Collagen gene expression and the altered accumulation of scleral collagen during the development of high myopia

Choroidal thickness in macular, nasal midperiphery, and temporal midperiphery regions and its relationship with axial length and refractive error

PURPOSE

This study aimed to investigate the choroidal thickness (ChT) distribution in adult myopic eyes, focusing on the macular, nasal midperiphery, and temporal midperiphery regions, and to explore its relationship with axial length (AL) and refractive error.

STUDY DESIGN

A cross-sectional, observational study.

METHODS

Twenty-nine eyes of 29 adult volunteers were examined. ChT was measured using high-speed swept-source optical coherence tomography covering an area of 50 degrees in three different regions: centered at macular, nasal side at 33 degrees, and temporal side at 33 degrees. Statistical analyses were performed to assess differences in ChT between regions and correlations with AL and spherical equivalent (SE).

RESULTS

ChT was found to be thickest in the macular region, followed by the nasal and temporal midperiphery regions. Significant correlations were observed between AL/SE and ChT in the macular and temporal regions, but not in the nasal region. The temporal midperiphery showed the strongest correlation with AL and SE.

CONCLUSION

This study revealed a nasal-temporal asymmetry in ChT distribution in myopic eyes, with the temporal midperiphery showing the thinnest ChT. The strong correlations between ChT in the temporal midperiphery and AL/SE suggest a role for the temporal choroid in axial elongation and myopia progression. These findings highlight the importance of considering peripheral ChT in understanding ocular growth and myopia management.

Animal modeling for myopia

Background

Myopia is one of the most common eye diseases globally, and has become an increasingly serious health concern among adolescents. Understanding the factors contributing to the onset of myopia and the strategies to slow its progression is critical to reducing its prevalence.

Main text

Animal models are key to understanding of the etiology of human diseases. Various experimental animal models have been developed to mimic human myopia, including chickens, rhesus monkeys, marmosets, mice, tree shrews, guinea pigs and zebrafish. Studies using these animal models have provided evidences and perspectives on the regulation of eye growth and refractive development. This review summarizes the characteristics of these models, the induction methods, common indicators of myopia in animal models, and recent findings on the pathogenic mechanism of myopia.

Conclusions

Investigations using experimental animal models have provided valuable information and insights into the pathogenic mechanisms of human myopia and its treatment strategies.

A Decrease in Autophagy Increases the Level of Collagen Type I Expression in Scleral Fibroblasts

PURPOSE

Autophagy dysregulation triggers extracellular matrix remodeling via changes in cellular collagen levels and protease secretion. However, the effect of autophagy on scleral extracellular matrix remodeling in the context of myopia is not fully understood. In this study, we measured the level of autophagy in sclera of form deprivation myopic guinea pigs; we also sought a correlation between the level of autophagy in human scleral fibroblasts and the extent of COL1A1 synthesis.

METHODS

We measured the level of COL1A1 expression and the levels of autophagic protein markers in scleral tissues in vivo using a form deprivation myopic guinea pig model. Rapamycin and chloroquine were respectively used to activate and inhibit autophagy in cultured human scleral fibroblasts. COL1A1 gene and protein expression levels were analyzed via quantitative real-time polymerase chain reaction, Western blotting, and immunofluorescence. Levels of autophagy-related proteins were assessed via Western blotting.

RESULTS

The sclera of form deprivation myopic guinea pig eyes exhibited decreased expression of COL1A1 and increased expression level of autophagy. After chloroquine exposure, human scleral fibroblasts exhibited decreased autophagy and increased COL1A1 expression.

CONCLUSION

Inhibition of scleral fibroblast autophagy increased COL1A1 expression at the gene and protein levels, thus explaining the effect of autophagy on collagen synthesis by scleral fibroblasts.

Identification of LRRC46 as a novel candidate gene for high myopia

High myopia (HM) is the primary cause of blindness, with the microstructural organization and composition of collagenous fibers in the cornea and sclera playing a crucial role in the biomechanical behavior of these tissues. In a previously reported myopic linkage region, MYP5 (17q21-22), a potential candidate gene, LRRC46 (c.C235T, p.Q79X), was identified in a large Han Chinese pedigree. LRRC46 is expressed in various eye tissues in humans and mice, including the retina, cornea, and sclera. In subsequent cell experiments, the mutation (c.C235T) decreased the expression of LRRC46 protein in human corneal epithelial cells (HCE-T). Further investigation revealed that Lrrc46-/- mice (KO) exhibited a classical myopia phenotype. The thickness of the cornea and sclera in KO mice became thinner and more pronounced with age, the activity of limbal stem cells decreased, and microstructural changes were observed in the fibroblasts of the sclera and cornea. We performed RNA-seq on scleral and corneal tissues of KO and normal control wild-type (WT) mice, which indicated a significant downregulation of the collagen synthesis-related pathway (extracellular matrix, ECM) in KO mice. Subsequent in vitro studies further indicated that LRRC46, a member of the important LRR protein family, primarily affected the formation of collagens. This study suggested that LRRC46 is a novel candidate gene for HM, influencing collagen protein VIII (Col8a1) formation in the eye and gradually altering the biomechanical structure of the cornea and sclera, thereby promoting the occurrence and development of HM.

Effect of Resveratrol on MMP-2 Expression in Scleral Fibroblasts: An In Vitro Study

PURPOSE

To investigate the effects of resveratrol (Res) on human fetal scleral fibroblasts (HFSFs) and its potential mechanism.

METHODS

HFSFs were randomly divided into the Res-treated group and the control group. Following, HFSFs were treated with or without a concentration of 10 μM Res for 48 h. To detect the expression of related genes, reverse transcription quantitative PCR (RT-qPCR) and western blotting were used. The apoptosis rate of different groups was determined using flow cytometry.

RESULTS

The mRNA expression of matrix metalloproteinase 2 (MMP-2), Collagen, Type I, Alpha 1 (COL1A1), Janus Kinase 2 (JAK2), and Signal Transducer and Activator of Transcription 3 (STAT3)" was downregulated in the Res-treatment group compared to the control group, according to RT-qPCR. Western blotting revealed that Res therapy reduced the expression of MMP-2, JAK2, P-JAK2, STAT3, P-STAT3, and Bcl-2 associated protein X (Bax) while increasing the expression of COL1A1 and B-cell lymphoma-2 (Bcl-2). Flow cytometry showed that the cell apoptosis rate was significantly lower in HFSFs treated with Res.

CONCLUSIONS

In conclusion, these findings suggest that Res increases COL1A1 expression while inhibiting MMP-2 and cell apoptosis in HFSFs, possibly through modulation of the JAK2/STAT3 signaling pathway.

Gut microbiota-derived indole-3-acetic acid suppresses high myopia progression by promoting type I collagen synthesis

High myopia (HM) is a leading cause of blindness worldwide with currently no effective interventions available. A major hurdle lies in its often isolated perception as a purely ocular morbidity, disregarding potential systemic implications. Recent evidence suggests the existence of a gut-eye axis; however, the role of gut microbiota in the pathogenesis of HM remains largely unexplored. Herein, we provide a potential crosstalk among HM's gut dysbiosis, microbial metabolites, and scleral remodeling. Utilizing 16S rRNA gene sequencing, we observed an altered gut microbiota profile in HM patients with a significant reduction in probiotic abundance compared with healthy controls. Subsequent targeted metabolic profiling revealed a notable decrease in plasma levels of the gut microbiota-derived metabolite indole-3-acetic acid (3-IAA) among HM patients, which is closely associated with the reduced probiotics, both negatively correlated with HM severity. Genetic analyses determined that gut microbiota are causally associated with myopia risk. Importantly, when mice subjected to HM modeling receive fecal microbiota transplantation from healthy donors, there is an increase in 3-IAA plasma levels and simultaneous retardation of HM progression along with better maintenance of collagen type I alpha 1 (COL1A1) expression in the sclera. Furthermore, 3-IAA gavage achieves similar effects. Mechanistic investigations confirm the transcriptional activation of COL1A1 by 3-IAA via promoting the enrichment of SP1 to its promoter. Together, our findings provide novel insights into the gut microbiota-eye axis in the pathogenesis of HM and propose new strategies for HM intervention by remodeling the gut microbiota and indole supplementation.

Collagen is crucial target protein for scleral remodeling and biomechanical change in myopia progression and control

In recent decades, the prevalence of myopia has been on the rise globally, attributed to changes in living environments and lifestyles. This increase in myopia has become a significant public health concern. High myopia can result in thinning of the sclera and localized ectasia of the posterior sclera, which is the primary risk factor for various eye diseases and significantly impacts patients' quality of life. Therefore, it is essential to explore effective prevention strategies and programs for individuals with myopia. Collagen serves as the principal molecule in the extracellular matrix (ECM) of scleral tissue, consisting of irregular collagen fibrils. Collagen plays a crucial role in myopia progression and control. During the development of myopia, the sclera undergoes a thinning process which is primarily influenced by collagen expression decreased and remodeled, thus leading to a decrease in its biomechanical properties. Improving collagen expression and promoting collagen crosslinking can slow down the progression of myopia. In light of the above, improving collagen expression or enhancing the mechanical properties of collagen fibers via medication or surgery represents a promising approach to control myopia.

