Form-deprivation Myopia Research Articles

KCNQ5 Participates in Form Deprivation Myopia by Regulating Potassium Ion Transport Pathway

KCNQ5 Participates in Form Deprivation Myopia by Regulating Potassium Ion Transport Pathway

Efficacy and safety of scleral crosslinking using poly(ethylene glycol)ether tetrasuccinimidyl glutarate for form-deprivation myopia progression in rabbits.

Myopia is becoming increasingly prevalent worldwide at an alarming rate. However, no effective treatment is available for inhibiting myopia progression. Materials chemistry advancements have made it possible to regulate mechanical properties and rate of degradation with good compatibility by developing newly crosslinking systems such as the branched polyethylene glycol (PEG) systems. Herein, we presented a PEG molecule with N-hydroxysuccinimide (NHS) ester functional groups at the chain ends as a macromolecular crosslinking agent for the treatment of myopia. We found that the scleral collagen crosslinked with the four-armed star-shaped PEG molecule with NHS ester functional group (4S-PEG) showed better biomechanical properties, increased thermal stability and higher resistance to degradation. 4S-PEG exhibited relatively low cytotoxicity for human fetal scleral fibroblasts. The retrobulbar injection of 4S-PEG at a relatively low concentration (2.5 mM) showed good effective control of the progression of form-deprivation myopia in rabbits. There were no signs of adverse effect or damage by repeated injections with 4S-PEG in rabbits. The results of this work demonstrate that 4S-PEG can serve as a robust macromolecular crosslinking agent and is expected to have promise for application in the treatment of the progression of myopia.

Increased Choroidal Blood Perfusion Can Inhibit Form Deprivation Myopia in Guinea Pigs.

PurposeIn guinea pigs, choroidal thickness (ChT) and choroidal blood perfusion (ChBP) simultaneously decrease in experimental myopia, and both increase during recovery. However, the causal relationship between ChBP and myopia requires further investigation. In this study, we examined the changes of ChBP with three different antimyopia treatments. We also actively increased ChBP to examine the direct effect on myopia development in guinea pigs.MethodsExperiment 1: Guinea pigs wore occluders on the right eye for two weeks to induce form-deprivation myopia (FDM). Simultaneously they received daily antimyopia treatments: peribulbar injections of atropine or apomorphine or exposure to intense light. Experiment 2: The vasodilator prazosin was injected daily into the form-deprivation eyes to increase ChBP during the two-week induction of FDM. Other FDM animals received appropriate control treatments. Changes in refraction, axial length, ChBP, ChT, and hypoxia-labeled pimonidazole adducts in the sclera were measured.ResultsThe antimyopia treatments atropine, apomorphine, and intense light all significantly inhibited myopia development and the decrease in ChBP. The treatments also reduced scleral hypoxia, as indicated by the decrease in hypoxic signals. Furthermore, actively increasing ChBP with prazosin inhibited the progression of myopia, as well as the increase in axial length and scleral hypoxia.ConclusionsOur data strongly indicate that increased ChBP attenuates scleral hypoxia, and thereby inhibits the development of myopia. Thus ChBP may be a promising target for myopia retardation. As such, it can serve as an immediate predictor of myopia development as well as a long-term marker of it.

PPARγ modulates refractive development and form deprivation myopia in Guinea pigs

Form deprivation myopia (FDM) is characterized by loss of choroidal thickness (ChT), reduced choroidal blood perfusion (ChBP), and consequently scleral hypoxia. In some tissues, changes in levels of peroxisome proliferator-activated receptor γ (PPARγ) expression modulate hypoxia-induced pathological responses. We determined if PPARγ modulates FDM through changes in ChT, ChBP, scleral hypoxia-inducible transcription factor (HIF-1α) that in turn regulate scleral collagen type 1 (COL1) expression levels in guinea pigs. Myopia was induced by occluding one eye, while the fellow eye served as control. They received daily peribulbar injections of either the PPARγ antagonist GW9662, or the GW1929 agonist, with or without ocular occlusion for 4 weeks. Ocular refraction and biometric parameters were estimated at baseline, 2 and 4 weeks post-treatment. ChT and ChBP were measured at the 2- and 4-week time points. Western blot analysis determined the expression levels of scleral HIF-1α and COL1. GW9662 induced a myopic shift in unoccluded eyes. Conversely, GW1929 inhibited FDM progression without affecting the refraction in unoccluded eyes. GW9662 reduced both ChT and ChBP in unoccluded eyes, while GW1929 inhibited their declines in occluded eyes. Scleral HIF-1α expression rose in GW9662-treated unoccluded eyes whereas GW1929 reduced HIF-1α upregulation in occluded eyes. GW9662 downregulated scleral COL1 expression in unoccluded eyes, while GW1929 reduced their decreases in occluded eyes. Therefore, PPARγ modulates collagen expression levels and FDM through an inverse relationship between changes in PPARγ and HIF-1α expression levels.

