The relationship between retinal disease, diet, and the gut microbiome has shown increasing importance over recent years. In particular, high-fat diets (HFDs) are associated with development and progression of several retinal diseases, including age-related macular degeneration (AMD) and diabetic retinopathy. However, the complex, overlapping interactions between diet, gut microbiome, and retinal homeostasis are poorly understood. Using high-throughput RNA-sequencing (RNA-seq) of whole retinas, we compare the retinal transcriptome from germ-free (GF) mice on a regular diet (ND) and HFD to investigate transcriptomic changes without influence of gut microbiome. After correction of raw data, 53 differentially expressed genes (DEGs) were identified, of which 19 were upregulated and 34 were downregulated in GF-HFD mice. Key genes involved in retinal inflammation, angiogenesis, and RPE function were identified. Enrichment analysis revealed that the top 3 biological processes affected were regulation of blood vessel diameter, inflammatory response, and negative regulation of endopeptidase. Molecular functions altered include endopeptidase inhibitor activity, protease binding, and cysteine-type endopeptidase inhibitor activity. Human and mouse pathway analysis revealed that the complement and coagulation cascades are significantly affected by HFD. This study demonstrates novel data that diet can directly modulate the retinal transcriptome independently of the gut microbiome.

Background and aimsConnections between the gut microbiome and retinal diseases such as age-related macular degeneration (AMD), diabetic retinopathy (DR), retinopathy of prematurity (ROP), and primary open-angle glaucoma (POAG) are recently being established. Communication between the gut microbiome and retina, referred to as the gut-retina axis, has been proposed; however, the biologic pathways and mediators involved in the interactions have not yet been elucidated. Using high-throughput RNA sequencing (RNA-seq) of whole retinas, we compare the retinal transcriptome from germ-free (GF) and specific pathogen-free (SPF) mice to investigate effects of the gut-microbiome on both retinal gene expression and biologic pathways.MethodsRNA was extracted from whole retinas of GF and SPF mice (four animals per group) and cDNA libraries were created. RNA-seq was performed on NovaSEQ6000 using the paired-end method. After preprocessing the RNA-seq data, gene expression value was calculated by count per million (CPM). The differentially expressed genes (DEGs) were identified with edgeR Bioconductor analysis of expression data. Functional enrichment and protein-protein interaction (PPI) network analyses were created for the differentially expressed genes (DEGs).ResultsRNA-sequencing reveals a cohort of 396 DEGs, of which, 173 are upregulated and 223 are downregulated in GF mouse retina. Enrichment analysis reveals that the DEGs are involved in glucocorticoid effects, transcription factor binding, cytoskeletal stability, lipid metabolism, and mitogen-activated protein kinase (MAPK). Multiple biologic pathways, including obesity/metabolic syndrome, longevity, and 5’ AMP-activated protein kinase (AMPK) signaling pathway are affected in the GF retinas. PPARG1a (PGC1a) gene is involved in 12 of the 16 significantly modulated pathways. Proteins with the most number of interactions in the PPI are E1A binding protein P300(EP300), forkhead box O3(FOXO3) and PGC1a.ConclusionsTo our knowledge, this is the first study demonstrating the involvement of the gut microbiome in driving the retinal transcriptome, providing evidence for the presence of a gut-retina axis. Future studies are needed to define the precise role of the gut-retina axis in the pathogenesis of retinal diseases.

PurposeWe used the juvenile rabbit as a model for investigating therapeutic interventions for postoperative inflammation and fibrin formation following intraocular lens (IOL) insertion for management of pediatric cataracts.MethodsTwelve 6- to 7-week-old, 600 to 900 g rabbits underwent bilateral clear-cornea lensectomy via irrigation and aspiration with IOL insertion. Following wound closure, enoxaparin 8 mg (n = 6 eyes), preservative-free triamcinolone 0.5 mg (n = 6), 8 mg enoxaparin plus 0.5 mg triamcinolone (n = 6), or balanced salt solution (n = 6) was injected into the anterior chamber. Slit-lamp examinations and optical coherence tomography (OCT) scans were performed postoperatively on days 3 through 7, and 14 to characterize levels of inflammation and fibrin. Using 17 additional rabbits, enzyme-linked immunosorbent assays (ELISAs) with 100 μL of aqueous humor were performed to quantify the amount of fibrinogen and fibrin preoperatively and on postoperative day 3. Immunohistochemistry was performed to confirm the presence of fibrin.ResultsEnoxaparin alone and combined with triamcinolone reduced the amount of fibrin present in the anterior chamber compared to untreated eyes, which corresponded to an increase in OCT signal strength. Despite the clear visual axis shown in clinical images, the combination treatment group had the highest levels of soluble fibrin when assessed by ELISA. Immunohistochemistry confirmed the presence of insoluble fibrin seen clinically.ConclusionsA combination of enoxaparin and triamcinolone appears to provide the most therapeutic benefit by reducing fibrin formation and postoperative inflammation.Translational RelevanceThe juvenile rabbit is an excellent model to investigate inflammation and fibrin formation following lensectomy with IOL insertion and possibly any intraocular surgery in children.