates surgery, and abnormalities of the vitreoretinal interface including vitreomacular traction (VMT) and early stage macular hole (MH) could be resolved. Ocriplasmin is a recombinant protease, active against fibronectin and laminin, which are important components of the vitreoretinal interface. Ocriplasmin has been approved for symptomatic treatment of VMT and MH with visible traction, and it functions by dissolving the proteins that link the vitreous to the macula, thereby creating a complete posterior vitreous detachment (PVD).

AREAS COVERED

This paper reviews the current knowledge and status of investigations regarding the use of ocriplasmin for pharmacologic vitreolysis and its safety.

EXPERT OPINION

Ocriplasmin is a non-specific enzyme; therefore, it dissolves vitreal proteins as well as possibly proteins associated with visual function in the retina, choroid, and lens. Ocular adverse events (OAEs) of ocriplasmin include transient visual loss, intraocular inflammation, vitreous floaters, lens opacification, zonular instability of the lens, and intraocular hemorrhage. The prevalence of the OAEs is very low; however, on rare occasions, they can result in widespread retinal dysfunction. Research into the acute and long-term safety of ocriplasmin is required.

Age-dependent vitreous separation from the macula in a clinic population

Background

Vitreous degeneration begins soon after birth and accelerates throughout life. Vitreous liquefaction with a slowly progressive separation of the posterior hyaloid from the peripheral macula usually leads to complete posterior vitreous detachment. The purpose of this study is to measure the age-related prevalence of partial vitreous separation and the length of residual vitreous adhesion in an ophthalmology clinic population.

Methods

Patients examined by the senior author (MWS) during a 6-month period were included in a retrospective chart review. Demographic data and spectral domain optical coherence tomography scan results were gathered. Data analysis with descriptive statistics focused on the prevalence and extent of partial vitreous separation.

Results

The mean age of the study patients was 69.9 years, and 62% were phakic. The highest prevalence of partial posterior hyaloid separation from the internal limiting membrane (71.2%) was seen in the 50- to 54-year age group. This prevalence rate steadily decreased to 5.6% in the 95- to 99-year age group. The prevalence of complete vitreous detachment as determined by slit-lamp biomicroscopy increased from 1.7% in the <50-year age group to a maximum of 29.2% in the 75- to 79-year group. The length of vitreomacular adhesion averaged 4.6 mm in the 50- to 54-year age group and steadily decreased to 2.1 mm in the 90- to 95-year group.

Conclusion

Vitreomacular separation affects the majority of eyes in the sixth decade of life. The prevalence of partial vitreous separation decreases with advancing age, probably because an increasing number of these patients progress to complete posterior vitreous detachment.

Differential Expression of Vitreous Proteins in Young and Mature New Zealand White Rabbits

Different anatomical regions have been defined in the vitreous humor including central vitreous, basal vitreous, vitreous cortex, vitreoretinal interface and zonule. In this study we sought to characterize changes in the proteome of vitreous humor (VH) related to compartments or age in New Zealand white rabbits (NZW). Vitreous humor was cryo-collected from young and mature New Zealand white rabbit eyes, and dissected into anterior and posterior compartments. All samples were divided into 4 groups: Young Anterior (YA), Young Posterior (YP), Mature Anterior (MA) and Mature Posterior (MP) vitreous. Tryptic digests of total proteins were analyzed by liquid chromatography followed by tandem mass spectrometry. Spectral count was used to determine the relative protein abundances and identify proteins with statistical differences between compartment and age groups. Western blotting was performed to validate some of the differentially expressed proteins. Our results showed that 231, 375, 273 and 353 proteins were identified in the YA, YP, MA and MP respectively. Fifteen proteins were significantly differentially expressed between YA and YP, and 11 between MA and MP. Carbonic anhydrase III, lambda crystallin, alpha crystallin A and B, beta crystallin B1 and B2 were more abundant in the anterior region, whereas vimentin was less abundant in the anterior region. For comparisons between age groups, 4 proteins were differentially expressed in both YA relative to MA and YP relative to MP. Western blotting confirmed the differential expression of carbonic anhydrase III, alpha crystallin B and beta crystallin B2. The protein profiles of the vitreous humor showed age- and compartment-related differences. This differential protein profile provides a baseline for understanding the vitreous compartmentalization in the rabbit and suggests that further studies profiling proteins in different compartments of the vitreous in other species may be warranted.