The Role of C-Jun N-terminal Kinase-1 in Controlling Aquaporin-1 and Choroidal Thickness during Recovery from Form-deprivation Myopia in Guinea Pigs

ABSTRACT Purpose The development and recovery(REC) of myopia is associated with changing of choroidal thickness(CT) in model of guinea pigs. Aquaporin-1 (AQP-1) is related to the changes of CT during the recovery from myopia, but the corresponding signaling pathway has not been clarified. This study aimed to investigate the effect of JNK1 on CT/AQP-1 and the recovery from myopia. Materials and Methods According to the different single intravitreal injections in eyes that underwent form deprivation for 21 days, guinea pigs were divided into four groups: the REC group, the REC+anisomycin (REC-AN, agonist for JNK1, 0.2 nmol) group, the REC+SP600125 (REC-SP, inhibitor for JNK1, 0.2 nmol) group, and the REC+dimethyl sulfoxide (REC-DM) group. Each group was divided into three subgroups based on the duration of the form deprivation: 3 days (d), 7 d and 10 d. All animals underwent biometric measurements (refractive error, axial length (AL), and CT), and the protein expression of AQP-1 and p-JNK1 in the choroid was also measured. Results In REC and REC-DM groups, significant differences in CT/refractive error/AL/p-JNK1 or AQP-1 were only found in the 3d group compared with normal control (NC) group (all p < .05). In REC-AN group, CT/p-JNK1 or AQP-1 in 3d group was significantly higher than that in other 3d groups (all p < .05), but no significant difference in refractive error or AL was found compared with NC group at three time points (all p > .05). In REC-SP group, a significant difference in refractive error/CT/p-JNK1 or AQP1 was found in 3d/7d group compared with NC group (all p < .05), but AL was only found in 3d groups (p = .001). Conclusions Changes in JNK1 phosphorylation can regulate AQP-1 and CT during the recovery from myopia and the recovery time. Thus, JNK1 may be a potential therapeutic target for preventing/treating myopia.

Form-Deprivation and Lens-Induced Myopia Are Similarly Affected by Pharmacological Manipulation of the Dopaminergic System in Chicks.

PurposeAnimal models have demonstrated a link between decreases in retinal dopamine levels and the development of form-deprivation myopia (FDM). However, the consistency of dopamine's role in the other major form of experimental myopia, that of lens-induced myopia (LIM), is less clear, raising the question as to what extent dopamine plays a role in human myopia. Therefore, to better define the role of dopamine in both forms of experimental myopia, we examined how consistent the protection afforded by dopamine and the dopamine agonist 6-amino-5,6,7,8-tetrahydronaphthalene-2,3-diol hydrobromide (ADTN) is between FDM and LIM.MethodsIntravitreal injections of dopamine (0.002, 0.015, 0.150, 1.500 µmol) or ADTN (0.001, 0.010, 0.100, 1.000 µmol) were administered daily to chicks developing FDM or LIM. Axial length and refraction were measured following 4 days of treatment. To determine the receptor subtype by which dopamine and ADTN inhibit FDM and LIM, both compounds were coadministered with either the dopamine D2-like antagonist spiperone (0.005 µmol) or the D1-like antagonist SCH-23390 (0.005 µmol).ResultsIntravitreal administration of dopamine or ADTN inhibited the development of FDM (ED50 = 0.003 µmol and ED50 = 0.011 µmol, respectively) and LIM (ED50 = 0.002 µmol and ED50 = 0.010 µmol, respectively) in a dose-dependent manner, with a similar degree of protection observed in both paradigms (P = 0.471 and P = 0.969, respectively). Coadministration with spiperone, but not SCH-23390, inhibited the protective effects of dopamine and ADTN against the development of both FDM (P = 0.214 and P = 0.138, respectively) and LIM (P = 0.116 and P = 0.100, respectively).Conclusionspharmacological targeting of the retinal dopamine system inhibits FDM and LIM in a similar dose-dependent manner through a D2-like mechanism.