A novel variant in the keratin 12 gene in a four-generation Chinese family with high myopia

BACKGROUND

High myopia is a major cause of visual impairment, and genetic factors play crucial roles in the pathogenesis. We performed this study to identify candidate genes for the development of high myopia in a four-generation Chinese family with myopia.

METHODS

All family members with myopia and 100 healthy participants were included in this study. Data were obtained on demographics, disease history, and ocular examination results. We performed whole exome sequencing of the genomic DNA and Sanger sequencing to verify the variants. Functional analyses of the variant were performed using software programmes.

RESULTS

Nine of thirteen family members were found to have high myopia, amongst which two members were also diagnosed keratoconus. A missense variant in the keratin 12 gene (KRT12, p.Val410Gly) was detected in all high myopia cases but not in other family members without high myopia or the controls. The variant was predicted to be benign by online software programmes. However, modelling of the three-dimensional structure of the protein clearly revealed conformational changes caused by the mutation.

CONCLUSIONS

A missense mutation in the KRT12 gene was identified in this Chinese family, which may be associated with the pathogenesis of high myopia.

In-vivo high-frequency quantitative ultrasound-derived parameters of the anterior sclera correlated with level of myopia and presence of staphyloma

BACKGROUND

A high-frequency point-of-care (POC) ultrasound instrument was used to evaluate the microstructural and biomechanical properties of the anterior sclera in vivo using parameters computed from quantitative ultrasound (QUS) methods.

METHODS

In this cross-sectional study, both eyes of 85 enrolled patients were scanned with the POC instrument and ultrasound data were processed to obtain QUS parameters. Pearson correlation and multi-linear regression were used to identify relationships between QUS parameters and refractive error (RE) or axial length. After categorising eyes based on RE, binary support vector machine (SVM) classifiers were trained using the QUS or ophthalmic parameters (anterior chamber depth, central corneal thickness, corneal power, and intraocular pressure) to classify each eye. Classifier performance was evaluated by computing the area under the receiver-operating characteristic curve (AUC).

RESULTS

Individual QUS parameters correlated with RE and axial length (p < 0.05). Multi-linear regression revealed significant correlation between the set of QUS parameters and both RE (R = 0.49, p < 0.001) and axial length (R = 0.46, p = 0.001). Classifiers trained with QUS parameters achieved higher AUC (𝑝 = 0.06) for identifying myopic eyes (AUC = 0.71) compared to classifiers trained with ophthalmic parameters (AUC = 0.63). QUS-based classifiers attained the highest AUC when identifying highly myopic eyes (AUC = 0.77).

CONCLUSIONS

QUS parameters correlate with progressing myopia and may be indicative of myopia-induced microstructural and biomechanical changes in the anterior sclera. These methods may provide critical clinical information complementary to standard ophthalmic measurements for predicting myopia progression and risk assessment for posterior staphyloma formation.

Targeting MicroRNA in myopia: Current insights

Myopia, the most prevalent eye condition, has sparked notable interest regarding its origin and prevention. MicroRNAs (miRNAs) are short, non-coding RNA strands typically consisting of 18-24 nucleotides. They play a central role in post-transcriptional gene regulation and are closely associated with both normal and pathological processes in organisms. Recent advances in next-generation sequencing and bioinformatics have provided novel insights into miRNA expression and its regulatory role in myopia. This review discusses the distinct expression patterns, regulatory functions, and potential pathways of miRNAs involved in the onset and progression of myopia. The primary objective of this review was to provide valuable insights into molecular mechanisms underlying myopia and the contribution of miRNAs. These insights are expected to pave the way for further exploration of the molecular mechanisms, diagnosis, treatment, and clinical applications of myopia.

Microphthalmia and congenital cataract in two patients with Stickler syndrome type II: a case report

BACKGROUND

Stickler syndrome (STL) is a collagenopathy caused by pathogenic variants in collagen-coding genes, mainly COL2A1 or COL11A1 associated with Stickler syndrome type 1 (STL1) or type 2 (STL2), respectively. Affected individuals manifest ocular, auditory, articular, and craniofacial findings in varying degrees. Previous literature and case reports describe high variability in clinical findings for patients with STL. With this case report, we broaden the clinical spectrum of the phenotype.

MATERIALS AND METHODS

Case report on two members of a family (mother and son) including clinical examination and genetic testing using targeted trio whole exome sequencing (trio-WES).

RESULTS

A boy and his mother presented with microphthalmia, congenital cataract, ptosis, and moderate-to-severe sensorineural hearing loss. Trio-WES found a novel heterozygote missense variant, c.4526A>G; p(Gln1509Arg) in COL11A1 in both affected individuals.

CONCLUSIONS

We report a previously undescribed phenotype associated with a COL11A1-variant in a mother and son, expanding the spectrum for phenotype-genotype correlation in STL2, presenting with microphthalmia, congenital cataract, and ptosis not normally associated with Stickler syndrome.

3D printed fibroblast-loaded hydrogel for scleral remodeling to prevent the progression of myopia

Pathologic myopia has seriously jeopardized the visual health of adolescents in the past decades. The progression of high myopia is associated with a decrease in collagen aggregation and thinning of the sclera, which ultimately leads to longer eye axis length and image formation in front of the retina. Herein, we report a fibroblast-loaded hydrogel as a posterior scleral reinforcement (PSR) surgery implant for the prevention of myopia progression. The fibroblast-loaded gelatin methacrylate (GelMA)-poly(ethylene glycol) diacrylate (PEGDA) hydrogel was prepared through bioprinting with digital light processing (DLP). The introduction of the PEGDA component endowed the GelMA-PEGDA hydrogel with a high compression modulus for PRS surgery. The encapsulated fibroblasts could consistently maintain a high survival rate during 7 days of in vitro incubation, and could normally secrete collagen type I. Eventually, both the hydrogel and fibroblast-loaded hydrogel demonstrated an effective shortening of the myopic eye axis length in a guinea pig model of visual deprivation over three weeks after implantation, and the sclera thickness of myopic guinea pigs became significantly thicker after 4 weeks, verifying the success of sclera remodeling and showing that myopic progression was effectively controlled. In particular, the fibroblast-loaded hydrogel demonstrated the best therapeutic effect through the synergistic effect of cell therapy and PSR surgery.

Scleral remodeling during myopia development in mice eyes: a potential role of thrombospondin-1

BACKGROUND

Scleral extracellular matrix (ECM) remodeling plays a crucial role in the development of myopia, particularly in ocular axial elongation. Thrombospondin-1 (THBS1), also known as TSP-1, is a significant cellular protein involved in matrix remodeling in various tissues. However, the specific role of THBS1 in myopia development remains unclear.

METHOD

We employed the HumanNet database to predict genes related to myopic sclera remodeling, followed by screening and visualization of the predicted genes using bioinformatics tools. To investigate the potential target gene Thbs1, we utilized lens-induced myopia models in male C57BL/6J mice and performed Western blot analysis to detect the expression level of scleral THBS1 during myopia development. Additionally, we evaluated the effects of scleral THBS1 knockdown on myopia development through AAV sub-Tenon's injection. The refractive status and axial length were measured using a refractometer and SD-OCT system.

RESULTS

During lens-induced myopia, THBS1 protein expression in the sclera was downregulated, particularly in the early stages of myopia induction. Moreover, the mice in the THBS1 knockdown group exhibited alterations in myopia development in both refraction and axial length changed compared to the control group. Western blotting analysis confirmed the effectiveness of AAV-mediated knockdown, demonstrating a decrease in COLA1 expression and an increase in MMP9 levels in the sclera.

CONCLUSION

Our findings indicate that sclera THBS1 levels decreased during myopia development and subsequent THBS1 knockdown showed a decrease in scleral COLA1 expression. Taken together, these results suggest that THBS1 plays a role in maintaining the homeostasis of scleral extracellular matrix, and the reduction of THBS1 may promote the remodeling process and then affect ocular axial elongation during myopia progression.

Induced Attenuation of Scleral TGF-β Signaling in Mutant Mice Increases Susceptibility to IOP-Induced Optic Nerve Damage

Purpose

Axonal optic nerve (ON) damage in glaucoma is characteristically associated with increased amounts of active transforming growth factor-beta 2 (TGF-β2) in the ON head. Here we investigated the functional role of scleral TGF-β signaling in glaucoma.

