Retinal and choroidal TGF-beta in the tree shrew model of myopia: isoform expression, activation and effects on function

Ciliary muscles contraction leads to axial length extension--The possible initiating factor for myopia

PURPOSE

This study aimed to investigate the underlying factors driving the onset of myopia, specifically the role of the ciliary muscle's contraction in the elongation of the axial length of the eye.

METHODS

The retrospective study was conducted utilizing data from three ophthalmic centers in Shanghai and Beijing. Both Chinese and Caucasian children were involved. The axial length of the subjects' eyes was measured in both relaxed and contracted state of the ciliary muscle. A comprehensive mechanical model was also developed to observe the influence of ciliary muscle contraction on the axial length.

RESULTS

This study included a sample of 198 right eyes of 198 myopic children. Of these, 97 were male and 101 were female, 126 were of Chinese ethnicity and 72 were Caucasian. The age of onset for myopia ranged from 5.9 to 16.9 years old. The axial length of the eye decreased 0.028 ± 0.007mm following dilation, indicating relaxation of the ciliary muscle (t paired student = 15.16, p = 6.72 x 10-35). In contrast, ciliary muscle contraction resulted in an increase in axial length. Considering proportionality, a significant 90.4% (179 eyes) exhibited a reduced axial length, while a minor 9.6% (19 eyes) demonstrated an increase post-mydriasis. Finite element modeling demonstrated that muscle contraction caused a tension force that transmits towards the posterior pole of the eye, causing it to extend posteriorly.

CONCLUSION

The contraction of the ciliary muscle leads to an extension of the axial length. This could potentially be the initiating factor for myopia.

The role of transforming growth factor beta in myopia development

Myopia is widely recognized as an epidemic. Studies have found a link between Transforming Growth Factor-beta (TGF-β) and myopia, but the specific molecular mechanisms are not fully understood. In this study, a monocular model in tree shrews (Tupaia belangeri) was established to verify the molecular mechanism of TGF-β in myopia. The results indicated that there were significant changes in TGF-βs during the treatment of myopia, which could enhance the refractive ability and axial length of the eye. Immunohistochemical staining, real-time fluorescent quantitative PCR, and immunoblotting results showed a significant upregulation of MMP2 and NF-κB levels, and a significant downregulation of COL-I expression in the TGF-β treated eyes, suggesting that NF-κB and MMP2 are involved in the signaling pathways of TGF-βs induced myopia and axial elongation. Moreover, the expression levels of IL-6, IL-8, MCP-1, IL-1β, TNF-α, TAK1, and NF-κB in the retina were all significantly elevated. This indicates that TGF-β stimulates the inflammatory response of retinal pigment epithelial cells through the TAK1-NF-κB signaling pathway. In conclusion, this study suggests that TGF-β promotes the progression of myopia by enhancing intraocular inflammation.

Reduction of experimental ocular axial elongation by neuregulin-1 antibody

Background

Since the mechanisms underlying myopic axial elongation have remained unclear, we examined the effect of neuregulin-1 (NRG-1), an epidermal growth factor family member, on myopic axial elongation.

Methods

The guinea pigs aged two to three weeks were subjected to bilateral negative lens-induced axial elongation and received weekly intravitreal injections into their right eyes of NRG-1 antibody (doses: 5 μg, n = 8; 10 μg, n = 8, 20 μg, n = 9) or of NRG-1 (doses: 0.05 μg, n = 8; 0.01 μg, n = 9; 0.2 μg, n = 8), underwent only bilateral negative lens-induced axial elongation (myopia control group, n = 10), or underwent no intervention (control group, n = 10). The contralateral eyes received corresponding intravitreal phosphate-buffered solution injections. One week after the last injection, the guinea pigs were sacrificed, the eyeballs were removed, the thicknesses of the retina and sclera were histologically examined, the expression of NRG-1 and downstream signal transduction pathway members (ERK1/2 and PI3K/AKT) and the mRNA expression of NRG-1 in the retina was assessed.

Results

The inter-eye difference in axial length at study end increased (p < 0.001) from the normal control group (-0.02 ± 0.09 mm) and the myopia control group (-0.01 ± 0.09 mm) to the low-dose NRG-1 antibody group (-0.11 ± 0.05 mm), medium-dose NRG-1 antibody group (-0.17 ± 0.07 mm), and high-dose NRG-1 antibody group (-0.28 ± 0.06 mm). The relative expression of NRG-1, ERK1/2, and PI3K/AKT in the retina decreased in a dose-dependent manner from the myopia control group to the NRG-1 antibody groups and the normal control group. The relative NRG-1 mRNA expression in the retina was higher (p < 0.01) in the myopic control group than in the NRG-1 antibody groups and normal control group. Scleral and retinal thickness decreased from the normal control group to the NRG-1 antibody groups to the myopic control group. After intraocular injection of NRG-1 protein, there was a slight dose-dependent increase in the difference in axial length between the right and left eye, however not statistically significantly, from the normal control group (-0.02 ± 0.09 mm) to the high-dose NRG-1 protein group (0.03 ± 0.03 mm; p = 0.12).

Conclusion

Intravitreal NRG-1 antibody application was dose-dependently and time-dependently associated with a reduction in negative lens-induced axial elongation in young guinea pigs.

Myopia: Histology, clinical features, and potential implications for the etiology of axial elongation

Myopic axial elongation is associated with various non-pathological changes. These include a decrease in photoreceptor cell and retinal pigment epithelium (RPE) cell density and retinal layer thickness, mainly in the retro-equatorial to equatorial regions; choroidal and scleral thinning pronounced at the posterior pole and least marked at the ora serrata; and a shift in Bruch's membrane opening (BMO) occurring in moderately myopic eyes and typically in the temporal/inferior direction. The BMO shift leads to an overhang of Bruch's membrane (BM) into the nasal intrapapillary compartment and BM absence in the temporal region (i.e., parapapillary gamma zone), optic disc ovalization due to shortening of the ophthalmoscopically visible horizontal disc diameter, fovea-optic disc distance elongation, reduction in angle kappa, and straightening/stretching of the papillomacular retinal blood vessels and retinal nerve fibers. Highly myopic eyes additionally show an enlargement of all layers of the optic nerve canal, elongation and thinning of the lamina cribrosa, peripapillary scleral flange (i.e., parapapillary delta zone) and peripapillary choroidal border tissue, and development of circular parapapillary beta, gamma, and delta zone. Pathological features of high myopia include development of macular linear RPE defects (lacquer cracks), which widen to round RPE defects (patchy atrophies) with central BM defects, macular neovascularization, myopic macular retinoschisis, and glaucomatous/glaucoma-like and non-glaucomatous optic neuropathy. BM thickness is unrelated to axial length. Including the change in eye shape from a sphere in emmetropia to a prolate (rotational) ellipsoid in myopia, the features may be explained by a primary BM enlargement in the retro-equatorial/equatorial region leading to axial elongation.

The Genetic Determinants of Axial Length: From Microphthalmia to High Myopia in Childhood

The axial length of the eye is critical for normal visual function by enabling light to precisely focus on the retina. The mean axial length of the adult human eye is 23.5 mm, but the molecular mechanisms regulating ocular axial length remain poorly understood. Underdevelopment can lead to microphthalmia (defined as a small eye with an axial length of less than 19 mm at 1 year of age or less than 21 mm in adulthood) within the first trimester of pregnancy. However, continued overgrowth can lead to axial high myopia (an enlarged eye with an axial length of 26.5 mm or more) at any age. Both conditions show high genetic and phenotypic heterogeneity associated with significant visual morbidity worldwide. More than 90 genes can contribute to microphthalmia, and several hundred genes are associated with myopia, yet diagnostic yields are low. Crucially, the genetic pathways underpinning the specification of eye size are only now being discovered, with evidence suggesting that shared molecular pathways regulate under- or overgrowth of the eye. Improving our mechanistic understanding of axial length determination will help better inform us of genotype-phenotype correlations in both microphthalmia and myopia, dissect gene-environment interactions in myopia, and develop postnatal therapies that may influence overall eye growth.

Aqueous humor cytokine levels are associated with the severity of visual field defects in patients with primary open-angle glaucoma

BACKGROUND

To evaluate the aqueous humor (AH) levels of cytokines in primary open-angle glaucoma (POAG) patients and cataract patients.

METHODS

Thirty-eight POAG patients and 26 cataract patients were recruited. Peripheral blood (PB) was collected from each subject. The POAG group was divided into 2 subgroups according to the severity of visual field defects. The cutoff point of the mean deviation (MD) of the visual field was -12 dB. AH was obtained at the time of anterior chamber puncture during cataract or glaucoma surgery by using a 27-gauge needle attached to a microsyringe. AH and PB levels of interleukin-2 (IL-2), tumor necrosis factor-alpha (TNF-α), transforming growth factor-beta2 (TGF-β2) and IL-4 were assayed by enzyme-linked immunosorbent assay. Postoperative intraocular pressures (IOPs) of POAG patients were recorded during the follow-up period.

