Vascular Endothelial Growth Factor in Tear Samples of Patients with Systemic Sclerosis

Lipids from ocular meibum and tears may serve as biomarkers for depression and post-traumatic stress disorder

BACKGROUND

There is a need to develop biomarkers for diagnosis and prediction of treatment responses in depression and post-traumatic stress disorder (PTSD).

METHODS

Cross-sectional study examining correlations between tear inflammatory proteins, meibum and tear sphingolipids, and symptoms of depression and PTSD-associated anxiety. Ninety individuals filled depression (Patient Health Questionnaire 9, PHQ-9) and PTSD-associated anxiety (PTSD Checklist-Military Version, PCL-M) questionnaires. In 40 patients, a multiplex assay system was used to quantify 23 inflammatory proteins in tears. In a separate group of 50 individuals, liquid chromatography-mass spectrometry was performed on meibum and tears to quantify 34 species of sphingolipids, encompassing ceramides, monohexosyl ceramides and sphingomyelins.

RESULTS

The mean age of the population was 59.4 ± 11.0 years; 89.0% self-identified as male, 34.4% as White, 64.4% as Black, and 16.7% as Hispanic. The mean PHQ-9 score was 11.1 ± 7.6, and the mean PCL-M score was 44.3 ± 19.1. Symptoms of depression and PTSD-associated anxiety were highly correlated (ρ =0.75, p < 0.001). Both PHQ9 and PCL-M scores negatively correlated with multiple sphingolipid species in meibum and tears. In multivariable models, meibum Monohexosyl Ceramide 26:0 (pmol), tear Ceramide 16:0 (mol%), meibum Monohexosyl Ceramide 16:0 (mol%), and tear Ceramide 26:1 (mol%) remained associated with depression and meibum Monohexosyl Ceramide 16:0 (mol%), meibum Monohexosyl Ceramide 26:0 (pmol), tear Sphingomyelin 20:0 (mol%), and tear Sphingosine-1-Phosphate (mol%) remained associated with PTSD-associated anxiety.

CONCLUSIONS

Certain meibum and tear sphingolipid species were related to mental health indices. These interactions present opportunities for innovative diagnostic and therapeutic approaches for mental health disorders.

The role of endothelial growth factor and tear levels in diabetic retinopathy in type 2 diabetes

PURPOSE

To evaluate the tear level of VEGF and the quantity of tear film in type 2 diabetic patients.

METHODS

Thirty patients with diabetic retinopathy (DR group) and 30 patients with no DR (NDR group), and 30 healthy subjects with age and gender matching were enrolled in this prospective comparative study. The tear samples were collected using the Schirmer strips, and the amount of moisture absorbed by the strips was used to determine the quantitative level of the tear film. The concentration of VEGF in the tear samples was measured using the enzyme-linked immunosorbent assay method. The variables were compared with an independent t-test and covariance analysis.

RESULTS

Mean tear level of VEGF was significantly higher in DR group (235.42 pg/ml) compared to NDR (75.11 pg/ml) and control (58.77 pg/ml) groups (P ≤ 0.001). There was no significant difference in the mean of VEGF between NDR and control patients (P = 1.00). Mean quantitative tear film levels were 7.15%, 9.72%, and 15.11% in DR, NDR, and healthy subjects, respectively (P < 0.05). The pairwise analysis showed significant differences in the level of VEGF between DR and both NDR (P = 0.001) and normal (P = 0.017) groups. However, there was no significant difference observed between NDR and normal eyes (P = 0.743).

CONCLUSION

The VEGF level in tear was higher in diabetic patients with DR, independent of tear volume. The tear VEGF measurement can be used as a valuable predictor to prevent DR in diabetic patients.