Methods

A deficiency of Tgfbr2, which encodes for TGF-β receptor type II (TGF-βRII), the essential receptor for canonical TGF-β signaling, was induced in fibroblasts (including those of the sclera) of mutant mice. To this end, 5-week-old mice were treated with tamoxifen eye drops. Experimental glaucoma was induced in 8-week-old mice using a magnetic microbead (MB) model. After 6 weeks of high intraocular pressure (IOP), the ON axons and their somata in the retina were labeled by paraphenylenediamine (PPD) and RNA-binding protein with multiple splicing (RBPMS) immunohistochemistry, respectively, and quantified.

Results

Tamoxifen treatment resulted in a significant decrease of TGF-βRII and its mRNA in the sclera. After 6 weeks of high IOP, reduced numbers of PPD-stained ON axons were seen in MB-injected eyes in comparison with not-injected contralateral eyes. Moreover, MB injection also led to a decrease of retinal ganglion cell (RGC) somata as seen in RBPMS-stained retinal wholemounts. Axon loss and RGC loss were significantly higher in mice with a fibroblast specific deficiency of TGF-βRII in comparison with control animals.

Conclusions

We conclude that the ablation of scleral TGF-β signaling increases the susceptibility to IOP-induced ON damage. Scleral TGF-β signaling in mutant mice appears to be beneficial for ON axon survival in experimentally induced glaucoma.

[Features of genetic mutations in children with high myopia combined with peripheral retinal degenerations]

Degenerative changes in the peripheral regions of the ocular fundus allow a closer look at both the role of collagen genes and their mutations in children with high myopia.

PURPOSE

The study investigates the features of genetic mutations in children with high myopia combined with peripheral retinal degenerations.

MATERIAL AND METHODS

Study group was formed from the database of genetic studies of the Scientific and Clinical Center OOO Oftalmic, which consists of 4362 patients referred for medical genetic counseling and molecular genetic testing from 2016 to 2021. Selection criteria were: male and female patients, aged 5-18 years old, who had the following clinical signs: high myopia (>6.00 D) and the presence of peripheral retinal degenerations (PRD). The study considered both isolated cases of ophthalmic pathology, as well as its syndromic forms. The final selection included 40 children. All patients had consulted with a geneticist. Whole-exome sequencing (WES), next generation sequencing (NGS), and single gene sequencing were conducted by taking 5 mL of peripheral venous blood and extracting deoxyribonucleic acid (DNA).

RESULTS

In patients with isolated cases of ophthalmic pathology (peripheral retinal degenerations and high myopia) with a confirmed genetic diagnosis, mutations in the COL2A1 gene were detected in 77.4% of cases, and in the COL11A1 gene - in 22.6% of cases. In Stickler syndrome with a confirmed genetic diagnosis, mutations in the COL2A1 gene were detected in 33.3% of cases. In Marshall syndrome, the mutation in the COL11A1 gene was detected in 11.1% of cases. In children with Ehlers-Danlos, Knobloch type 1, Cohen, Marfan, Wagner syndromes mutations in the genes COL5A1, COL18A1, VPS13B, FBN1, VCAN were detected in 55.6% of cases. In 33.3% of cases of Knobloch type 1, Cohen, Wagner syndromes the mutation is found in both copies of the gene (i.e., in both chromosomes), which leads to the development of peripheral retinal degenerations with high myopia.

CONCLUSION

The results of the conducted molecular genetic testing expand our understanding of the mutation spectrum in the genes of children with both isolated cases of ophthalmic pathology, as well as syndromic pathology.

Lipid Metabolism Regulators Are the Possible Determinant for Characteristics of Myopic Human Scleral Stroma Fibroblasts (HSSFs)

The purpose of the current investigation was to elucidate what kinds of responsible mechanisms induce elongation of the sclera in myopic eyes. To do this, two-dimensional (2D) cultures of human scleral stromal fibroblasts (HSSFs) obtained from eyes with two different axial length (AL) groups, <26 mm (low AL group, n = 2) and >27 mm (high AL group, n = 3), were subjected to (1) measurements of Seahorse mitochondrial and glycolytic indices to evaluate biological aspects and (2) analysis by RNA sequencing. Extracellular flux analysis revealed that metabolic indices related to mitochondrial and glycolytic functions were higher in the low AL group than in the high AL group, suggesting that metabolic activities of HSSF cells are different depending the degree of AL. Based upon RNA sequencing of these low and high AL groups, the bioinformatic analyses using gene ontology (GO) enrichment analysis and ingenuity pathway analysis (IPA) of differentially expressed genes (DEGs) identified that sterol regulatory element-binding transcription factor 2 (SREBF2) is both a possible upstream regulator and a causal network regulator. Furthermore, SREBF1, insulin-induced gene 1 (INSIG1), and insulin-like growth factor 1 (IGF1) were detected as upstream regulators, and protein tyrosine phosphatase receptor type O (PTPRO) was detected as a causal network regulator. Since those possible regulators were all pivotally involved in lipid metabolisms including fatty acid (FA), triglyceride (TG) and cholesterol (Chol) biosynthesis, the findings reported here indicate that FA, TG and Chol biosynthesis regulation may be responsible mechanisms inducing AL elongation via HSSF.

Collagen Mimetic Peptides Promote Repair of MMP-1-Damaged Collagen in the Rodent Sclera and Optic Nerve Head

The structural and biomechanical properties of collagen-rich ocular tissues, such as the sclera, are integral to ocular function. The degradation of collagen in such tissues is associated with debilitating ophthalmic diseases such as glaucoma and myopia, which often lead to visual impairment. Collagen mimetic peptides (CMPs) have emerged as an effective treatment to repair damaged collagen in tissues of the optic projection, such as the retina and optic nerve. In this study, we used atomic force microscopy (AFM) to assess the potential of CMPs in restoring tissue stiffness in the optic nerve head (ONH), including the peripapillary sclera (PPS) and the glial lamina. Using rat ONH tissue sections, we induced collagen damage with MMP-1, followed by treatment with CMP-3 or vehicle. MMP-1 significantly reduced the Young's modulus of both the PPS and the glial lamina, indicating tissue softening. Subsequent CMP-3 treatment partially restored tissue stiffness in both the PPS and the glial lamina. Immunohistochemical analyses revealed reduced collagen fragmentation after MMP-1 digestion in CMP-3-treated tissues compared to vehicle controls. In summary, these results demonstrate the potential of CMPs to restore collagen stiffness and structure in ONH tissues following enzymatic damage. CMPs may offer a promising therapeutic avenue for preserving vision in ocular disorders involving collagen remodeling and degradation.

Association between inflammatory cytokines and oxidative stress levels in aqueous humor with axial length in human myopia

This study investigated the content of inflammatory cytokines and oxidative stress levels in the aqueous humor (AH) of patients with high myopia (HM) and explored the relationship between these factors and the axial length (AL) of the eye, to explore the roles of mild intraocular inflammation and oxidative stress imbalance in the occurrence and development of myopia. AH samples from 40 patients (70 eyes) were collected during implantable collamer lens (ICL-V4c) surgery. The subjects were divided into three groups according to AL: group A (AL ≤ 26 mm), group B (26 < AL ≤ 28 mm), and group C (AL ≥ 28 mm). The concentrations of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), matrix metalloproteinase-2 (MMP-2), and interleukin-1β (IL-1β) in the AH of the three groups were measured using the Luminex system. Oxidative stress levels were measured using reagent kits targeting total antioxidant capacity (T-AOC), catalase (CAT), and nitric oxide (NO) and malonaldehyde (MDA) content. The results showed compared with group A, IL-1β, MMP-2, and IL-6 concentrations were significantly higher and T-AOC levels were significantly lower in group C. There were no significant differences in CAT, NO, MDA, or TNF-α levels among the groups. The concentrations of IL-6 (r = 0.379, p = 0.016), MMP-2 (r = 0.469, p = 0.002), and MDA (r = 0.354, p = 0.025) in AH were positively correlated with the AL, whereas T-AOC (r = -0.678, p = 0.000) was negatively correlated with AL. These results suggest that mild intraocular inflammation and oxidative stress imbalance may be associated with myopia. Further experiments are needed to confirm the role of mild intraocular inflammation and oxidative stress imbalance in the occurrence and development of myopia.

Scleral remodeling in early adulthood: the role of FGF-2

Emmetropization, a natural process of ocular elongation, is closely associated with scleral remodeling. The Fibroblast growth factor-2 (FGF-2) was reported involved in scleral remodeling in myopia models. Herein, we aimed to investigate the role of scleral fibroblast-to-myofibroblast differentiation and FGF-2 in scleral remodeling during maturation. Our findings revealed that the posterior scleral fibroblasts (SFs) from mature guinea pigs exhibit increased stiffness compared to those from young guinea pigs. Moreover, mature SFs displayed decreased cell proliferation but increased levels of α-SMA, matrix metalloproteinase 2 (MMP2), and collagen 1, when compared to young SFs. Additionally, the mRNA expression of scleral Fgf-2, Fgf receptor 1 (Fgfr1), Fgfr2, Fgfr3, and Fgfr4 was increased in mature SFs. Notably, exogenous FGF-2 showed increased cell proliferation and led to decreased expression of α-SMA, MMP2, and collagen 1 in mature SFs. Overall, our findings highlight the influence of maturation on SFs from posterior scleral shells, resulting in increased stiffness and the manifestation of fibroblast-to-myofibroblast differentiation during development. Exogenous FGF-2 increased cell proliferation and reversed the age-related fibroblast-to-myofibroblast differentiation, suggesting a potential role of FGF-2 in regulating scleral remodeling.