RESULTS

TNF-α and TGF-β2 showed significantly higher AH levels in the POAG group than in the cataract group (P < 0.001 and P = 0.001, respectively). For the POAG group, preoperative IOPs were significantly positively correlated with AH levels of TNF-α (r² = 0.129, P = 0.027) and TGF-β2 (r² = 0.273, P = 0.001). AH levels of TGF-β2 were significantly different among cataract patients, POAG patients with MD> -12 dB and POAG patients with MD≤ -12 dB (P = 0.001). AH levels of TNF-α were significantly positively associated with IOP reduction after trabeculectomy (P = 0.025). AH and PB levels of cytokines were not related to the long-term success of trabeculectomy.

CONCLUSION

The levels of TNF-α and TGF-β2 showed different profiles in POAG patients and cataract patients. AH levels of TGF-β2 were correlated with the severity of glaucomatous neuropathy in POAG patients. The findings suggest possible roles for cytokines in the pathogenesis and development of POAG.

Lrpap1 deficiency leads to myopia through TGF-β-induced apoptosis in zebrafish

BACKGROUND

Frameshift mutations in LRPAP1 are responsible for autosomal recessive high myopia in human beings but its underlying mechanism remains elusive. This study aims to investigate the effect of LRPAP1 defect on ocular refractive development and its involved mechanism.

METHODS

A lrpap1 mutant zebrafish line with homozygous frameshift mutation was generated by CRISPR/Cas9 technology and confirmed by Sanger sequencing. The ocular refractive phenotype was analyzed by calculating the relative refractive error (RRE) with vivo photography and histological analysis at different development stages, together with examining ocular structure change via transmission electron microscopy. Further, RNA sequencing and bioinformatics analysis were performed. The potentially involved signaling pathway as well as the interacted protein were investigated in vivo.

RESULTS

The lrpap1 homozygous mutant zebrafish line showed myopic phenotype. Specifically, the mutant lines showed larger eye axial length-to-body length in one-month old individuals and a myopic shift with an RRE that changed after two months. Collagen fibers became thinning and disordered in the sclera. Further, RNA sequencing and bioinformatics analysis indicated that apoptosis signaling was activated in mutant line; this was further confirmed by acridine orange and TUNEL staining. Moreover, the expression of TGF-β protein was elevated in the mutant lines. Finally, the treatment of wild-type embryos with a TGF-β agonist aggravated the degree of eyeball apoptosis; conversely, the use of a TGF-β inhibitor mitigated apoptosis in mutant embryos.

CONCLUSION

The study provides functional evidence of a link between lrpap1 and myopia, suggesting that lrpap1 deficiency could lead to myopia through TGF-β-induced apoptosis signaling. Video abstract.

The Effect of Citicoline on the Expression of Matrix Metalloproteinase-2 (MMP-2), Transforming Growth Factor-β1 (TGF-β1), and Ki-67, and on the Thickness of Scleral Tissue of Rat Myopia Model

Citicoline, presumed to be involved in the dopaminergic pathway, might play a role as a candidate agent in controlling myopia. However, its study with respect to myopia is limited. The aim of this study is to demonstrate the effect of citicoline on the expression of MMP-2, TGF-β1, and Ki-67, and on the thickness of scleral tissue of a rat myopia model. Immunohistochemistry was performed to evaluate the expression of MMP-2, TGF-β1, and Ki-67 as the markers for fibroblast proliferation. Hematoxylin and eosin staining were used to evaluate scleral thickness. An electronic digital caliper was used to evaluate the axial length. The treatment group administered with 200 mg/kg BW/day had the lowest mean MMP-2 expression, axial elongation, and fibroblast proliferation, but it had the highest mean scleral thickness. The treatment group administered with 300 mg/kg BW/day had the highest mean TGF-β1 expression. Citicoline is able to decrease MMP-2 expression and fibroblast proliferation and increase TGF-β1 expression and scleral tissue thickness significantly in the scleral tissue of rat models for myopia.

Epiregulin, epigen and betacellulin antibodies and axial elongation in young guinea pigs with lens-induced myopization

Background

To examine an effect of intravitreally applied antibodies against epidermal growth factor family members, namely epiregulin, epigen and betacellulin, on ocular axial elongation.

Methods

The experimental study included 30 guinea pigs (age:3–4 weeks) which underwent bilateral lens-induced myopization and received three intraocular injections of 20 µg of epiregulin antibody, epigen antibody and betacellulin antibody in weekly intervals into their right eyes, and of phosphate-buffered saline into their left eyes. Seven days after the last injection, the animals were sacrificed. Axial length was measured by sonographic biometry.

Results

At baseline, right eyes and left eyes did not differ (all P > 0.10) in axial length in neither group, nor did the interocular difference in axial length vary between the groups (P = 0.19). During the study period, right and left eyes elongated (P < 0.001) from 8.08 ± 0.07 mm to 8.59 ± 0.06 mm and from 8.08 ± 0.07 mm to 8.66 ± 0.07 mm, respectively. The interocular difference (left eye minus right eye) in axial elongation increased significantly in all three groups (epiregulin-antibody:from 0.03 ± 0.06 mm at one week after baseline to 0.16 ± 0.08 mm at three weeks after baseline;P = 0.001); epigen-antibody group:from -0.01 ± 0.06 mm to 0.06 ± 0.08 mm;P = 0.02; betacellulin antibody group:from -0.05 ± 0.05 mm to 0.02 ± 0.04 mm;P = 0.004). Correspondingly, interocular difference in axial length increased from -0.02 ± 0.04 mm to 0.13 ± 0.06 mm in the epiregulin-antibody group (P < 0.001), and from 0.01 ± 0.05 mm to 0.07 ± 0.05 mm in the epigen-antibody group (P = 0.045). In the betacellulin-antibody group the increase (0.01 ± 0.04 mm to 0.03 ± 0.03 mm) was not significant (P = 0.24).

Conclusions

The EGF family members epiregulin, epigen and betacellulin may be associated with axial elongation in young guinea pigs, with the effect decreasing from epiregulin to epigen and to betacellulin.

Quantitative evaluation of retinal and choroidal vascularity and retrobulbar blood flow in patients with myopic anisometropia by CDI and OCTA

AIMS

To investigate the association between the myopic severity and retinal microvascular density, choroidal vascularity and retrobulbar blood flow in adult anisomyopes.

METHODS

This study comprised 90 eyes of 45 myopic anisomyopes who were recruited for Colour Doppler imaging (CDI) and optical coherence tomography angiography (OCTA). The superficial vessel density (SVD), deep vessel density (DVD), choroidal thickness (ChT) and choroidal vascularity, including total choroidal area (TCA), luminal area (LA), stromal area (SA) and Choroidal Vascularity Index (CVI), were measured using OCTA. Moreover, the Pulsatile Index, peak systolic velocity (PSV) and end diastolic velocity (EDV) of posterior ciliary artery (PCA), central retinal artery (CRA) and ophthalmic artery (OA) were quantified by CDI, and all parameters were compared between two eyes and the correlations among parameters were analysed.

RESULTS

The mean difference of spherical equivalent (SE) and axial lengths (AL) between eyes were -6.00±2.94 D and 2.48±1.31 mm, respectively. The SVD, DVD, ChT, TCA, LA, SA and CVI were significantly lower in more myopic eyes compared with the contralateral eyes. In more myopic eyes, CDI parameters of CRA and PSV and EDV of PCA were also significantly lower. After adjusting for age and sex, the binocular asymmetry in LA and ChT was independent risk factor affecting interocular difference in both AL and SE.

CONCLUSION

Retinal microvascular density, choroidal vascularity and retrobulbar blood flow were simultaneously lower in adult myopic anisomyopes with more myopic eyes and disturbed choroid circulation was related to the severity of myopia. Further longitudinal study was helped to identify the effect of choroidal parameters for myopic progression.

Hsa-miR-142-3p reduces collagen I in human scleral fibroblasts by targeting TGF-β1 in high myopia

High myopia has been continually increasing globally until now and often results in visual impairment. Scleral extracellular matrix (ECM) remodeling is considered a common factor contributing to progression of myopia. However, the role of microRNAs (miRNAs) in regulating scleral ECM organization is not well understood. We aimed to explore the effect and regulatory mechanism of hsa-miR-142-3p on collagen I in human scleral fibroblasts in high myopia. First, next-generation sequencing was conducted to identify 37 miRNAs differentially expressed in the aqueous humor of high myopia samples and control samples. Furthermore, hsa-miR-142-3p in the aqueous humor was found to positively relate to the ocular axial length. Besides, the results of immunofluorescence and Western blot assay indicated that hsa-miR-142-3p overexpression decreased collagen I expression in the human fetal scleral fibroblasts (HFSFs); while hsa-miR-142-3p downregulation increased collagen I. Moreover, hsa-miR-142-3p targets TGFβ-1 gene expression. Quantitative polymerase chain reaction (qPCR) and Western blot analysis showed that miRNA 142-3p reduced TGFβ-1 expression while an inhibitor had an opposite effect. Therefore, there is an inverse relationship between changes in miR-142-3p expression levels and those of collagen1a1 in human scleral fibroblasts. Such a dependence suggests that miR-142-3p may be a target to improve therapeutic management of this condition.

