iridoids and Myopia

Topics: Animals; Guinea Pigs; Intraocular Pressure; Iridoids; Myopia; Sclera

Scleral crosslinking using genipin has been identified as a promising treatment approach for myopia control. The efficacy of genipin to alter biomechanical properties of the sclera has been shown in several animal models of myopia but its safety profile remains unclear. In this safety study, we aim to investigate the effect of scleral crosslinking using retrobulbar injections of genipin on retinal structure and function at genipin doses that were shown to be effective in slowing myopia progression in juvenile tree shrews. To this end, three or five retrobulbar injections of genipin at 0 mM (sham), 10 mM, or 20 mM were performed in one eye every other day. Form deprivation myopia was induced in the injected eye. We evaluated retinal function using full-field electroretinography and retinal structure using in vivo optical coherence tomography imaging and ex vivo histology. The optical coherence tomography results revealed significant thinning of the peripapillary retinal nerve fiber layer in all genipin treated groups including the lowest dose group, which showed no significant treatment effect in slowing myopia progression. In contrast, inducing form deprivation myopia alone and in combination with sham injections caused no obvious thinning of the retinal nerve fiber layer. Electroretinography results showed a significant desensitizing shift of the b-wave semi-saturation constant in the sham group and the second highest genipin dose group, and a significant reduction in b-wave maxima in the two highest genipin dose groups. The ex vivo histology revealed noticeable degeneration of photoreceptors and retinal pigment epithelium in one of two investigated eyes of the highest genipin dose group. While scleral crosslinking using genipin may still be a feasible treatment option for myopia control, our results suggest that repeated retrobulbar injections of genipin at 10 mM or higher are not safe in tree shrews. An adequate and sustained delivery strategy of genipin at lower concentrations will be needed to achieve a safe and effective scleral crosslinking treatment for myopia control in tree shrews. Caution should be taken if the proposed treatment approach is translated to humans.

Topics: Animals; Iridoids; Myopia; Sclera; Tupaiidae

High myopia can lead to blindness. Genipin is a collagen cross-linking agent that may be used to treat myopia. However, the mechanism of action of genipin for the treatment of myopia is unclear. This study investigated the effect of genipin on the scleral expression of the miR-29 cluster, matrix metalloproteinase 2 (MMP2), and collagen alpha1 chain of type I (COL1A1) in a guinea pig model of myopia.. The model of myopia was established by treating guinea pigs with a - 8D lens on both eyes for 21 days, and eyes with a refractive error of - 6D or greater were included. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) and western blot were used to examine the mRNA and protein expression, respectively. A dual-luciferase assay was used to determine the direct targeting of the miR-29 cluster on the 3'-untranslated region (UTR) of the COL1A1 gene.. The scleral expression of miR-29a, miR-29b, and miR-29c as well as MMP2 was significantly increased, and the scleral expression of COL1A1 was significantly decreased in the myopia group. Genipin treatment reversed these effects in myopic eyes. The dual-luciferase assay showed that the luciferase activities were significantly decreased in human embryonic kidney (HEK) cells transfected with miR-29a and miR-29b, but not miR-29c, compared with those transfected with control miRNAs.. Genipin inhibits the scleral expression of the miR-29 cluster and MMP2 and promotes COL1A1 expression in a guinea pig model of myopia. Thus, genipin may promote COL1A1 expression by reducing the expression of the miR-29 cluster.

Topics: Animals; Blotting, Western; Cells, Cultured; Cholagogues and Choleretics; Collagen Type I; Collagen Type I, alpha 1 Chain; Disease Models, Animal; Female; Gene Expression Regulation; Guinea Pigs; HEK293 Cells; Humans; Iridoids; Male; Matrix Metalloproteinase 2; MicroRNAs; Myopia; Real-Time Polymerase Chain Reaction; RNA, Messenger; Sclera

Scleral stiffening has been proposed as a therapy for glaucoma and myopia. Previous