Evaluation of new robust silk fibroin hydrogels for posterior scleral reinforcement in rabbits

Background: Currently, there is no ideal material available for posterior scleral reinforcement (PSR) to prevent the progression of high myopia. In this study, we investigated robust regenerated silk fibroin (RSF) hydrogels as potential grafts for PSR in animal experiments to evaluate their safety and biological reactions. Methods: PSR surgery was performed on the right eye of twenty-eight adult New Zealand white rabbits, with the left eye serving as a self-control. Ten rabbits were observed for 3 months, while 18 rabbits were observed for 6 months. The rabbits were evaluated using intraocular pressure (IOP), anterior segment and fundus photography, A- and B-ultrasound, optical coherence tomography (OCT), histology, and biomechanical tests. Results: No complications such as significant IOP fluctuation, anterior chamber inflammation, vitreous opacity, retinal lesion, infection, or material exposure were observed. Furthermore, no evidence of pathological changes in the optic nerve and retina, or structural abnormalities on OCT, were found. The RSF grafts were appropriately located at the posterior sclera and enclosed in fibrous capsules. The scleral thickness and collagen fiber content of the treated eyes increased after surgery. The ultimate stress of the reinforced sclera increased by 30.7%, and the elastic modulus increased by 33.0% compared to those of the control eyes at 6 months after surgery. Conclusion: Robust RSF hydrogels exhibited good biocompatibility and promoted the formation of fibrous capsules at the posterior sclera in vivo. The biomechanical properties of the reinforced sclera were strengthened. These findings suggest that RSF hydrogel is a potential material for PSR.

Myopic tilted disc: Mechanism, clinical significance, and public health implication

Myopic tilted disc is a common structural change of myopic eyes. With advancing ocular imaging technology, the associated structural changes of the eye, particularly the optic nerve head, have been extensively studied. These structural changes may increase patients' susceptibility to axonal damage and the risk of developing serious optic neuropathies including glaucoma. They also lead to diagnostic difficulties of disease suspects and treatment dilemmas of patients, which implicate clinical practice and subsequently the health care system. In the context of the mounting prevalence of myopia worldwide and its implications to irreversible visual impairment and blindness, it is essential to gain a thorough understanding of the structural changes of myopia. Myopic tilted disc has been extensively investigated by different study groups. However, generalizing the knowledge could be difficult because of the variable definitions of myopic tilted disc utilized in these studies and the complexities of the changes. The current review aimed to clarify the concepts and discuss various aspects of myopic tilted disc, including the definitions, association with other myopia-related changes, mechanism of tilted disc development, structural and functional changes, and clinical implications.

MicroRNA-29a inhibits collagen expression and induces apoptosis in human fetal scleral fibroblasts by targeting the Hsp47/Smad3 signaling pathway

Members of the microRNA-29 (miR-29) gene family have been implicated as suppressors of collagen in several human diseases. The present study aimed to explore the function of miR-29a in human fetal scleral fibroblasts (HFSFs) and to investigate potential mechanisms by which the molecule regulates cellular functioning. First, HFSFs were transfected with miR-29a mimic, miR-29a inhibitor, or their corresponding controls. Then, cell proliferation and apoptosis were assessed using a CCK-8 assay and flow cytometry, respectively. Further, using real-time PCR, western blotting, and immunofluorescence staining, levels of miR-29a, heat shock protein 47 (Hsp47), COL1A1, Smad3, P-Smad3, Bax, and Bcl-2 were investigated. Next, empty vectors and SERPINH1-overexpressing vectors were used to transfect HFSFs. Western blotting and flow cytometry were performed to assess changes in levels of HFSF protein expression and apoptosis, respectively. Results indicated that the miR-29a mimic significantly inhibited Hsp47, Smad3, P-Smad3, and COL1A1 expression. Conversely, the miR-29a inhibitor enhanced the expression of the same genes. Furthermore, miR-29a overexpression inhibited HFSFs proliferation and enhanced the rate of HFSFs apoptosis. Consistent with this finding, miR-29a overexpression led to the downregulation of Bcl-2 and upregulation of Bax. In contrast, miR-29a suppression led to the upregulation of Bcl-2 and downregulation of Bax expression and reduced the rate of apoptosis. Additional research revealed that overexpression of Hsp47 prevented HFSFs apoptosis and enhanced collagen production. Findings that miR-29a overexpression reduces collagen expression levels, slows proliferation, and promotes apoptosis in HFSFs highlight the key role of miR-29a in scleral remodeling. The effects of miR-29a on scleral remodeling might mediate by targeting Hsp47 and repressing the Smad3 pathway.

Scleral PERK and ATF6 as targets of myopic axial elongation of mouse eyes

Axial length is the primary determinant of eye size, and it is elongated in myopia. However, the underlying mechanism of the onset and progression of axial elongation remain unclear. Here, we show that endoplasmic reticulum (ER) stress in sclera is an essential regulator of axial elongation in myopia development through activation of both PERK and ATF6 axis followed by scleral collagen remodeling. Mice with lens-induced myopia (LIM) showed ER stress in sclera. Pharmacological interventions for ER stress could induce or inhibit myopia progression. LIM activated all IRE1, PERK and ATF6 axis, and pharmacological inhibition of both PERK and ATF6 suppressed myopia progression, which was confirmed by knocking down above two genes via CRISPR/Cas9 system. LIM dramatically changed the expression of scleral collagen genes responsible for ER stress. Furthermore, collagen fiber thinning and expression of dysregulated collagens in LIM were ameliorated by 4-PBA administration. We demonstrate that scleral ER stress and PERK/ATF6 pathway controls axial elongation during the myopia development in vivo model and 4-PBA eye drop is promising drug for myopia suppression/treatment.

The relationship between axial length/corneal radius of curvature ratio and stress–strain index in myopic eyeballs: Using Corvis ST tonometry

Purpose: This study aimed to investigate the correlation of axial length/corneal radius of curvature ratio with stress–strain index (SSI).

Methods: Retrospective analysis was conducted to compare the right eyes of those with high myopia (HM, n = 132; age and 10–48 years) with those without high myopia (NHM, n = 135; age and 7–48 years), where the baseline axial length, corneal radius of curvature ratio, and central corneal thickness were analyzed; the differences in two groups were compared; and the relationship of axial length and axial length/corneal radius of curvature ratio with SSI were explored.

Results: Compared with AL &lt; 26mm, SSI significantly decreased when AL ≥ 26 mm (p = 0.001), while there was no correlation with AL in the NHM group (r = -0.14, p = 0.12) or HM group (r = -0.09, p = 0.32). AL/CR was significantly associated with SSI in both the NHM (r = -0.4, p &lt; 0.001) and HM (r = -0.18, p = 0.04) groups. In the NHM group, AL/CR was significantly associated with SSI (unstandardized beta = -0.514, se = 0.109, p &lt; 0.001) with the adjustment of age and gender. Additionally, a significant association of SSI with AL/CR was also found after adjusting for age and gender (unstandardized beta = -0.258, se = 0.096, and p = 0.0082) in the HM group.

Conclusion: SSI showed a significant negative correlation with AL/CR in patients without high myopia and in patients with high myopia. However, SSI exhibited no decrease with the worsening of myopia, but it gradually remained stable at a low level. The findings of this study validate, to some extent, the possibility of analyzing the dynamic changes in ocular wall stiffness during the development of myopia by measuring in vivo corneal biomechanical parameters.

The Anterior Segment Biometrics in High Myopia Eyes

INTRODUCTION

The aim of this study was to investigate and compare the anterior segment biometrics in high myopia and control groups.

METHODS

Thirty-four eyes of 34 high myopia patients and 42 eyes of 42 control subjects were included. Schlemm's canal (SC) area, trabecular meshwork (TM) thickness and length, scleral spur (SS) length, and anterior scleral thickness (AST) were measured using swept-source optical coherence tomography. Associations between SC area, TM thickness, TM length, SS length, and AST were also estimated.

RESULTS

SC area, TM thickness, and SS length were significantly associated with AST0 (AST at 0 mm from SS) in both high myopia and control groups. AST0 (702.61 ± 78.05 vs. 729.12 ± 95.87 μm, p = 0.085) and SS length (206.25 ± 52.25 vs. 212.09 ± 51.86 μm, p = 0.556) were not significantly different between high myopia and control groups, whereas SC area (6,622.68 ± 1,130.06 vs. 6,105.85 ± 1,297.84 μm2, p = 0.015) was significantly greater and TM thickness (96.15 ± 34.40 vs. 107.93 ± 29.97 μm, p = 0.048) was significantly thinner in high myopia group than in control group.

