Levels of lactoferrin, secretory IgA and serum albumin in the tear film of people with keratoconus

Tear levels of apoptotic, matrix-degrading and antioxidant biomarkers in patients with and without keratoconus: A cross sectional study

PURPOSE

To assess the tear levels of a set of apoptotic, matrix-degrading and antioxidant biomarkers, including Metalloproteinase 9 (MMP9), High Mobility Group Box 1 (HMGB1) and Superoxide Dismutase 3-Extracellular (SOD3).

METHODS

Sandwich-ELISA commercial kits were used to test the expression of the three tear biomarkers in the lacrimal fluid of eligible participants. Linear logistic regression analysis was performed todetermine whether the set of tear biomarkers could be associated with clinically manifest keratoconus. ROC curve analysis using 10-fold cross-validation was performedto evaluate the prediction accuracy of the model.

RESULTS

Eighty-one participants aged 30-48 years old were enrolled in this study; 48 were patients with keratoconus and 33 were age-matched healthy subjects. The linear combination of the three tear biomarkers levels (AUC = 0.811; CI 95 %: 0.712-0.911) accurately indicated the existence of keratoconus; higher levels of MMP9 (Odd Ratio: 1.069; CI 95 %: 1.029-1.130) and HMGB1 (OR: 1.011; CI 95 %: 1.003-1.022) and lower levels of SOD3 (OR: 0.994; CI 95 %: 0.989-0.997) were significantly associated with a higher probability of keratoconus.

CONCLUSION

Multivariable analysis of the set of tear levels of MMP9, HMGB1 and SOD3 biomarkers confirmed a chronic state of inflammation in the ocular surface of patients with keratoconus.

Paper integrated microfluidic contact lens for colorimetric glucose detection

Contact lenses offer a simple, cost-effective, and non-invasive method for in situ real-time analysis of various biomarkers. Electro-chemical sensors are integrated into contact lenses for analysis of various biomarkers. However, they suffer from rigid electronic components and connections, leading to eye irritation and biomarker concentration deviation. Here, a flexible and microfluidic integrated paper-based contact lens for colorimetric analysis of glucose was implemented. Facilitating a three-dimensional (3D) printer for lens fabrication eliminates cumbersome cleanroom processes and provides a simple, batch compatible process. Due to the capillary force of the filter paper, the sample was routed to detection chambers inside microchannels, and it allowed further colorimetric detection. The paper-embedded microfluidic contact lens successfully detects glucose down to 2 mM within ∼10 s. The small dimension of the microfluidic system enables detection of glucose levels as low as 5 μl. The results show the potential of the presented approach to analyze glucose concentration in a rapid manner. It is demonstrated that the fabricated contact lens can successfully detect glucose levels of diabetic patients.

Tear meniscus particle analysis with anterior segment optical coherence tomography in keratoconus

PURPOSE

To perform tear meniscus particle analysis using anterior segment spectral domain-optical coherence tomography (SD-OCT) and ImageJ software in keratoconus patients.

METHODS

A total of 76 participants (76 eyes) were included in the study. A comprehensive analysis of tear meniscus parameters, including tear meniscus height (TMH), tear meniscus depth (TMD), tear meniscus turbidity (TMT), and percentage of area occupied by particles (PAOP) within the meniscus, was performed in kerataconus patients and healthy controls.

RESULTS

TMT was significantly higher in the keratoconus group, while PAOP was significantly lower (P < 0.05). However, TMH and TMD did not show significant differences between the two groups (P > 0.05). There was a negative correlation observed between TMT and PAOP. In binary logistic regression analysis, TMT and Schirmer score were found to be the most influential factors in predicting keratoconus (odds ratio [OR] = 0.995, P = 0.039 and OR = 1.143, P = 0.021, respectively).

CONCLUSION

This study revealed novel findings on analysis of the tear film in keratoconus patients, with higher TMT and lower POAP levels in the keratoconus group compared to the healthy control group.

Systemic and Ocular Associations of Keratoconus

Introduction

Keratoconus (KC) is the most prevalent corneal ectasia in the world and its pathogenesis is influenced by both ocular and systemic factors. This review explores the multifaceted associations between keratoconus and systemic health conditions, ocular characteristics, and various other environmental/exogenous factors, aiming to illuminate how these relationships influence the pathophysiology of the disease.

Areas Covered

This review will summarize the fundamental attributes of KC, review and discuss the systemic and ocular association of KC including molecular biomarkers, and provide an organized overview of the parallel alterations occurring within various biological pathways in KC.

Expert Opinion

Despite the substantial volume of research on keratoconus, the precise etiology of the disease remains elusive. Further studies are necessary to deepen our understanding of this intricate disorder and improve its management.

Tear biomarkers

An extensive exploration of lacrimal fluid molecular biomarkers in understanding and diagnosing a spectrum of ocular and systemic diseases is presented. The chapter provides an overview of lacrimal fluid composition, elucidating the roles of proteins, lipids, metabolites, and nucleic acids within the tear film. Pooled versus single-tear analysis is discussed to underline the benefits and challenges associated with both approaches, offering insights into optimal strategies for tear sample analysis. Subsequently, an in-depth analysis of tear collection methods is presented, with a focus on Schirmer's test strips and microcapillary tubes methods. Alternative tear collection techniques are also explored, shedding light on their applicability and advantages. Variability factors, including age, sex, and diurnal fluctuations, are examined in the context of their impact on tear biomarker analysis. The main body of the chapter is dedicated to discussing specific biomarkers associated with ocular discomfort and a wide array of ocular diseases. From dry eye disease and thyroid-associated ophthalmopathy to keratoconus, age-related macular degeneration, diabetic retinopathy, and glaucoma, the intricate relationship between molecular biomarkers and these conditions is thoroughly dissected. Expanding beyond ocular pathologies, the chapter explores the applicability of tear biomarkers in diagnosing systemic diseases such as multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer's disease, Parkinson's disease, and cancer. This broader perspective underscores the potential of lacrimal fluid analysis in offering non-invasive diagnostic tools for conditions with far-reaching implications.

Nutraceutical and Health-Promoting Potential of Lactoferrin, an Iron-Binding Protein in Human and Animal: Current Knowledge

Lactoferrin is a natural cationic iron-binding glycoprotein of the transferrin family found in bovine milk and other exocrine secretions, including lacrimal fluid, saliva, and bile. Lactoferrin has been investigated for its numerous powerful influences, including anticancer, anti-inflammatory, anti-oxidant, anti-osteoporotic, antifungal, antibacterial, antiviral, immunomodulatory, hepatoprotective, and other beneficial health effects. Lactoferrin demonstrated several nutraceutical and pharmaceutical potentials and have a significant impact on improving the health of humans and animals. Lactoferrin plays a critical role in keeping the normal physiological homeostasis associated with the development of pathological disorders. The current review highlights the medicinal value, nutraceutical role, therapeutic application, and outstanding favorable health sides of lactoferrin, which would benefit from more exploration of this glycoprotein for the design of effective medicines, drugs, and pharmaceuticals for safeguarding different health issues in animals and humans.

