Targeting scleral remodeling and myopia development in form deprivation myopia through inhibition of EFEMP1 expression

The role of extracellular matrix (ECM) remodeling in the axial elongation associated with myopia has not been fully elucidated, although it is considered a significant factor. EFEMP1, a regulator of ECM, has been associated with various pathological conditions. This study aimed to examine the involvement of EFEMP1 in scleral remodeling during form deprivation myopia. The results indicate a progressive increase in EFEMP1 expression following prolonged form deprivation treatment, followed by a subsequent decrease upon recovery. To gain a deeper understanding of the mechanism of EFEMP1, we conducted transcriptome sequencing on primary scleral fibroblasts that were subjected to lentivirus-mediated overexpression of EFEMP1. Validation was performed using lentivirus-induced overexpression and shRNA targeting EFEMP1 in combination with LY294002, a PI3K inhibitor. Our findings suggest that EFEMP1 may be involved in the development of FDM by regulating the expression of the PI3K/AKT/MMP2 axis. The AAV-mediated injection of shEFEMP1 under Tenon's capsule in guinea pigs was observed to effectively delay the progression of myopia and posterior scleral remodeling. In contrast, the AAV-mediated overexpression of EFEMP1 exacerbated the development of myopia and resulted in further thinning of collagen fibers in the posterior sclera. In summary, adjusting EFEMP1 concentrations could potentially serve as a viable approach to prevent and treat myopia by influencing the remodeling process of the posterior sclera.

Biomechanical changes in myopic sclera correlate with underlying changes in microstructure

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

The effect of Wnt/β-catenin pathway on the scleral remolding in the mouse during form deprivation

BACKGROUND

Many reports have shown that Wnt/β-Catenin pathway is associated with a variety of diseases, but its role in the pathogenesis of myopia is still unknown. In order to clarify the role of Wnt/β-catenin pathway in the development of form deprivation myopia (FDM), this study investigated the expression of scleral Wls, β-catenin and TCF4 in mice model of form deprivation (FD) myopia.

METHODS

Three parallel experimental groups, including FD, monocular exposure (SC) and binocular exposure (NC) group, were designed to investigate the effects of Wnt/β-Catenin pathway on scleral remodeling mouse during form deprivation in three-week-old C57BL/6 mice. Diopters and axial lengths (AL) in each sample were measured with an infrared eccentric refractometer or spectral-domain optical coherence tomography. The expression of scleral Wls, β-catenin and TCF4 were detected with Western blot. Morphological changes of posterior sclera were observed with a transmission electron microscope (TEM). The above characterization and analysis were performed on the 0th, 7th, 14th, 21st and 28th days, respectively.

RESULTS

The difference of diopter and AL between the three groups (SC, NC and FD group) gradually increased with the prolongation of FD time (except AL between SC and NC groups). The changes of diopter and AL gradually increased with the prolongation of FD time. Especially, the diopter and AL will increase sharply after FD lasts for a long time, such as the measurement on the 21st for diopter and 28th days for AL. Most notably, the AL of FD eyes significantly increased after 28 days of deprivation. Thinning and disordered arrangement of collagen fibers and a decrease of extracellular matrix were observed with TEM. The expression of scleral Wls, β-catenin and TCF4 increased with age in the NC and SC group. In FD group, they increased significantly on the 7th, 14th and 21st days but decreased on the 28th day.

CONCLUSIONS

The expression of Wls, β-Catenin and TCF4 to FD were more sensitive indicators than that of diopter and AL. Within the first 7 days of FD, the expression of Wls, β-Catenin and TCF4 in sclera increased sharply. With the extension of FD duration, it gradually decreased. It is suggested that the Wnt/β-catenin pathway might be involved in the scleral remodeling induced in FDM mice.