Dynamic changes of activator protein 1 and collagen I expression in the sclera of myopia guinea pigs

Expression of SCO1 and SCO2 after form-deprivation myopia in Guinea pigs

PURPOSE

The retina is a highly energy-consuming tissue associated with visual development, and the reduced quality of retinal imaging can be related to myopia. Synthesis of cytochrome c oxidase 1 (SCO1) and synthesis of cytochrome c oxidase 2 (SCO2) are involved in ATP (adenosine triphosphate) synthesis and energy metabolism. This study aimed to observe the morphologic changes and investigate the expression of SCO1 and SCO2 induced by form-deprivation myopia (FDM) in the retina and sclera of guinea pigs.

METHODS

Thirty-six 3-week-old male guinea pigs were randomly assigned to one of two groups: (1) the model group (n  =  18), in which the right eyes were covered by a thin opaque balloon as FDM group, and the left eyes were uncovered and served as the contralateral control group; (2) the blank control group (n  =  18), in which bilateral eye received no manipulation. Eyeballs were enucleated for histological analysis. The retina and sclera of the guinea pigs were separated to determine the protein and mRNA expression levels of SCO1 and SCO2, respectively.

RESULTS

After four weeks of form deprivation (FD), the refractive degree and axial length increased significantly (P < 0.001). The retinal and scleral tissues were moderately thinner, and the ganglion cells and the cells of inner and outer nuclear layers in the retina became fewer. Compared with the contralateral control group (P < 0.001) and the blank control group (P < 0.001), the collagen content of the sclera became less in the FDM group. The protein and mRNA expression levels of SCO1 and SCO2 in the FDM group were significantly lower than those in the contralateral control group and the blank control group (P < 0.05).

CONCLUSIONS

The morphologies of the retina and sclera were changed, and the expression of SCO1 and SCO2 at the protein and transcription levels was significantly reduced in the FDM group. Given these changes, SCO1 and SCO2 genes may be involved in myopic progression.

Drug Delivery via the Suprachoroidal Space for the Treatment of Retinal Diseases

The suprachoroidal space (SCS), a potential space between the sclera and choroid, is becoming an applicable method to deliver therapeutics to the back of the eye. In recent years, a vast amount of research in the field has been carried out, with new discoveries in different areas of interest, such as imaging, drug delivery methods, pharmacokinetics, pharmacotherapies in preclinical and clinical trials and advanced therapies. The SCS can be visualized via advanced techniques of optical coherence tomography (OCT) in eyes with different pathologies, and even in healthy eyes. Drugs can be delivered easily and safely via hollow microneedles fitted to the length of the approximate thickness of the sclera. SCS injections were found to reach greater baseline concentrations in the target layers compared to intravitreal (IVT) injection, while agent clearance was faster with highly aqueous soluble molecules. Clinical trials with SCS injection of triamcinolone acetonide (TA) were executed with promising findings for patients with noninfectious uveitis (NIU), NIU implicated with macular edema and diabetic macular edema (DME). Gene therapy is evolving rapidly with viral and non-viral vectors that were found to be safe and efficient in preclinical trials. Here, we review these novel different aspects and new developments in clinical treatment of the posterior segment of the eye.

IMI 2021 Yearly Digest

Purpose

The International Myopia Institute (IMI) Yearly Digest highlights new research considered to be of importance since the publication of the first series of IMI white papers.

Methods

A literature search was conducted for articles on myopia between 2019 and mid-2020 to inform definitions and classifications, experimental models, genetics, interventions, clinical trials, and clinical management. Conference abstracts from key meetings in the same period were also considered.

Results

One thousand articles on myopia have been published between 2019 and mid-2020. Key advances include the use of the definition of premyopia in studies currently under way to test interventions in myopia, new definitions in the field of pathologic myopia, the role of new pharmacologic treatments in experimental models such as intraocular pressure-lowering latanoprost, a large meta-analysis of refractive error identifying 336 new genetic loci, new clinical interventions such as the defocus incorporated multisegment spectacles and combination therapy with low-dose atropine and orthokeratology (OK), normative standards in refractive error, the ethical dilemma of a placebo control group when myopia control treatments are established, reporting the physical metric of myopia reduction versus a percentage reduction, comparison of the risk of pediatric OK wear with risk of vision impairment in myopia, the justification of preventing myopic and axial length increase versus quality of life, and future vision loss.