Effects of latanoprost on the expression of TGF-β1 and Wnt / β-catenin signaling pathway in the choroid of form-deprivation myopia rats

In this study, we investigated the effect of latanoprost on the expression of TGF- β1 and Wnt / β - Catenin signal pathway in the choroid of form-deprivation myopia model rats. Forty rats were randomly divided into two groups: the control group and the FDM model group. Each group had 20 rats. The FDM model group was established by feeding latanoprost daily for 28 days. 15 rats in each group were used to measure the length of the ocular axis and the level of TGF-β1 in choroidal tissue; the remaining 5 rats in each group were used for choroidal fibroblast culture. After modeling, the rats were killed, the length of the ocular axis was measured with a vernier caliper, and the level of TGF - β1 protein and mRNA in the choroidal tissue of each group were measured with RT-PCR method. Results showed that compared with the control group, there was a significant difference in the axial length of the FDM model group (P&lt; 0.05). There was a significant difference in the expression of TGF- β1 protein and mRNA between the two groups (P&lt;0.05). The cultured cells were identified as choroidal fibroblasts by immunocytochemistry. There was no significant difference (P&gt;0.05) in the comparison of GSK3 β protein in choroidal fibroblasts of rats in each group. TGF-β 1 and APC protein in FDM group were significantly lower than those in the control group (P&lt;0.05), while dcl3, p21-gsk3 β and β - Catenin proteins were significantly higher (P&lt;0.05), and there was no significant difference (P&gt;0.05) in the ratio of various indexes protein in FDM + ddk1 group and the comparison of TGF - β1 and APC protein in FDM + ddk1 group and FDM group The expression of dcl3, p21-gsk3 β and β - Catenin decreased significantly (P&lt;0.05). There was no significant difference in the expression of GSK3 β mRNA in the choroidal fibroblasts of each group (P&gt;0.05). The expression of TGF - β 1 and APC mRNA in FDM group was significantly lower than that in the control group (P&lt;0.05), while the expression of dcl3, p21-gsk3 β and β-catenin mRNA in FDM + ddk1 group was significantly higher than that in the control group (P&lt;0.05) &gt;In FDM + ddk1 group, TGF-β 1 and APC mRNA were significantly lower than those in FDM group (P&lt;0.05), while dcl3, p21-gsk3 β and β-Catenin mRNA were significantly higher (P&lt;0.05).

The Spatial Frequency Content of Urban and Indoor Environments as a Potential Risk Factor for Myopia Development.

PurposeTo examine the hypothesis that the spatial frequency spectra of urban and indoor environments differ from the natural environment in ways that may promote the development of myopia.MethodsA total of 814 images were analyzed from three datasets; University of California Berkeley (UCB), University of Texas (UT), and Botswana (UPenn). Images were processed in Matlab (Mathworks Inc) to map the camera color characteristics to human cone sensitivities. From the photopic luminance images generated, two-dimensional spatial frequency (SF) spectra were calculated and converted to one-dimensional spectra by rotational averaging. The spatial filtering profile of a 0.4 Bangerter foil, which has been shown to induce myopia experimentally, was also determined.ResultsThe SF slope for natural scenes followed the recognized 1/fα relationship with mean slopes of −1.08, −0.90, and −1.04 for the UCB, UT and UPenn image sets, respectively. Indoor scenes had a significantly steeper slope (−1.48, UCB; −1.52, UT; P < 0.0001). Urban environments showed an intermediate slope (−1.29, UCB; −1.22, UT) that was significantly different from the slopes derived from the natural scenes (P < 0.0001). The change in SF content between natural outdoor scenes and indoors was comparable to that induced by a 0.4 Bangerter foil, which reduced the SF slope of a natural scene from −0.88 to −1.47.ConclusionsCompared to natural outdoor images, man-made outdoor and indoor environments have spatial frequency characteristics similar to those known to induce form-deprivation myopia in animal models. The spatial properties of the man-made environment may be one of the missing drivers of the human myopia epidemic.