CONCLUSION

SC area and TM thickness were significantly associated with AST0, while AST0 and SS length were not significantly different between high myopia and control groups. The changes in SC and TM dimensions in high myopia eyes might be caused by factors other than AST0 and SS length.

Association between TGF-β gene polymorphism and myopia: A systematic review and meta-analysis

INTRODUCTION

The present study was conducted to determine the association of transforming growth factor-beta (TGF-β) gene polymorphism and myopia.

METHOD

Four hundred twelve articles were identified, of which 11 articles with 5213 participants in 4 countries were included in the final analysis. Review Manager software (RevMan, version 5.4) was used for data analysis.

RESULT

Odds ratio (OR) value of TGF-β1 rs1800469 is 1.33 (95% confidence interval [CI] = 1.15-1.54) in the allelic model; in the dominant model is 1.76 (95% CI = 1.16-2.67); in homozygous model is 5.98 (95% CI = 4.31-8.06). OR value of TGF-β1 rs4803455 is 0.62 (95% CI = 0.43-0.88) in recessive model. TGF-β2 is not associated with myopia. Relevant study on TGF-β3 is scarce.

CONCLUSION

Our systematic review and meta-analysis found that TGF-β1 rs4803455 and rs1800469 were correlated with myopia.

Biomechanical changes in myopic sclera correlate with underlying changes in microstructure

Myopia alters the microstructural and biomechanical properties of the posterior sclera, which is characterized as a layered structure with potentially different inter-layer collagen fibril characteristics. Scanning acoustic microscopy (SAM) has been used to investigate how the micron-scale bulk mechanical properties of the posterior sclera are affected by myopia. Other investigators have employed second harmonic generation (SHG) imaging to characterize the collagen microstructure of tissues. In the present study, SAM and SHG imaging were used to investigate the existence of biomechanically-distinct scleral layers and identify relationships between mechanical properties and tissue microstructure in myopic guinea pig (GP) eyes. Diffusers were worn over the right eyes of six, 1-week-old GPs for one week to induce unilateral form-deprivation myopia. GPs were euthanized, enucleated, and eyes were cryosectioned. Twelve-micron-thick adjacent vertical cryosections were scanned with SAM or SHG. SAM maps of bulk modulus, mass density, and acoustic attenuation were estimated. A fiber-extraction algorithm applied to SHG images estimated collagen fiber length, width, straightness, alignment, and number density. Results revealed that the posterior sclera may exhibit biomechanically distinct layers that are affected differently in myopia. Specifically, a layered structure was observed in the mechanical-parameter maps of control eyes that was less apparent in myopic eyes. Collagen fibers in myopic eyes had smaller diameters and were more aligned. Myopia-associated biomechanical changes were most significant in the outermost and innermost scleral layers. SAM-measured mechanical parameters were correlated with collagen fiber microstructure, particularly fiber length, alignment, and number density, which may imply the biomechanical parameters estimated from SAM measurements are related to tissue microstructure. Interestingly, some changes were greatest in more-peripheral regions, suggesting interventions to strengthen the sclera may be effective away from the optic nerve and efficacy may be achieved best when intervention is applied to the outermost layer.

MicroRNA expression profiling in myopia: a meta-analysis and systematic review

BACKGROUND

Myopia (nearsightedness) is currently the most common human eye disorder worldwide. In the recent years, several studies have addressed the role of microRNAs (miRNAs) in the pathogenesis of myopia.

OBJECTIVES

The aim of this study was to perform a meta-analysis on the miRNA expression profiling studies in myopia to identify commonly dysregulated miRNAs in myopic tissues.

METHOD

Seven independent studies were included in the meta-analysis. A vote-counting strategy were employed as the meta-analysis method. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis and Gene Ontology (GO) functional enrichment analysis were performed to identify the pathways most strongly affected by the dysregulated mouse miRNAs.

RESULTS

According to the vote-counting method, eighteen miRNAs were reported in at least two studies with the consistent direction, of which 13 miRNAs were commonly up-regulated in myopic samples compared with control samples and five miRNAs were commonly down-regulated. Subgroup analyses divided and compared the differentially expressed miRNAs according to species (human and animal) and ocular tissue types. The KEGG analysis showed that the dysregulated mouse miRNAs were most enriched in extracellular matrix (ECM)-receptor interaction signal pathway. The most enriched GO processes regulated by the dysregulated mouse miRNAs was cellular protein modification process.

CONCLUSIONS

Our meta-analysis recommends several miRNAs may provide some clues of the potential biomarkers in myopia. Further mechanistic studies are warranted to elucidate the biological role of the dysregulated miRNAs in the development of myopia.

Comparing the Differences in Slowing Myopia Progression by Riboflavin/Ultraviolet A Scleral Cross-linking before and after Lens-induced Myopia in Guinea Pigs

PURPOSE

To compare the effectiveness and differences in slowing myopia progression in Guinea pigs by riboflavin/ultraviolet A (UVA) scleral cross-linking (sCXL) before and after lens-induced myopia (LIM).

METHODS

Forty 4-week-old Guinea pigs were randomly divided into four groups (n = 10 per group): CXL-A, CXL-B, LIM, and Control groups. The right eyes in CXL-A, CXL-B, LIM groups were treated with -10.00 D lenses from 4 to 10-week old and the left eyes were untreated. In CXL-A and CXL-B groups, riboflavin/UVA sCXL was performed on the right eyes at 4 weeks and 8 weeks of age, respectively. Both eyes were untreated in Control group. The intraocular pressure (IOP), the axial length (AXL), and the refraction were measured in vivo at 4, 8, and 10 weeks of age. At 10 weeks of age, the right eyes were enucleated for the tensile test and transmission electron microscopy observations.

RESULTS

The myopia has been successfully induced in LIM and CXL-B groups during 4-8 weeks. In CXL-A group, the growth rate of AXL and myopic refraction was markedly inhibited during 4-8 weeks and the inhibitory effects diminished during 8-10 weeks. During 8-10 weeks, the growth rate of AXL and myopic refraction in CXL-B were marked suppressed. At 10 weeks of age, the myopia refraction was lower and the AXL was shorter in CXL-A group in comparison to CXL-B group. The IOP was not significantly different among the 4 groups of eyes at 4, 8, and 10 weeks of age. The scleral stiffness, the fibril diameters, and the fibril density of the sclera were significantly increased in CXL-A and CXL-B groups compared to LIM group.

CONCLUSION

Riboflavin/UVA sCXL administrated before and after the myopia modeling could both slow the myopia progression in Guinea pigs. The before-myopia preventative sCXL showed lower myopic refraction in the same age comparison between the cross-linked groups. The effect of riboflavin/UVA sCXL might reduce over time and the long-term effect should be further investigated. This sCXL intervention might control the ultrastructure alterations of the sclera during the myopia remodeling.

Association of Corneal Biomechanics Properties with Myopia in a Child and a Parent Cohort: Hong Kong Children Eye Study

Associations between corneal biomechanics, axial elongation and myopia are important but previous results are conflicting. Our population-based study aimed to investigate factors associated with corneal biomechanics, and their relationships with myopia in children and adults. Data from 3643 children and 1994 parents showed that children had smaller deformation amplitudes (DA) than parents (p < 0.001). A larger DA was significantly associated with elongated axial length (AL; children: ß = 0.011; adults: ß = 0.0013), higher corneal curvature (children: ß = 0.0086; adults: ß = 0.0096), older age (children: ß = 0.010; adults: ß = 0.0013), and lower intraocular pressure (IOP; children: ß = −0.029; adults: ß = −0.031) in both cohorts. The coefficient of age for DA in children was larger than in adults (p < 0.001), indicating that the DA change with age in children is faster than in adults. DA was significantly associated with spherical equivalent (p < 0.001) resulting from its correlation with AL and corneal curvature. In conclusion, the cornea is more deformable in adults than in children, whereas corneal deformation amplitude increases faster with age in children than that in adults, along with AL elongation. Longer AL, steeper corneal curvature, older age and smaller IOP correspond to a more deformable cornea. The association between corneal deformation amplitude and refraction was mediated via AL and corneal curvature.

Association of genetic variants in PDGFRA with high myopia in the Han population of southwestern China

PURPOSE

To investigate the associations of 11 genetic single nucleotide polymorphisms (SNPs) in FRAP1 and PDGFRA with high myopia (HM) in a Han Chinese population.

METHODS

A total of 442 HM patients and 947 healthy controls were recruited for this study. Five genetic models were analysed to further evaluate the association of target SNPs with HM. SNP functional annotation database tools were used to predict and analyse the potential function of these SNPs.

