Discovery of microRNA expression profiles involved in regulating TGF-2 expression in the tears of dry eye patients

MicroRNA expression profiling in tears and blood as predictive biomarkers for anti-VEGF treatment response in wet age-related macular degeneration

PURPOSE

This study aimed to investigate the potential of microRNAs (miRNAs) in tears, blood, and aqueous humor as biomarkers for predicting treatment response in wet age-related macular degeneration (AMD) patients undergoing anti-vascular endothelial growth factor (anti-VEGF) therapy.

METHODS

In a single-center prospective cohort study, treatment-naïve wet AMD patients and age-matched controls were enrolled. Clinical data and miRNA levels (miR-199a-3p, miR-365-3p, miR-200b-3p, miR-195-5p, miR-335-5p, and miR-185-5p) in tears, blood, and aqueous humor were collected. Treatment response was categorized into responders and non-responders based on visual acuity and central subfield thickness. MiRNA levels were quantified using reverse-transcription PCR. Statistical analyses were performed, including ROC analysis, to evaluate predictive accuracy.

RESULTS

Dysregulated miRNA profiles were observed in wet AMD tears and blood compared to controls. Specifically, miR-199a-3p, miR-195-5p, and miR-185-5p were upregulated, while miR-200b-3p was downregulated in tears. All six miRNAs were elevated in wet AMD blood samples. Notably, responders showed higher tear expression of miR-195-5p and miR-185-5p. Combining these miRNAs yielded the highest predictive power (AUC = 0.878, p = 0.006) for anti-VEGF responders.

CONCLUSIONS

Dysregulated miRNA profiles in tears and blood suggest their potential as biomarkers for wet AMD. MiR-195-5p and miR-185-5p in tears demonstrate predictive value for anti-VEGF treatment responders. This study underscores the non-invasive prediction potential of miRNA tear analysis in wet AMD treatment responses.

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.

Tear Film MicroRNAs as Potential Biomarkers: A Review

MicroRNAs are non-coding RNAs that serve as regulatory molecules in a variety of pathways such as inflammation, metabolism, homeostasis, cell machinery, and development. With the progression of sequencing methods and modern bioinformatics tools, novel roles of microRNAs in regulatory mechanisms and pathophysiological states continue to expand. Advances in detection methods have further enabled larger adoption of studies utilizing minimal sample volumes, allowing the analysis of microRNAs in low-volume biofluids, such as the aqueous humor and tear fluid. The reported abundance of extracellular microRNAs in these biofluids has prompted studies to explore their biomarker potential. This review compiles the current literature reporting microRNAs in human tear fluid and their association with ocular diseases including dry eye disease, Sjögren's syndrome, keratitis, vernal keratoconjunctivitis, glaucoma, diabetic macular edema, and diabetic retinopathy, as well as non-ocular diseases, including Alzheimer's and breast cancer. We also summarize the known roles of these microRNAs and shed light on the future progression of this field.

Key methodological challenges in detecting circulating miRNAs in different biofluids

The technological advancement in diagnostic techniques has immensely improved the capability of predicting disease progression. Yet, there is a great interest in developing newer biomarkers that can enhance disease risk prediction thereby minimising the associated morbidity and mortality. Circulating miRNAs, a non-coding RNA molecule, are critical regulators in the pathophysiology of various complex multifactorial diseases. In recent years, circulating miRNAs have been enormously studied and are considered as an emerging biomarker due to their easy accessibility, stability, and detection by sequence-specific amplification methods. However, there is a distinct lack of consensus regarding the preanalytical factors such as preferred sample selection, methodological aspects, etc that may independently or together influence the detection of circulating miRNAs resulting in erroneous expression profiles. Therefore, the present review makes an attempt to highlight the various pre-analytical and analytical factors that can potentially influence the circulating miRNA levels. Literature on circulating miRNA's stability, processing and quantitation in different biofluids along with the effect of various controllable and uncontrollable factors influencing circulating miRNA expression have been summarised in the current review.

