Evaluation of tear and aqueous humor level, and genetic variants of connective tissue growth factor as biomarkers for early detection of pseudoexfoliation syndrome/glaucoma

Circulating miRNAs and their functional genetic variants in pseudoexfoliative glaucoma: potential of miR-146a-5p as a diagnostic biomarker

PURPOSE

The etiology and pathogenesis of pseudoexfoliation syndrome (PEX) and its advancement into pseudoexfoliative glaucoma (PEG) are not fully understood. In this study, we aimed to evaluate the possible role played by two circulating microRNAs (miR-146a-5p and miR-196a-5p) in plasma and their functional genetic variants MIR146A rs2910164 and MIR196A2 rs11614913 in susceptibility to PEG or PEX.

METHODS

Plasma miRNA relative expression of 27 patients with PEG, 25 patients with PEX and 27 controls was determined using quantitative RT-PCR, and fold change was calculated using the 2-ΔΔCt method. Genotyping of 300 patients with PEG, 300 patients with PEX, and 300 controls was performed using a PCR-restriction fragment length polymorphism analysis.

RESULT

Plasma miR-146a-5p relative expression was significantly elevated in patients with PEG (3.9-fold) (P < .000) and patients with PEX (2.7-fold) relative to controls (P = .001). The diagnostic ability of plasma miR-146a-5p expression fold change was good for discriminating PEG vs. controls (AUC = 0.897, P < .000), and the optimal decision threshold was 1.83 (sensitivity = 74%, specificity = 93%). Plasma miR-196a-5p relative expression did not differ significantly between study groups. No significant difference in terms of the minor allele frequency or the distribution of genotypes for MIR146A rs2910164 G/C or MIR196A2 rs11614913 C/T was observed between study groups.

CONCLUSIONS

Circulating miR-146a-5p can contribute to the risk of PEX/PEG. Therefore, we propose that plasma miR-146a-5p can be developed as a potential biomarker for the minimally invasive diagnoses of PEX/PEG and as a potential therapeutic target with further studies.

Dickkopf-1 and ROCK2 upregulation and associated protein aggregation in pseudoexfoliation syndrome and glaucoma

AIMS

The etiology of pseudoexfoliation (PEX), a stress-induced fibrillopathy and a leading cause of secondary glaucoma worldwide, remains limited. This study aims to understand the role of the Wnt antagonist Dickkopf-related protein 1 (DKK1) in PEX pathophysiology and assess its candidature as a biomarker for PEX.

MAIN METHODS

Expression levels of DKK1 and Wnt signaling genes were assayed in the anterior ocular tissues of study subjects by qRT-PCR, Western blotting, and immunohistochemistry. Protein aggregation was studied through Proteostat staining. Role of DKK1 in protein aggregation and regulation of target Wnt signaling genes was elucidated through overexpression and knockdown studies in Human Lens Epithelial cells (HLEB3). Levels of DKK1 in circulating fluids were assayed through ELISA.

KEY FINDINGS

DKK1 upregulation was observed in lens capsule and conjunctiva tissues of PEX individuals compared to controls correlating with an upregulation of the Wnt signaling target, ROCK2. Proteostat staining showed increased protein aggregates in lens epithelial cells of PEX patients. HLE B-3 cells overexpressed with DKK1 showed increased protein aggregates along with upregulation of ROCK2, and knockdown of DKK1 in HLE B-3 cells demonstrated downregulation of ROCK2. Further, ROCK2 inhibition by Y-27632 in DKK1 overexpressed cells showed that DKK1 regulated protein aggregation via ROCK2. Also, increased levels of DKK1 were observed in patients' plasma and aqueous humor compared to controls.

SIGNIFICANCE

This study shows that DKK1 and ROCK2 might play a role in protein aggregation in PEX. Further, elevated levels of DKK1 in aqueous humor serve as a fair classifier of pseudoexfoliation glaucoma.

