Form-deprivation Myopia Group Research Articles

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

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. 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. 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. 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.

Effects of Constant Flickering Light on Refractive Status, 5-HT and 5-HT2A Receptor in Guinea Pigs

PurposeTo investigate the effects of constant flickering light on refractive development, the role of serotonin (i.e.5-hydroxytryptamine, 5-HT)and 5-HT2A receptor in myopia induced by flickering light in guinea pigs.MethodsForty-five guinea pigs were randomly divided into three groups: control, form deprivation myopia (FDM) and flickering light induced myopia (FLM) groups(n = 15 for each group). The right eyes of the FDM group were covered with semitransparent hemispherical plastic shells serving as eye diffusers. Guinea pigs in FLM group were raised with illumination of a duty cycle of 50% at a flash frequency of 0.5Hz. The refractive status, axial length (AL), corneal radius of curvature(CRC) were measured by streak retinoscope, A-scan ultrasonography and keratometer, respectively. Ultramicroscopy images were taken by electron microscopy. The concentrations of 5-HTin the retina, vitreous body and retinal pigment epithelium (RPE) were assessed by high performance liquid chromatography, the retinal 5-HT2A receptor expression was evaluated by immunohistofluorescence and western blot.ResultsThe refraction of FDM and FLM eyes became myopic from some time point (the 4th week and the 6th week, respectively) in the course of the experiment, which was indicated by significantly decreased refraction and longer AL when compared with the controls (p<0.05). The concentrations of 5-HT in the retina, vitreous body and RPE of FDM and FLM eyes were significantly increased in comparison with those of control eyes (both p<0.05). Similar to FDM eyes, the expression of retinal 5-HT2A receptor in FLM eyes was significantly up-regulated compared to that of control eyes (both p<0.05). Western blot analysis showed that retinal 5-HT2A receptor level elevated less in the FLM eyes than that in the FDM eyes. Moreover, the levels of norepinephrine and epinephrine in FDM and FLM groups generally decreased when compared with control groups (all p<0.05).ConclusionsConstant flickering light could cause progressive myopia in guinea pigs. 5-HT and 5-HT2A receptor increased both in form deprivation myopia and flickering light induced myopia, indicating that 5-HT possibly involved in myopic development via binding to5-HT2A receptor.

Scleral TGF-β1 and Smad3 expression is altered by TCM Bu Jing Yi Shi Tablets in guinea pigs with form-deprivation myopia

ObjectiveTo explore whether the traditional Chinese medicine (TCM) Bu Jing Yi Shi Tablets alters the expression of scleral TGF-β1 and Smad3 in guinea pigs with form-deprivation myopia (FDM). MethodsSixty-five guinea pigs were randomly divided into control, model, low-, medium-, and high-dose treatment groups. Except for the control group, FDM was induced by covering the right eye of each animal with opaque latex. The treatment groups were gavaged with different suspension concentrations of Bu Jing Yi Shi Tablets. Refraction and axial length were performed before and after myopia induction. At the end of the experiment, all right eyes were extracted, and scleral sections were prepared for staining and TGF-β1 and Smad3 immunohistochemistry. Scleral thickness and area, the scleral fibroblast quantity, and scleral TGF-β1 and Smad3 expressions were measured. ResultsThe 5 FDM groups had the same initial axial length and diopter, the final diopter and axial length of the model group were significantly increased compared with the control group and treatment groups (P < .01). The axial length of each treatment group decreased as the dose decreased compared with the model group (P < .01); the total scleral area (P < .05–.01) and the number of scleral fibroblasts (P < .01) in the model group were significantly lower than the treatment groups. Both the TGF-β1 and Smad3 integral optical densities in the model group were significantly lower than the control and medium- and high-dose treatment groups (P < .01). TGF-β1 and Smad3 mRNAs in the model group were decreased compared with the control group, but increased in expression after treatment. ConclusionBu Jing Yi Shi Tablets may restore the expression of scleral TGF-β1 and Smad3 in FDM guinea pigs and impede myopia development.