Tear Fluid Inflammatory Proteome Analysis Highlights Similarities Between Keratoconus and Allergic Conjunctivitis

Purpose

Keratoconus is characterized by the progressive thinning of the cornea, which leads to a cone-like appearance of the eye over time. Although conventionally defined as a noninflammatory condition, a number of recent studies have associated keratoconus (KC) with allergic conjunctivitis (AC) based on clinical parameters. This study aimed to consolidate this association by performing a proteomic analysis of tear fluid from patients with keratoconus and/or allergic conjunctivitis.

Methods

Of 51 patients, 17 were diagnosed with KC, 17 were diagnosed with AC, and 17 were diagnosed with both KC and AC (combined). Nine of 34 patients with KC had a progressive form of the disease. Tear fluid samples (n = 51, one eye per patient) were collected by the Schirmer's strips. Tear proteins were extracted from the Schirmer's strips. Proteomic profiling of 384 inflammatory proteins was assessed by a multiplex proximity extension assay (Olink Explore 384 Inflammation Panel I).

Results

A total of 384 inflammatory proteins were measured. Two hundred seventy-two of the 384 proteins passed stringent data cleaning and were compared among the patient groups. Compared to the 2 other groups, LGALS9 was upregulated uniquely in KC, whereas FGF19, PDGFB, HPCAL1, OSM, and FCAR were downregulated in KC. Similarly, TNFRSF4 and CCL13 were specifically upregulated in AC, whereas ectodysplasin A receptor (EDAR) was uniquely downregulated in AC.

Conclusions

High-throughput proteomic profiling of tear fluid confirms the association between KC and AC on a molecular level and raise the importance of redefining KC as an inflammatory condition.

Lactoferrin-Anchored Tannylated Mesoporous Silica Nanomaterials-Induced Bone Fusion in a Rat Model of Lumbar Spinal Fusion

Lactoferrin (LF) is a potent antiviral, anti-inflammatory, and antibacterial agent found in cow and human colostrum which acts as an osteogenic growth factor. This study aimed to investigate whether LF-anchored tannylated mesoporous silica nanomaterials (TA-MSN-LF) function as a bone fusion material in a rat model. In this study, we created TA-MSN-LF and measured the effects of low (1 μg) and high (100 μg) TA-MSN-LF concentrations in a spinal fusion animal model. Rats were assigned to four groups in this study: defect, MSN, TA-MSN-LF-low (1 μg/mL), and TA-MSN-LF-high (100 μg/mL). Eight weeks after surgery, a greater amount of radiological fusion was identified in the TA-MSN-LF groups than in the other groups. Hematoxylin and eosin staining showed that new bone fusion was induced in the TA-MSN-LF groups. Additionally, osteocalcin, a marker of bone formation, was detected by immunohistochemistry, and its intensity was induced in the TA-MSN-LF groups. The formation of new vessels was induced in the TA-MSN-LF-high group. We also confirmed an increase in the serum osteocalcin level and the mRNA expression of osteocalcin and osteopontin in the TA-MSN-LF groups. TA-MSN-LF showed effective bone fusion and angiogenesis in rats. We suggest that TA-MSN-LF is a potent material for spinal bone fusion.

Smart Contact Lenses as Wearable Ophthalmic Devices for Disease Monitoring and Health Management

The eye contains a complex network of physiological information and biomarkers for monitoring disease and managing health, and ocular devices can be used to effectively perform point-of-care diagnosis and disease management. This comprehensive review describes the target biomarkers and various diseases, including ophthalmic diseases, metabolic diseases, and neurological diseases, based on the physiological and anatomical background of the eye. This review also includes the recent technologies utilized in eye-wearable medical devices and the latest trends in wearable ophthalmic devices, specifically smart contact lenses for the purpose of disease management. After introducing other ocular devices such as the retinal prosthesis, we further discuss the current challenges and potential possibilities of smart contact lenses.

Biomedical Applications of Lactoferrin on the Ocular Surface

Lactoferrin (LF) is a first-line defense protein with a pleiotropic functional pattern that includes anti-inflammatory, immunomodulatory, antiviral, antibacterial, and antitumoral properties. Remarkably, this iron-binding glycoprotein promotes iron retention, restricting free radical production and avoiding oxidative damage and inflammation. On the ocular surface, LF is released from corneal epithelial cells and lacrimal glands, representing a significant percentage of the total tear fluid proteins. Due to its multifunctionality, the availability of LF may be limited in several ocular disorders. Consequently, to reinforce the action of this highly beneficial glycoprotein on the ocular surface, LF has been proposed for the treatment of different conditions such as dry eye, keratoconus, conjunctivitis, and viral or bacterial ocular infections, among others. In this review, we outline the structure and the biological functions of LF, its relevant role at the ocular surface, its implication in LF-related ocular surface disorders, and its potential for biomedical applications.

Pre-analytical sample handling effects on tear fluid protein levels

Tear fluid is emerging as a source of non-invasive biomarkers, both for ocular and systemic conditions. Accurate quantification of tear proteins can be improved by standardizing methods to collect and process tear fluid. The aim of this study was to determine sample handling factors that may influence the tear protein biomarker profile. Tear fluid was collected using Schirmer's strips. Tear proteins were extracted by elution through centrifugation. Total protein content was determined using the bicinchoninic acid assay. Key concepts that apply to the entire sample processing cycle are tear sampling, tear storage, protein extraction and data normalization. Differences in wetting or migration length were observed between Schirmer's strips from different manufacturers, and between protein-free and protein-rich solutions. One unit of migration length (mm) did not correspond to one unit of volume (µL). A positive correlation (r = 0.6671, p < 0.0001) was observed between migration length and total tear protein content. The most beneficial storage conditions were strips that were not stored (+ 21.8%), or underwent 'wet' storage (+ 11.1%). Protein recovery was the highest in 400 µL extraction buffer and independent of protein molecular weight. This study helps to explain inter- and intra-variability that is often seen with tear biomarker research. This information is critical to ensure accuracy of test results, as tear biomarkers will be used for patient management and in clinical trials in the near future. This study also highlights the need for standardization of Schirmer's strip manufacturing, tear fluid processing and analyte concentration normalization.

Oxidative Stress in the Anterior Ocular Diseases: Diagnostic and Treatment

The eye is a metabolically active structure, constantly exposed to solar radiations making its structure vulnerable to the high burden of reactive oxygen species (ROS), presenting many molecular interactions. The biomolecular cascade modification is caused especially in diseases of the ocular surface, cornea, conjunctiva, uvea, and lens. In fact, the injury in the anterior segment of the eye takes its origin from the perturbation of the pro-oxidant/antioxidant balance and leads to increased oxidative damage, especially when the first line of antioxidant defence weakens with age. Furthermore, oxidative stress is related to mitochondrial dysfunction, DNA damage, lipid peroxidation, protein modification, apoptosis, and inflammation, which are involved in anterior ocular disease progression such as dry eye, keratoconus, uveitis, and cataract. The different pathologies are interconnected through various mechanisms such as inflammation, oxidative stress making the diagnostics more relevant in early stages. The end point of the molecular pathway is the release of different antioxidant biomarkers offering the potential of predictive diagnostics of the pathology. In this review, we have analysed the oxidative stress and inflammatory processes in the front of the eye to provide a better understanding of the pathomechanism, the importance of biomarkers for the diagnosis of eye diseases, and the recent treatment of anterior ocular diseases.