The influence of the choroid on the onset and development of myopia: from perspectives of choroidal thickness and blood flow

Myopia is the most common type of refractive errors characterized by excessive elongation of the ocular globe. With the increasing prevalence of myopia, improved knowledge of factors involved in myopia development is of particular importance. There are growing evidence suggesting that the choroid plays an important role in the regulation of eye growth and the development of myopia. Studies have demonstrated that thinning choroid is a structural feature of myopia, with a negative correlation between choroidal thickness and axial length, suggesting that the change in choroidal thickness may be a predictive biomarker for long-term changes in ocular elongation. Given the fact that the choroid is primarily a vascular structure capable of rapidly changing blood flow, variations of choroidal thickness might be primarily caused by changes in choroidal blood flow. Considering that hypoxia is associated with myopia and choroidal blood flow is the main source of oxygen and nourishment supply, apart from the effect on myopia possibly by changing choroidal thickness, decreasing choroidal blood flow may contribute to scleral ischaemia and hypoxia, resulting in alterations in the scleral structure and thus leading to myopia. This review aims to provide an overview of recent work exploring the influence of the choroid on myopia from perspectives of choroidal thickness and blood flow, which may present new predictive indicators for the onset of myopia and new targets for the development of novel therapeutic approaches for myopia.

SLC39A5 dysfunction impairs extracellular matrix synthesis in high myopia pathogenesis

High myopia is one of the leading causes of visual impairment worldwide with high heritability. We have previously identified the genetic contribution of SLC39A5 to nonsyndromic high myopia and demonstrated that disease‐related mutations of SLC39A5 dysregulate the TGF‐β pathway. In this study, the mechanisms underlying SLC39A5 involvement in the pathogenesis of high myopia are determined. We observed the morphogenesis and migration abnormalities of the SLC39A5 knockout (KO) human embryonic kidney cells (HEK293) and found a significant injury of ECM constituents. RNA‐seq and qRT‐PCR revealed the transcription decrease in COL1A1, COL2A1, COL4A1, FN1 and LAMA1 in the KO cells. Further, we demonstrated that TGF‐β signalling, the regulator of ECM, was inhibited in SLC39A5 depletion situation, wherein the activation of receptor Smads (R‐Smads) via phosphorylation was greatly blocked. SLC39A5 re‐expression reversed the phenotype of TGF‐β signalling and ECM synthesis in the KO cells. The fact that TGF‐β signalling was zinc‐regulated and that SLC39A5 was identified as a zinc transporter urged us to check the involvement of intracellular zinc in TGF‐β signalling impairment. Finally, we determined that insufficient zinc chelation destabilized Smad proteins, which naturally inhibited TGF‐β signalling. Overall, the SLC39A5 depletion–induced zinc deficiency destabilized Smad proteins, which inhibited the TGF‐β signalling and downstream ECM synthesis, thus contributing to the pathogenesis of high myopia. This discovery provides a deep insight into myopic development.

Characterization of tree shrew telomeres and telomerase

The use of tree shrews as experimental animals for biomedical research is a new practice. Several recent studies suggest that tree shrews are suitable for studying cancers, including breast cancer, glioblastoma, lung cancer, and hepatocellular carcinoma. However, the telomeres and the telomerase of tree shrews have not been studied to date. Here, we characterize telomeres and telomerase in tree shrews. The telomere length of tree shrews is approximately 23 kb, which is longer than that of primates and shorter than that of mice, and it is extended in breast tumor tissues according to Southern blot and flow-fluorescence in situ hybridization analyses. Tree shrew spleen, bone marrow, testis, ovary, and uterus show high telomerase activities, which are increased in breast tumor tissues by telomeric repeat amplification protocol assays. The telomere length becomes shorter, and telomerase activity decreases with age. The tree shrew TERT and TERC are more highly similar to primates than to rodents. These findings lay a solid foundation for using tree shrews to study aging and cancers.

Whole-Exome Sequencing in a Cohort of High Myopia Patients in Northwest China

High myopia (HM) is one of the leading causes of visual impairment worldwide. In order to expand the myopia gene spectrum in the Chinese population, we investigated genetic mutations in a cohort of 27 families with HM from Northwest China by using whole-exome sequencing (WES). Genetic variations were filtered using bioinformatics tools and cosegregation analysis. A total of 201 candidate mutations were detected, and 139 were cosegregated with the disease in the families. Multistep analysis revealed four missense variants in four unrelated families, including c.904C>T (p.R302C) in CSMD1, c.860G>A (p.R287H) in PARP8, c.G848A (p.G283D) in ADAMTSL1, and c.686A>G (p.H229R) in FNDC3B. These mutations were rare or absent in the Exome Aggregation Consortium (ExAC), 1000 Genomes Project, and Genome Aggregation Database (gnomAD), indicating that they are new candidate disease-causing genes. Our findings not only expand the myopia gene spectrum but also provide reference information for further genetic study of heritable HM.

Relationship between Axial Length and Levels of TGF-β in the Aqueous Humor and Plasma of Myopic Patients

Purpose

To investigate the levels of transforming growth factor-β (TGF-β) in human aqueous humor (AH) and plasma (PL) of patients with myopia, and verify whether there is an association between these levels and their association with axial length (AL).

Methods

Thirty-eight myopic patients who received intraocular collamer lens (ICL) implantation were enrolled in this cross-sectional study. Patients were divided into three groups based on AL with cut-off points of 26 and 28 mm. AH and PL samples were obtained during ICL implantation surgery. The levels of TGF-β1, TGF-β2, and TGF-β3 in the AH and PL samples were measured using Luminex xMAP Technology kits (Milliplex xMAP kits). The protein levels of TGF-βs in both AH and PL samples and their relationships with AL were analyzed.

Results

In all, 38 patients (59 eyes) were enrolled and divided into the three groups: group A contained 7 people (10 eyes), group B contained 22 people (37 eyes), and group C contained 9 people (12 eyes). In the AH group, we detected TGF-β1 (P₅₀: 19.97 pg/mL), TGF-β2 (2446.00 pg/mL), and TGF-β3 (26.33 pg/mL); in PL, these concentrations were 8984.00, 523.44, and 210.47 pg/mL, respectively. The levels of TGF-β1 and TGF-β3 in AH were positively associated with AL. None of the three isoforms in PL were related to those in AH or to AL.

Conclusions

The levels of TGF-β1 and TGF-β3 in AH were more strongly associated with the severity of myopia than the types of TGF-β in PL.

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.

Blockade of epidermal growth factor and its receptor and axial elongation in experimental myopia

To examine the influence of epidermal growth factor (EGF) and its receptor (EGFR) on axial ocular elongation, we intraocularly injected an EGF antibody and an EGFR antibody into young guinea pigs with lens-induced axial elongation (myopization). Mean axial elongation was reduced in the eyes injected with the EGF/EGFR-antibody compared with the contralateral control eyes injected with PBS (phosphate-buffered solution) (0.43 ± 0.13 mm vs 0.53 ± 0.13 mm; P < .001). The intereye difference in axial length increased (P = .005) as the doses of the EGF antibody and EGFR antibody increased. As a corollary, the thickness of the retina at the posterior pole was dose-dependently increased in the injected eyes compared to the contralateral control eyes. Immunohistochemical staining for EGF and the relative mRNA expression of EGF and EGFR were the highest in eyes not injected with the EGF antibody or EGFR antibody and decreased (P < .05) as the dose of EGF antibody or EGFR antibody increased. In an in vitro study, EGF had a stimulating effect and the EGF antibody had an inhibitory effect on the proliferation and migration of RPE cells. The findings showed that the intravitreal application of an EGF antibody and EGFR antibody is associated with a dose-dependent reduction in lens-induced axial elongation in young guinea pigs. The EGFR family may play a role in axial elongation of the eye and in the development of myopia.

