Canonical Wnt Signaling Drives Myopia Development and Can Be Pharmacologically Modulated

Regulatory Effects of the Wnt7b/β-Catenin/MMP-2 Signaling Pathway on Scleral Stiffness in Guinea Pigs With Form-Deprivation Myopia

Purpose

The development and progression of myopia are influenced by the Wnt7b/β-catenin signaling pathway. This study investigated the specific impacts of this pathway on the biomechanical properties of the sclera by altering the expression of matrix metalloproteinase-2 (MMP-2) to regulate type I collagen (collagen I) levels.

Methods

We examined the effects of the Wnt7b/β-catenin signaling pathway and MMP-2 on human fetal scleral fibroblasts (HFSFs) and the sclera of guinea pigs with form-deprivation myopia (FDM). To explore the effects of the Wnt7b/β-catenin pathway and the role of MMP-2 in this context, we treated HFSFs and guinea pig sclera with specific agonists and inhibitors targeting Wnt7b/β-catenin and MMP-2. The expression levels of Wnt7b, MMP-2, and collagen I were subsequently analyzed quantitatively via western blot (WB) analysis, immunofluorescence, and quantitative real-time PCR (qRT-PCR) to assess protein and mRNA changes in response to pathway manipulation. Atomic force microscopy (AFM) was used to measure the elastic modulus of the treated HFSFs and guinea pig sclera to directly evaluate changes in cell and tissue stiffness. In the FDM model, essential ocular parameters such as refractive error and axial length (AL) were also assessed.

Results

In vivo and in vitro activation of the Wnt7b/β-catenin signaling pathway significantly upregulated MMP-2 expression, which was accompanied by a notable decrease in collagen I levels. This change led to a reduction in the elastic modulus of both HFSFs and the sclera of guinea pigs with FDM. These significant biomechanical changes in the scleral tissue were indicated by a reduction in stiffness. Alterations in scleral biomechanics were associated with changes in ocular parameters, including an increase in AL and a myopic shift in refraction.

Conclusions

The Wnt7b/β-catenin pathway regulates scleral biomechanics by upregulating MMP-2 expression, which leads to increased collagen I degradation and, consequently, an increase in axial elongation and a myopic shift in refractive error.

Inhibitory effect of Zhujing Pill on myopia progression: Mechanistic insights based on metabonomics and network pharmacology

OBJECTIVES

This study endeavored to uncover the mechanisms by which Zhujing pill (ZJP) slows myopia progression.

METHODS

We employed biometric analyses to track diopter and axial length changes in guinea pigs with negative lens-induced myopia (LIM). Through integrating metabonomics and network pharmacology, we aimed to predict the anti-myopic targets and active ingredients of ZJP. Subsequent analysis, including real-time fluorescent quantitative PCR (qPCR) and Western blotting (WB), assessed the expression levels of CHRNA7, LPCAT1, and NOS2 in retinal tissues.

KEY FINDINGS

Our findings demonstrate that ZJP significantly mitigates diopter increase and axial elongation in LIM guinea pigs. Metabonomic analysis revealed significant changes in 13 serum metabolites, with ZJP reversing the expression of 5 key metabolites. By integrating metabonomics with network pharmacology, we identified core targets of ZJP against myopia and constructed a compound-gene-disease-metabolite network. The expressions of LPCAT1 and CHRNA7 were found to decrease in the LIM group but increase with ZJP treatment, whereas NOS2 expression showed the opposite pattern.

CONCLUSIONS

This investigation provides the first evidence of ZJP's multifaceted effectiveness in managing myopia, highlighting its impact on multiple components, targets, and pathways, including the novel involvement of LPCAT1 and CHRNA7 in myopia pathogenesis.

Insights into Myopia from Mouse Models

Animal models are critical for understanding the initiation and progression of myopia, a refractive condition that causes blurred distance vision. The prevalence of myopia is rapidly increasing worldwide, and myopia increases the risk of developing potentially blinding diseases. Current pharmacological, optical, and environmental interventions attenuate myopia progression in children, but it is still unclear how this occurs or how these interventions can be improved to increase their protective effects. To optimize myopia interventions, directed mechanistic studies are needed. The mouse model is well-suited to these studies because of its well-characterized visual system and the genetic experimental tools available, which can be combined with pharmacological and environmental manipulations for powerful investigations of causation. This review describes aspects of the mouse visual system that support its use as a myopia model and presents genetic, pharmacological, and environmental studies that significantly contribute to our understanding of the mechanisms that underlie myopigenesis.