Immunomodulatory Effect of Human Lactoferrin on Toll-like Receptors 2 Expression as Therapeutic Approach for Keratoconus

Keratoconus (KC) is a corneal disorder whose etiology shares a close relationship with Lactoferrin (LTF) dysregulation and Toll-like Receptors 2 (TLR2) overexpression. This study shows how these two important biomarkers are clinically and molecularly interrelated, increasing knowledge about KC pathophysiology, and opening the door to future therapies. In this prospective clinical study, serum and tear LTF concentrations were quantified in 90 KC patients and 60 controls. A correlation analysis with multiple blood and tear immunoinflammatory mediators, and KC-associated tomographic parameters, was performed. An in vitro study using HEK-BlueTMhTLR2 cell cultures was also conducted to determine the expression and functionality of TLR2 under the influence of LTF treatment. As a result, a LTF decreased was observed in KC patients compared to controls (p < 0.0001), evidencing the strong correlation with TLR2 overexpression at systemic and ocular surface level, with inflammatory mediator upregulation and with KC severity. In stimulated cell cultures, TLR2 expression was decreased using 2 mg/mL of LTF. The levels of secreted embryonic alkaline phosphatase (SEAP) and interleukin-8 (IL-8) were also reduced in supernatants after LTF treatment. As conclusions, the dysregulation of LTF and TLR2 in the ocular surface of KC patients contributes to KC severity by maintaining a detrimental chronic immune−inflammatory state. The immunomodulatory properties of LTF on TLR2 expression suggest its potential as a therapeutic approach for KC.

Tear proteome profile in eyes with keratoconus after intracorneal ring segment implantation or corneal crosslinking

Purpose

Keratoconus (KC) is a corneal ectasia characterized by structural changes, resulting in progressive thinning and biomechanical weakening that can lead to worsening visual acuity due to irregular astigmatism. Corneal collagen Crosslinking (CXL) and Intracorneal Ring Segment (ICRS) are widely used treatments in KC disease, but the alterations they cause in biomechanical mediators are still poorly understood. The aim of this study was to analyze the tear proteome profile before and after treatments to identify biomarkers altered by surgery.

Materials and methods

An observational, prospective, case-control pilot study was conducted, analyzing tear samples from KC patients by nano-liquid chromatography-mass spectrometry (nLC-MS/MS). Data are available via ProteomeXchange with identifier PXD035655. Patients with KC who underwent ICRS surgery (n = 4), CXL (n = 4), and healthy subjects (Ctrl, n = 4) were included in this study. Clinical parameters were measured and tear samples were collected before and 18 months after surgery. Proteins with ≥2 expression change and p-value &lt; 0.05 between groups and times were selected to study their role in post-operative corneal changes.

Results

These analyses led to the identification of 447 tear proteins, some of which were dysregulated in KC patients. In comparisons between the two surgical groups and Ctrls, the biological processes that were altered in KC patients at baseline were those that were dysregulated as a consequence of the disease and not of the surgical intervention. Among the biological processes seen to be altered were: immune responses, cytoskeleton components, protein synthesis and metabolic reactions. When comparing the two treatment groups (ICRS and CXL), the process related to cytoskeleton components was the most altered, probably due to corneal thinning which was more pronounced in patients undergoing CXL.

Conclusion

The changes observed in tears after 18 months post-operatively could be due to the treatments performed and the pathology. Among the deregulated proteins detected, A-kinase anchor protein 13 (AKAP-13) deserves special attention for its involvement in corneal thinning, and for its strong overexpression in the tears of patients with more active KC and faster disease progression. However, it should be kept in mind that this is a pilot study conducted in a small number of patients.

Host Defense Peptides at the Ocular Surface: Roles in Health and Major Diseases, and Therapeutic Potentials

Sight is arguably the most important sense in human. Being constantly exposed to the environmental stress, irritants and pathogens, the ocular surface – a specialized functional and anatomical unit composed of tear film, conjunctival and corneal epithelium, lacrimal glands, meibomian glands, and nasolacrimal drainage apparatus – serves as a crucial front-line defense of the eye. Host defense peptides (HDPs), also known as antimicrobial peptides, are evolutionarily conserved molecular components of innate immunity that are found in all classes of life. Since the first discovery of lysozyme in 1922, a wide range of HDPs have been identified at the ocular surface. In addition to their antimicrobial activity, HDPs are increasingly recognized for their wide array of biological functions, including anti-biofilm, immunomodulation, wound healing, and anti-cancer properties. In this review, we provide an updated review on: (1) spectrum and expression of HDPs at the ocular surface; (2) participation of HDPs in ocular surface diseases/conditions such as infectious keratitis, conjunctivitis, dry eye disease, keratoconus, allergic eye disease, rosacea keratitis, and post-ocular surgery; (3) HDPs that are currently in the development pipeline for treatment of ocular diseases and infections; and (4) future potential of HDP-based clinical pharmacotherapy for ocular diseases.

Shotgun Proteomics for the Identification and Profiling of the Tear Proteome of Keratoconus Patients

Purpose

The qualitative approach followed in this study aims to obtain an extensive view of the keratoconus (KC) tear proteome, which could highlight proteins previously undetected and enlarge our knowledge of the disease's pathophysiology.

Methods

Twenty-five patients diagnosed with KC and 25 control subjects were studied in a prospective, cross-sectional study. KC screening examinations, including clinical and tomographic examinations, were performed on all participants. Tear samples were collected using Schirmer strips and analyzed by liquid chromatography-tandem mass spectrometry in a data-dependent workflow. A spectral count was used as a semiquantification tool. The tear proteomes of both groups were identified and profiled, and the functional interactions and biological characterization of differential proteins were analyzed using in silico tools.

Results

We identified a total of 232 proteins, of whom 133 were expressed in both groups’ samples; 41 were observed only in control samples and 58 were identified just in tears of patients with KC. A semiquantitative analysis showed the dysregulation of 17 proteins in the KC samples. An in silico analysis linked proteins only expressed in KC samples to oxidative stress, skin development, and apoptosis. The dysregulation of proteins involved in iron transport, inflammation, oxidative stress, and protease inhibition was observed in the semiquantitative results.

Conclusions

A shotgun analysis showed that the tear proteome of patients with KC differed from controls by more than one-third of the total proteins identified, highlighting the relationship of the proteins only expressed in KC tears with processes of cell death, oxidative damage, and inflammation. The underexpression of proteins involved in iron pathways might support the iron imbalance as a contributing factor to cellular damage and death in KC disease.

Comprehensive Transcriptome Analysis of Patients With Keratoconus Highlights the Regulation of Immune Responses and Inflammatory Processes

Keratoconus (KTCN), characterized by the steeper curvature of the cornea and the thinner central corneal thickness, was a degenerative corneal ectasia with ambiguous etiology and mechanism. We aim to reveal underlying pathological mechanisms of KTCN by multi-level transcriptomic, integrative omics analyses. We performed RNA-sequencing on corneal epithelial samples from seven patients and seven control donors, as well as peripheral matched blood samples from three of the patients and three control donors. After RNA extraction, library construction, and sequencing, differentially expressed genes and splicing events were identified, followed by over-representation analysis. In total, 547 differential expressed genes were identified in KTCN corneal epithelial samples, which were mainly enriched in immune responses and inflammatory processes. WGCNA module analysis, the transcriptomic analysis of peripheral blood samples, multiple omics data, and the meta-analysis of GEO samples confirmed the involvement of immune and inflammatory factors. Besides, 190 and 1,163 aberrant splicing events were identified by rMATS combined with CASH methods in corneal epithelial and blood samples with KCTN. In conclusion, this comprehensive transcriptome analysis of KTCN patients based on patients’ tissue and blood samples uncovered a significant association between immune-inflammatory genes and pathways with KCTN, highlighting the contribution of the perturbed immune signaling to the pathogenesis of KCTN. Our study suggested the importance of measures to control inflammation in the treatment of KCTN.