Retinal defocus and form-deprivation induced regional differential gene expression of bone morphogenetic proteins in chick retinal pigment epithelium

We previously reported bidirectional gene expression regulation of the Bone Morphogenetic Proteins (BMP2, 4, and 7) in chick retinal pigment epithelium (RPE) in response to imposed optical defocus and form-deprivation (FD). This study investigated whether there are local (regional) differences in these effects. 19-day old White-Leghorn chicks wore monocular +10 or - 10 D lenses, or diffusers (FD) for 2 or 48 hr, after which RPE samples were collected from both eyes, from a central circular zone (3 mm radius), and 3 mm wide annular mid-peripheral and peripheral zones in all cases. BMP2, 4, and 7 gene expression levels in RPE from treated and fellow control eyes were compared as well as differences across zones. With the +10 D lens, increased expression of both BMP2 and BMP4 genes was observed in central and mid-peripheral zones but not the peripheral zone after 2 and 48 hr. In contrast, with the -10 D lens BMP2 gene expression was significantly decreased in all three zones after 2 and 48 hr. Similar patterns of BMP2 gene expression were observed in all three zones after 48 hr of FD. Smaller changes were recorded for BMP4 and BMP7 gene expression for both myopia-inducing treatments. That optical defocus- and FD-induced changes in BMP gene expression in chick RPE show treatment-dependent local (regional) differences suggest important differences in the nature and contributions of local retinal and underlying RPE regions to eye growth regulation.

Mutation screening of 17 candidate genes in a cohort of 67 probands with early-onset high myopia

PURPOSE

To detect variants in 17 known potentially causative genes for non-syndromic myopia in 67 Tujia Chinese patients with early-onset high myopia (eo-HM).

METHODS

DNA from 67 unrelated patients with early onset (<7 years old) high myopia (refraction error ≤ -6.00D or axial length > 26 mm) were subjected to whole-exome sequencing (WES). Variants in 17 candidate genes were analysed by multistep bioinformatics analysis. Subsequently, Sanger sequencing was used to verify identified candidate mutations and to assess available family members for co-segregation with myopia.

RESULTS

A multistep systematic analysis of variants in 17 potentially causative genes for eo-HM revealed four novel pathogenic mutations and three potential pathogenic mutations in 4 of 17 genes in 7 of 67 (10.4%) probands. The pathogenic group included one missense mutation (c.100G > C, p.Asp34His) and one splice donor mutation (c.989 + 1G >A) in ARR3, one missense mutation (c.995C > A, p.Thr332Lys) in NDUFAF7 and one novel frameshift mutation (c.726dupA, p.Arg243fs*140) in SLC39A5. The potential pathogenic group included two missense mutations (c.3266A > G, p.Tyr1089Cys; c.913G > A, p.Glu305Lys) in ZNF644 and one missense mutation (c.960T > A, p.His320Gln) in NDUFAF7. Sequence changes were confirmed by Sanger sequencing; all had an allele frequency <0.01 in the 1000G, EVS, ExAC and gnomAD databases. Additionally, both the pathogenic and potentially pathogenic mutations were predicted to be damaging by SIFT, Polyphen-2, PROVEAN, MutationTaster2, CADD and REVEL except the p.Tyr1089Cys and p.Glu305Lys changes were predicted to be neutral by PROVEAN.

CONCLUSION

Our research provides more evidence to support the hypothesis that mutations in ARR3, SLC39A5 and NDUFAF7 are disease-causing genes for eo-HM and broadens the eo-HM mutation spectrum among different ethnic groups. It also deepens understanding of the contributions of ARR3, SLC39A5, and NDUFAF7 to eo-HM.

Change in subfoveal choroidal thickness secondary to orthokeratology and its cessation: a predictor for the change in axial length

PURPOSE

To investigate changes in subfoveal choroidal thickness (SFChT) during orthokeratology (Ortho-K) lens wear and after its cessation and the association of short-term change in SFChT with the long-term eye elongation in Ortho-K subjects.

DESIGN

A prospective clinical trial.

METHODS

Fifty myopic children aged between 9 and 14 years were enrolled. Twenty-nine subjects continuously wore Ortho-K lens for 12 months and discontinued for 1 month. Twenty-one subjects wearing single vision distance spectacles for 12 months were included as the control group. SFChT was assessed using optical coherence tomography. Ocular parameters, including axial length (AL), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT) and apical corneal power (ACP), were also measured.

RESULTS

After 12 months of follow-up, AL elongation was larger and SFChT change was smaller in the control group compared to the Ortho-K group (both p < 0.001). In the Ortho-K group, SFChT increased by 16 μm from baseline at the 1-month visit (p < 0.001), and the magnitude of choroidal thickening remained unchanged at the 6- and 12-month visit (p = 0.289). One month after discontinuation of Ortho-K lens, SFChT and ocular parameters of the anterior segment, including ACP, CCT and ACD recovered to baseline level (All p > 0.05), and AL increased by 0.23 ± 0.18 mm compared to baseline (p = 0.018). SFChT change at 1-month was negatively associated with AL change at 13-month (standard β, -0.581, p = 0.001) after adjusting for other influencing factors, including baseline age and the ocular parameters.

CONCLUSION

Subfoveal ChT (SFChT) significantly increased after short-term Ortho-K lens treatment and the increase maintained throughout the period of treatment. One month after Ortho-K lens cessation, SFChT, ACP, CCT and ACD returned to baseline. Short-term response in SFChT is associated with long-term change in AL in children undergoing Ortho-K lens and may be a predictor for the effectiveness of the treatment.

Amphiregulin and ocular axial length

PURPOSE

To assess the potential role of amphiregulin as messenger molecule in ocular axial elongation.

METHODS

The experimental study included guinea pigs (total n = 78) (age: 3-4 weeks) which underwent bilateral lens-induced myopization and received 15 days later three intraocular injections in weekly intervals of amphiregulin antibody (doses:5 μg, 10 μg, 20 μg) into their right eyes, and three phosphate-buffered saline injections into their left eyes; and guinea pigs without lens-induced myopization and which received three unilateral intraocular injections of amphiregulin antibody (dose: 20 μg) or amphiregulin (doses: 1 ng; 10 ng; 20 ng) into their right eyes, and three phosphate-buffered saline injections into their left eyes. Seven days later, the animals were sacrificed. Intravitally, we performed biometry, and histology and immunohistochemistry post-mortem.

RESULTS

In animals with bilateral lens-induced myopization, the right eyes receiving amphiregulin antibody showed reduced axial elongation in a dose-dependent manner (dose: 5 μg: side difference: 0.14 ± 0.05 mm;10 μg: 0.22 ± 0.06 mm; 20 μg: 0.32 ± 0.06 mm; p < 0.001), thicker sclera (all p < 0.05) and higher cell density in the retinal nuclear layers and retinal pigment epithelium (RPE) (all p < 0.05). In animals without lens-induced myopia, the right eyes with amphiregulin antibody application (20 μg) showed reduced axial elongation (p = 0.04), and the right eyes with amphiregulin injections experienced increased (p = 0.02) axial elongation in a dose-dependent manner (1 ng: 0.04 ± 0.06 mm; 10 ng: 0.10 ± 0.05 mm; 20 ng: 0.11 ± 0.06 mm). Eyes with lens-induced axial elongation as compared to eyes without lens-induced axial elongation revealed an increased visualization of amphiregulin upon immunohistochemistry and higher expression of mRNA of endogenous amphiregulin and epidermal growth factor receptor, in particular in the outer part of the retinal inner nuclear layer and in the RPE.

CONCLUSION

Amphiregulin may be associated with axial elongation in young guinea pigs.

IMI - Report on Experimental Models of Emmetropization and Myopia

The results of many studies in a variety of species have significantly advanced our understanding of the role of visual experience and the mechanisms of postnatal eye growth, and the development of myopia. This paper surveys and reviews the major contributions that experimental studies using animal models have made to our thinking about emmetropization and development of myopia. These studies established important concepts informing our knowledge of the visual regulation of eye growth and refractive development and have transformed treatment strategies for myopia. Several major findings have come from studies of experimental animal models. These include the eye's ability to detect the sign of retinal defocus and undergo compensatory growth, the local retinal control of eye growth, regulatory changes in choroidal thickness, and the identification of components in the biochemistry of eye growth leading to the characterization of signal cascades regulating eye growth and refractive state. Several of these findings provided the proofs of concepts that form the scientific basis of new and effective clinical treatments for controlling myopia progression in humans. Experimental animal models continue to provide new insights into the cellular and molecular mechanisms of eye growth control, including the identification of potential new targets for drug development and future treatments needed to stem the increasing prevalence of myopia and the vision-threatening conditions associated with this disease.

Differential expression of connective tissue growth factor and hepatocyte growth factor in the vitreous of patients with high myopia versus vitreomacular interface disease

Background

To determine the levels of connective tissue growth factor (CTGF) and hepatocyte growth factor (HGF) in the vitreous of patients with high myopia, in comparison with those with a vitreomacular interface disease (VMID).

Methods

Patients with either high myopia (high myopia group) or a VMID (VMID group) were included in this study. Each of the two groups were further subdivided into two subgroups: group A (high myopia with macular hole), group B (high myopia with macular retinoschisis), group C (idiopathic macular hole), and group D (idiopathic epiretinal membrane). Vitreal specimens were collected during vitrectomy, and enzyme-linked immunosorbent assay was used to quantitatively measure the CTGF and HGF levels in the vitreous.