Influence of clusterin genetic variants on IOP elevation in pseudoexfoliation syndrome and pseudoexfoliative glaucoma in Turkish population

PURPOSE

Pseudoexfoliation syndrome (PEX) is distinguished by the deposition of fibrillary material within the aqueous humor and, in most cases, causes pseudoexfoliative glaucoma (PEG). The pathophysiologies of PEX and PEG are not completely explained. Therefore, this study aimed to assess the potential relationship between single nucleotide polymorphisms (SNPs) in the 3' untranslated region or introns of the clusterin gene (CLU) and the susceptibility to developing PEG or PEX.

METHODS

Two hundred and forty patients with PEX, 239 patients with PEG, and 240 control subjects were included. Genotyping was carried out using real-time PCR (rs2279590 C/T and rs1532278 C/T) or PCR followed by restriction endonuclease digestion (rs11136000 C/T and rs3087554 T/C).

RESULTS

The minor alleles or genotypes of CLU SNPs were not significantly associated with PEX or PEG. IOP values of patients with PEX carrying the homozygote polymorphic TT genotype were significantly elevated compared with PEX cases with the CT or CC genotypes for rs2279590, rs11136000 and rs1532278 (P = .009, P = .007, P = .010, respectively).

CONCLUSION

We present the first evidence that three SNPs in CLU gene (rs2279590, rs11136000 and rs1532278) might induce a rise in IOP in patients with PEX, conferring susceptibility to develop PEG.

Changes in Tear Proteomic Profile in Ocular Diseases

The search for proteomic biomarkers in ocular disease is one of the most important research directions in recent years. Reliable biomarkers can be an immense adjuvant for both diagnostic and therapeutic approaches. There is no more readily available ocular tissue for proteomic analysis than tear film, which makes an interesting target for the biomarker search. Tear film is a complex fluid consisting of a superficial lipid layer, which covers the aqueous-mucous layer. Its complexity makes it a perfect candidate for all the "omics" approaches. Glaucoma, cataract, age-related macular degeneration, and other diseases are commonly thought to have a multifactorial background. Currently, no reliable non-invasive tests are available that would help physicians with screening and further patient management. The aim of the study is to present modern methods of measuring biomarkers in tears, with particular emphasis on spectrometric methods, and to discuss their diagnostic and therapeutic usefulness.

Clinical Tear Fluid Proteomics—A Novel Tool in Glaucoma Research

Tear fluid forms the outermost layer of the ocular surface and its characteristics and composition have been connected to various ocular surface diseases. As tear proteomics enables the non-invasive investigation of protein levels in the tear fluid, it has become an increasingly popular approach in ocular surface and systemic disease studies. Glaucoma, which is a set of multifactorial diseases affecting mainly the optic nerve and retinal ganglion cells, has also been studied using tear proteomics. In this condition, the complete set of pathophysiological changes occurring in the eye is not yet fully understood, and biomarkers for early diagnosis and accurate treatment selection are needed. More in-depth analyses of glaucoma tear proteomics have started to emerge only more recently with the implementation of LC-MS/MS and other modern technologies. The aim of this review was to examine the published data of the tear protein changes occurring during glaucoma, its topical treatment, and surgical interventions.

Single nucleotide variants around the connective tissue growth factor (CTGF/CCN2) gene and their association with multiple sclerosis risk, disability scores, and rate of disease progression

BACKGROUND

This study aimed to explore the possible association of single nucleotide polymorphisms (SNPs) in the upstream (rs9402373) and downstream regions (rs9399005 and rs12526196) of the gene encoding connective tissue growth factor (CTGF/CCN2) with relapsing-remitting multiple sclerosis (RRMS) risk and clinical parameters including disability scores and rate of disability progression.

MATERIALS AND METHODS

In total, 200 patients with RRMS and 305 controls were genotyped using real-time PCR (rs1252696 C/T and rs9402373 G/C) or PCR-RFLP (rs9399005 C/T) methods. Furthermore, the association between these genotypes and clinical parameters including Expanded Disability Status Scale (EDSS) score, Multiple Sclerosis Severity Score (MSSS), age at onset, duration of disease, duration of treatment, and presence of contrast-enhancing lesions was analyzed.