Nutritional and Metabolic Imbalance in Keratoconus

Keratoconus (KC) is a progressive corneal degeneration characterized by structural changes consisting of progressive thinning and steepening of the cornea. These alterations result in biomechanical weakening and, clinically, in vision loss. While the etiology of KC has been the object of study for over a century, no single agent has been found. Recent reviews suggest that KC is a multifactorial disease that is associated with a wide variety of genetic and environmental factors. While KC is typically considered a disease of the cornea, associations with systemic conditions have been well described over the years. In particular, nutritional and metabolic imbalance, such as the redox status, hormones, metabolites, and micronutrients (vitamins and metal ions), can deeply influence KC initiation and progression. In this paper, we comprehensively review the different nutritional (vitamins and minerals) and metabolic (hormones and metabolites) factors that are altered in KC, discussing their possible implication in the pathophysiology of the disease.

The Pathomechanism, Antioxidant Biomarkers, and Treatment of Oxidative Stress-Related Eye Diseases

Oxidative stress is an important pathomechanism found in numerous ocular degenerative diseases. To provide a better understanding of the mechanism and treatment of oxidant/antioxidant imbalance-induced ocular diseases, this article summarizes and provides updates on the relevant research. We review the oxidative damage (e.g., lipid peroxidation, DNA lesions, autophagy, and apoptosis) that occurs in different areas of the eye (e.g., cornea, anterior chamber, lens, retina, and optic nerve). We then introduce the antioxidant mechanisms present in the eye, as well as the ocular diseases that occur as a result of antioxidant imbalances (e.g., keratoconus, cataracts, age-related macular degeneration, and glaucoma), the relevant antioxidant biomarkers, and the potential of predictive diagnostics. Finally, we discuss natural antioxidant therapies for oxidative stress-related ocular diseases.

Model Systems for Evidencing the Mediator Role of Riboflavin in the UVA Cross-Linking Treatment of Keratoconus

Riboflavin under UVA radiation generates reactive oxygen species (ROS) that can induce various changes in biological systems. Under controlled conditions, these processes can be used in some treatments for ocular or dermal diseases. For instance, corneal cross-linking (CXL) treatment of keratoconus involves UVA irradiation combined with riboflavin aiming to induce the formation of new collagen fibrils in cornea. To reduce the damaging effect of ROS formed in the presence of riboflavin and UVA, the CXL treatment is performed with the addition of polysaccharides (dextran). Hyaluronic acid is a polysaccharide that can be found in the aqueous layer of the tear film. In many cases, keratoconus patients also present dry eye syndrome that can be reduced by the application of topical solutions containing hyaluronic acid. This study presents physico-chemical evidence on the effect of riboflavin on collagen fibril formation revealed by the following methods: differential scanning microcalorimetry, rheology, and STEM images. The collagen used was extracted from calf skin that contains type I collagen similar to that found in the eye. Spin trapping experiments on collagen/hyaluronic acid/riboflavin solutions evidenced the formation of ROS species by electron paramagnetic resonance measurements.

Protein expression of the tear film of domestic cats before and after inoculation with Toxoplasma gondii

BACKGROUND

Tear film (TF) helps maintain and protect ocular function against damage to the ocular surface. Proteins are one of its main constituents, whose expression pattern can be used as a biomarker of ocular changes and systemic diseases. The aim of this study was to evaluate the expression of proteins in the TF of domestic cats before and after infection with Toxoplasma gondii, in the phases of acute infection and chronicity. Twelve healthy cats received orally homogenized brain matter obtained from mice inoculated with T. gondii oocysts, strain ME49. Cat feces were collected daily from the third day after infection to assess the release of oocysts. TF samples were obtained from cats, by Schirmer's Tear Test 1, on day 0 (before infection), day 5 after infection (acute phase of infection, with maximum peak release of oocysts in feces) and on day 21 after infection (start of chronic phase, 7 days after total absence of oocyst release in feces). Tear samples were also submitted to proteomic analysis in a Q-Tof-Premier mass spectrometer.

RESULTS

A total of 37 proteins with scores equal to or greater than 100 were identified on D0, followed by 36 on D5 and 42 on D21. Of these, 27 were common to D0 and D5, 33 to D0 and D21, 27 to D5 and D21, and 26 were common to the three groups, totaling 54 proteins. The most abundant proteins were lipocalin allergen Fel d, serum albumin, aldehyde dehydrogenase, lactoperoxidase and lactotransferrin. There was no significant difference in the abundance of proteins found on D0 and D5, but there was a statistical difference between D0 and D21 for ACT1_AEDAE, CERU_HUMAN and GELS_HUMAN. Regarding D5 and D21, there were significant differences for KV1_CANLF, LAC_PIG, TRFL_PIG, ACT1_AEDAE, CERU_HUMAN, GELS_HUMAN and OVOS2_HUMAN.

CONCLUSIONS

The main proteins identified in the TF of domestic cats are similar to those found in humans and other animal species. Most are part of the ocular surface defense system against injuries. The most expressed proteins in animals in the chronic phase of T. gondii infection are associated with the immune response to the parasite.

Electrostatic and Covalent Assemblies of Anionic Hydrogel-Coated Gold Nanoshells for Detection of Dry Eye Biomarkers in Human Tears

Although dry eye is highly prevalent, many challenges exist in diagnosing the symptom and related diseases. For this reason, anionic hydrogel-coated gold nanoshells (AuNSs) were used in the development of a label-free biosensor for detection of high isoelectric point tear biomarkers associated with dry eye. A custom, aldehyde-functionalized oligo(ethylene glycol)acrylate (Al-OEGA) was included in the hydrogel coating to enhance protein recognition through the formation of dynamic covalent (DC) imine bonds with solvent-accessible lysine residues present on the surface of select tear proteins. Our results demonstrated that hydrogel-coated AuNSs, composed of monomers that form ionic and DC bonds with select tear proteins, greatly enhance protein recognition due to changes in the maximum localized surface plasmon resonance wavelength exhibited by AuNSs in noncompetitive and competitive environments. Validation of the developed biosensor in commercially available pooled human tears revealed the potential for clinical translation to establish a method for dry eye diagnosis.

Assessing the role of systemic inflammation in the etiopathogenesis of advanced stage keratoconus

PURPOSE

It was aimed to compare the levels of inflammation-related parameters, such as neutrophil/lymphocyte ratio (NLR) and platelet/lymphocyte ratio (PLR), in patients with advanced keratoconus (KC) and healthy controls. Also, we evaluated the relationships between these parameters and several corneal topography values used in the KC diagnostic index.