Results

The average axial length was markedly longer in the high myopia group than in the VMID group. The vitreal CTGF level was significantly higher in the high myopia group than in the VMID group. Subgroup analysis revealed significantly higher vitreal CTGF in group A than in the other three subgroups. The vitreal HGF level was not significantly different between the high myopia and VMID groups, but was significantly higher in group D than in group C in the subgroup analysis. Correlation analysis showed that the vitreal CTGF level was positively correlated with the axial length.

Conclusions

The vitreal CTGF level is elevated in highly myopic eyes and may be related to the pathogenesis of high myopia, whereas increased expression of HGF may be involved in the development of idiopathic epiretinal membrane.

All-trans retinoic acid stimulates the secretion of TGF-β2 via the phospholipase C but not the adenylyl cyclase signaling pathway in retinal pigment epithelium cells

Background

By investigating that (i) all-trans retinoic acid (ATRA) affects human retinal pigment epithelium (RPE) in expressing and secreting transforming growth factor (TGF)-β₂ and (ii) U73122 (phospholipase C inhibitor) and SQ22536 (adenylyl cyclase inhibitor) regulate the ATRA-induced secretion of TGF-β₂ in human RPE, we sought to interpret the signaling pathway of ATRA in promoting the development of myopia.

Methods

The RPE cell line (D407) was treated with (i) ATRA (10 μM), (ii) U73122 (5–40 μM) and ATRA (10 μM), or (iii) SQ22536 (5–40 μM) and ATRA (10 μM). The control group was no-treated. After stimulated at 2, 4, 8, 16, 24, and 48 h, The expression and secretion of TGF-β₂ was detected.

Results

TGF-β2 in the cytoplasm was time-dependent increased by ATRA (p < 0.001). A time-dependent increase in the TGF-β2 protein of the supernatant was induced by ATRA (p < 0.001). U73122 (in the range of 5 to 40 μM) could suppress the secretion of TGF-β2 induced by ATRA (p < 0.001), and 40 μM U73122 could completely inhibit the up-regulated effect of 10 μM ATRA. However, SQ22536 (in the range of 5 to 40 μM) had no impact on the secretion of TGF-β₂ induced by ATRA (p > 0.05).

Conclusions

In RPE cells, ATRA stimulates the secretion of TGF-β₂ via the phospholipase C signaling pathway but not the adenylyl cyclase signaling pathway. U73122 may inhibit the promotion of ATRA in the development of myopia.

Prevention of Progression in Myopia: A Systematic Review

The prevalence of myopia has increased worldwide in recent decades and now is endemic over the entire industrial world. This increase is mainly caused by changes in lifestyle and behavior. In particular, the amount of outdoor activities and near work would display an important role in the pathogenesis of the disease. Several strategies have been reported as effective. Spectacles and contact lenses have shown only slight results in the prevention of myopia and similarly ortokerathology should not be considered as a first-line strategy, given the high risk of infectious keratitis and the relatively low compliance for the patients. Thus, to date, atropine ophthalmic drops seem to be the most effective treatment for slowing the progression of myopia, although the exact mechanism of the effect of treatment is still uncertain. In particular, low-dose atropine (0.01%) was proven to be an effective and safe treatment in the long term due to the lowest rebound effect with negligible side effects.

INVOLVEMENT OF MULTIPLE MOLECULAR PATHWAYS IN THE GENETICS OF OCULAR REFRACTION AND MYOPIA

PURPOSE

The prevalence of myopia has increased dramatically worldwide within the last three decades. Recent studies have shown that refractive development is influenced by environmental, behavioral, and inherited factors. This review aims to analyze recent progress in the genetics of refractive error and myopia.

METHODS

A comprehensive literature search of PubMed and OMIM was conducted to identify relevant articles in the genetics of refractive error.

RESULTS

Genome-wide association and sequencing studies have increased our understanding of the genetics involved in refractive error. These studies have identified interesting candidate genes. All genetic loci discovered to date indicate that refractive development is a heterogeneous process mediated by a number of overlapping biological processes. The exact mechanisms by which these biological networks regulate eye growth are poorly understood. Although several individual genes and/or molecular pathways have been investigated in animal models, a systematic network-based approach in modeling human refractive development is necessary to understand the complex interplay between genes and environment in refractive error.

CONCLUSION

New biomedical technologies and better-designed studies will continue to refine our understanding of the genetics and molecular pathways of refractive error, and may lead to preventative and therapeutic measures to combat the myopia epidemic.

Super-Resolution Track-Density Imaging Reveals Fine Anatomical Features in Tree Shrew Primary Visual Cortex and Hippocampus

Diffusion-weighted magnetic resonance imaging (dMRI) is widely used to study white and gray matter (GM) micro-organization and structural connectivity in the brain. Super-resolution track-density imaging (TDI) is an image reconstruction method for dMRI data, which is capable of providing spatial resolution beyond the acquired data, as well as novel and meaningful anatomical contrast that cannot be obtained with conventional reconstruction methods. TDI has been used to reveal anatomical features in human and animal brains. In this study, we used short track TDI (stTDI), a variation of TDI with enhanced contrast for GM structures, to reconstruct direction-encoded color maps of fixed tree shrew brain. The results were compared with those obtained with the traditional diffusion tensor imaging (DTI) method. We demonstrated that fine microstructures in the tree shrew brain, such as Baillarger bands in the primary visual cortex and the longitudinal component of the mossy fibers within the hippocampal CA3 subfield, were observable with stTDI, but not with DTI reconstructions from the same dMRI data. The possible mechanisms underlying the enhanced GM contrast are discussed.

Human aqueous humor levels of transforming growth factor-β2: Association with matrix metalloproteinases/tissue inhibitors of matrix metalloproteinases

The present study aims to investigate the association of transforming growth factor-β2 (TGF-β2) and matrix metalloproteinases (MMPs), MMP-2 and MMP-3, and tissue inhibitors of matrix metalloproteinases (TIMPs), TIMP-1, TIMP-2 and TIMP-3 in the aqueous humor of patients with high myopia or cataracts. The levels of TGF-β2 and MMPs/TIMPs were measured with the Luminex xMAP Technology using commercially available Milliplex xMAP kits. The association between TGF-β2 and MMPs/TIMPs levels was analyzed using the Spearmans correlation test. The levels of TGF-β2 were identified to be positively correlated with the levels of TIMP-1 and TIMP-3 (TIMP-1: r=0.334; P=0.007; TIMP-3: r=0.309; P=0.012). The levels of MMP-2, MMP-3 and TIMP-2 did not significantly correlate with TGF-β2 levels (P>0.05). A positive correlation was identified between TGF-β2 and TIMPs in the aqueous humor of human eyes with elongated axial length. It appears that TGF-β2 stimulates the expression of TIMPs as a compensatory reaction to the development of high myopia.

Effect of MT3 on Retinal and Choroidal TGF-β2 and HAS2 Expressions in Form Deprivation Myopia of Guinea Pig

Purpose

To confirm its dose-dependent effect on form deprivation myopia and evaluate the effect of MT3 at different tissue concentrations on changes in mRNA and protein expression for TGF-β2 and HAS2.

Methods

MT3 was intravitreally injected into deprived eyes at two-day intervals. Refraction was measured by streak retinoscopy after cycloplegia. The axial dimensions were measured by A-scan ultrasound. The quantitative RT-PCR and Western blot were used to detect the changes of TGF-β2 and HAS2 expressions in the retina and choroid of guinea pigs.

Results

MT3 treatment produced a significant dose-dependent reduction in relative myopia compared to FD group (both p < 0.001). There were statistically significant increases in retinal and choroidal mRNA levels for both TGF-β2 and HAS2 after injections of 10 μM of MT3, when compared to the FD group. There were no significant differences in retinal and choroidal TGF-β2 protein expression levels between the MT3 treatment groups and FD group (all p > 0.05). The injections of 10 μM of MT3 caused a marked decrease in retinal HAS2 protein expression level, when compared to the FD group (p = 0.001).

Conclusion

MT3 can inhibit form deprivation myopia, and MT3 treatment can result in changes of retinal and choroidal TGF-β2 and HAS2 mRNA and protein expressions.

Isotope-coded protein label based quantitative proteomic analysis reveals significant up-regulation of apolipoprotein A1 and ovotransferrin in the myopic chick vitreous

This study used isotope-coded protein label (ICPL) quantitative proteomics and bioinformatics analysis to examine changes in vitreous protein content and associated pathways during lens-induced eye growth. First, the vitreous protein profile of normal 7-day old chicks was characterized by nano-liquid chromatography electrospray ionization tandem mass spectrometry. A total of 341 unique proteins were identified. Next, myopia and hyperopia were induced in the same chick by attaching -10D lenses to the right eye and +10D lenses to the left eye, for 3 and 7 days. Protein expression in lens-induced ametropic eyes was analyzed using the ICPL approach coupled to LCMS. Four proteins (cystatin, apolipoprotein A1, ovotransferrin, and purpurin) were significantly up-regulated in the vitreous after 3 days of wearing -10D lenses relative to +10D lens contralateral eyes. The differences in protein expression were less pronounced after 7 days when the eyes approached full compensation. In a different group of chicks, western blot confirmed the up-regulation of apolipoprotein A1 and ovotransferrin in the myopic vitreous relative to both contralateral lens-free eyes and hyperopic eyes in separate animals wearing +10D lenses. Bioinformatics analysis suggested oxidative stress and lipid metabolism as pathways involved in compensated ocular elongation.