The sonic hedgehog signaling pathway induces myopic development by activating matrix metalloproteinase (MMP)-2 in Guinea pigs.

PurposeTo investigate whether the Sonic hedgehog (Shh) signaling induces myopic development by increasing the expression of matrix metalloproteinase (MMP)-2 in guinea pigs.MethodsA translucent diffuser was glued onto the right eye to induce form-deprivation myopia (FDM) in 10 guinea pigs. Four guinea pigs were served as a control group. The other 100 guinea pigs were subdivided into 5 groups (20 per group) and received a 10 µl intravitreal injection every 2 days for 4 times. Two groups were injected with 20 or 50 µg/ml Shh amino-terminal peptide (Shh-N) into the right eye and 0.1% bovine serum albumin into the other. FDM was induced in the right eyes of the three cyclopamine-treated groups and both eyes were injected with 50, 100, or 200 µg/ml cyclopamine. Retinoscopic refraction and eye dimensions were assessed on Day 14 of treatment. MMP-2 protein expression was determined in both scleras by western blotting.ResultsBoth concentrations of Shh-N stimulated myopic development and axial growth as compared with control eyes. Myopia and axial elongation were significantly greater in the 50 µg/ml than in the 20 µg/ml Shh-N group (P<0.001 and P = 0.0019, respectively). All three doses of cyclopamine significantly attenuated myopic development compared with the FDM group (P<0.0001). Cyclopamine at 100 or 200 µg/ml significantly reduced axial elongation compared with the FDM group (P = 0.044 and P = 0.001, respectively). FDM-induced myopia and axial elongation were significantly greater in the 50 µg/ml than in the 200 µg/ml cyclopamine group (P<0.0001 and P = 0.008, respectively). MMP-2 expression was significantly greater in Shh-N–treated eyes than in the control eyes, and was lower in the cyclopamine plus FDM groups than in the FDM group.ConclusionsThe Shh signaling pathway induces myopic development by activating MMP-2 in guinea pigs.

The correlation between the regulation of recombinant human IGF-2 on eye growth and form-deprivation in guinea pig

By investigating the effects of recombinant human IGF-2 (rhIGF-2) on the diopter, axial eye length and the expression of IGF-2 in non-form-deprivation (FD) and FD eyes of guinea pig, we tried to elucidate the relationship between the effects of rhIGF-2 on eye growth and FD in guinea pig. Eighty 3-week-old guinea pigs were included in the study, which were divided into two groups randomly. Group A (n = 40) was the non-FD group, Thirty-two guinea pigs received intravitreal injections of either 1 ng, 10 ng, 100 ng rhIGF-2 or bovine serum albumin (BSA) to the right eye; eight guinea pigs who received no intravitreal injections served as control. Group B (n = 40) was the FD group; the right eyes were form-deprived, and received the same disposals as group A. The diopter and the axial eye length of all guinea pigs were measured at day 14. The expression of IGF-2 in the retina was measured by Western blot. After 14 days, FD eyes were high myopia. The axial length of FD eyes was significant for longer than that of non-FD eyes. The expression of IGF-2 in the retina of FD eyes was up-regulated. In non-FD group, there was no significant difference in the diopter and axial eye length among rhIGF-2 injection eyes, BSA injection eyes and control eyes, but the expression of IGF-2 in the retina of 10 ng and 100 ng rhIGF-2 injection eyes was obviously down-regulated. In the FDM (form-deprivation myopia) group, the myopic diopter and axial eye length increased in 10 ng and 100 ng rhIGF-2 injection eyes compared with those in BSA injection eyes and control eyes. The level of IGF-2 expression in the retina of 10 ng and 100 ng rhIGF-2 injection eyes was obviously down-regulated. The diopter and expression of IGF-2 in the retina of rhIGF-2 injection eyes was negatively correlated with the dose of each injection, which was positively correlated with the axial length. RhIGF-2 intravitreous injection does not affect the diopter and axial length in non-FD eyes of guinea pig, while it can induce a significant increase in myopic diopter and axial length of FD eyes. RhIGF-2 can promote the development of FDM on the condition of FD.