METHODS

Forty patients with advanced and 40 healthy volunteers were included in this study. In the KC group, 20 patients were nonprogressive KC and 20 patients were progressive KC. In all participating individuals, we evaluated detailed ophthalmologic examination findings and complete blood count data, while corneal topographic measurements were also recorded in patients with KC.

RESULTS

The mean NLR value was 2.3 ± 1.19 in the progressive KC group; nonprogressive KC values were 1.99 ± 1.69 and 1.81 ± 0.72 in the control group. Mean PLR value was 113.24 ± 48.44 in the progressive KC group, nonprogressive KC values were 96.47 ± 31.04 and 104.09 ± 35.14 in the control group. No statistically significant difference was found between patients with progressive KC, nonprogressive KC, and healthy volunteers in terms of mean NLR and PLR values (P > 0.05). NLR values were found to demonstrate significant positive correlations with the corneal topography parameters, Symmetry Index front (r = 0.278, P = 0.025), KC Vertex front (r = 0.247, P = 0.048), and Baiocchi Calossi Versaci front (r = 0.273, P = 0.028); there was no significant relationship between corneal topography parameters and PLR values.

CONCLUSION

Although there was no significant difference between the progressive KC, nonprogressive KC, and control groups in inflammation parameters such as NLR and PLR, a positive correlation was observed between the NLR value and some corneal topography findings used in the diagnosis of KC. The role of inflammation in the etiology of KC can be better understood by clinical studies and laboratory tests conducted with prospective studies involving a higher number of patients.

Longitudinal Tear Protein Changes Correlate with Ocular Chronic GVHD Development in Allogeneic Hematopoietic Stem Cell Transplant Patients

Ocular graft-versus-host disease (oGVHD) is a manifestation of chronic GVHD, frequently occurring in patients after allogeneic hematopoietic stem cell transplant (HSCT). We analyzed tear protein changes before and after allogeneic HSCT, and correlated their levels with the oGVHD development. This retrospective study included 102 patients, and data were recorded before the conditioning treatment, and after 3 to 6 months postoperatively. Tear protein analysis was performed with the Agilent-2100 Bioanalyzer on individual tears sampled by aspiration. Total protein (TP), Lysozyme-C (LYS-C), Lactoferrin (LACTO), Lipocalin-1 (LIPOC-1), Transferrin (TRANSF), Albumin (ALB), and Zinc-alpha-2-glycoprotein (ZAG-2) levels were retrieved and statistically analyzed. Following HSCT forty-three patients developed oGVHD. TP, LACTO, LYS-C, and ZAG-2 levels significantly decreased post-HSCT as compared to pre HSCT levels. In univariate analysis, TP, LACTO, and ZAG-2 decrease was associated with an increased development of oGVHD (OR = 4.49; 95% CI, 1.9 to 10.5; p < 0.001; OR = 3.08; 95% CI 1.3 to 7.6; p = 0.01; OR = 11.1; 95% CI 2.7 to 46.6; p < 0.001, respectively). TRANSF post-HSCT levels significantly increased (OR 15.7; 95% CI, 4.1 to 52.2; p = 0.0001). No pre-post-HSCT changes were shown in ALB and LIPOC-1 levels. Data suggest that TP content, LACTO, TRANSF, and ZAG-2 pre-post changes might be significant predictors of oGVHD development.

Oxidative and antioxidative stress markers in keratoconus: a systematic review and meta-analysis

PURPOSE

To conduct a systematic review and meta-analysis on the levels of oxidative stress markers and antioxidants in keratoconus compared to healthy subject.

METHOD

The PubMed, Cochrane Library, Embase, Science Direct and Google Scholar databases were searched on 1st June 2020 for studies reporting oxidative and antioxidative stress markers in keratoconus and healthy controls. Main meta-analysis was stratified by type of biomarkers, type of samples (tears, cornea, aqueous humour and blood) and type of corneal samples (stromal cells, epithelium and endothelium).

RESULTS

We included 36 articles, for a total of 1328 keratoconus patients and 1208 healthy controls. There is an overall increase in oxidative stress markers in keratoconus compared with healthy controls (standard mean deviation (SMD) = 0.94, 95% confidence interval (95% CI) 0.55-1.33), with a significant increase in reactive oxygen and nitrogen species (1.09, 0.41-1.78) and malondialdehyde (1.78, 0.83-2.73). There is an overall decrease in antioxidants in keratoconus compared with healthy controls (-0.63, -0.89 to -0.36), with a significant decrease in total antioxidant capacity/status (-1.65, -2.88 to -0.43), aldehyde/NADPH dehydrogenase (-0.77, -1.38 to -0.17), lactoferrin/transferrin/albumin (-1.92, -2.96 to -0.89) and selenium/zinc (-1.42, -2.23 to -0.61). Oxidative stress markers were higher in tears and in cornea of keratoconus than in aqueous humour, and antioxidants were decreased in tears, aqueous humour and blood without difference between sample type. Oxidative stress markers increased in stromal cells and antioxidants decreased in endothelium.

CONCLUSION

Oxidative stress markers and antioxidants were dysregulated in keratoconus, involving an imbalance of redox homeostasis in tears, cornea, aqueous humour and blood.

Tear Proteomics in Keratoconus: A Quantitative SWATH-MS Analysis

Purpose

To elucidate dysregulated proteins in keratoconus (KC) to provide a better understanding of the molecular mechanisms that lead to the development of the disease using sequential window acquisition of all theoretical mass spectra (SWATH-MS) as a protein quantification tool of the tear proteomic profile.

Methods

Prospective cross-sectional study that includes 25 keratoconic eyes and 25 healthy eyes. All participants underwent a clinical, tomographic, and aberrometric exam. Tear sample was collected using Schirmer strips and analyzed by liquid chromatography with tandem mass spectrometry. SWATH-MS was used as a quantification tool of the tear proteomic profile. The expression of the quantified proteins was compared between groups, and the biological and molecular functions of the dysregulated proteins as well as their functional relationships were studied by in silico analysis.

Results

A total of 203 proteins were quantified in tear samples of patients with KC and control participants, of which 18 showed differential expression between groups (P < 0.05). An increase in the expression of 7 proteins and a decrease in the expression of 11 proteins were observed. Protein–protein interactions and gene ontology analysis showed the involvement of these dysregulated proteins in structural, inflammatory-immune, iron homeostasis, oxidative stress, and extracellular matrix proteolysis processes.

Conclusions

Tear protein quantification has revealed the dysregulation of proteins involved in biological processes previously associated with KC. Among them, iron homeostasis should be highlighted as a relevant pathway in the KC pathophysiology, and it should be taken into account in the development of therapeutic targets to cope with tissue damage derived from iron accumulation and toxicity.

Tear Film Proteome of Healthy Domestic Cats

The aim of this study was to investigate the proteins found in tear film of healthy domestic cats. Schirmer tear test strips were used to collect tear samples of twelve healthy cats, which were mixed, centrifuged, and placed in a single 1.5 mL microtube that was frozen at −20°C, until analysis by two-dimensional polyacrylamide gel and mass spectrometry associated with high-performance liquid chromatography. The resulting spectra were analyzed and compared with the Swiss-Prot search tool. Forty peptides were detected in the analyzed protein fragments of 90 spots, with 16 proteins identified. Of these, the authors confirmed what has been already found in other studies: lactotransferrin, serum albumin, allergenic lipocalins, and neutrophil gelatinase-associated lipocalin. Others were considered novel in tear film samples of all species: cyclin-dependent protein kinase, serine/arginine repetitive matrix protein, apelin receptor, secretory protein related to C1q/TNF, Wee1, α-1,4 glucan phosphorylase, and WD repeat domain 1. The network was divided into 11 clusters, and a biological function was assigned. Most of the proteins have functions in the defense and maintenance of feline ocular surface homeostasis. Serum albumin is a bottleneck protein, with a high betweenness value. This paper is a pioneer in reporting, in-depth, the tear film proteome of domestic cats.