Conjunctival Intraepithelial Lymphocytes, Lacrimal Cytokines and Ocular Commensal Microbiota: Analysis of the Three Main Players in Allergic Conjunctivitis

Conjunctival intraepithelial lymphocytes, tear soluble molecules and commensal microbiota have important roles in the ocular mucosal immune response in healthy and diseased subjects. For the purpose of this study, the cellular and microbial populations of the conjunctiva and the lacrimal soluble molecules were analyzed to find the main biomarkers in allergic conjunctivitis. A total of 35 healthy subjects, 28 subjects with seasonal allergic conjunctivitis and 32 subjects with perennial allergic conjunctivitis were recruited to obtain peripheral blood, conjunctival brush cytology, tear fluid and microbiota samples. Flow cytometry for lymphocytes, multiplex bead assays for cytokines and high-throughput DNA sequencing for microbiome analysis were used. For perennial allergic conjunctivitis, an increased proportion of Th2 and NKT lymphocytes was found, while CD3+TCRγδ+ lymphocytes and double negative MAIT cells were decreased. In contrast, seasonal allergic conjunctivitis was distinguished by an increase in Th17 and Th22 cell proportions, while the Th1 cell proportion decreased. Among tear fluid, the vast majority of pro-inflammatory cytokines (especially Th2 and Th17 cytokines) in perennial allergies and MMP-9 together with IgA in seasonal allergies were increased. In contrast, TGF-β2 was decreased in both forms of conjunctivitis. Finally, fungal (Malassezia species) and bacterial (Kocuria and Propionobacterium acnes species) colonization were observed in the perennial allergic conjunctivitis group. These results provide the basis for the development of a disease profile for perennial allergic conjunctivitis and open the door to new therapeutic and diagnostic strategies.

MicroRNA Profiling of the Tears of Children With Vernal Keratoconjunctivitis

Vernal Keratoconjunctivitis (VKC) is a chronic conjunctival inflammatory condition that typically affects children. Extracellular microRNAs (miRNAs) are small noncoding RNA molecules, the expression of which is reported to regulate cellular processes implicated in several eye diseases. The aim of this preliminary study is to identify the miRNA expression profile in the tears of children with VKC vis-à-vis controls, and to statistically evaluate these miRNAs as potential diagnostic biomarkers of VKC. The study involved a VKC group and a control group. Tear specimens were collected using Schirmer’s strips. RNA was isolated using miRNeasy Micro kit and quantification was performed using an Agilent Bioanalyzer RNA 6000 Nano kit and Small RNA kit. miRNA profiling was performed using the Agilent microarray technique. A total of 51 miRNAs (48 upregulated and three downregulated) were differentially expressed in the tears of children with VKC and controls. The three most significantly upregulated miRNAs were hsa-miR-1229-5p, hsa-miR-6821-5p, and hsa-miR-6800-5p, and the three most significantly downregulated miRNAs were hsa-miR-7975, hsa-miR-7977, and hsa-miR-1260a. All the upregulated miRNAs are potential diagnostic biomarkers of VKC pending validation due to their larger discriminatory area under the curve (AUC) values. miRNA target prediction analysis revealed multiple overlapping genes that are known to play a role in conjunctival inflammation. We identified a set of differentially expressed miRNAs in the tears of children with VKC that may play a role in VKC pathogenesis. This study serves as the platform study for future miRNA studies that will provide a deeper understanding of the pathophysiology of VKC.

MicroRNA Therapy for Dry Eye Disease

Purpose: We tested the role of microRNA-328 in dry eye disease (DED). Benzalkonium chloride (BAC) has been used to induce DED in animal models. We first demonstrated that both BAC and hyperosmotic stress induced overexpression of miR-328 in corneal cells and then tested whether anti-miR-328 could be a new therapy. Methods: BAC was instilled to both eyes of 41 rabbits and 19 mice from day 0 to 21 to induce DED. Animals of each species were divided to receive topical instillation of saline or anti-miR-328 eye drops between day 8 and 21. The DED signs were assessed by corneal fluorescein staining, histological examination, apoptosis of corneal cells, and inflammatory cytokines in rabbit eyes. For mice, only corneal fluorescein staining was assessed for the therapeutic effects. The corneal fluorescein staining scores ranged from 0 of no staining to 4 of coalescent. Results: For the rabbits, the staining score was significantly reduced (P = 0.038) after the 14-day anti-miR-328 treatment (n = 42 eyes), but the score was not improved by saline treatment (n = 40 eyes). Furthermore, rabbit eyes treated with anti-miR-328 had thicker corneal epithelium (P = 9.4 × 10^-5), fewer apoptotic cells in corneal epithelium (P = 0.002), and stroma (P = 0.029) compared with the saline-treated eyes. Anti-miR-328 was more effective than saline to reduce the block of orifices of Meibomian glands, although such an effect was only marginally significant (P = 0.059). Similarly, anti-miR-328 was more effective than saline in reducing corneal staining in mouse eyes (P = 0.005). Conclusion: Overexpression of miR-328 may contribute to DED. Anti-miR-328 protects corneal cells and promotes re-epithelialization for DED treatment.