Tyrosine Metabolic Pathway And Complement Pathway In Myopia-induced Retinal Degeneration

The prevalence of myopia is increasing globally at alarming rate,as a result,the proportion of high myopia and pathological myopia also increase greatly.There is urgent need to elucidate the underlying mechanism of myopic retinal degeneration and pathological myopia.The objectives or our study were(1)to establish an animal model of myopic retinal degeneration,and(2)to investigate the mechanism of myopic retinal degeneration using the animal model and clinical data from myopic patients undergoing Implantable Collamer Lens(ICLs)surgery.Part 1.Establishment of a Myopia-induced Retinal Degeneration Animal Model in Guinea PigsPurpose:To establish and characterize a myopic retinal degeneration animal model in guinea pigs.Method:Two-to three-week-old guinea pigs were randomly assigned to two groups(n=24/group):form deprivation(FDM)and na?ve nontreatment controls.In the form-deprivation group,the right eyes were occluded with nontoxic balloons as translucent masks for 15 weeks.The left eye remained untreated and served as a self-control.In the na?ve nontreatment controls,age-matched animals were maintained under normal housing conditions without any interventions.The refractive error and ocular biometrics were measured at 3,7,9,12 and 15 weeks post-FDM induction.Visual function was evaluated by electroretinography.Retinal neurons and synaptic structures were examined in retinal sections by confocal microscopy following immunolabelling with relevant antibodies.Results:The FDM eyes presented a progressive axial length elongation and refractive error development.After 15 weeks of intervention,the change of refractive power was-6.33±2.05 D in the FDM eyes,-0.15±1.37 D and 1.11±1.05 D in the self-control and na?ve control eyes,respectively.The change of axial length was-1.27±0.28 mm in the FDM,0.78±0.19 mm and 0.89±0.14 mm in the self-control and na?ve control eyes,respectively.The a-wave amplitude was significantly lower in FDM eyes and these eyes had a significantly lower number of rods,secretagogin~+bipolar cells,and GABAergic amacrine cells in selected retinal areas.Conclusions:The long-term(15-week)FDM in the guinea pigs induced high myopia and an early-stage retinal degeneration.Part 2.An Essential Role of the Tyrosine Metabolic Pathway and Inflammation in Myopia-induced Retinal Degeneration in Guinea PigsPurpose:To investigate the mechanism of action underlying retinal degeneration caused by myopia using a model of myopia-induced early-stage retinal degeneration in guinea pigs.Method:Two-to three-week-old guinea pigs were randomly assigned to two groups(n=18/group):form deprivation and na?ve nontreatment controls using the methods detailed in Part 1.After 15weeks,the total RNAs were extracted from the retinas and processed for RNA sequencing analysis.RT-q PCR were verified for the relevant genes.The differentially expressed genes(DEGs)were further analyzed to identify molecular pathways involved in myopic induced retinal degeneration.Results:RNA-seq analysis showed that 288 genes were upregulated and 119 genes were downregulated in FDM retinas compared to na?ve control retinas.In addition,152 genes were upregulated and 12 were downregulated in FDM retinas compared to self-control retinas.The Kyoto Encyclopedia of Genes and Genomes(KEGG)enrichment analysis showed that tyrosine metabolism,ATP-binding cassette transporter(ABC transporters)and inflammatory pathways were upregulated,whereas tight junction,lipid and glycosaminoglycan biosynthesis were downregulated in FDM eyes.Conclusions:The dysregulation of the tyrosine metabolism and the upregulation of the inflammatory pathways may contribute to the pathogenesis of early-stage retinal degeneration caused by form deprivation-induced myopia.Part 3.The Link between Intraocular Complement Activation and Pathological MyopiaPurpose:To investigate the relationship between the intraocular levels of complements and pathological myopia and its related retinal degeneration.Method:147 patients with Implantable Collamer Lens(ICLs)implantation were enrolled in this study.All participants received comprehensive ophthalmic examination,including log MAR best corrected visual acuity(BCVA),slit lamp examination,visual function and optical coherence tomography(OCT)and OCT angiography(OCTA).100?l of aqueous humor were collected immediately prior to ICL surgery.The levels of complements in aqueous humor,including C1q,C3,C3b,C4,CFB,CFH,C2,C4b,C5,C5a,CFD,MBL,and CFI,were assayed using Luminex Multiplexing system following manufacture’s instructions.Results:With the progression of pathological myopia,the aqueous levels of C1q,C3,C3b,C4,CFB,CFH,C2,C4b,C5 and CFI were significantly increased(p<0.05),the whole superficial and deep retinal vessel density/thickness in macular area(Whole DRVD and Whole DRT)were decreased(p<0.05).The average retinal nerve fiber layers(Average RNFL)and the whole vessel RPC density around the optic nerve head also decreased with the progression of pathological myopia(p<0.05).Furthermore,those aqueous levels of complement factors showed negative correlations with Whole DRVD and Whole DRT in macular area(C1q vs Whole DRT:β=-0.171,p<0.001;C2 vs Whole DRT:β=-0.038,p<0.001;C3b vs Whole DRT:β=-1.950,p<0.001;C1q vs Whole DRVD:β=-0.456,p<0.001;C2 vs Whole DRVD:β=-0.108,p<0.001;C3b vs Whole DRVD:β=-0.488,p<0.001).Conclusion:The intraocular classical pathway and alternative pathway of the complement system are activated with the progression of pathological myopia.The intraocular complement activation is related to the thinning of deep nerve layer thickness and the reduction of vascular density in the macula.