Characterization and phylogenetic analysis of Krüppel-like transcription factor (KLF) gene family in tree shrews (Tupaia belangeri chinensis)

Krüppel-like factors (KLFs) are a family of zinc finger transcription factors regulating embryonic development and diseases. The phylogenetics of KLFs has not been studied in tree shrews, an animal lineage with a closer relationship to primates than rodents. Here, we identified 17 KLFs from Chinese tree shrew (Tupaia belangeri chinensis). KLF proteins are highly conserved among humans, monkeys, rats, mice and tree shrews compared to zebrafish and chickens. The CtBP binding site, Sin3A binding site and nuclear localization signals are largely conserved between tree shrews and human beings. Tupaia belangeri (Tb) KLF5 contains several conserved post-transcriptional modification motifs. Moreover, the mRNA and protein expression patterns of multiple tbKLFs are tissue-specific. TbKLF5, like hKLF5, significantly promotes NIH3T3 cell proliferation in vitro. These results provide insight for future studies regarding the structure and function of the tbKLF gene family.

Changes in retinal metabolic profiles associated with form deprivation myopia development in guinea pigs

Retinal metabolic changes have been suggested to be associated with myopia development. However, little is known about either their identity or time dependent behavior during this sight compromising process. To address these questions, gas chromatography time-of-flight mass spectrometry (GC-TOF/MS) was applied to compare guinea pig retinal metabolite levels in form deprivation (FD) eyes at 3 days and 2 weeks post FD with normal control (NC) eyes. Orthogonal partial least squares (OPLS) models discriminated between time dependent retinal metabolic profiles in the presence and absence of FD. Myopia severity was associated with more metabolic pattern differences in the FD than in the NC eyes. After 3 days of FD, 11 metabolite levels changed and after 2 weeks the number of differences increased to 16. Five metabolites continuously decreased during two weeks of FD. Two-way ANOVA of the changes identified by OPLS indicates that 15 out of the 22 metabolites differences were significant. Taken together, these results suggest that myopia progression is associated with an inverse relationship between increases in glucose accumulation and lipid level decreases in form-deprived guinea pig eyes. Such changes indicate that metabolomic studies are an informative approach to identify time dependent retinal metabolic alterations associated with this disease.

Expression and role of specificity protein 1 in the sclera remodeling of experimental myopia in guinea pigs

AIM

To study the expression of collagen I and transcription factor specificity protein 1 (Sp1), a transforming growth factor-β1 (TGF-β1) downstream target, and reveal the impact of the TGF-β1-Sp1 signaling pathway on collagen remodeling in myopic sclera.

METHODS

Seventy-five 1-week-old guinea pigs were randomly divided into normal control, form deprivation myopia (FDM), and self-control groups. FDM was induced for different times using coverage with translucent latex balloons and FDM recovery was performed for 1wk after 4wk treatment; then, changes in refractive power and axial length were measured. Immunohistochemistry and reverse transcription-polymerase chain reaction were used to evaluate dynamic changes in collagen I and Sp1 expression in the sclera of guinea pigs with emmetropia and experimental myopia, and the relationship between collagen I and Sp1 levels was analyzed.

RESULTS

In the FDM group, the refractive power was gradually changed (from 2.09±0.30 D at week 0 to -1.23±0.69 D, -4.17±0.59 D, -7.07±0.56 D, and -4.30±0.58 D at weeks 2, 4, 6, and 1wk after 4wk, respectively; P<0.05), indicating deepening of myopia. The axial length was increased (from 5.92±0.39 mm at week 0 to 6.62±0.36 mm, 7.30±0.34 mm, 7.99±0.32 mm, and 7.41±0.36 mm at weeks 2, 4, 6, and 1wk after 4wk; P<0.05). The mRNA and protein expression of Sp1 and collagen I in the sclera of the FDM group was lower than that of the control groups (P<0.05), and the reduction was eye-coverage time-dependent. Furthermore, correlation between Sp1 and collagen I down-regulation in the myopic sclera was observed.

CONCLUSION

Our data indicate that transcription factor Sp1 may be involved in the regulation of type I collagen synthesis/degradation during myopic sclera remodeling, suggesting that TGF-β1 signaling plays a role in the development and progression of myopia.

Amphiregulin Antibody and Reduction of Axial Elongation in Experimental Myopia

To examine the mechanism of ocular axial elongation in myopia, guinea pigs (age: 2–3 weeks) which either underwent unilateral or bilateral lens-induced myopization (group 1) or which were primarily myopic at baseline (group 2) received unilateral intraocular injections of amphiregulin antibody (doses: 5, 10, or 15 μg) three times in intervals of 9 days. A third group of emmetropic guinea pigs got intraocular unilateral injections of amphiregulin (doses: 0.25, 0.50 or 1.00 ng, respectively). In each group, the contralateral eyes received intraocular injections of Ringer's solution. In intra-animal inter-eye comparison and intra-eye follow-up comparison in groups 1 and 2, the study eyes as compared to the contralateral eyes showed a dose-dependent reduction in axial elongation. In group 3, study eyes and control eyes did not differ significantly in axial elongation. Immunohistochemistry revealed amphiregulin labelling at the retinal pigment epithelium in eyes with lens-induced myopization and Ringer's solution injection, but not in eyes with amphiregulin antibody injection. Intraocular injections of amphiregulin-antibody led to a reduction of lens-induced axial myopic elongation and of the physiological eye enlargement in young guinea pigs. In contrast, intraocularly injected amphiregulin in a dose of ≤ 1 ng did not show a significant effect. Amphiregulin may be one of several essential molecular factors for axial elongation.

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Intraocular injections of amphiregulin-antibody led to a reduction of lens-induced axial myopic elongation in guinea pigs.

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Intraocular injections of amphiregulin-antibody also led to a reduction of the physiological eye growth in guinea pigs.

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Amphiregulin may be one of several essential molecular factors for axial elongation in young guinea pigs.

Due to an increase in its prevalence, myopia has been feared to become one of the most common causes of irreversible visual impairment worldwide. Although staying indoors in childhood has been identified as the most important factor for the development of myopia, the underlying mechanism leading to myopia has remained elusive so far. In the present experimental study, young guinea pigs which were myopized by a lens, developed less myopia if they simultaneously received intraocular injections of an antibody of amphiregulin, a member of the epithelial growth factor family. It suggests that amphiregulin is associated with axial elongation in myopia.

Simultaneous Recording of Electroretinography and Visual Evoked Potentials in Anesthetized Rats

The electroretinogram (ERG) and visual evoked potential (VEP) are commonly used to assess the integrity of the visual pathway. The ERG measures the electrical responses of the retina to light stimulation, while the VEP measures the corresponding functional integrity of the visual pathways from the retina to the primary visual cortex following the same light event. The ERG waveform can be broken down into components that reflect responses from different retinal neuronal and glial cell classes. The early components of the VEP waveform represent the integrity of the optic nerve and higher cortical centers. These recordings can be conducted in isolation or together, depending on the application. The methodology described in this paper allows simultaneous assessment of retinal and cortical visual evoked electrophysiology from both eyes and both hemispheres. This is a useful way to more comprehensively assess retinal function and the upstream effects that changes in retinal function can have on visual evoked cortical function.

Imposed Optical Defocus Induces Isoform-Specific Up-Regulation of TGFβ Gene Expression in Chick Retinal Pigment Epithelium and Choroid but Not Neural Retina

PURPOSE

This study investigated the gene expression of TGFβ isoforms and their receptors in chick retina, retinal pigment epithelium (RPE), and choroid and the effects of short-term imposed optical defocus.

METHODS

The expression of TGFβ isoforms (TGF-β1, 2, 3) and TGFβ receptors (TGFBR1, 2, 3) was examined in the retina, RPE, and choroid of young White-Leghorn untreated chicks (19 days-old). The effects on the expression of the same genes of monocular +10 and -10 D defocusing lenses, worn for either 2 or 48 h by age-matched chicks, were also examined by comparing expression in treated and untreated fellow eyes. RNA was purified, characterized and then reverse transcribed to cDNA. Differential gene expression was quantified using real-time PCR.

RESULTS

All 3 isoforms of TGFβ and all 3 receptor subtypes were found to be expressed in all 3 ocular tissues, with apparent tissue-dependent differences in expression profiles. Data are reported as mean normalized expression relative to GAPDH. Sign-dependent optical defocus effects were also observed. Optical defocus did not affect retinal gene expression but in the RPE, TGF-β2 expression was significantly up-regulated with +10 D lenses, worn for either 2 h (349% increase ± 88%, p < 0.01) or 48 h (752% increase ± 166%, p < 0.001), and in the choroid, the expression of TGF-β3 was up-regulated with -10 D lenses, worn for 48 h (147% increase ± 9%, p < 0.01).