RESULTS

Our findings indicated that rs2114039 located in PDGFRA had significant association with HM in a Han Chinese population (P = 2.00E-06, OR = 0.647, 95%CI = 0.542-0.773). The common genotypes rs2114039CC, rs2114039CT and rs2114039CT+TT all had a decreased risk of HM when compared with rs2114039TT (P = 4.10E-05, OR = 0.290, 95%CI = 0.161-0.524; P = 1.00E-03, OR = 0.626, 95%CI = 0.479-0.819; P = 9.00E-06, OR = 0.560, 95%CI = 0.433-0.724, respectively). In addition, compared with rs2114039CT+TT, rs2114039CC also had a decreased risk of HM (P = 3.59E-04, OR = 0.347, 95% CI = 0.194-0.620).

CONCLUSIONS

Our findings indicated that rs2114039, located in PDGFRA, was significantly associated with HM in the southwest Han Chinese population. Additionally, rs2114039 might influence the function of PDGFRA by regulating the growth of human vision through different pathways. Furthermore, functional research on the role of PDGFRA in myopia pathogenesis should be conducted in the future.

Decreased Choroidal Blood Perfusion Induces Myopia in Guinea Pigs

Purpose

The development of myopia in guinea pigs can be inhibited by attenuating scleral hypoxia by increasing choroidal blood perfusion (ChBP). In this study, we reduced ChBP through surgical and pharmacological methods to determine the effect on myopia development. We also determined whether ChBP was reduced by quinpirole, a drug that enhances form-deprivation myopia (FDM).

Methods

ChBP was reduced in the right eyes of guinea pigs via transection of the temporal ciliary arteries or daily injections of phenylephrine into the inferior peribulbar space for one week during normal ocular growth. Other guinea pigs were subjected to two weeks of monocular FDM—with facemasks, along with daily injections of quinpirole, a dopamine D2 receptor agonist, to enhance the FDM. Changes in refraction, axial length, ChBP, and choroidal thickness (ChT) were measured in both treated and fellow eyes of the treatment and control groups. Scleral hypoxia labeling with pimonidazole adducts and α-smooth muscle actin (α-SMA) protein were also measured.

Results

Surgical and pharmacological reduction of ChBP induced myopia development in the treated eyes. These treatments rendered the scleral hypoxia and increased scleral α-SMA expression. Furthermore, quinpirole injections, which increased the magnitude of myopia, augmented the FDM-associated reductions in ChBP and ChT and increased the levels of scleral hypoxia and α-SMA protein.

Conclusions

Decreased ChBP in guinea pigs leads to scleral hypoxia and scleral myofibroblast transdifferentiation with increased α-SMA expression, ultimately resulting in myopia development. In future clinical trials, ChBP reduction can serve as a potential biomarker for early detection of myopia development.

MicroRNA-29a May Influence Myopia Development by Regulating Collagen I

PURPOSE

The aim of this study was to characterize the regulatory role of microRNA-29a (miR-29a) in myopia, providing support for potential biomarkers and new therapeutic targets of myopia in humans.

METHODS

The miR-29a expression level was detected in the aqueous humor and peripheral blood plasma of 21 high myopic patients and eight cataract control patients using quantitative polymerase chain reaction. iTRAQ analysis of proteomes was conducted to show the regulatory effect of miR-29a on human scleral fibroblasts (SFs) cultured in vitro. We also assessed proliferation, migration, and collagen I synthesis in SF cells, mediated by miR-29a.

RESULTS

MiR-29a expression was significantly higher in the aqueous humor of highly myopic patients than in the cataract control patients (fold change: 4.861, p = 0.001). miR-29a inhibited the synthesis of type I collagen in human SF cells and enhanced cell migration, but had no significant effect on cell proliferation.

CONCLUSION

MiR-29a was highly expressed in aqueous humor of myopia patients and inhibited the synthesis of type I collagen in human SF cells in vivo, thereby it may play an important role in myopia development.

Modulation of the Physical Properties of 3D Spheroids Derived from Human Scleral Stroma Fibroblasts (HSSFs) with Different Axial Lengths Obtained from Surgical Patients

In the current study, to elucidate the pathological characteristics of myopic scleral stroma, three-dimensional (3D) cultures of human scleral stroma fibroblasts (HSSFs) with several axial lengths (AL, 22.80–30.63 mm) that were obtained from patients (n = 7) were examined. Among the three groups of ALs, <25 mm (n = 2), 25–30 mm (n = 2), and >30 mm (n = 3), the physical properties of the 3D HSSFs spheroids with respect to size and stiffness, the expressions of extracellular matrix (ECM) molecules, including collagen (COL) 1, 4, and 6 and fibronectin (FN) by qPCR and immunohistochemistry (IHC), and the mRNA expression of ECM metabolism modulators including hypoxia-inducible factor 1A (HIF 1A), HIF 2A, lysyl oxidase (LOX), tissue inhibitor of metalloproteinase (TIMP) 1–4, and matrix metalloproteinase (MMP) 2, 9, and 14 as well as several endoplasmic reticulum (ER) stress-related factors were compared. In the largest AL group (>30 mm), the 3D HSSFs spheroids were (1) significantly down-sized and less stiff compared to the other groups, and (2) significant changes were detected in the expression of some ECMs (qPCR; the up-regulation of COL1 and COL4, and the down-regulation of FN, IHC; the up-regulation of COL1 and FN, and down-regulation of COL4). The mRNA expressions of ECM modulators and ER stress-related genes were also altered with increasing AL length (up-regulation of HIF2A, MMP2, XBP1, and MMP14, down-regulation of LOX, TIMP 2 and 3, GRP78, GRP94, IRE1, and ATF6). In addition, a substantial down-regulation of some ER stress-related genes (ATF4, sXPB1 and CHOP) was observed in the 25–30 mm AL group. The findings presented herein suggest that small and stiffer 3D HSSFs spheroids in the largest AL group may accurately replicate the pathological significance of scleral thinning and weakening in myopic eyes. In addition, the modulation of several related factors among the different AL groups may also provide significant insights into our understanding of the molecular mechanisms responsible for causing myopic changes in the sclera.

Mechanical Strain Regulates Myofibroblast Differentiation of Human Scleral Fibroblasts by YAP

Scleral extracellular matrix (ECM) remodeling is thought to play a critical role in the pathogenesis of glaucoma. Mechanical strain induced by elevated intraocular pressure can promote myofibroblast differentiation of fibroblasts and result in scleral ECM remodeling; however, the underlying mechanism remains poorly understood. Yes-associated protein (YAP) is a mechanosensory protein and the key downstream transcriptional effector of the Hippo signaling pathway. Here, we investigated the role of YAP in mechanical strain-induced myofibroblast transformation during glaucoma scleral ECM remodeling. Integrative bioinformatics analyses were performed to identify the key pathways for the ECM remodeling of the sclera in glaucoma. Sprague–Dawley rats were used to establish a chronic ocular hypertension model, and the expression of collagen type I (COL1) and YAP in the sclera was analyzed by immunohistochemical analysis and Western blotting. Furthermore, human scleral fibroblasts (HSFs) were cultured and subjected to mechanical strain. In groups with or without the YAP siRNA or YAP inhibitor, cell proliferation, migration capacity, and the expression levels of YAP, COL1, and α-smooth muscle actin (α-SMA) were evaluated by Cell Counting Kit-8 assay, scratch assay, and Western blotting. The interactions between YAP and Smad3 were demonstrated by coimmunoprecipitation, and the expression levels of COL1 and α-SMA were evaluated in groups treated with or without the Smad3 inhibitor. We first revealed that the Hippo signaling pathway may be involved in mechanical strain-induced scleral ECM remodeling through bioinformatics analysis. Furthermore, the in vivo study showed upregulated YAP, COL1, and α-SMA expression in the hypertensive sclera of rats. In vitro, mechanical strain increased YAP and COL1 expression in HSFs and promoted myofibroblast differentiation. After YAP knockdown or inhibition with verteporfin, mechanical strain-induced fibrotic changes in HSFs were markedly suppressed. Additionally, YAP showed a protein interaction with Smad3, and the upregulation of a-SMA and COL1 in response to mechanical strain was also significantly downregulated following the inhibition of Smad3. In conclusion, mechanical strain activated scleral myofibroblast differentiation via YAP. The YAP pathway may play an important role in regulating scleral myofibroblast differentiation and ECM remodeling of the sclera in glaucoma.

Estimation of scleral mechanical properties from air-puff optical coherence tomography

We introduce a method to estimate the biomechanical properties of the porcine sclera in intact eye globes ex vivo, using optical coherence tomography that is coupled with an air-puff excitation source, and inverse optimization techniques based on finite element modeling. Air-puff induced tissue deformation was determined at seven different locations on the ocular globe, and the maximum apex deformation, the deformation velocity, and the arc-length during deformation were quantified. In the sclera, the experimental maximum deformation amplitude and the corresponding arc length were dependent on the location of air-puff excitation. The normalized temporal deformation profile of the sclera was distinct from that in the cornea, but similar in all tested scleral locations, suggesting that this profile is independent of variations in scleral thickness. Inverse optimization techniques showed that the estimated scleral elastic modulus ranged from 1.84 ± 0.30 MPa (equatorial inferior) to 6.04 ± 2.11 MPa (equatorial temporal). The use of scleral air-puff imaging holds promise for non-invasively investigating the structural changes in the sclera associated with myopia and glaucoma, and for monitoring potential modulation of scleral stiffness in disease or treatment.