Topical application of dopaminergic compounds can inhibit deprivation myopia in chicks

PurposeAnimal models have demonstrated a link between dysregulation of the retinal dopamine system and the development of experimental myopia (short-sightedness). However, pharmacological investigations of dopamine in animal models rely heavily on intravitreal or systemic administration, which have several limitations for longer-term experiments. We therefore investigated whether administration of dopamine as a topical eye drop can inhibit the development of form-deprivation myopia (FDM) in chicks. We also examined whether chemical modification of dopamine through deuterium substitution, which might enhance stability and bioavailability, can increase dopamine's effectiveness against FDM when given topically. MethodsDopamine or deuterated dopamine (Dopamine-1,1,2,2-d4 hydrochloride) was administered as a daily intravitreal injection or as daily topical eye drops to chicks developing FDM over an ascending dose range (min. n = 6 per group). Axial length and refraction were measured following 4 days of treatment. ResultsBoth intravitreal (ED50 = 0.002μmoles) and topical application (ED50 = 6.10μmoles) of dopamine inhibited the development of FDM in a dose-dependent manner. Intravitreal injections, however, elicited a significantly higher level of protection relative to topical eye drops (p < 0.01). Deuterated dopamine inhibited FDM to a similar extent as unmodified dopamine when administered as intravitreal injections (p = 0.897) or topical eye drops (p = 0.921). ConclusionsBoth intravitreal and topical application of dopamine inhibit the development of FDM in a dose-dependent manner, indicating that topical administration may be an effective avenue for longer-term dopamine experiments. Deuterium substitution does not alter the protection afforded by dopamine against FDM when given as either an intravitreal injection or topical eye drop.

Topical bendazol inhibits experimental myopia progression and decreases the ocular accumulation of HIF-1α protein in young rabbits.

To investigate the inhibitory effect of bendazol on form-deprivation myopia (FDM) in rabbits as well as the underlying biochemical processes. Forty-eight 3-week-old New Zealand white rabbits were randomly assigned to three groups: a control group, a form-deprivation (FD) group and an FD+bendazol group (treated with 1% bendazol in the FD eyes). Refraction, corneal curvature, vitreous chamber depth (VCD) and axial length (AL) were assessed using streak retinoscopy, keratometry, and A-scan ultrasonography, respectively. Eyeballs were enucleated for histological analysis, and ocular tissues were homogenized to determine the mRNA and protein expression of hypoxia-inducible factor-1α (HIF-1α) and muscarinic acetylcholine receptors (mAChRs). Bendazol inhibited the progression of FDM and suppressed the upregulation of HIF-1α. At week 6, in the control, FD and FD+bendazol groups, the refraction values were 1.38±0.43, 0.03±0.47 and 1.25±0.35 D, respectively (p<0.001); the ALs were 13.91±0.11, 14.15±0.06 and 13.97±0.10mm, respectively (p<0.001) and the VCDs were 6.56±0.06, 6.69±0.07 and 6.61±0.06mm, respectively (p<0.001). HIF-1α was upregulated in FD eyes but downregulated in FD+bendazol eyes, while the mAChRs were the opposite. In the FD rabbit model, bendazol significantly inhibits the development of myopia and downregulates HIF-1α expression, which may provide a novel therapeutic approach for myopia control.

Levodopa inhibits the development of lens-induced myopia in chicks

Animal models have demonstrated a link between dysregulation of the retinal dopamine system and the development of myopia (short-sightedness). We have previously demonstrated that topical application of levodopa in chicks can inhibit the development of form-deprivation myopia (FDM) in a dose-dependent manner. Here, we examine whether this same protection is observed in lens-induced myopia (LIM), and whether levodopa’s protection against FDM and LIM occurs through a dopamine D1- or D2-like receptor mechanism. To do this, levodopa was first administered daily as an intravitreal injection or topical eye drop, at one of four ascending doses, to chicks developing LIM. Levodopa’s mechanism of action was then examined by co-administration of levodopa injections with D1-like (SCH-23390) or D2-like (spiperone) dopamine antagonists in chicks developing FDM or LIM. For both experiments, levodopa’s effectiveness was examined by measuring axial length and refraction after 4 days of treatment. Levodopa inhibited the development of LIM in a dose-dependent manner similar to its inhibition of FDM when administered via intravitreal injections or topical eye drops. In both FDM and LIM, levodopa injections remained protective against myopia when co-administered with SCH-23390, but not spiperone, indicating that levodopa elicits its protection through a dopamine D2-like receptor mechanism in both paradigms.