Ocular Involvement in Systemic Sclerosis: Updated Review and New Insights on Microvascular Impairment

Systemic sclerosis (SSc) is a chronic multisystemic disease characterized by immunological activation, diffuse vasculopathy, and generalized fibrosis exhibiting a variety of symptoms. A recognized precursor of SSc is Raynaud's phenomenon, which is part of the very early disease of systemic sclerosis (VEDOSS) in combination with nailfold videocapillaroscopy (NVC) impairment. The pathophysiology of ocular involvement, alterations in internal organs, and body integumentary system involvement in SSc patients are complicated and poorly understood, with multiple mechanisms presumptively working together. The most prevalent ocular symptoms of SSc are abnormalities of the eyelids and conjunctiva as well as dry eye syndrome, due to fibroblasts' dysfunction and inflammation of the ocular surface. In particular, lagophthalmos, blepharophimosis limitation of eyelid motion, eyelid telangiectasia, and rigidity or tightening of the lids may affect up to two-third of the patients. In addition, reduction in central corneal thickness, iris defects and higher rates of glaucoma were reported. In the first reports based on retinography or fluorescein angiography, about 50% of SSc patients showed signs of vascular disease: peripheral artery occlusion, thinning of retinal pigment epithelium and choroidal capillaries, ischemic areas surrounded by intraretinal extravasation and microaneurysms, and peripheral capillary non-perfusion. Successively, thanks to the advent of optical coherence tomography angiography (OCTA), several studies highlighted significant impairment of either the choriocapillaris and retinal vascular plexuses, also correlating with NVC involvement and skin disease, even in VEDOSS disease. Given the sensitivity of this technique, ocular micro-vasculopathy may act as a tool for early SSc identification and discriminate between disease stages.

Fluorescence Sensing Technologies for Ophthalmic Diagnosis

Personalized and point-of-care (POC) diagnoses are critical for ocular physiology and disease diagnosis. Real-time monitoring and continuous sampling abilities of tear fluid and user-friendliness have become the key characteristics for the applied ophthalmic techniques. Fluorescence technologies, as one of the most popular methods that can fulfill the requirements of clinical ophthalmic applications for optical sensing, have been raised and applied for tear sensing and diagnostic platforms in recent decades. Wearable sensors in this case have been increasingly developed for ocular diagnosis. Contact lenses, as one of the commercialized and popular tools for ocular dysfunction, have been developed as a platform for fluorescence sensing in tears diagnostics and real-time monitoring. Numbers of biochemical analytes have been examined through developed fluorescent contact lens sensors, including pH values, electrolytes, glucose, and enzymes. These sensors have been proven for monitoring ocular conditions, enhancing and detecting medical treatments, and tracking efficiency of related ophthalmic surgeries at POC settings. This review summarizes the applied ophthalmic fluorescence sensing technologies in tears for ocular diagnosis and monitoring. In addition, the cooperation of fabricated fluorescent sensor with mobile phone readout devices for diagnosing ocular diseases with specific biomarkers continuously is also discussed. Further perspectives for the developments and applications of fluorescent ocular sensing and diagnosing technologies are also provided.

VEGF-A in Serum and Plasma Rich in Growth Factors (PRGF) Eye Drops

BACKGROUND

Vascular endothelial growth factor (VEGF)-A, the most abundant subtype of the VEGF family in the eye, plays an important role in corneal homeostasis due to its ability to mediate corneal nerve repair. Repeated intravitreal anti-VEGF injections were shown to significantly reduce corneal nerve density, which might negatively affect corneal homeostasis and lead to a neuropathic dry eye disease. Currently, there are two effective modalities to treat dry eye while supplying VEGF to the ocular surface: serum eye drops (SED) and eye drops manufactured from plasma rich in growth factors (PRGF). The purpose of this study was to measure the VEGF-A concentration in SED and PRGF eye drops.

MATERIAL AND METHODS

Ten healthy volunteers donated blood on two separate occasions, 2 - 8 days apart. Thus, a total of 20 blood samples were processed to obtain both SED and PRGF. Concentrations of VEGF-A were quantified by a Simple Plex platform run in triplicate.