Topics: Animals; Glaucoma; Iridoids; Male; Myopia; Rats; Sclera

Myopia progression is thought to involve biomechanical weakening of the sclera, which leads to irreversible deformations and axial elongation of the eye. Scleral crosslinking has been proposed as a potential treatment option for myopia control by strengthening the mechanically weakened sclera. The biomechanical mechanism by which the sclera weakens during myopia and strengthens after crosslinking is not fully understood. Here, we assess the effect of lens-induced myopia and exogenous crosslinking using genipin on the inelastic mechanical properties of the tree shrew sclera measured by cyclic tensile tests.. Cyclic tensile tests were performed on 2-mm wide scleral strips at physiological loading conditions (50 cycles, 0-3.3 g, 30 s cycle. -5D lens treatment significantly increased the cyclic softening response of the sclera when compared to contralateral control eyes (0.10% ± 0.029%, mean ± standard error, P = 0.037). Exogenous crosslinking of the lens treated sclera significantly decreased the cyclic softening response (-0.12% ± 0.014%, P = 2.2 × 10. Results indicated that cyclic tensile loading leads to an inelastic, cyclic softening of the juvenile tree shrew sclera. The softening rate increased during lens-induced myopia and was diminished after genipin crosslinking. This finding suggests that axial elongation in myopia may involve a biomechanical weakening mechanism that increased the cyclic softening response of the sclera, which was inhibited by scleral crosslinking using genipin.

Topics: Adhesives; Animals; Biomechanical Phenomena; Cross-Linking Reagents; Disease Models, Animal; Disease Progression; Iridoids; Myopia; Refraction, Ocular; Sclera; Tensile Strength; Tupaiidae

Scleral cross-linking (CXL) is a novel attempt to slow down the axial elongation process in animal eyes. As a natural CXL reagent, genipin would be also effective for the prevention of myopia process. Thus, the present study was designed to evaluate the effects of scleral cross-linking using genipin on the form-deprivation (FD) myopia process of guinea pigs.. Twenty-seven 3-week-old pigmented guinea pigs were randomly divided into three groups. Group A (n = 8) is the untreated control group. Group B (n = 8) is the FD control group, where all eyes were induced with monocular FD for 21 days. In Group C (n = 11), a sub-Tenon injection of 0.10 mL 0.50 % genipin was performed on FD eyes at day 0, 7 and 14 during the 21-day monocular FD. The ocular refraction, axial length, biomechanical test and light and electron microscopy were measured on all eyes to check the efficacy and safety of this scleral CXL technique.. Compared with Group A, significant increases in myopic refractive errors, axial elongation and reductions of scleral fibril diameter and density were observed in the 21-day FD eyes of Group B (P < 0.05). In Group C, the scleral CXL resulted in less myopia and axial elongation as compared with Group B (P < 0.05); a significant thickening of scleral fibrils was found after sub-Tenon injections of genipin; no histological damage on the retina or choroid was observed in Group C at the end of this study.. The FD myopia in guinea pig eyes was effectively blocked by the scleral CXL using sub-Tenon injections of genipin. No histological damage was found on the retina or choroid of these treated eyes. Further studies are needed to examine the long-term efficacy and safety of this CXL technique.

Topics: Animals; Axial Length, Eye; Cholagogues and Choleretics; Cross-Linking Reagents; Disease Models, Animal; Elasticity; Guinea Pigs; Injections, Intraocular; Iridoids; Myopia; Refraction, Ocular; Sclera; Sensory Deprivation

To evaluate the effect of collagen cross-linking induced by genipin in porcine sclera.. Porcine cadaver eyes were treated with genipin at concentrations (by w/v) of 0.01%, 0.03%, 0.1%, 0.3%, 1.0% for 15 and 30 min. Riboflavin/ultraviolet A(UVA)-treated and untreated samples were used as controls. After treatment, scleral strips of 4.0 × 10.0 mm were cut. Twenty-four hours later, the stress-strain parameters of the strips were measured using a biomaterial microtester. The stress and Young's modulus at 8% strain were evaluated.. Compared with untreated groups, after treatment with genipin for 15 min, the stress was increased by 66-246%, depending on the concentration of genipin. As for the 30-min groups, the stress was 171-444% higher than that of the control. The difference of the Young's modulus between genipin 15-min groups, except the 0.01% groups (p = 0.095), also had statistical significance (p < 0.05). The Young's modulus had significant difference between the untreated group and the genipin 30-min groups (all p < 0.05). Of 0.3% genipin for 15 min or 0.01% genipin for 30 min had a similar stress-strain curve with those of eyes treated with the riboflavin/UVA group. The sclera exhibited a bluish colour which became deeper with increase concentration and cross-linking time.. Collagen cross-linking induced by genipin could increase the biomechanical strength in porcine sclera. The effect depends on the concentration and treatment time of genipin.

Topics: Adhesives; Animals; Collagen; Cross-Linking Reagents; Disease Models, Animal; Elasticity; Iridoids; Myopia; Sclera; Swine