The effect of optic nerve section on form deprivation myopia in the guinea pig.

Myopia is induced when a growing eye wears a diffuser that deprives it of detailed spatial vision (form deprivation, FD). In chickens with optic nerve section (ONS), FD myopia still occurs, suggesting that the signals underlying myopia reside within the eye. As avian eyes differ from mammals, we asked whether local mechanisms also underlie FD myopia in a mammalian model. Young guinea pigs underwent either sham surgery followed by FD (SHAM + FD, n = 7); or ONS followed by FD (ONS + FD, n = 7); or ONS without FD (ONS, n = 9). FD was initiated 3 days after surgery with a diffuser that was worn on the surgically treated eye for 14 days. Animals with ONS + FD developed -8.9 D of relative myopia and elongated by 135 μm more than in their untreated eyes after 2 weeks of FD. These changes were significantly greater than those in SHAM + FD animals (-5.5 D and 40 μm of elongation after 14 days of FD), and reflected exaggerated elongation of the posterior vitreous chamber. The myopia reversed when FD was discontinued, despite ONS, but eyes did not recover back to normal (30 days after surgery, ONS + FD eyes still retained -3 D of relative myopia when SHAM+FD animals had returned to normal). No long-term residual myopia was present after ONS alone, ruling out a surgical artifact. Although the gross mechanism signaling myopic ocular growth and its recovery in the young mammalian eye does not require an intact optic nerve, its fine-tuning is disrupted by ONS.

The Role of the Dopamine D2 Receptor in Form-Deprivation Myopia in Mice: Studies With Full and Partial D2 Receptor Agonists and Knockouts.

PurposeThe purpose of this study was to explore the role and mechanism of D2 receptor (D2R) involvement in myopia development and the effects of the full D2R agonist quinpirole and partial D2R agonist aripiprazole on postnatal refractive development and form-deprivation myopia (FDM).MethodsC57BL/6 (“B6”) mice, raised either in a visually normal or unilateral form-deprivation environment, were divided into three subgroups, including an intraperitoneally injected (IP) vehicle group and two quinpirole (1 and 10 µg/g body weight) treatment groups. The effects of quinpirole on FDM were further verified in D2R-knockout (KO) mice and corresponding wild-type littermates. Then, the modulation of normal vision development and FDM by aripiprazole (1 and 10 µg/g body weight, IP) was assessed in C57BL/6 mice. All biometric parameters were measured before and after treatments, and retinal cyclic adenosine phosphate (cAMP) and phosphorylated ERK (pERK) levels were analyzed to assess D2R-mediated signal transduction.ResultsNeither quinpirole nor aripiprazole affected normal refractive development. FDM development was inhibited by quinpirole at low dose but enhanced at high dose, and these bidirectional effects were validated by D2R-specificity. FDM development was attenuated by the partial D2R agonist aripiprazole, at high dose but not at low dose. Quinpirole caused a dose-dependent reduction in cAMP levels, but had no effect on pERK. Aripiprazole reduced cAMP levels at both doses, but caused a dose-dependent increase of pERK in the form-deprived eyes.ConclusionsReduction of D2R-mediated signaling contributes to myopia development, which can be selectively attenuated by partial D2R agonists that activate D2Rs under the low dopamine levels that occur with FDM.