RESULTS

The VEGF-A concentration in SED and PRGF was very similar between the two blood samples drawn from one individual donor but showed substantial interindividual variability. However, in all 20 samples, VEGF concentrations were substantially higher in SED samples (mean 238.7 ± 146.6 pg/mL) compared to PRGF samples (mean 67.4 ± 46.3 pg/mL). Based upon the analysis of variance (ANOVA) model for the measured concentrations with fixed effects for specimen (SED vs. PRGF) and subject, the mean difference between the SED and PRGF concentration was 168.1 pg/mL (95% confidence interval: [142.4, 193.9], p < 0.001).

CONCLUSION

Our study showed that the VEGF concentration was higher in SED than in PRGF. This is an important finding, particularly for potential treatment of dry eye disease in patients with neuropathic eye disease, especially in patients that received repeated anti-VEGF intravitreal injections, or in patients with Sjögren's disease, where the level of VEGF in tears might be pathologically decreased. Hypothetically, VEGF might be needed to restore ocular surface homeostasis. Although growing evidence has shown that VEGF-A plays an important role in corneal homeostasis, only a randomized prospective clinical trial will show whether supplying VEGF-A to the ocular surface might successfully restore the corneal homeostasis and overcome the problem of corneal neuropathy in these patients. For such a trial, based on our results, an undiluted SED should be preferred over a PRGF due to the higher content of VEGF-A.

Evaluation of vascular endothelial growth factor (VEGF) level in the tears and serum of age-related macular degeneration patients

Age-related macular degeneration (AMD) is an important cause of irreversible central blindness worldwide. Clinical manifestations range from asymptomatic in early and intermediate AMD to significant vision loss in late AMD. Approximately 10% of cases of early AMD eventually progress to the late advanced stage, influenced by the upregulation of vascular endothelial growth factor (VEGF). In this study, we evaluated VEGF concentration in the tears and serum of AMD patients. Our study revealed a significantly higher level of VEGF in the tears of patients with AMD compared with controls. The tear VEGF level has high sensitivity and specificity, and is significantly related to the severity of AMD, whilst serum VEGF level is non-specific and non-predictive of AMD severity. Thus, VEGF level in the tears may be used as a non-invasive biomarker for AMD progression. A large cohort study is needed for further verification.

The potential of tear proteomics for diagnosis and management of orbital inflammatory disorders including Graves' ophthalmopathy

BACKGROUND

Orbital compartments harbor a variety of tissues that can be independently targeted in a plethora of disorders resulting in sight-threatening risks. Orbital inflammatory disorders (OID) including Graves' ophthalmopathy, sarcoidosis, IgG4 disease, granulomatosis with polyangiitis, and nonspecific orbital inflammation constitute an important cause of pain, diplopia and vision loss. Physical examination, laboratory tests, imaging, and even biopsy are not always adequate to classify orbital inflammation which is frequently deemed "nonspecific". Tear sampling and testing provide a potential "window" to the orbital disease process through a non-invasive technique that allows longitudinal sampling as the disease evolves. Using PubMed/Medline, we identified potentially relevant articles on tear proteomics published in the English language between 1988 and 2021. Of 303 citations obtained, 225 contained empirical data on tear proteins, including 33 publications on inflammatory conditions, 15 in glaucoma, 15 in thyroid eye disease, 1 in sarcoidosis (75) and 2 in uveitis (77,78). Review articles were used to identify an additional 56 relevant articles through citation search. In this review, we provide a short introduction to the potential use of tears as a diagnostic fluid and tool to investigate the mechanism of ocular diseases. A general review of previous tear proteomics studies is also provided, with a focus on Graves' ophthalmopathy (GO), and a discussion of unmet needs in the diagnosis and treatment of orbital inflammatory disease (OID). The review concludes by pointing out current limitations of mass spectrometric analysis of tear proteins and summarizes future needs in the field.