Conclusions

Large amounts of research in myopia have been published since the IMI 2019 white papers were released. The yearly digest serves to highlight the latest research and advances in myopia.

Effects of lumican expression on the apoptosis of scleral fibroblasts: In vivo and in vitro experiments

Lumican serves an important role in the maintenance of sclera biomechanical properties. However, whether lumican expression is altered in myopia and the mechanisms of action involved are unknown. In the present study, the expression of lumican in cultured scleral fibroblasts and in the scleral tissue of a rat model of form-deprivation myopia was assessed. It was confirmed that diopter was decreased, whereas axial length was increased in modeled eyes relative to normal control eyes, indicating that the model of myopia was successfully established. These pathologic changes were accompanied by the upregulation of lumican and tissue inhibitor of metalloproteinases (TIMP)-2, as well as the downregulation of matrix metalloproteinase (MMP)-2 and MMP-14. The same trends in TIMP-2, MMP-2 and MMP-14 expression were observed when lumican was overexpressed in cultured scleral fibroblasts. Additionally, cell proliferation decreased whereas apoptosis increased compared with those of control cells. Inhibiting lumican expression had no effect on cell proliferation or apoptosis, but stimulated the expression of MMP-2 and MMP-14 while decreasing that of TIMP-2. The results suggested that lumican overexpression contributed to myopia by promoting apoptosis in scleral fibroblasts via the modulation of TIMP-2, MMP-2 and MMP-14 expression.

RNA sequencing analysis of long non-coding RNA expression in ocular posterior poles of guinea pig myopia models

Purpose

To detect the differential expression of long non-coding RNAs (lncRNAs) in the ocular posterior poles of two guinea pig myopia models and explore the pathogenic role of lncRNAs in myopia.

Methods

Form-deprived myopia (FDM) and lens-induced myopia (LIM) models were induced in guinea pig right eyes by wearing a translucent latex balloon head mask and a -10.00 diopter (D) lens, respectively. Ocular biometric parameters were measured biweekly. At 6 weeks after the induction of myopia, the guinea pig eyeballs were processed for hematoxylin and eosin staining to examine the ocular morphology. The ocular posterior poles from the normal control, FDM, and LIM groups were collected to analyze the differential expression of lncRNAs between the groups with high-throughput RNA sequencing (RNA-seq). Further, the lncRNA-mRNA colocation network was delineated to predict the functions of the differentially expressed lncRNAs. Last, Gene Ontology (GO) functional enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were performed on the colocated mRNAs of the differentially expressed lncRNAs. Additionally, the expression of the most differentially expressed lncRNAs in the myopia-induced eyes and the contralateral eyes was validated with quantitative real-time PCR (qPCR).

Results

Compared with the normal controls and the contralateral eyes, the myopia-induced eyes in the FDM and LIM groups exhibited decreased scleral and choroidal thicknesses, reduced refraction, and increased ocular axial length but without changes in the corneal curvature radius at 6 weeks after myopia was induced. RNA-seq showed that 372 and 247 lncRNAs were differentially expressed in the FDM and LIM groups, respectively, in comparison to the normal counterparts. There were 380 differentially expressed lncRNAs in the LIM group compared to the FDM group. The GO and KEGG analyses showed that the colocated mRNAs of the differentially expressed lncRNAs were enriched in cellular components such as the extracellular matrix (ECM) structural constituent; in molecular functions such as kinase activity, metabolism, and growth; as well as in pathways including ECM-receptor interaction, glycosaminoglycan degradation, and mucin type O-Glycan biosynthesis. The expression patterns of the selected lncRNAs were verified with qPCR.

Conclusions

High-throughput RNA-seq revealed previously undescribed lncRNA expression profiling in guinea pig FDM and LIM models. These results may shed light on the molecular pathogenesis of myopia and provide clues for interventional targets for this highly prevalent visual disorder.