Identification of Potential Drug Targets for Myopia Through Mendelian Randomization

Purpose

The purpose of this study was to identify potential drug targets for myopia and explore underlying mechanisms.

Methods

Mendelian randomization (MR) was implemented to assess the effect of 2684 pharmacologically targetable genes in the blood and retina on the risk of myopia from a genomewide association study (GWAS) for age-at-onset of spectacle wearing-inferred mean spherical equivalent (MSE; discovery cohort, N = 287,448, European), which was further validated in a GWAS for autorefraction-measured MSE (replication cohort, N = 95,619, European). The reliability of the identified significant potential targets was strengthened by colocalization analysis. Additionally, enrichment analysis, protein-protein interaction network, and molecular docking were performed to explore the functional roles and the druggability of these targets.

Results

This systematic drug target identification has unveiled 6 putative genetically causal targets for myopia-CD34, CD55, Wnt3, LCAT, BTN3A1, and TSSK6-each backed by colocalization evidence in adult blood eQTL datasets. Functional analysis found that dopaminergic neuron differentiation, cell adhesion, Wnt signaling pathway, and plasma lipoprotein-associated pathways may be involved in myopia pathogenesis. Finally, drug prediction and molecular docking corroborated the pharmacological value of these targets with LCAT demonstrating the strongest binding affinity.

Conclusions

Our study not only opens new avenues for the development of therapeutic interventions for myopia but may also help to understand the underlying mechanisms of myopia.

Diurnal gene expression patterns in retina and choroid distinguish myopia progression from myopia onset

The world-wide prevalence of myopia (nearsightedness) is increasing, but its pathogenesis is incompletely understood. Among many putative mechanisms, laboratory and clinical findings have implicated circadian biology in the etiology of myopia. Consistent with a circadian hypothesis, we recently reported a marked variability in diurnal patterns of gene expression in two crucial tissues controlling post-natal refractive development - the retina and choroid-at the onset of form-deprivation myopia in chick, a widely studied and validated model. To extend these observations, we assayed gene expression by RNA-Seq in retina and choroid during the progression of established unilateral form-deprivation myopia of chick. We assayed gene expression every 4 hours during a single day from myopic and contralateral control eyes. Retinal and choroidal gene expression in myopic vs. control eyes during myopia progression differed strikingly at discrete times during the day. Very few differentially expressed genes occurred at more than one time in either tissue during progressing myopia. Similarly, Gene Set Enrichment Analysis pathways varied markedly by time during the day. Some of the differentially expressed genes in progressing myopia coincided with candidate genes for human myopia, but only partially corresponded with genes previously identified at myopia onset. Considering other laboratory findings and human genetics and epidemiology, these results further link circadian biology to the pathogenesis of myopia; but they also point to important mechanistic differences between the onset of myopia and the progression of established myopia. Future laboratory and clinical investigations should systematically incorporate circadian mechanisms in studying the etiology of myopia and in seeking more effective treatments to normalize eye growth in children.

Canonical and noncanonical Wnt signaling: Multilayered mediators, signaling mechanisms and major signaling crosstalk

Wnt signaling plays a major role in regulating cell proliferation and differentiation. The Wnt ligands are a family of 19 secreted glycoproteins that mediate their signaling effects via binding to Frizzled receptors and LRP5/6 coreceptors and transducing the signal either through β-catenin in the canonical pathway or through a series of other proteins in the noncanonical pathway. Many of the individual components of both canonical and noncanonical Wnt signaling have additional functions throughout the body, establishing the complex interplay between Wnt signaling and other signaling pathways. This crosstalk between Wnt signaling and other pathways gives Wnt signaling a vital role in many cellular and organ processes. Dysregulation of this system has been implicated in many diseases affecting a wide array of organ systems, including cancer and embryological defects, and can even cause embryonic lethality. The complexity of this system and its interacting proteins have made Wnt signaling a target for many therapeutic treatments. However, both stimulatory and inhibitory treatments come with potential risks that need to be addressed. This review synthesized much of the current knowledge on the Wnt signaling pathway, beginning with the history of Wnt signaling. It thoroughly described the different variants of Wnt signaling, including canonical, noncanonical Wnt/PCP, and the noncanonical Wnt/Ca2+ pathway. Further description involved each of its components and their involvement in other cellular processes. Finally, this review explained the various other pathways and processes that crosstalk with Wnt signaling.