Ophthalmic sensing technologies for ocular disease diagnostics

Point-of-care diagnosis and personalized treatments are critical in ocular physiology and disease. Continuous sampling of tear fluid for ocular diagnosis is a need for further exploration. Several techniques have been developed for possible ophthalmological applications, from traditional spectroscopies to wearable sensors. Contact lenses are commonly used devices for vision correction, as well as for other therapeutic and cosmetic purposes. They are increasingly being developed into ocular sensors, being used to sense and monitor biochemical analytes in tear fluid, ocular surface temperature, intraocular pressure, and pH value. These sensors have had success in detecting ocular conditions, optimizing pharmaceutical treatments, and tracking treatment efficacy in point-of-care settings. However, there is a paucity of new and effective instrumentation reported in ophthalmology. Hence, this review will summarize the applied ophthalmic technologies for ocular diagnostics and tear monitoring, including both conventional and biosensing technologies. Besides applications of smart readout devices for continuous monitoring, targeted biomarkers are also discussed for the convenience of diagnosis of various ocular diseases. A further discussion is also provided for future aspects and market requirements related to the commercialization of novel types of contact lens sensors.

Dysregulated Tear Film Proteins in Macular Edema Due to the Neovascular Age-Related Macular Degeneration Are Involved in the Regulation of Protein Clearance, Inflammation, and Neovascularization

Macular edema and its further complications due to the leakage from the choroidal neovascularization in course of the age-related macular degeneration (AMD) is a leading cause of blindness among elderly individuals in developed countries. Changes in tear film proteomic composition have been reported to occur in various ophthalmic and systemic diseases. There is an evidence that the acute form of neovascular AMD may be reflected in the tear film composition. Tear film was collected with Schirmer strips from patients with neovascular AMD and sex- and age-matched control patients. Two-dimensional electrophoresis was performed followed by MALDI-TOF mass spectrometry for identification of differentially expressed proteins. Quantitative analysis of the differential electrophoretic spots was performed with Delta2D software. Altogether, 11 significantly differentially expressed proteins were identified; of those, 8 were downregulated, and 3 were upregulated in the tear film of neovascular AMD patients. The differentially expressed proteins identified in tear film were involved in signaling pathways associated with impaired protein clearance, persistent inflammation, and neovascularization. Tear film protein analysis is a novel way to screen AMD-related biomarkers.

Tear fluid collection methods: Review of current techniques

Tear fluid, composed of lipid, aqueous, and mucin layers, contains electrolytes, water, proteins, peptides, and glycoproteins. Its components may serve as diagnostic indicators of local and systemic diseases. The aim of the study was to conduct literature review in order to identify the current methods of tear collection. The most commonly used method which was relatively easy to perform and allowed to obtain sufficient tear volume for further chemical and physical analysis was selected through PubMed database search for the following keywords: tear sampling, human tears, chemical analysis of tears, physical tear analysis, animal tear sampling. Final criteria of articles selection were: human tears, tear sample collection, chemical and physical analysis of tears. Time of publication of the articles not older than 1995. The analysis of 70 articles revealed that the most common tear fluid collection methods are Schirmer tear strips and capillary tubes. Thus, we recommend the use of Schirmer strips and microcapillary tubes as the cheapest and easiest methods for sampling of tear fluid for further chemical analysis.

Ocular manifestations in patients with systemic sclerosis

Systemic sclerosis (SSc) is a rare, chronic autoimmune disease with unknown etiology. Its prominent features are fibrosis, vasculopathy and impaired immune response. Disease can also affect eyes leading to various findings in ophthalmological examination.

The objective of this study was to determine the prevalence and type of ocular involvement in patients with SSc. A systematic literature review was conducted using electronic databases. A combination of following keywords was used: “systemic sclerosis” and ophthalmology-related search terms, including the keywords “eye”, “ocular” and “ophthalmic”.

In conclusion, eyelid and conjunctival abnormalities and dry eye disease are among the most common ocular manifestations of SSc. Their diversity is connected to complexity of the disease.

Design principles of selective transport through biopolymer barriers

In biological systems, polymeric materials block the movement of some macromolecules while allowing the selective passage of others. In some cases, binding enables selective transport, while in others the most inert particles appear to transit most rapidly. To study the general principles of filtering, we develop a model motivated by features of the nuclear pore complex (NPC) which are highly conserved and could potentially be applied to other biological systems. The NPC allows selective transport of proteins called transport factors, which transiently bind to disordered flexible proteins called phenylalanine-glycine-nucleoporins. While the NPC is tuned for transport factors and their cargo, we show that a single feature is sufficient for selective transport: the bound-state motion resulting from transient binding to flexible filaments. Interchain transfer without unbinding can further improve selectivity, especially for cross-linked chains. We generalize this observation to model nanoparticle transport through mucus and show that bound-state motion accelerates transport of transient nanoparticle application, even with clearance by mucus flow. Our model provides a framework to control binding-induced selective transport in biopolymeric materials.

