Components of the fibrinolytic system in the vitreous body in patients with vitreoretinal disorders

Peptidomimetics Therapeutics for Retinal Disease

Ocular disorders originating in the retina can result in a partial or total loss of vision, making drug delivery to the retina of vital importance. However, effectively delivering drugs to the retina remains a challenge for ophthalmologists due to various anatomical and physicochemical barriers in the eye. This review introduces diverse administration routes and the accordant pharmacokinetic profiles of ocular drugs to aid in the development of safe and efficient drug delivery systems to the retina with a focus on peptidomimetics as a growing class of retinal drugs, which have great therapeutic potential and a high degree of specificity. We also discuss the pharmacokinetic profiles of small molecule drugs due to their structural similarity to small peptidomimetics. Lastly, various formulation strategies are suggested to overcome pharmacokinetic hurdles such as solubility, retention time, enzymatic degradation, tissue targeting, and membrane permeability. This knowledge can be used to help design ocular delivery platforms for peptidomimetics, not only for the treatment of various retinal diseases, but also for the selection of potential peptidomimetic drug targets.

Importance of the Use of Oxidative Stress Biomarkers and Inflammatory Profile in Aqueous and Vitreous Humor in Diabetic Retinopathy

Diabetic retinopathy is one of the leading causes of visual impairment and morbidity worldwide, being the number one cause of blindness in people between 27 and 75 years old. It is estimated that ~191 million people will be diagnosed with this microvascular complication by 2030. Its pathogenesis is due to alterations in the retinal microvasculature as a result of a high concentration of glucose in the blood for a long time which generates numerous molecular changes like oxidative stress. Therefore, this narrative review aims to approach various biomarkers associated with the development of diabetic retinopathy. Focusing on the molecules showing promise as detection tools, among them we consider markers of oxidative stress (TAC, LPO, MDA, 4-HNE, SOD, GPx, and catalase), inflammation (IL-6, IL-1ß, IL-8, IL-10, IL-17A, TNF-α, and MMPs), apoptosis (NF-kB, cyt-c, and caspases), and recently those that have to do with epigenetic modifications, their measurement in different biological matrices obtained from the eye, including importance, obtaining process, handling, and storage of these matrices in order to have the ability to detect the disease in its early stages.

Evaluation of D-dimer levels in aqueous humor of rabbit eyes with and without induced intraocular fibrin and fibrinolytic treatment

OBJECTIVE

To analyze D-dimer concentrations in aqueous humor (AH) of rabbit eyes under physiological conditions, after induction of fibrin clots, and following fibrinolytic therapy.

ANIMALS STUDIED

Prospective study measuring D-dimers in aqueous humor of rabbit eyes with induced fibrin clots (n = 44).

PROCEDURES

Rabbits were purchased in two groups, which led to two temporally separated experimentation groups. Different treatment protocols were compared for their efficacy in fibrin reduction (slit-lamp examination, high-resolution ultrasound). AH was taken from left eyes before clot induction (baseline, day 1), 24 hours later after clot establishment/prior to drug administration (post-induction, day 2) and 48 hours after clot induction (post-treatment, day 3). An enzyme-linked immunosorbent assay (ELISA) was performed to measure intraocular D-dimer concentrations RESULTS: D-dimer concentrations were measurable in all samples. There were no differences in D-dimer levels across time points or treatments within the arrival groups. However, a significant difference in mean D-dimer levels was observed between the two arrival groups (group 1:3.1 µg/mL; group 2:6.1 µg/mL; P < .0001), which made a direct comparison of treatment groups impossible. Clinically, all eyes displayed fibrin clots in the anterior chamber and different treatment types led to significant differences in clot resolution (clot size reduction after intracameral treatment: 98%, topical treatment: 60%, no treatment: 40%).

CONCLUSION

D-dimers were identified in all AH samples of rabbits with large variability between samples. D-dimer levels were neither predictive for differences in induced fibrin formation nor for drug efficacy.