Clinical outcomes in post-epikeratophakic eyes after removal of epikeratoplasty lenticule

Background

Assessment of the optical outcome and adverse events in post-epikeratopathic eyes after removal of the epikeratoplasty lenticule (EKPL).

Methods

This was a retrospective case-series study of patients who underwent EKPL removal between 2002 and 2020. Ten eyes were included in the analysis. We compared the clinical characteristics of the patients before surgery, 6 months after surgery, before lenticular removal, and after removal, and reported optical or ocular surface complications.

Results

We removed EKPL due to the lenticular opacity in five eyes (50%), intraocular lens (IOL) insertion (n = 4, 40%) after cataract surgery (n = 3) or in aphakic eyes (n = 1), and lenticule-induced irregular astigmatism in one eye (10%). After EKPL removal, the mean refractive power of the cornea (Km) revealed a tendency to increase. Out of nine cases, six cases showed corneal steepening and three cases revealed corneal flattening. When the keratometric readings of pre-epikeratoplasty and post-lenticular removal were compared within the same case, the average difference was 5.1 D ± 4.0 (n = 8). Complications were observed in 3 of 10 cases (excessive corneal flatness, ectatic change, and abnormal epithelial cell ingrowth) after removal.

Conclusions

The surgeon should expect the corneal refractive power to steepen or flatten in some cases with abnormal astigmatism and irregularity. Epikeratophakic eyes may exhibit serious ectatic changes, and abnormal epithelial cell ingrowth after removal of epikeratophakic lenticules.

Nonocular Influencing Factors for Primary Glaucoma: An Umbrella Review of Meta-Analysis

INTRODUCTION

Glaucoma is the main cause of irreversible blindness worldwide. Still, little is known about nonocular risk factors. We use an umbrella review to examine the meta-analytic evidence of the correlation between nonocular factors and glaucoma.

METHOD

We searched PubMed and Embase databases up to July 24, 2020. Eligible meta-analyses (MAs) included cohort, case-control, and randomized controlled study designs. Two authors independently extracted the data and evaluated the methodological quality of the MAs. AMSTAR 2 was used to assess the methodological quality of each included MA.

RESULTS

This umbrella review contains 22 MAs with 22 unique nonocular factors in total. We identified 11 factors that increase the risk of glaucoma: hyperlipidemia, nocturnal dip in blood pressure, infection with Helicobacter pylori, myopia, obstructive sleep apnea syndrome, corneal properties, diabetes, hypertension, hypothyroidism, migraine, and plasma homocysteine. We identified 3 factors that reduce the risk of glaucoma: dietary intake of vitamin A, dietary intake of vitamin C, and short-term statin use. We identified 8 factors that had no association with glaucoma: dietary intake of vitamin B, dietary intake of vitamin E, cigarette smoking, Alzheimer's disease, serum folic acid, serum vitamin B6, serum vitamin B12, and serum vitamin D.

CONCLUSIONS

In this umbrella review of MAs, evidence was found for associations of various nonocular factors with glaucoma to different degrees. However, risk factors were only mildly associated, suggesting low impact of systemic risk factors. Additional higher quality studies are needed to provide robust evidence.

Dynamic changes of scleral spur length in different accommodation stimuli states

This study aimed to evaluate the scleral spur length (SSL) in response to different accommodation stimuli states, as well as the correlation with Schlemm’s canal (SC) and trabecular meshwork (TM). 74 children were recruited for this study. The 0D, − 4D, and − 8.0 D accommodation stimuli state was achieved by looking at a variable distance optotype. The ciliary muscle (CM), scleral spur (SS), SC, and TM were imaged by swept-source optical coherence tomography. The SSL (Method III) increased significantly from 221.56 ± 30.74 μm at base state to 234.99 ± 30.11 μm at − 4D accommodation stimuli state (p = 0.028) and increased to 250.09 ± 29.87 μm at − 8D accommodation stimuli state (p = 0.011). Method III had the largest areas under receiver operating characteristic (ROC) curves (0.798, 95% CI 0.721–0.875). Moreover, CM 1, SC, and trabecular meshwork length (TML) were significantly correlated with SSL (Method III) (p < 0.05). These findings suggest that the contractile ability and compliance of the SS play an important role in maintaining the morphology of the SC. Moreover, the force of accommodation regulates the SC size by increasing the length of SS.

Functional integration of eye tissues and refractive eye development: Mechanisms and pathways

Refractive eye development is a tightly coordinated developmental process. The general layout of the eye and its various components are established during embryonic development, which involves a complex cross-tissue signaling. The eye then undergoes a refinement process during the postnatal emmetropization process, which relies heavily on the integration of environmental and genetic factors and is controlled by an elaborate genetic network. This genetic network encodes a multilayered signaling cascade, which converts visual stimuli into molecular signals that guide the postnatal growth of the eye. The signaling cascade underlying refractive eye development spans across all ocular tissues and comprises multiple signaling pathways. Notably, tissue-tissue interaction plays a key role in both embryonic eye development and postnatal eye emmetropization. Recent advances in eye biometry, physiological optics and systems genetics of refractive error have significantly advanced our understanding of the biological processes involved in refractive eye development and provided a framework for the development of new treatment options for myopia. In this review, we summarize the recent data on the mechanisms and signaling pathways underlying refractive eye development and discuss new evidence suggesting a wide-spread signal integration across different tissues and ocular components involved in visually guided eye growth.

Quantitative proteomic analysis of scleras in guinea pig exposed to wavelength defocus

Myopia is the most common optical disorder in the world, and wavelength defocus induced ametropia and myopia have attracted great attention. The objective was to identify and quantify scleral proteins involved in the response to the wavelength defocus. Guinea pigs were randomly divided into 3 groups that received different lighting conditions for 8 weeks: white light, short wavelength light, and long wavelength light. Refraction and axial length were measured, Hematoxylin-Eosin staining and transmission electron microscope were adopted to observe the scleral structure, and scleral proteome was also detected to analyze protein abundance by employing TMT labeling method. After light stimulation, the long- and short -wavelength light induced myopic and hyperopic effect on the guinea pig's eye and induced distinct protein signature, respectively. 186 dyregulated proteins between the short- and long-wavelength group were identified, which were mainly located in extracellular region and involved in metabolic process. We also found that 5 proteins in the guinea pigs scleras in response to wavelength defocus were also human myopic candidate targets, suggesting functional overlap between dyregulated proteins in scleral upon exposure to wavelength defocus and genes causing myopia in humans. SIGNIFICANCE: Wavelength defocus induces refractive errors and leads to myopia or hyperopia. However, sclera proteomics respond to wavelength defocus is lacking, which is crucial to understanding how wavelength defocus influences refractive development and induces myopia. In this proteome analysis, we identified unique protein signatures response to wavelength defocus in sclera of guinea pigs, identified potential mechanisms contributing to myopia formation, and found that several human myopia-related genes may involve in response to wavelength defocus. The results of this study provide a foundation to understand the mechanisms of myopia and wavelength defocus induced ametropia.

The plasminogen protein is associated with high myopia as revealed by the iTRAQ-based proteomic analysis of the aqueous humor

To explore the pathogenesis of high myopia (HM) using quantitative proteomics. The aqueous humor of patients with simple nuclear cataract and nuclear cataract complicated with HM (hereinafter referred to as "C" and "HM" groups, respectively) were collected. The isobaric tags for relative and absolute quantitation (iTRAQ)-based liquid chromatography-tandem mass spectrometry (LC-MS/MS) proteomics approach was employed to explore differentially expressed proteins (DEPs). Bioinformatics was used to interpret the proteomic results. Furthermore, the plasminogen (PLG) protein was confirmed by enzyme-linked immunosorbent assay (ELISA) as the candidate biomarker for HM through a receiver operating characteristic curve analysis. The study showed 32 upregulated and 26 downregulated proteins. The gene ontology analysis demonstrated that 58 DEPs corresponded to 325 biological processes, 33 cell components, and 45 molecular functional annotations. The Kyoto Encyclopedia of Genes and Genomes analysis showed that the upregulated DEPs were highly enriched in the coagulation and complement cascades, consistent with the gene set enrichment analysis. Our data suggested that some DEPs might be hallmarks of the development of HM. ELISA confirmed that the PLG expression levels were significantly upregulated in HM. This was a new study investigating alterations in protein levels and affected pathways in HM using iTRAQ-based quantitative proteomics. Our study provided a comprehensive dataset on overall protein changes and shed light on its potential molecular mechanism in human HM.