Up-Regulation of Matrix Metalloproteinase-2 by Scleral Monocyte–Derived Macrophages Contributes to Myopia Development

Myopia is a leading cause of visual impairment worldwide. This sight-compromising condition is associated with scleral thinning, extracellular matrix remodeling, and inappropriate optical axial length elongation. Although macrophages are present in the sclera, their involvement in this condition is unknown. By using a form-deprivation myopia (FDM) mouse model, we found that both the scleral macrophage density and their matrix metalloproteinase-2 (MMP-2) expression levels increased in myopic eyes. Partial scleral macrophage depletion by clodronate shifted the refraction toward hyperopia in both the form-deprived and the untreated fellow eyes compared with their respective counterparts in the vehicle-injected control mice. However, this procedure did not alter susceptibility to FDM. FDM development was 59% less in the macrophage-specific Mmp2 deletion (LysMCreMmp-2fl/fl) mice than in their Cre-negative littermates (Mmp2fl/fl mice). Moreover, the expression of scleral C-C motif chemokine ligand-2 (CCL2), which is a potent monocyte chemoattractant recruiting monocytes to tissue sites, was increased during myopia progression. However, the increase in the density of scleral macrophages and myopia development were suppressed in fibroblast-specific Ccl2 deletion mice. These declines suggested that the increase in scleral macrophage density in myopic eyes stems from the up-regulation of scleral Ccl2 expression in fibroblasts, which, in turn, promotes monocytes recruitment. In summary, scleral monocyte-derived macrophages contribute to myopia development through enhancing MMP-2 expression in mice.

Endoplasmic Reticulum Stress Regulates Scleral Remodeling in a Guinea Pig Model of Form-Deprivation Myopia.

Purpose This study aimed to investigate the role of endoplasmic reticulum (ER) stress in scleral remodeling in a guinea pig model of form-deprivation myopia (FDM). Methods Guinea pigs were form deprived to induce myopia. ER ultrastructural changes in the sclera were examined by transmission electron microscopy (TEM). The protein levels of ER stress chaperones, including GRP78, CHOP, and calreticulin (CRT), were analyzed by western blotting at 24 hours, 1 week, and 4 weeks of FD. Scleral fibroblasts from guinea pigs were cultured and exposed to the ER stress inducer tunicamycin (TM) or the ER stress inhibitor 4-phenylbutyric acid (4-PBA). CRT was knocked down by lentivirus-mediated CRT shRNA transfection. The expression levels of GRP78, CHOP, TGF-β1, and COL1A1 were analyzed by qRT-PCR or western blotting. Results The sclera of FDM eyes exhibited swollen and distended ER at 4 weeks, as well as significantly increased protein expression of GRP78 and CRT at 1 week and 4 weeks, compared to the sclera of the control eyes. In vitro, TM induced ER stress in scleral fibroblasts, which was suppressed by 4-PBA. The mRNA expression of TGF-β1 and COL1A1 was upregulated after TM stimulation for 24 hours, but downregulated for 48 hours. Additionally, change of TGF-β1 and COL1A1 transcription induced by TM was suppressed by CRT knockdown. Conclusions ER stress was an important modulator which could influence the expression of the scleral collagen. CRT might be a new target for the intervention of the FDM scleral remodeling process.

DNA methylation and mRNA expression of IGF-1 and MMP-2 after form-deprivation myopia in guinea pigs.

The molecular mechanism of form-deprivation myopia is unclear. This study was aimed to investigate the roles of scleral DNA methylation and mRNA expression of IGF-1 and MMP-2 in a guinea pig model of form-deprivation myopia. Seventy 2-week-old male guinea pigs were assigned to three groups: (1) zero week group that was used to collect baseline data; (2) monocular deprivation treatment (MDT) group, in which a thin slice of opaque latex glove was placed over the right eyes of the animals for four weeks, and the left eyes were untreated and served as the monocular contralateral control (MCC) group; (3) control group (CG), in which the animals grew four weeks, but received no manipulation. Animals in each group were evenly divided for DNA methylation assay and quantitative PCR (qPCR). After eye enucleation, the sclerae were harvested for DNA methylation assay and qPCR. The DNA methylation pattern in the promoter and exon regions of IGF-1 and MMP-2, along with the mRNA expression level of them, were determined by base-specific cleavage and mass spectrometry and qPCR, respectively. After four weeks of form-deprivation, DNA methylation at 4/8 cytosine-guanine sites in the IGF-1 promoter was significantly lower in the MDT eyes than in the MCC or CG eyes. In addition, the level of IGF-1 mRNA was moderately higher in MDT eyes compared to the MCC eyes and CG eyes. DNA methylation at 4/14 cytosine-guanine sites in the MMP-2 gene was very low, and no significant change was observed between the MDT eyes and the MCC or CG ones. However, the level of MMP-2 mRNA in MDT eyes was significant higher compared with MCC eyes and CG eyes, with an increase of 217% and 222%, respectively. In our guinea pig model of form-deprivation myopia, the methylation of four cytosine-guanine sites in the IGF-1 gene promoter was significantly lower in the sclera after four weeks of MDT, and the transcription level of scleral IGF-1 was moderately higher. Hence, the IGF-1 gene methylation might play a role in the pathogenesis of form-deprivation myopia in guinea pigs. The level of MMP-2 mRNA in the sclera of MDT eyes was significantly higher, but not regulated by the methylation pathway, as the methylation status of MMP-2 was unchanged.