CONCLUSIONS

The effects of short term exposure to optical defocus on TGFβ gene expression in the RPE and choroid, which were sign-dependent and isoform specific, provide further supporting evidence for important roles of members of the TGFβ family and these two tissues in local signal cascades regulating ocular growth.

Retinal and choroidal expression of BMP-2 in lens-induced myopia and recovery from myopia in guinea pigs

The present study investigated the retinal and choroidal expression of bone morphogenetic protein-2 (BMP-2) in myopia and in myopia recovery in a guinea pig model. For this investigation, two groups of guinea pigs, lens‑induced myopia and recovery from myopia, were used, and defocused myopia was induced the guinea pigs wearing ‑4.00 D lenses on the right eyes for 3 weeks, with the left eyes serving as the contralateral. In the following week, the lenses of the guinea pigs in the recovery group were removed, and the refractive power and axial length were measured. The expression of BMP‑2 in the eyeballs was observed using immunohistochemistry and analyzed using Western blot analysis. After 3 weeks, the eyes acquired relative myopia and longer axial lengths in the two groups of guinea pigs. After 1 week without lenses in the recovery group, the myopia and axial lengths regressed. Immunofluorescence staining showed that BMP‑2 was expressed in the posterior retina, RPE, choroid and sclera. The expression of BMP‑2 decreased in the myopic retina of the guinea pigs. Following the regression of myopia in the recovery group, no difference in the expression of BMP‑2 was observed between the recovered treated eyes and the contralateral eyes. The choroidal expression level of BMP‑2 in the treated eyes showed no significant changes in either group. Therefore, BMP‑2 may be involved in the development of myopia, however, it does not have a primary role in the retinal and choroidal signals regulating scleral remodeling.

RPE and Choroid Mechanisms Underlying Ocular Growth and Myopia

Myopia is the most common type of refractive errors and one of the world's leading causes of blindness. Visual manipulations in animal models have provided convincing evidence for the role of environmental factors in myopia development. These models along with in vitro studies have provided important insights into underlying mechanisms. The key locations of the retinal pigment epithelium (RPE) and choroid make them plausible conduits for relaying growth regulatory signals originating in the retina to the sclera, which ultimately determines eye size and shape. Identifying the key signal molecules and their targets may lead to the development of new myopia control treatments. This section summarizes findings implicating the RPE and choroid in myopia development. For RPE and/or choroid, changes in morphology, activity of ion channels/transporters, as well as in gene and protein expression, have been linked to altered eye growth. Both tissues thus represent potential targets for novel therapies for myopia.

BMP-2 Is Involved in Scleral Remodeling in Myopia Development

The development of myopia is associated with scleral remodeling, but it is unclear which factors regulate this process. This study investigated bone morphogenetic protein-2 (BMP-2) expression in the sclera of guinea pigs with lens-induced myopia (LIM) and after recovery from myopia and evaluated the effect of BMP-2 on extracellular matrix (ECM) synthesis in human scleral fibroblasts (HSFs) cultured in vitro. Lens-induced myopia was brought about in two groups of guinea pigs (the lens-induced myopia and myopia recovery groups) by placing -4.00 D lenses on the right eye for three weeks. The left eye served as a contralateral control. In the recovery group, the lenses were removed after one week. The refractive power and axial length of the eyes were measured, and the BMP-2 expression levels in the sclera were measured. After three weeks, the lens-induced eyes acquired relative myopia in both groups of guinea pigs. Immunostaining of the eyeballs revealed significantly decreased BMP-2 expression in the posterior sclera of the myopic eyes compared to the contralateral eyes. One week after lens removal, BMP-2 expression recovered, and no differences were observed between the experimental and contralateral eyes in the recovery group. HSFs were cultured with BMP-2 or transforming growth factor-β1 (TGF-β1). Type I and type III collagen synthesis was significantly up-regulated following BMP-2 treatment in culture after one and two weeks, but the ratio of type III to type I collagen mRNA was not increased. Biosynthesis of glycosaminoglycan (GAG) and aggrecan was increased in HSFs treated with BMP-2. Some chondrogenesis-associated genes expression increased in HSFs treated with BMP-2. From this study, we concluded that BMP-2 is involved in scleral remodeling in the development and recovery of lens-induced myopia.

SLC39A5 mutations interfering with the BMP/TGF-β pathway in non-syndromic high myopia

Background

High myopia, with the characteristic feature of refractive error, is one of the leading causes of blindness worldwide. It has a high heritability, but only a few causative genes have been identified and the pathogenesis is still unclear.

Methods

We used whole genome linkage and exome sequencing to identify the causative mutation in a non-syndromic high myopia family. Direct Sanger sequencing was used to screen the candidate gene in additional sporadic cases or probands. Immunofluorescence was used to evaluate the expression pattern of the candidate gene in the whole process of eye development. Real-time quantitative PCR and immunoblot was used to investigate the functional consequence of the disease-associated mutations.

Results

We identified a nonsense mutation (c.141C>G:p.Y47*) in SLC39A5 co-segregating with the phenotype in a non-syndromic severe high myopia family. The same nonsense mutation (c.141C>G:p.Y47*) was detected in a sporadic case and a missense mutation (c.911T>C:p.M304T) was identified and co-segregated in another family by screening additional cases. Both disease-associated mutations were not found in 1276 control individuals. SLC39A5 was abundantly expressed in the sclera and retina across different stages of eye development. Furthermore, we found that wild-type, but not disease-associated SLC39A5 inhibited the expression of Smadl, a key phosphate protein in the downstream of the BMP/TGF-β (bone morphogenic protein/transforming growth factor-β) pathway.

Conclusions

Our study reveals that loss-of-function mutations of SLC39A5 are associated with the autosome dominant non-syndromic high myopia, and interference with the BMP/TGF-β pathway may be one of the molecular mechanisms for high myopia.

Gene expression signatures in tree shrew choroid during lens-induced myopia and recovery

Gene expression in tree shrew choroid was examined during the development of minus-lens induced myopia (LIM, a GO condition), after completion of minus-lens compensation (a STAY condition), and early in recovery (REC) from induced myopia (a STOP condition). Five groups of tree shrews (n = 7 per group) were used. Starting 24 days after normal eye-opening (days of visual experience [DVE]), one minus-lens group wore a monocular -5 D lens for 2 days (LIM-2), another minus-lens group achieved stable lens compensation while wearing a monocular -5 D lens for 11 days (LIM-11); a recovery group also wore a -5 D lens for 11 days and then received 2 days of recovery starting at 35 DVE (REC-2). Two age-matched normal groups were examined at 26 DVE and 37 DVE. Quantitative PCR was used to measure the relative differences in mRNA levels in the choroid for 77 candidate genes that were selected based on previous studies or because a whole-transcriptome analysis suggested their expression would change during myopia development or recovery. Small myopic changes were observed in the treated eyes of the LIM-2 group (-1.0 ± 0.2 D; mean ± SEM) indicating eyes were early in the process of developing LIM. The LIM-11 group exhibited complete refractive compensation (-5.1 ± 0.2 D) that was stable for five days. The REC-2 group recovered by 1.3 ± 0.3 D from full refractive compensation. Sixty genes showed significant mRNA expression differences during normal development, LIM, or REC conditions. In LIM-2 choroid (GO), 18 genes were significantly down-regulated in the treated eyes relative to the fellow control eyes and 10 genes were significantly up-regulated. In LIM-11 choroid (STAY), 10 genes were significantly down-regulated and 12 genes were significantly up-regulated. Expression patterns in GO and STAY were similar, but not identical. All genes that showed differential expression in GO and STAY were regulated in the same direction in both conditions. In REC-2 choroid (STOP), 4 genes were significantly down-regulated and 18 genes were significantly up-regulated. Thirteen genes showed bi-directional regulation in GO vs. STOP. The pattern of differential gene expression in STOP was very different from that in GO or in STAY. Significant regulation was observed in genes involved in signaling as well as extracellular matrix turnover. These data support an active role for the choroid in the signaling cascade from retina to sclera. Distinctly different treated eye vs. control eye mRNA signatures are present in the choroid in the GO, STAY, and STOP conditions. The STAY signature, present after full compensation has occurred and the GO visual stimulus is no longer present, may participate in maintaining an elongated globe. The 13 genes with bi-directional expression differences in GO and STOP responded in a sign of defocus-dependent manner. Taken together, these data further suggest that a network of choroidal gene expression changes generate the signal that alters scleral fibroblast gene expression and axial elongation rate.