Pharmacokinetics of Intravitreal Anti-VEGF Drugs in Age-Related Macular Degeneration

Intravitreal administration of anti-vascular endothelial growth factor (VEGF) antibodies has become the standard treatment for Age-Related Macular Degeneration; however, the knowledge of their pharmacokinetics is limited. A comprehensive review of the preclinical and clinical pharmacokinetic data that were obtained in different studies with intravitreal bevacizumab, ranibizumab, and aflibercept has been conducted. Moreover, the factors that can influence the vitreous pharmacokinetics of these drugs, as well as the methods that were used in the studies for analytical determination, have been exposed. These anti-VEGF drugs present different charge and molecular weights, which play an important role in vitreous distribution and elimination. The pharmacokinetic parameters that were collected differ depending on the species that were involved in the studies and on physiological and pathological conditions, such as vitrectomy and lensectomy. Knowledge of the intravitreal pharmacokinetics of the anti-VEGF drugs that were used in clinical practice is of vital importance.

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.

Nanoparticle-motivated gene delivery for ophthalmic application

Ophthalmic gene therapy is an intellectual and intentional manipulation of desired gene expression into the specific cells of an eye for the treatment of ophthalmic (ocular) genetic dystrophies and pathological conditions. Exogenous nucleic acids such as DNA, small interfering RNA, micro RNA, and so on, are used for the purpose of managing expression of the desired therapeutic proteins in ocular tissues. The delivery of unprotected nucleic acids into the cells is limited because of exogenous and endogenous degradation modalities. Nanotechnology, a promising and sophisticated cutting edge tool, works as a protective shelter for these therapeutic nucleic acids. They can be safely delivered to the required cells in order to modulate anticipated protein expression. To this end, nanotechnology is seen as a potential and promising strategy in the field of ocular gene delivery. This review focused on current nanotechnology modalities and other promising nonviral strategies being used to deliver therapeutic genes in order to treat various devastating ocular diseases.

Proteomic Analysis of the Vitreous following Experimental Retinal Detachment in Rabbits

Purpose. The pathogenesis of rhegmatogenous retinal detachment (RRD) remains incompletely understood, with no clinically effective treatment for potentially severe complications such as photoreceptor cell death and proliferative vitreoretinopathy. Here we investigate the protein profile of the vitreous following experimental retinal detachment using a comparative proteomic based approach. Materials and Methods. Retinal detachment was created in the right eyes of six New Zealand red pigmented rabbits. Sham surgery was undertaken in five other rabbits that were used as controls. After seven days the eyes were enucleated and the vitreous was removed. The vitreous samples were evaluated with two-dimensional polyacrylamide gel electrophoresis and the differentially expressed proteins were identified with tandem mass spectrometry. Results. Ten protein spots were found to be at least twofold differentially expressed when comparing the vitreous samples of the sham and retinal detachment surgery groups. Protein spots that were upregulated in the vitreous following retinal detachment were identified as albumin fragments, and those downregulated were found to be peroxiredoxin 2, collagen-Iα1 fragment, and α-1-antiproteinase F. Conclusions. Proteomic investigation of the rabbit vitreous has identified a set of proteins that help further our understanding of the pathogenesis of rhegmatogenous retinal detachment and its complications.

Proteomic analyses of the vitreous humour

The human vitreous humour (VH) is a transparent, highly hydrated gel, which occupies the posterior segment of the eye between the lens and the retina. Physiological and pathological conditions of the retina are reflected in the protein composition of the VH, which can be sampled as part of routine surgical procedures. Historically, many studies have investigated levels of individual proteins in VH from healthy and diseased eyes. In the last decade, proteomics analyses have been performed to characterise the proteome of the human VH and explore networks of functionally related proteins, providing insight into the aetiology of diabetic retinopathy and proliferative vitreoretinopathy. Recent proteomic studies on the VH from animal models of autoimmune uveitis have identified new signalling pathways associated to autoimmune triggers and intravitreal inflammation. This paper aims to guide biological scientists through the different proteomic techniques that have been used to analyse the VH and present future perspectives for the study of intravitreal inflammation using proteomic analyses.