Morphological ciliary muscle changes associated with form deprivation-induced myopia

Myopic children have larger ciliary muscles than non-myopic children, suggesting that the ciliary muscle may have an impact on or be affected by refractive error development. The guinea pig represents an attractive model organism for myopia development research. The purpose of the study was to investigate whether form deprivation-induced myopia in one or more strains of guinea pig causes thickening of the ciliary muscle as seen in human myopia. Thirty-nine guinea pigs were bred from in-house progenitors obtained from Cincinnati Children's Hospital (Cincinnati) and the United States Army (Strain 13). At 2–4 days of age the right eyes of animals were exposed to form deprivation for 7 days while the fellow eyes served as controls. Refractive error was determined with retinoscopy while vitreous chamber depth (VCD) and axial length (AL) were determined with A-scan ultrasound. Ciliary muscle characteristics (ciliary muscle length, cross-sectional area, volume, cell number, cell size, and smooth muscle actin concentration) were determined histologically with antibody labeling and analyzed according to whether the animal developed axial myopia (anisometropia > −2.00 D with VCD and/or AL differences > 0.1 mm) or was unresponsive. This analysis method yielded four groups with Group 1 having no induced myopia but with axial elongation (n = 11), Group 2 having myopia without vitreous or axial elongation (n = 8), Group 3 having myopia with either vitreous or axial elongation (n = 11), and Group 4 having myopia with both vitreous and axial elongation (n = 8). There were no post-treatment inter-ocular differences between strains or for the overall group of animals for any ciliary muscle variable; however, a higher response group number in multivariate ordinal regression was related to having a treated compared to fellow eye that had a lower smooth muscle actin concentration (p = 0.006), with a shorter ciliary muscle length (p = 0.042), and a less oblate eye shape (p = 0.010). Guinea pig ciliary muscle length and smooth muscle actin concentration were significantly less in the treated eyes of axially myopic animals suggesting that 7 days of form deprivation induced ciliary muscle cellular atrophy or inhibited ciliary muscle growth. Form deprivation myopia in the guinea pig does not result in the increase in ciliary muscle thickness associated with human juvenile and adult myopia.

Increased endogenous dopamine prevents myopia in mice

Experimental evidence suggests that dopamine (DA) modulates refractive eye growth. We evaluated whether increasing endogenous DA activity using pharmacological or genetic approaches decreased myopia susceptibility in mice. First, we assessed the effects of systemic L-3,4-dihydroxyphenylalanine (L-DOPA) injections on form deprivation myopia (FDM) in C57BL/6 J (WTC57) mice. WTC57 mice received daily systemic injections of L-DOPA (n = 11), L-DOPA + ascorbic acid (AA, n = 22), AA (n = 20), or Saline (n = 16). Second, we tested transgenic mice with increased or decreased expression of vesicular monoamine transporter 2 (VMAT2HI, n = 22; WTHI, n = 18; VMAT2LO, n = 18; or WTLO, n = 9) under normal and form deprivation conditions. VMAT2 packages DA into vesicles, affecting DA release. At post-natal day 28 (P28), monocular FD was induced in each genotype. Weekly measurements of refractive error, corneal curvature, and ocular biometry were performed until P42 or P49. WTC57 mice exposed to FD developed a significant myopic shift (treated-contralateral eye) in AA (−3.27 ± 0.73D) or saline (−3.71 ± 0.80D) treated groups that was significantly attenuated by L-DOPA (−0.73 ± 0.90D, p = 0.0002) or L-DOPA + AA (−0.11 ± 0.46D, p = 0.0103). The VMAT2LO mice, with under-expression of VMAT2, were most susceptible to FDM. VMAT2LO mice developed significant myopic shifts to FD after one week compared to VMAT2HI and WT mice (VMAT2LO: −5.48 ± 0.54D; VMAT2HI: −0.52 ± 0.92D, p < 0.05; WT: −2.13 ± 0.78D, p < 0.05; ungoggled control: −0.22 ± 0.24D, p < 0.001). These results indicate that endogenously increasing DA synthesis and release by genetic and pharmacological methods prevents FDM in mice.