Ophthalmic Sensors and Drug Delivery

Advances in multifunctional materials and technologies have allowed contact lenses to serve as wearable devices for continuous monitoring of physiological parameters and delivering drugs for ocular diseases. Since the tear fluids comprise a library of biomarkers, direct measurement of different parameters such as concentration of glucose, urea, proteins, nitrite, and chloride ions, intraocular pressure (IOP), corneal temperature, and pH can be carried out non-invasively using contact lens sensors. Microfluidic contact lens sensor based colorimetric sensing and liquid control mechanisms enable the wearers to perform self-examinations at home using smartphones. Furthermore, drug-laden contact lenses have emerged as delivery platforms using a low dosage of drugs with extended residence time and increased ocular bioavailability. This review provides an overview of contact lenses for ocular diagnostics and drug delivery applications. The designs, working principles, and sensing mechanisms of sensors and drug delivery systems are reviewed. The potential applications of contact lenses in point-of-care diagnostics and personalized medicine, along with the significance of integrating multiplexed sensing units together with drug delivery systems, have also been discussed.

Lactoferrin/Calcium Phosphate-Modified Porous Ti by Biomimetic Mineralization: Effective Infection Prevention and Excellent Osteoinduction

The surface modification of titanium (Ti) can enhance the osseointegration and antibacterial properties of implants. In this study, we modified porous Ti discs with calcium phosphate (CaP) and different concentrations of Lactoferrin (LF) by biomimetic mineralization and examined their antibacterial effects and osteogenic bioactivity. Firstly, scanning electron microscopy (SEM), the fluorescent tracing method, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and the releasing kinetics of LF were utilized to characterize the modified Ti surface. Then, the antibacterial properties against S. sanguis and S. aureus were investigated. Finally, in vitro cytological examination was performed, including evaluations of cell adhesion, cell differentiation, extracellular matrix mineralization, and cytotoxicity. The results showed that the porous Ti discs were successfully modified with CaP and LF, and that the LF-M group (200 μg/mL LF in simulated body fluid) could mildly release LF under control. Further, the LF-M group could effectively inhibit the adhesion and proliferation of S. sanguis and S. aureus and enhance the osteogenic differentiation in vitro with a good biocompatibility. Consequently, LF-M-modified Ti may have potential applications in the field of dental implants to promote osseointegration and prevent the occurrence of peri-implantitis.

Advances in the diagnosis and treatment of keratoconus

Keratoconus had traditionally been considered a rare disease at a time when the imaging technology was inept in detecting subtle manifestations, resulting in more severe disease at presentation. The increased demand for refractive surgery in recent years also made it essential to more effectively detect keratoconus before attempting any ablative procedure. Consequently, the armamentarium of tools that can be used to diagnose and treat keratoconus has significantly expanded. The advances in imaging technology have allowed clinicians and researchers alike to visualize the cornea layer by layer looking for any early changes that might be indicative of keratoconus. In addition to the conventional geometrical evaluation, efforts are also underway to enable spatially resolved corneal biomechanical evaluation. Artificial intelligence has been exploited in a multitude of ways to enhance diagnostic efficiency and to guide treatment. As for treatment, corneal cross-linking treatment remains the mainstay preventive approach, yet the current main focus of research is on increasing oxygen availability and developing new strategies to improve riboflavin permeability during the procedure. Some new combined protocols are being proposed to simultaneously halt keratoconus progression and correct refractive error. Bowman layer transplantation and additive keratoplasty are newly emerging alternatives to conventional keratoplasty techniques that are used in keratoconus surgery. Advances in tissue engineering and regenerative therapy might bring new perspectives for treatment at the cellular level and hence obviate the need for invasive surgeries. In this review, we describe the advances in the diagnosis and treatment of keratoconus primarily focusing on newly emerging approaches and strategies.

Biochemical Markers and Alterations in Keratoconus

Keratoconus (KC) is a corneal ectatic condition characterized by focal structural changes, resulting in progressive thinning, biomechanical weakening, and steeping of the cornea that can lead to worsening visual acuity due to irregular astigmatism and corneal scarring in more advanced cases. It is a relatively common ectatic disease of the cornea predominantly affecting the younger population. Despite its worldwide prevalence, its incidence is rather varied with a higher incidence among the Middle Eastern and South Asian population. Dysregulated corneal extracellular matrix remodeling underlies KC pathogenesis. However, a lack of absolute clarity regarding the factors that initiate and drive progression poses a significant challenge in its prevention and management. KC is a complex multifactorial disease as it is associated with a wide variety of etiological factors such as environmental stimuli/insults, oxidative stress, genetic predisposition, comorbidities, and eye rubbing. A series of studies using corneal tissues (epithelium, stroma), cultured corneal fibroblasts/keratocytes, tear fluid, aqueous humor, and blood from KC subjects has reported significant alterations in various biochemical factors such as extracellular matrix components, cellular homeostasis regulators, inflammatory factors, hormones, metabolic products, and chemical elements. It has become apparent that alterations in the biochemical mediators (related to various etiologies) could contribute to KC pathogenesis by altering the dynamics of extracellular matrix remodeling events such as collagen deposition, degradation, and cross-linking in the cornea. Determining key disease contributing biochemical mediators would aid in disease monitoring, prediction or abatement of disease progression, and development of targeted therapeutics to improve disease prognosis.

Lactoferrin Concentration in Human Tears and Ocular Diseases: A Meta-Analysis

Purpose

To evaluate the potential of lactoferrin (Lf) as a diagnostic biomarker for ocular diseases using a meta-analytic approach.

Methods

All original studies reporting an estimate of the average Lf concentration in healthy subjects and those affected by ocular diseases were searched up to March 2020. The DerSimonian and Laird method was used to calculate the random effects pooled mean difference and the corresponding 95% confidence interval (CI) in Lf concentration between healthy subjects and those affected by dry eye (DE), Sjögren syndrome (SS), and diabetic retinopathy, separately. The presence of between-study heterogeneity was evaluated using the Cochran's Q test and the I2 index. Stratified analyses were performed to assess potential sources of heterogeneity and influence and cumulative analyses to evaluate the robustness of the results obtained. Publication bias was also evaluated using funnel plot and the Egger's test.

Results

The pooled mean differences in Lf concentrations between healthy subjects and those with DE, Sjögren syndrome, and diabetic retinopathy were respectively 0.62 (95% CI, 0.35-0.89) for DE, 3.78 (95% CI, -6.64 to 14.17), and 0.19 (95% CI, -4.00 to 4.39). Regarding DE, the stratified analysis showed that geographical area (P value Q test < 0.0001) and sample size (P < 0.0005) were sources of heterogeneity. Moreover, no study substantially influenced the results obtained and the pooled mean difference became statistically significant after a sample size of 220. Publication bias may affect the results of DE.