RESULTS

rs9399005 genotypes TT and CT in the dominant model were significant predictors of RRMS vs. control status by logistic regression analysis (OR = 1.45, 95% CI = 1.01-2.08, P = .04). Moreover, these genotypes for rs9399005 were associated with a MSSS ≥ 2.4 (OR = 3.54, 95% CI = 1.56-8.05, P = .003). In addition, MSSS was lower in patients who had at least one rs12526196C allele than in the corresponding patients with the TT genotype (P = .02).

CONCLUSION

To our knowledge, this is the first evidence of the involvement of variants around the CTGF gene in MS risk and disability progression.

Multifunctional regulatory protein connective tissue growth factor (CTGF): A potential therapeutic target for diverse diseases

Connective tissue growth factor (CTGF), a multifunctional protein of the CCN family, regulates cell proliferation, differentiation, adhesion, and a variety of other biological processes. It is involved in the disease-related pathways such as the Hippo pathway, p53 and nuclear factor kappa-B (NF-κB) pathways and thus contributes to the developments of inflammation, fibrosis, cancer and other diseases as a downstream effector. Therefore, CTGF might be a potential therapeutic target for treating various diseases. In recent years, the research on the potential of CTGF in the treatment of diseases has also been paid more attention. Several drugs targeting CTGF (monoclonal antibodies FG3149 and FG3019) are being assessed by clinical or preclinical trials and have shown promising outcomes. In this review, the cellular events regulated by CTGF, and the relationships between CTGF and pathogenesis of diseases are systematically summarized. In addition, we highlight the current researches, focusing on the preclinical and clinical trials concerned with CTGF as the therapeutic target.

Candidate Glaucoma Biomarkers: From Proteins to Metabolites, and the Pitfalls to Clinical Applications

Glaucoma is an insidious group of eye diseases causing degeneration of the optic nerve, progressive loss of vision, and irreversible blindness. The number of people affected by glaucoma is estimated at 80 million in 2021, with 3.5% prevalence in people aged 40-80. The main biomarker and risk factor for the onset and progression of glaucoma is the elevation of intraocular pressure. However, when glaucoma is diagnosed, the level of retinal ganglion cell death usually amounts to 30-40%; hence, the urgent need for its early diagnosis. Molecular biomarkers of glaucoma, from proteins to metabolites, may be helpful as indicators of pathogenic processes observed during the disease's onset. The discovery of human glaucoma biomarkers is hampered by major limitations, including whether medications are influencing the expression of molecules in bodily fluids, or whether tests to validate glaucoma biomarker candidates should include human subjects with different types and stages of the disease, as well as patients with other ocular and neurodegenerative diseases. Moreover, the proper selection of the biofluid or tissue, as well as the analytical platform, should be mandatory. In this review, we have summarized current knowledge concerning proteomics- and metabolomics-based glaucoma biomarkers, with specificity to human eye tissue and fluid, as well the analytical approach and the main results obtained. The complex data published to date, which include at least 458 different molecules altered in human glaucoma, merit a new, integrative approach allowing for future diagnostic tests based on the absolute quantification of local and/or systemic biomarkers of glaucoma.

Native fluorescence of tear fluid as a tool for diagnostics of glaucoma

Glaucoma is one of the leading causes of irreversible vision loss worldwide. There is an enormous need for the detection of its early stages and also speeding up and simplifying regular examinations. Among the new diagnostic approaches, the use of tear fluid has been intensively investigated in recent years. For this purpose, we analyzed the tear fluid of patients with glaucoma and related diseases. To sensitively capture the subtle ocular abnormalities related to glaucoma and manifested in tear fluid, we used synchronous fluorescence spectroscopy. In this observational case-control study, we detected significant differences in the intensity of tear fluid fluorescence located at λ ex/Δλ = 280/70 nm between the groups of primary open-angle glaucoma (p < 0.01), suspected glaucoma (p < 0.0001), and ocular hypertension (p < 0.05), when compared to the healthy control group. The signal was not significantly higher in women than in men (p = 0.05), and no correlation was found with age (r = -0.05, p > 0.05), nor treatment (p > 0.05). Taken together, tear fluid fluorescence could serve as a discriminative parameter between patients with glaucoma, related diseases, and healthy control subjects and might contribute to the improvement of diagnostics of these diseases.