Identification of Rare Variants Involved in High Myopia Unraveled by Whole Genome Sequencing

Purpose

Myopia (nearsightedness) is a condition in which a refractive error (RE) affects vision. Although common variants explain part of the genetic predisposition (18%), most of the estimated 70% heritability is missing. Here, we investigate the contribution of rare genetic variation because this might explain more of the missing heritability in the more severe forms of myopia. In particular, high myopia can lead to blindness and has a tremendous impact on a patient and at the societal level. The exact molecular mechanisms behind this condition are not yet completely unraveled, but whole genome sequencing (WGS) studies have the potential to identify novel (rare) disease genes, explaining the high heritability.

Design

Cross-sectional study performed in the Netherlands.

Participants

We investigated 159 European patients with high myopia (RE > -10 diopters).

Methods

We performed WGS using a stepwise filtering approach and burden analysis. The contribution of common variants was calculated as a genetic risk score (GRS).

Main Outcome Measures

Rare variant burden, GRS.

Results

In 25% (n = 40) of these patients, there was a high (> 75th percentile) contribution of common predisposing variants; that is, these participants had higher GRSs. In 7 of the remaining 119 patients (6%), deleterious variants in genes associated with known (ocular) disorders, such as retinal dystrophy disease (prominin 1 [PROM1]) or ocular development (ATP binding cassette subfamily B member 6 [ABCB6], TGFB induced factor homeobox 1 [TGIF1]), were identified. Furthermore, without using a gene panel, we identified a high burden of rare variants in 8 novel genes associated with myopia. The genes heparan sulfate 6-O-sulfotransferase 1 (HS6ST1) (proportion in study population vs. the Genome Aggregation Database (GnomAD) 0.14 vs. 0.03, P = 4.22E-17), RNA binding motif protein 20 (RBM20) (0.15 vs. 0.06, P = 4.98E-05), and MAP7 domain containing 1 (MAP7D1) (0.19 vs. 0.06, P = 1.16E-10) were involved in the Wnt signaling cascade, melatonin degradation, and ocular development and showed most biologically plausible associations.

Conclusions

We found different contributions of common and rare variants in low and high grade myopia. Using WGS, we identified some interesting candidate genes that could explain the high myopia phenotype in some patients.

Financial Disclosures

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

The sleep quality- and myopia-linked PDE11A-Y727C variant impacts neural physiology by reducing catalytic activity and altering subcellular compartmentalization of the enzyme

Recently, a Y727C variant in the dual-specific 3',5'-cyclic nucleotide phosphodiesterase 11A (PDE11A-Y727C) was linked to increased sleep quality and reduced myopia risk in humans. Given the well-established role that the PDE11 substrates cAMP and cGMP play in eye physiology and sleep, we determined if 1) PDE11A protein is expressed in the retina or other eye segments in mouse, 2) PDE11A-Y7272C affects catalytic activity and/or subcellular compartmentalization more so than the nearby suicide-associated PDE11A-M878V variant, and 3) Pde11a deletion alters eye growth or sleep quality in male and female mice. Western blots show distinct protein expression of PDE11A4, but not PDE11A1-3, in eyes of Pde11a WT-but not KO mice-that vary by eye segment and age. In HT22 and COS-1 cells, PDE11A4-Y727C reduces PDE11A4 catalytic activity far more than PDE11A4-M878V, with both variants reducing PDE11A4-cAMP more so than PDE11A4-cGMP activity. Despite this, Pde11a deletion does not alter age-related changes in retinal or lens thickness, axial length, nor vitreous or anterior chamber depth. Further, Pde11a deletion only minimally changes refractive error and sleep quality. That said, both variants also dramatically alter the subcellular compartmentalization of human and mouse PDE11A4, an effect occurring independently of dephosphorylating PDE11A4-S117/S124 or phosphorylating PDE11A4-S162. Rather, re-compartmentalization of PDE11A4-Y727C is due to the loss of the tyrosine changing how PDE11A4 is packaged/repackaged via the trans-Golgi network. Therefore, the protective impact of the Y727C variant may reflect a gain-of-function (e.g., PDE11A4 displacing another PDE) that warrants further investigation in the context of reversing/preventing sleep disturbances or myopia.

Refractive Status and Biometric Characteristics of Children With Familial Exudative Vitreoretinopathy

Purpose

To compare biometric characteristics between patients with early-stage familial exudative vitreoretinopathy (FEVR) and healthy controls.