Conclusions

The results of the current meta-analysis suggest that Lf level in tears is a good candidate as dry eye syndrome diagnostic biomarker.

Review of proteomics approach to eye diseases affecting the anterior segment

Visual impairment and blindness is a major health burden worldwide, and major ocular diseases causing visual impairment pertain to the anterior segment of the eye. Anterior segment ocular diseases are common, yet complex entities. Although many treatment options and surgical techniques are available for these ailments, the underlying cause and pathogenesis is still unclear. Finding ways to fundamentally treat these patients and rectify the underlying dysregulations leading to the disease may help cure patients completely without major complications. Proteomics approaches are a novel way to distinguish dysregulated proteins in a variety of biological tissues in a hypothesis-free manner, thus helping to find the responsible pathways leading to a certain disease. The aim of the current study is to review the available knowledge in scientific literature regarding the proteomics studies done on anterior segment eye diseases and suggest potential clinical implications to exploit the results of these studies. SIGNIFICANCE: Anterior segment ocular diseases are responsible for a major proportion of visual impairment and blindness worldwide. Although ophthalmologists have several treatment options that can alleviate or control the progression of these diseases, no definite cure is available for most of them. Moreover, because these diseases are progressive, prompt diagnosis is of utmost important. Proteomics studies enable us to identify and quantify the dysregulated proteins in a biological specimen in a hypothesis-free manner. Understanding the dysregulated protein pathways shines a light on the pathogenesis of the disease. Moreover, these dysregulated proteins may act as biomarkers to help in diagnosis and treatment follow-up. Hence, in this article we sought out to review the available scientific literature regarding the proteomics studies of anterior segment ocular diseases and to identify potential applications of proteomic studies in clinic.

Effect of rigid gas permeable contact lens on keratoconus progression: a review

The prevalence of keratoconus is 1/2000 in the general population and is high in adolescents. Keratoconus is a progressive disease, which has a great impact on patients' quality of life and mental health. It can be managed by surgical and non-surgical means, rigid gas permeable (RGP) contact lens as its main non-surgical method is widely used in clinic. The efficacy of wearing RGP contact lens has been confirmed to some extent, but some studies have found that wearing RGP contact lens has adverse effects, which may promote disease progression. In this paper, the advantages and disadvantages of RGP contact lens in controlling keratoconus were reviewed to provide more suggestions and references for the clinical application of RGP contact lens.

IgE Ratio in Tears: A Predictive Tool of Ocular Allergic Inflammation

PURPOSE

To demonstrate the tear IgE (measured/exuded) ratio (R) as a useful biological marker of ocular allergy in order to distinguish severe from less severe inflammatory status.

METHODS

Tear samples and sera from 78 ocular allergy patients and 19 control subjects were analyzed. Total IgE and albumin were measured for calculating the tear IgE-R defining two subgroups (SG) of samples: R ≥ 4-SG and R < 4-SG. Eosinophil cationic protein, Th1 and Th2 cytokines (IFN-γ, IL-4, -5, -6, -8 and -10) and protein electrophoretic profiles were also investigated in tears.

RESULTS

The R < 4-SG compared to the R ≥ 4-SG shows higher levels of tear albumin, eosinophil cationic protein, and Th1 and Th2 cytokines. Moreover, each subgroup presents a specific protein profile.

CONCLUSION

This study showed that an IgE-R lower than four must be carefully interpreted as a warning sign of a severe inflammatory context and should be also associated with an exploration of immunological profile.

Characterization of Tear Immunoglobulins in a Small-Cohort of Keratoconus Patients

Keratoconus (KC) is classically considered a non-inflammatory condition caused by central corneal thinning that leads to astigmatism and reduced visual acuity. Previous studies have identified increased systemic levels of pro-inflammatory factors, including interleukin-6, tumor necrosis factor-α, and matrix metalloproteinase-9, suggesting that KC may have an inflammatory component in at least a subset of patients. In this study, we evaluated the levels of different immunoglobulins (light and heavy chains) based on Ig α, Ig λ, Ig κ, Ig µ, and Ig heavy chain subunits in non-KC tears (n = 7 control individuals) and KC tears (n = 7 KC patients) using tandem-liquid chromatography mass spectrometry. The most abundant Ig heavy chains detected in both control individuals and KC patients were Ig α-1 and Ig α-2 likely correlating to the higher IgA levels reported in human tears. We identified significant differences in immunoglobulin κ-chain V-II levels in KC patients compared to control individuals with no significant difference in Ig κ/Ig λ ratios or heavy chain levels. Our study supports previous findings suggesting that KC possesses a systemic component that may contribute to the KC pathology. Further studies are required to define causality and establish a role for systemic immune system-dependent factors and pro-inflammatory processes in KC development or progression.

Nanogel receptors for high isoelectric point protein detection: influence of electrostatic and covalent polymer-protein interactions

An aldehyde acrylate-based functional monomer was incorporated into poly(N-isopropylacrylamide-co-methacrylic acid) nanogels for use as protein receptors. The aldehyde component forms dynamic imines with surface exposed lysine residues, while carboxylic acid/carboxylate moieties form electrostatic interactions with high isoelectric point proteins. Together, these interactions effect protein adsorption and recognition.

Levels of lactoferrin, lysozyme and albumin in the tear film of keratoconus patients and their correlations with important parameters of the disease

Background: Despite the fact that keratoconus has been tipically defined as a noninflammatory condition, recent research has promoted the role of inflammatory factors and protein changes of tear film in disease progression.

Aims: to determine the level of serum albumin, lactoferrin and lyzozyme in tears of keratoconic patients and their correlations with corneal biomechanical properties.

Subjects and methods: 16 eyes of keratoconus patients and 14 eyes of control cases were enrolled in an observational prospective study. We performed a complete ophthalmological examination on all participants. In order to determine the concentration of tear film proteins, a minimum of 20 microlitres of tears from the lower conjunctival fornix were collected from each subject and measured by enzyme-linked immunosorbent assay (ELISA) analysis.

Results: The level of lactoferrin measured in the tear film was significantly decreased in the keratoconus group compared to the normal subjects in all cases (p<0.05). We also found an increased level of lyzozyme and albumin in the keratoconus patients when compared to the controls, only the lyzozyme beeing statistically significant. In the keratoconus group, the correlations between proteins and important parameters such as keratometry, pachymetry and corneal biomechanics were statistically relevant in our study.

Conclusions: We can state that the protein composition of tears is modified in keratoconus by increased levels of protein with inflammatory properties such as albumin or by decreased levels of protein with anti-inflammatory properties such as lactoferrin.

Tear Mediators NGF along with IL-13 Predict Keratoconus Progression

Purpose: To find immunomediator combinations which could sensitively indicate keratoconus progression.Methods: Tear samples of 42 patients with keratoconus were collected at baseline and at the end of a one-year follow-up. The concentrations of 13 mediators were measured by CBA. Based on Pentacam HR examination, eyes were divided into a non-progressive and a progressive group.Results: At the end of the follow-up, significant differences were observed in the release of IFNγ, IL-13, IL-17A, CCL5, MMP-13 and PAI-1 between the two groups. Changes in five Pentacam parameters correlated positively with changes in IFNγ, IL-13, IL-17A, CXCL8, CCL5, TIMP-1 and t-PA. We found that tear level of IL-13 in combination with NGF can predict the progression of keratoconus with 100% specificity and 80% sensitivity.Conclusion: The findings of our longitudinal study may underscore the importance of NGF and IL-13 tear levels in the prediction of keratoconus progression.