The biological basis of myopic refractive error

Myopia is among the most common refractive errors and is associated with the greatest risk of pathological outcomes. Most animals, including humans, are born with hyperopic errors. During development, axial elongation of the eye occurs and is regulated through a vision-dependent process, known as emmetropisation The extremely rapid changes in the prevalence of myopia and the dependence of myopia on the level of education indicate that there are very strong environmental impacts on the development of myopia. This conflicts with the common occurrence of familial patterns of inheritance of myopia, which suggests a role for genetic determination. There are more than 150 defined genetic syndromes in which familial high myopia is one of the features, including some that are not associated with other syndromes. The evidence for the roles of both nature and nurture in the aetiology of myopia is discussed. This review also examines the experimentally induced refractive errors associated with form-deprivation, recovery from form deprivation and the effects of both negative and positive lenses. In addition, it looks at the local and optical control of eye growth. Finally, the various control pathways for growth are considered. These include dopamine, ZENK-glucagon, retinoic acid and retinoic acid receptors, crystallin, seratonin and melatonin, vasoactive intestinal peptide and enkephalins, nitric oxide and various growth factors.

Decreased choroidal and scleral thicknesses in highly myopic eyes with posterior staphyloma

In this cross-sectional study, we investigated choroidal thickness (CT) and scleral thickness (ST) in highly myopic eyes and their associations with ocular factors. Patients underwent widefield swept-source optical coherence tomography (OCT) to measure the CT and ST at the subfovea and 3000 μm superior, inferior, temporal, and nasal to the fovea and macular curvature. A total of 237 eyes (154 patients) were included. At all five measurement points, thinner CTs and STs were associated with longer axial lengths (r = − 0.548 to − 0.357, all P < 0.001) and greater macular curvatures (r = − 0.542 to − 0.305, all P < 0.001). The CT and ST were significantly thinner in eyes with posterior staphyloma than in those without at all measurement points (all P ≤ 0.006) but did not differ between eyes with the wide macular and narrow macular type of staphyloma. Eyes with myopic maculopathy of category ≥ 3 according to the International Meta-Analysis for Pathologic Myopia classification had significantly thinner CTs and STs than those with category ≤ 2 (all P ≤ 0.005). In highly myopic eyes, a decrease in the CT and ST was more pronounced in eyes with more structural changes, such as longer axial length, steeper macular curvature, and the presence of posterior staphyloma.

The development of and recovery from form-deprivation myopia in infant rhesus monkeys reared under reduced ambient lighting

Although reduced ambient lighting ("dim" light) can cause myopia in emmetropizing chicks, it does not necessarily lead to myopic changes in emmetropizing rhesus monkeys. Because myopia is rarely spontaneous, a question remained whether dim light would hasten the progression of visually induced myopia. To determine the effects of dim light on the development of and recovery from form-deprivation myopia (FDM), seven 3-week-old infant rhesus monkeys were reared under dim light (mean ± SD = 55 ± 9 lx) with monocular diffuser spectacles until ~154 days of age, then maintained in dim light with unrestricted vision until ~337 days of age to allow for recovery. Refractive errors, corneal powers, ocular axial dimensions and sub-foveal choroidal thicknesses were measured longitudinally and compared to those obtained from form-deprived monkeys reared under typical laboratory lighting (504 ± 168 lx). Five of the seven subjects developed FDMs that were similar to those observed among their normal-light-reared counterparts. The average degree of form-deprivation-induced myopic anisometropia did not differ significantly between dim-light subjects (-3.88 ± 3.26D) and normal-light subjects (-4.45 ± 3.75D). However, three of the five dim-light subjects that developed obvious FDM failed to exhibit any signs of recovery and the two monkeys that were isometropic at the end of the treatment period manifest abnormal refractive errors during the recovery period. All refractive changes were associated with alterations in vitreous chamber elongation rates. It appears that dim light is not a strong myopiagenic stimulus by itself, but it can impair the optical regulation of refractive development in primates.

Advanced Research in Scleral Cross-Linking to Prevent From Progressive Myopia

ABSTRACT

Riboflavin-ultraviolet A (UVA) collagen cross-linking (CXL) has been applied in clinical settings to prevent the progression of keratoconus and corneal dilatation caused by other reasons in past decades. As CXL with riboflavin-UVA can enhance the stiffness of collagen-rich tissues, this technique has been further used on sclera to investigate as a safe and effective myopia prevention treatment. Despite the riboflavin-UVA scleral CXL is still in the animal and in vitro experimental phases and the mechanism is not very clear, it is promising to control myopia development clinically. In this article, researches on the laboratory experiments of riboflavin-UVA scleral CXL on scheme exploration and mechanism were reviewed in order to provide more laboratory evidence for scleral CXL in clinical myopia prevention and control in the future.

Pharmacotherapeutic candidates for myopia: A review

This review provides insights into the mechanism underlying the pathogenesis of myopia and potential targets for clinical intervention. Although the etiology of myopia involves both environmental and genetic factors, recent evidence has suggested that the prevalence and severity of myopia appears to be affected more by environmental factors. Current pharmacotherapeutics are aimed at inhibiting environmentally induced changes in visual input and subsequent changes in signaling pathways during myopia pathogenesis and progression. Recent studies on animal models of myopia have revealed specific molecules potentially involved in the regulation of eye development. Among them, the dopamine receptor plays a critical role in controlling myopia. Subsequent studies have reported pharmacotherapeutic treatments to control myopia progression. In particular, atropine treatment yielded favorable outcomes and has been extensively used; however, current studies are aimed at optimizing its efficacy and confirming its safety. Furthermore, future studies are required to assess the efficacy of combinatorial use of low-dose atropine and contact lenses or orthokeratology.

Oral Bovine Milk Lactoferrin Administration Suppressed Myopia Development through Matrix Metalloproteinase 2 in a Mouse Model

Recent studies have reported an association between myopia development and local ocular inflammation. Lactoferrin (LF) is an iron-binding protein present in saliva, tears, and mother’s milk. Furthermore, sequestering iron by LF can cause its antibacterial property. Moreover, LF has an anti-inflammatory effect. We aimed to determine the suppressive effect of LF against the development and progress of myopia using a murine lens-induced myopia (LIM) model. We divided male C57BL/6J mice (3 weeks old) into two groups. While the experimental group was orally administered LF (1600 mg/kg/day, from 3-weeks-old to 7-weeks-old), a similar volume of Ringer’s solution was administered to the control group. We subjected the 4-week-old mice to −30 diopter lenses and no lenses on the right and left eyes, respectively. We measured the refraction and the axial length at baseline and 3 weeks after using a refractometer and a spectral domain optical coherence tomography (SD-OCT) system in both eyes. Furthermore, we determined the matrix metalloproteinase-2 (MMP-2) activity, and the amount of interleukin-6 (IL-6), MMP-2, and collagen 1A1 in the choroid or sclera. The eyes with a minus lens showed a refractive error shift and an axial length elongation in the control group, thus indicating the successful induction of myopia. However, there were no significant differences in the aforementioned parameters in the LF group. While LIM increased IL-6 expression and MMP-2 activity, it decreased collagen 1A1 content. However, orally administered LF reversed these effects. Thus, oral administration of LF suppressed lens-induced myopia development by modifying the extracellular matrix remodeling through the IL-6–MMP-2 axis in mice.

Effect of Regulating the Expression of HSP47 on Collagen Metabolism in Scleral Fibroblasts

PURPOSE

To explore the effect of heat shock protein 47 (HSP 47) on collagen (types I, III, and V) metabolism in scleral fibroblasts.

METHODS

Scleral fibroblasts with over- or low-expression of HSP 47 were constructed by plasmid transfection. The mRNA and intracellular proteins expression of HSP 47, collagen (types I, III, and V) and α-smooth muscle actin (α-SMA) were detected by quantitative real-time polymerase chain reaction and western blot. The proteins expression of collagen (types I, III, and V), matrix metalloproteinase 2 (MMP-2), and tissue inhibitor of matrix metalloproteinases 1 and 2 (TIMP-1 and -2) in extracellular matrix (ECM) were detected by ELISA. The migration and proliferation activities of cells were detected by scratch-wound assay and MTS. The internal structure of scleral fibroblasts was observed by transmission electron microscopy (TEM).

RESULTS

The results obtained demonstrated significant increases in the expression of the mRNA and protein expression of collagen I in HSP47 up-regulated cells. Overexpression of HSP 47 promotes the expression of α-SMA and cell migration. Down-regulated expression of HSP 47 results in decreased mRNA and protein expression of collagen. Low expression of HSP 47 significantly inhibits cell migration and proliferation, and affects the internal structure of cells.

CONCLUSION

HSP 47 affects collagen metabolism in scleral fibroblasts. It appears to promote the synthesis and secretion of collagen I as well as inhibit degradation.