Alterações dinâmicas de periostina e colágeno I na esclera durante miopia progressiva em cobaias

To investigate periostin and collagen I expression during a scleral remodeling in myopic eyes and to determine their role in collagen remodeling of the myopic sclera. Fifty one-week-old guinea pigs were divided into the control and form-deprivation myopia (FDM) groups. The eyes of animals in the form-deprivation myopia group were covered for 2, 4, and 8 weeks, or were covered for 4 weeks and then uncovered for 2 weeks. The diopters and axial lengths in the eyes in each group of guinea pigs were measured. Immunohistochemistry and reverse transcription polymerase chain reaction were used to detect the relative protein and mRNA expressions of periostin and collagen I in the scleral tissues of guinea pig. Before masking, guinea pigs in the control and form-deprivation myopia groups were hypermetropic and did not differ significantly (p>0.05). Hypermetropic refraction in the control group gradually decreased. In guinea pigs from the form-deprivation myopia group, the refractive power gradually changed from +2.14 ± 0.33 D to -7.22 ± 0.51 D, and the axial length gradually changed from 5.92 ± 0.37 mm to 8.05 ± 0.34 mm from before until the end of masking. Before covering, no significant difference was observed in the relative collagen I and periostin mRNA and protein expression levels in the sclera of the guinea pig control and form-deprivation myopia groups (p>0.05). The relative collagen I and periostin protein and mRNA expression levels in the sclera of guinea pigs in the form-deprivation myopia group at 2, 4, and 8 weeks, and after covering the eyes for 4 weeks followed by uncovering for 2 weeks, were significantly lower than those in the control group (p<0.05). The collagen I and periostin mRNA expression levels were positively correlated with protein expression levels in the sclera of guinea pigs (protein: r=0.936, p<0.05; mRNA: r=0.909, p<0.05). Periostin was expressed in the myopic sclera of guinea pigs, and changes in periostin and collagen I expression were highly consistent. Periostin and collagen I may be involved in the regulation of scleral remodeling in myopia.

Relationship between Aquaporin-1 Protein Expression and Choroidal Thickness during the Recovery of Form-deprivation Myopia in Guinea Pigs

ABSTRACTPurpose: The purpose of this study was to investigate the relationship between aquaporin-1 (AQP-1) protein expression in the choroid and choroid thickness (CT) during the recovery of form-deprivation (FD) myopia in guinea pigs.Materials and Methods: Seventy-two guinea pigs were randomly assigned to the normal control (NC) group, FD 21 group (animals wore a latex facemask in the right eye for 21 days to induce FD myopia) and four recovery (REC) groups. Guinea pigs in the REC groups also wore the facemask for 21 days to induce myopia; then, the facemask was removed, and the eye was re-exposed to the normal environment for 12 hours (REC ½ group), 1 day (REC 1 group), 2 days (REC 2 group), and 7 days (REC 7 group). All animals underwent biometric measurements (refraction, axial length, and CT), and the protein expression of AQP-1 in the choroid was determined using western blotting.Results: The protein expression of AQP-1 and CT were significantly decreased in the FD 21 group as compared with those in the NC group (p = .007 and p < .001). Both AQP-1 protein expression and CT gradually increased and peaked in the REC 2 group. Additionally, there were significant differences in AQP-1 protein expression and CT between the REC 2 group and all other groups (all p < .05). We observed a complete recovery in the in REC 7 group as compared with the NC group (p > .05). AQP-1 protein expression was significantly associated with CT (p = .001) in all groups; however, there was a significant negative correlation (p = .029) between AQP-1 protein expression and axial length in the REC groups.Conclusions: AQP-1 protein expression in the choroid was upregulated following recovery of FD myopia in guinea pigs, and these changes correlated with alterations in CT and axial length.