Human aqueous humor levels of TGF- β2: relationship with axial length

Purpose. To analyze the relationship between transforming growth factor-beta 2 (TGF-β2) levels in the anterior chamber aqueous humor and axial length of patients with myopia. Methods. TGF-β2 was measured with the Luminex xMAP Technology by using commercially available Milliplex xMAP Kits. Sixty-five aqueous humor samples were collected during cataract or clear lens extraction surgery and TGF-β2 levels in these specimens were analyzed. According to the axial length, the samples were divided into three groups: A (AL ≤24 mm), B (24~29 mm), and C (AL ≥ 29 mm). Results. Aqueous humor samples were analyzed from subjects with an average age of 67.0 ± 11.7 years. Mean TGF-β2 concentration of all aqueous samples was 422.2 ± 258.8 pg/mL. TGF-β2 concentration in group C (543 ± 317 pg/mL) was significantly greater than that in group A (390 ± 212 pg/mL) and group B (337 ± 217 pg/mL). The concentration of TGF-β2 was positively correlated with axial length (r = 0.308, P = 0.013). Conclusions. TGF-β2 is likely to be acting as a critical factor in axial elongation and development of myopia.

TGF-β2 promotes RPE cell invasion into a collagen gel by mediating urokinase-type plasminogen activator (uPA) expression

Transforming growth factor-beta (TGF-β) is one of the main epithelial-mesenchymal transition (EMT)-inducing factors. In general, TGF-β-induced EMT promotes cell migration and invasion. TGF-β also acts as a potent regulator of pericellular proteolysis by regulating the expression and secretion of plasminogen activators. Urokinase-type plasminogen activator (uPA) is a serine protease that binds to its cell surface receptor (uPAR) with high affinity. uPA binding to uPAR stimulates uPAR's interaction with transmembrane proteins, such as integrins, to regulate cytoskeletal reorganization and cell migration, differentiation and proliferation. However, the influence of TGF-β and the uPA/uPAR system on EMT in retinal pigment epithelial (RPE) cells is still unclear. The purpose of this study was to determine the effect of TGF-β2, which is the predominant isoform in the retina, and the uPA/uPAR system on RPE cells. In this study, we first examined the effect of TGF-β2 and/or the inhibitor of uPA (u-PA-STOP(®)) on the proliferation of a human retinal pigment epithelial cell line (ARPE-19 cells). Treatment with TGF-β2 or u-PA-STOP(®) suppressed cell proliferation. Combination treatment of TGF-β2 and u-PA-STOP(®) enhanced cell growth suppression. Furthermore, western blot analysis, fibrin zymography and real-time reverse transcription PCR showed that that TGF-β2 induced EMT in ARPE-19 cells and that the expression of uPA and uPAR expression was up-regulated during EMT. The TGF-β inhibitor SB431542 suppressed TGF-β2-stimulated uPA expression and secretion but did not suppress uPAR expression. Furthermore, we seeded ARPE-19 cells onto Transwell chambers and allowed them to invade the collagen matrix in the presence of TGF-β2 alone or with TGF-β2 and u-PA-STOP(®). TGF-β2 treatment induced ARPE-19 cell invasion into the collagen gel. Treatment with a combination of TGF-β2 and the uPA inhibitor strongly inhibited ARPE-19 cell invasion compared with treatment with TGF-β2 alone. Furthermore, the interaction between uPA and ARPE-19 cells was analyzed using a surface plasmon biosensor system. The binding of uPA to ARPE-19 cells was observed. In addition, TGF-β2 significantly promoted the binding activity of uPA to ARPE-19 cells in a time-dependent or cell-number-dependent fashion. These results indicate that TGF-β-induced EMT-associated phenotype changes in ARPE-19 cells and the invasiveness of ARPE-19 cells into a collagen gel matrix are mediated, at least in part, by uPA.

Mechanism of the DL-alpha-aminoadipic acid inhibitory effect on form-deprived myopia in guinea pig

AIM

To investigate the effect of intravitreal injection of DL-alpha-aminoadipic acid (DL-α-AAA) on ocular refractive state and retinal dopamine, transforming growth factor-β2 (TGFβ2), vasoactive intestinal polypeptide (VIP) in guinea pig form-deprived myopia.

METHODS

Four-week-old pigmented guinea pigs were randomly assigned to 4 groups: normal control, deprivation, deprivation plus DL-α-AAA, deprivation plus saline. Form deprivation was induced with the self-made translucent eye shields, and lasted for 14 days. 8µg DL-α-AAA was injected into the vitreous chamber of deprived eyes. The corneal radius of curvature, refraction and axial length were measured. Retinal dopamine content was evaluated by the high-performance liquid chromatography with electrochemical detection, and TGFβ2 and VIP protein were detected by Western blotting.

RESULTS

Fourteen days of eye occlusion caused the axial length to elongate and become myopic in the form-deprived eyes, with the decrease of retinal dopamine and the increase of TGFβ2 and vasoactive intestinal polypeptide (VIP) protein. Intravitreal injection of DL-α-AAA could inhibit the myopic shift from (-3.65±1.06)D to (-1.48±0.63)D, P<0.01 due to goggles occluding and cause the decrease of retinal TGFβ2 protein in the deprived eyes. However, intravitreal injection of DL-α-AAA had no significant effect on retinal dopamine and VIP protein in deprived eyes. Retinal TGFβ2 protein correlated highly with the ocular refraction (y=-3.34+0.31/x, F=74.75, P<0.001) and axial length (y=8.39-0.02/x, F=48.32, P<0.001) in different treatment groups.

CONCLUSION

Intravitreal injection of DL-α-AAA is effectively able to suppress the development of form deprivation myopia, which may be associated with retinal TGFβ2 protein in guinea pigs.

Regulation of scleral metabolism in myopia and the role of transforming growth factor-beta

Myopia is one of the most prevalent ocular conditions and is the result of a mismatch between the power of the eye and axial length of the eye. In the vast majority of cases the structural cause of myopia is an excessive axial length of the eye, or more specifically the vitreous chamber depth. In about 3% of the general population in Europe, USA and Australia, the degree of myopia is above 6 dioptres and is termed high myopia. In South East Asia the figure is closer to 20% of the general population with high myopia. The prevalence of sight threatening ocular pathology is markedly increased in eyes with high degrees of myopia (>-6 D). This results from the excessive axial elongation of the eye which, by necessity, must involve the outer coat of the eye, the sclera. Current theories of refractive development acknowledge the pivotal role of the sclera in the control of eye size and the development of myopia. This review details the major structural, biochemical and biomechanical changes that underlie abnormal development of the mammalian sclera in myopia. In describing the changes in regulation of sclera metabolism in myopia, the pivotal role of transforming growth factor-β signalling is highlighted as the responsible factor for certain critical events in myopia development that ultimately result in the scleral pathology observed in high myopia.

Genetic contributions to myopic refractive error: Insights from human studies and supporting evidence from animal models

Genetic studies of both population-based and recruited affected patient cohorts have identified a number of genomic regions and candidate genes that may contribute to myopic development. Scientists have developed animal models of myopia, as collection of affected tissues from patents is impractical. Recent advances in whole exome sequencing technology show promise for further elucidation of disease causing variants as in the recent identification of rare variants within ZNF644 segregating with pathological myopia. We present a review of the current research trends and findings on genetic contributions to myopic refraction including candidate loci for myopic development and their genomic convergence with expression studies of animal models inducing myopic development.

Insulin-like growth factor-2 antisense oligonucleotides inhibits myopia by expression blocking of retinal insulin-like growth factor-2 in guinea pig

OBJECTIVE

  To clarify the role of IGF-2 on the development of myopia, the dynamic expression of IGF-2 was investigated in the FD eyes' retina, and the effects of intravitreous injection with IGF-2 ASON was studied on the diopter and axial eye length of FD eyes.

METHODS

  64 guinea pigs were divided into 2 groups. In group A (n = 24), the right eyes were covered. On days 7, 14 and 21, the diopter, axial eye length and level of IGF-2 of both eyes were measured in every 8 guinea pigs. In group B (n = 40), the right eyes were covered. On day 1, the right eyes were received intravitreal injection with 40 µg IGF-2SON, 10 µg, 20 µg or 40 µg IGF-2 ASON. The diopter, axial eye length and level of IGF-2 were measured on day 14.

RESULTS

  FD eyes showed myopic shift, axial length enlongation, and up-regulation in retinal IGF-2 from day 7 to day 21. The level of retinal IGF-2 in FD eyes was higher than that in non-FD eyes. Compare with FD eyes without injection, the myopia diopter of FD eyes decreased in received intravitreous injection with IGF-2 ASON, axial length shortened, and down-regulated with retinal IGF-2. With the increase dose of IGF-2 ASON, the change of myopic diopter, axial length, and level of retinal IGF-2 were showed more and more significant.

CONCLUSIONS

  FD is effective to up-regulate the level of retinal IGF-2 expression in guinea pig. Intravitreous injection with IGF-2 ASON can inhibit the development of myopia.