Evaluation of vascular endothelial growth factor levels in tears and serum among diabetic patients

Objective

Detection of vascular endothelial growth factor (VEGF) levels in ocular tissue may perhaps provide insight into the role of VEGF in the pathogenesis and progression of diabetic retinopathy (DR). The aim of this study was to evaluate the levels of VEGF in tears and serum amongst type 2 diabetes mellitus (DM) patients.

Methods

A comparative cross-sectional study was conducted between August 2016 and May 2018 involving type 2 DM patients with no DR, non-proliferative DR (NPDR), and proliferative DR (PDR). Tear samples were collected using no.41 Whatman filter paper (Schirmer strips) and 5 mL blood samples were drawn by venous puncture. VEGF levels in tears and serum were measured by enzyme-linked immunosorbent assay.

Results

A total of 88 type 2 DM patients (no DR: 30 patients, NPDR: 28 patients, PDR: 30 patients) were included in the study. Mean tear VEGF levels were significantly higher in the NPDR and PDR groups (114.4 SD 52.5 pg/mL and 150.8 SD 49.7 pg/mL, respectively) compared to the no DR group (40.4 SD 26.5 pg/mL, p < 0.001). There was no significant difference in the mean serum VEGF levels between the three groups. There was a fair correlation between serum and tear VEGF levels (p = 0.015, r = 0.263).

Conclusion

VEGF levels in tears were significantly higher amongst diabetic patients with DR compared to those without DR and were significantly associated with the severity of DR. There was a fair correlation between serum and tear VEGF levels. Detection of VEGF in tears is a good non-invasive predictor test for the severity of DR. A large cohort study is needed for further evaluation.

Contact Lens Technology: From Fundamentals to Applications

Contact lenses are ocular prosthetic devices used by over 150 million people worldwide. Primary applications of contact lenses include vision correction, therapeutics, and cosmetics. Contact lens materials have significantly evolved over time to minimize adverse effects associated with contact lens wearing, to maintain a regular corneal metabolism, and to preserve tear film stability. This article encompasses contact lens technology, including materials, chemical and physical properties, manufacturing processes, microbial contamination, and ocular complications. The function and the composition of the tear fluid are discussed to assess its potential as a diagnostic media. The regulatory standards of contact lens devices with regard to biocompatibility and contact lens market are presented. Future prospects in contact lens technology are evaluated, with particular interest given to theranostic applications for in situ continuous monitoring the ocular physiology.

Tear fluid biomarkers in ocular and systemic disease: potential use for predictive, preventive and personalised medicine

In the field of predictive, preventive and personalised medicine, researchers are keen to identify novel and reliable ways to predict and diagnose disease, as well as to monitor patient response to therapeutic agents. In the last decade alone, the sensitivity of profiling technologies has undergone huge improvements in detection sensitivity, thus allowing quantification of minute samples, for example body fluids that were previously difficult to assay. As a consequence, there has been a huge increase in tear fluid investigation, predominantly in the field of ocular surface disease. As tears are a more accessible and less complex body fluid (than serum or plasma) and sampling is much less invasive, research is starting to focus on how disease processes affect the proteomic, lipidomic and metabolomic composition of the tear film. By determining compositional changes to tear profiles, crucial pathways in disease progression may be identified, allowing for more predictive and personalised therapy of the individual. This article will provide an overview of the various putative tear fluid biomarkers that have been identified to date, ranging from ocular surface disease and retinopathies to cancer and multiple sclerosis. Putative tear fluid biomarkers of ocular disorders, as well as the more recent field of systemic disease biomarkers, will be shown.