Methods

This case-control study included 50 FEVR eyes in stage 1-2 and 50 control eyes matched by age, gender and spherical equivalent (SE). Biometric parameters including axial length (AL), white-to-white diameter (WTW), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), pupil diameter, vitreous chamber depth, anterior and posterior corneal surface curvature radius (ACR and PCR), anterior lens surface curvature radius (ALR) and posterior lens surface curvature radius were measured using IOLMaster 700 and compared between cases and controls using paired t-test. Correlations between SE and biometric measures were assessed using Pearson correlation coefficient (r) in cases and controls.

Results

Both FEVR cases and matched controls had a mean age of 7.6 years, 48% female and mean SE of -5.3 D (80% myopia). Compared to controls, FEVR eyes had smaller AL (P = 0.009), WTW (P = 0.001), ACD (P < 0.001), and ALR (P = 0.03), but larger CCT (P = 0.02) and LT (P = 0.01). In FEVR eyes, SE was negatively correlated with AL (r = -0.79, P < 0.001), positively correlated with ACR (r = 0.29, P = 0.04) and PCR (r = 0.33, P = 0.02), whereas in controls, SE was negatively correlated with AL (r = -0.82, P < 0.001) and LT (r = -0.34, P = 0.02), positively correlated with ALR (r = 0.29, P = 0.04).

Conclusions

Patients at early stage of FEVR exhibited a unique eye morphology resembling ocular development arrest, which may help to develop screening and early detection tools for FEVR. In FEVR patients, myopia is very prevalent and significantly associated with corneal curvature increase.

Effects of inflammation on myopia: evidence and potential mechanisms

As the most common type of refractive error, myopia has become one of the leading causes of visual impairment. With the increasing prevalence of myopia, there is a growing need to better understand the factors involved in its development. Inflammation, one of the most fundamental pathophysiological processes in humans, is a rapid response triggered by harmful stimuli and conditions. Although controlled inflammatory responses are necessary, over-activated inflammation is the common soil for many diseases. The impact of inflammation on myopia has received rising attention in recent years. Elevated inflammation may contribute to myopia progression either directly or indirectly by inducing scleral remodeling, and myopia development may also increase ocular inflammation. This article provides a comprehensive review of the interplay between inflammation and myopia and the potential biological mechanisms, which may present new targets for understanding the pathology of myopia and developing myopia therapies.

Targeting choroidal vasculopathy via up-regulation of tRNA-derived fragment tRF-22 expression for controlling progression of myopia

BACKGROUND

Myopia has emerged as a major public health concern globally, which is tightly associated with scleral extracellular matrix (ECM) remodeling and choroidal vasculopathy. Choroidal vasculopathy has gradually been recognized as a critical trigger of myopic pathology. However, the precise mechanism controlling choroidal vasculopathy remains unclear. Transfer RNA-derived fragments (tRFs) are known as a novel class of small non-coding RNAs that plays important roles in several biological and pathological processes. In this study, we investigated the role of tRF-22-8BWS72092 (tRF-22) in choroidal vasculopathy and myopia progression.

METHODS

The tRF-22 expression pattern under myopia-related stresses was detected by qRT-PCR. MTT assays, EdU incorporation assays, Transwell migration assays, and Matrigel assays were conducted to detect the role of tRF-22 in choroidal endothelial cell function in vitro. Isolectin B4 staining and choroidal sprouting assay ex vivo were conducted to detect the role of tRF-22 in choroidal vascular dysfunction in vivo. Immunofluorescent staining, western blot assays and ocular biometric parameters measurement were performed to examine whether altering tRF-22 expression in choroid affects scleral hypoxia and ECM remodeling and myopia progression in vivo. Bioinformatics analysis and luciferase activity assays were conducted to identify the downstream targets of tRF-22. RNA-sequencing combined with m6A-qPCR assays were used to identify the m6A modified targets of METTL3. Gain-of-function and Loss-of-function analysis were performed to reveal the mechanism of tRF-22/METTL3-mediated choroidal vascular dysfunction.

RESULTS

The results revealed that tRF-22 expression was significantly down-regulated in myopic choroid. tRF-22 overexpression alleviated choroidal vasculopathy and retarded the progression of myopia in vivo. tRF-22 regulated choroidal endothelial cell viability, proliferation, migration, and tube formation ability in vitro. Mechanistically, tRF-22 interacted with METTL3 and blocked m6A methylation of Axin1 and Arid1b mRNA transcripts, which led to increased expression of Axin1 and Arid1b.

CONCLUSIONS

Our study reveals that the intervention of choroidal vasculopathy via tRF-22-METTL3- Axin1/Arid1b axis is a promising strategy for the treatment of patients with myopic pathology.