Tear film, contact lenses and tear biomarkers

This article summarises research undertaken since 1993 in the Willcox laboratory at the University of New South Wales, Sydney on the tear film, its interactions with contact lenses, and the use of tears as a source of biomarkers for ocular and non-ocular diseases. The proteome, lipidome and glycome of tears all contribute to important aspects of the tear film, including its structure, its ability to defend the ocular surface against microbes and to help heal ocular surface injuries. The tear film interacts with contact lenses in vivo and interactions between tears and lenses can affect the biocompatibility of lenses, and may be important in mediating discomfort responses during lens wear. Suggestions are made for follow-up research.

Clinical and biochemical analysis of the ageing tear film

BACKGROUND

Tear film stability is important for healthy visual function, and yet little is known of the ageing mechanisms. The aim of this study was to investigate parallels between biochemical changes and clinical physical parameters, which occur in the tear film of two subject populations differing in age by over 30 years.

METHODS

Two distinct age groups were chosen: 11 'younger' (23.7±2.1 years) and 19 'older' (63.0±4.0 years) subjects. A series of clinical tests were performed to access tear volume, tear film stability and general ocular health. Tear protein analyses from extracted Schirmer strips were conducted with the Agilent 2100 Bioanalyzer.

RESULTS

Clinical investigations highlighted significant differences between the age groups. For example: McMonnies scores (p=0.009) and bulbar redness (p=0.038) were higher for the older group, whereas tear meniscus height was larger (p=0.018) in the younger group. Similarly, relative plasma-derived albumin levels were higher (17.1%±12.4%) in the tears of the older, compared with the younger (5.0%±9.6%) group. A protein peak at ∼23 kDa was observed in 53% of the older group samples but in only 36% of the samples of the younger subjects (p=0.122).

CONCLUSIONS

Distinct differences in tear film composition between the two age groups were observed. Parallels in terms of clinical symptoms which reflected a biochemical response (and vice versa) were found, but specific correlations between clinical measurements and biomarkers for individual subjects were not observed.

A Review of Structural and Biomechanical Changes in the Cornea in Aging, Disease, and Photochemical Crosslinking

The study of corneal biomechanics is motivated by the tight relationship between biomechanical properties and visual function within the ocular system. For instance, variation in collagen fibril alignment and non-enzymatic crosslinks rank high among structural factors which give rise to the cornea's particular shape and ability to properly focus light. Gradation in these and other factors engender biomechanical changes which can be quantified by a wide variety of techniques. This review summarizes what is known about both the changes in corneal structure and associated changes in corneal biomechanical properties in aging, keratoconic, and photochemically crosslinked corneas. In addition, methods for measuring corneal biomechanics are discussed and the topics are related to both clinical studies and biomechanical modeling simulations.

Tears and ocular surface disorders: Usefulness of biomarkers

INTRODUCTION

Corroborating data suggest that the analysis of tear fluid might represent an additional tool in the ophthalmological practice.

AREAS COVERED

The purpose of this review was to sum up the tear protein profiles in healthy and diseased ocular surface and to highlight biomarker usefulness in the early diagnosis as well as at follow-up. This analysis encompasses a deep examination of the protein profile expression under physiological and pathological conditions. Tear protein profile analysis will allow in the near future discriminating between different grades of inflammation, from acute trauma toward immune-, endocrine-, and nervous-related disorders of the ocular surface.

CONCLUDING REMARKS

The review provides an overview of old and recent findings about inflammatory mediators identified at the ocular surface, under physiological and pathological conditions. To date, the analysis of tear fluid represents a new additional approach for diagnosis and management of ocular surface diseases. Understanding the pathophysiological mechanism could also offer significant advantages to develop strategies addressed to better clarify some complex ocular surface disorders. To sum up, the possibility to provide selective biomarkers as a future target of specific diseases should be considered for supporting diagnosis and management of ocular surface diseases.

Comparative proteome analysis of the tear samples in patients with low-grade keratoconus

PURPOSE

To elucidate the metabolic processes playing roles in the formation of keratoconus (KC).

METHODS

Tears samples were collected using capillary glass tubes without stimulation and without prior anesthesia from 17 patients and 16 controls. Proteomic analysis by fluorescent 2D gel electrophoresis (DIGE) coupled with MALDI-TOF/TOF was performed. The identified proteins that were differentially regulated were subjected to Ingenuity Pathway Analysis (IPA). Corneal topography analyses with Sirius topography system (Costruzioni Strumenti Oftalmici, Florence, Italy) were performed on all participants. The steepest keratometry index was lower than 50 diopters in all keratoconus patients.

RESULTS

DIGE analysis showed changes in abundance of nine proteins. Six of these proteins, namely serum albumin, Keratin Type II Cytoskeletal 1, IgG gamma chain-1, GAPDH, alpha-1 antitrypsin and ApoA-I, were down-regulated in the KC samples in comparison with the controls. In addition, we detected up-regulation of lysozyme C, keratin type I cytoskeletal 10 and lipocalin. The subsequent IPA predicted that NADH repair pathway is activated in the KC patients. This pathway involves generation of NADHX as a by-product via catalysis by GAPDH. NADHX is an inhibitor of several dehydrogenases and must be removed.

CONCLUSION

The involvement of NADHX repair pathway in KC should be investigated, since preliminary clues obtained in this study point to that direction. In particular, showing the presence of ATP-dependent NAD(P)H-hydrate dehydratase that eliminates NADHX would strengthen our findings and would be a major step toward understanding KC.

Label-Free Detection of Tear Biomarkers Using Hydrogel-Coated Gold Nanoshells in a Localized Surface Plasmon Resonance-Based Biosensor

The dependence of the localized surface plasmon resonance (LSPR) of noble-metal nanomaterials on refractive index makes LSPR a useful, label-free signal transduction strategy for biosensing. In particular, by decorating gold nanomaterials with molecular recognition agents, analytes of interest can be trapped near the surface, resulting in an increased refractive index surrounding the nanomaterial, and, consequently, a red shift in the LSPR wavelength. Ionic poly( N-isopropylacrylamide- co-methacrylic acid) (PNM) hydrogels were used as protein receptors because PNM nanogels exhibit a large increase in refractive index upon protein binding. Specifically, PNM hydrogels were synthesized on the surface of silica gold nanoshells (AuNSs). This composite material (AuNS@PNM) was used to detect changes in the concentration of two protein biomarkers of chronic dry eye: lysozyme and lactoferrin. Both of these proteins have high isoelectric points, resulting in electrostatic attraction between the negatively charged PNM hydrogels and positively charged proteins. Upon binding lysozyme or lactoferrin, AuNS@PNM exhibits large, concentration-dependent red shifts in LSPR wavelength, which enabled the detection of clinically relevant concentration changes of both biomarkers in human tears. The LSPR-based biosensor described herein has potential utility as an affordable screening tool for chronic dry eye and associated conditions.