Presumed veterinary niclosamide-induced retinal toxicity in a human: a case report

BACKGROUND

To report the first case of bull's eye maculopathy associated with veterinary niclosamide.

CASE PRESENTATION

A 27-year-old Iranian female presented with a history of reduced vision and photopsia since 3 years, after accidental ingestion of four boluses of veterinary niclosamide. Fundus examination showed atrophy in parafoveal retinal pigmentary epithelium, appearing as bilateral bull's-eye maculopathy. Optical coherence tomography revealed disruption of the parafoveal ellipsoid zone and outer retinal thinning, appearing as a flying saucer sign. Electroretinography displayed decreased scotopic and photopic amplitudes with normal waveform in both eyes. The causality score was 4, showing "possible" retinopathy due to niclosamide according to Naranjo's causality assessment algorithm. Based on clinical and ancillary findings, a diagnosis of niclosamide-induced maculopathy was made.

CONCLUSION

Veterinary niclosamide is an anthelmintic drug that in higher doses could be detrimental to the human retina. Awareness about its side effects and appropriate drug labeling could prevent accidental toxicity.

Gap junction Delta-2b (gjd2b/Cx35.1) depletion causes hyperopia and visual-motor deficiencies in the zebrafish

The zebrafish is a powerful model to investigate the developmental roles of electrical synapses because many signaling pathways that regulate the development of the nervous system are highly conserved from fish to humans. Here, we provide evidence linking the mammalian connexin-36 (Cx36) ortholog gjd2b/Cx35.1, a major component of electrical synapses in the zebrafish, with a refractive error in the context of morphological, molecular, and behavioral changes of zebrafish larvae. Two abnormalities were identified. The optical coherence tomography analysis of the adult retina confirmed changes to the refractive properties caused by eye axial length reduction, leading to hyperopic shifts. The gjd2b/Cx35.1 depletion was also correlated with morphological changes to the head and body ratios in larvae. The differential expression of Wnt/ß-catenin signaling genes, connexins, and dopamine receptors suggested a contribution to the observed phenotypic differences. The alteration of visual-motor behavioral responses to abrupt light transitions was aggravated in larvae, providing evidence that cone photoreceptor cell activity was enhanced when gjd2b/Cx35.1 was depleted. The visual disturbances were reversed under low light conditions in gjd2b ^-/- /Cx35.1^-/- larvae. Since qRT-PCR data demonstrated that two rhodopsin genes were downregulated, we speculated that rod photoreceptor cells in gjd2b/Cx35.1^-/- larvae were less sensitive to bright light transitions, thus providing additional evidence that a cone-mediated process caused the VMR light-ON hyperactivity after losing Cx35.1 expression. Together, this study provides evidence for the role of gjd2b/Cx35.1 in the development of the visual system and visually guided behaviors.

Genome-wide association meta-analysis of 88,250 individuals highlights pleiotropic mechanisms of five ocular diseases in UK Biobank

BACKGROUND

Ocular diseases may exhibit common clinical symptoms and epidemiological comorbidity. However, the extent of pleiotropic mechanisms across ocular diseases remains unclear. We aim to examine shared genetic etiology in age-related macular degeneration (AMD), diabetic retinopathy (DR), glaucoma, retinal detachment (RD), and myopia.

METHODS

We analyzed genome-wide association analyses for the five ocular diseases in 43,877 cases and 44,373 controls of European ancestry from UK Biobank, estimated their genetic relationships (LDSC, GNOVA, and Genomic SEM), and identified pleiotropic loci (ASSET and METASOFT).

FINDINGS

The genetic correlation of common SNPs revealed a meaningful genetic structure within these diseases, identifying genetic correlations between AMD, DR, and glaucoma. Cross-trait meta-analysis identified 23 pleiotropic loci associated with at least two ocular diseases and 14 loci unique to individual disorders (non-pleiotropic). We found that the genes associated with these shared genetic loci are involved in neuron differentiation (P = 8.80 × 10^-6) and eye development systems (P = 3.86 × 10^-5), and single cell RNA sequencing data reveals their heightened gene expression from multipotent progenitors to other differentiated retinal cells during retina developmental process.

INTERPRETATION

These results highlighted the potential common genetic architectures among these ocular diseases and can deepen the understanding of the molecular mechanisms underlying the related diseases.

FUNDING

The National Natural Science Foundation of China (61871294), Zhejiang Provincial Natural Science Foundation of China (LR19C060001), and the Scientific Research Foundation for Talents of Wenzhou Medical University (QTJ18023).