Purpose Abnormal angiogenesis is a defining feature in a couple of ocular neovascular diseases. The application of anti-VEGFA therapy has achieved certain benefits in the clinic, accompanying side effects and poor responsiveness in many patients. The present study investigated the role of irisin in retinal neovascularization. Methods Western blot and quantitative PCR were used to determine irisin expression in the oxygen-induced retinopathy mice model. The pathological angiogenesis and inflammation index were examined after irisin administration. Primary retinal astrocytes were cultured and analyzed for VEGFA expression in vitro. Astrocyte-conditioned medium was collected for transwell assay and tube formation assay in human microvascular endothelial cells-1. Results Irisin was downregulated in the oxygen-induced retinopathy mice retinae. Additional irisin attenuated pathological angiogenesis, inflammation, and apoptosis in vivo. In vitro, irisin decreased astrocyte VEGFA production, and the conditioned medium suppressed human microvascular endothelial cells-1 migration. Last, irisin inhibited hypoxia-inducible factor-2α, nuclear factor-κB, and pNF-κB (Phospho-Nuclear Factor-κB) expression. Conclusions Irisin mitigates retinal pathological angiogenesis. Chinese Abstract

Age-related decline in visual functions is a prevalent health problem among elderly people, and no effective therapies are available up-to-date. Axon degeneration and myelin loss in optic nerves (ONs) are age-dependent and become evident in middle-aged (13-18 months) and old (20-22 months) mice of either sex as compared to adult mice (3-8 months), accompanied by functional deficits. Oligodendrocyte (OL) turnover is actively going on in adult ONs. However, the longitudinal change and functional significance of OL turnover in aging ONs remain largely unknown. Here, using cell-lineage labeling and tracing, we reported oligodendrogenesis displays an age-dependent decrease in aging ONs. To understand whether active OL turnover is required for maintaining axons and visual function, we conditionally deleted the transcription factor Olig2 in the OPCs of young mice. Genetically dampening OL turnover by Olig2 ablation resulted in accelerated axon loss and retinal degeneration, and subsequently impaired ON signal transmission, suggesting that OL turnover is an important mechanism to sustain axon survival and visual function. To test whether enhancing oligodendrogenesis can prevent age-related visual deficits, 12-month-old mice were treated with clemastine, a pro-myelination drug, or induced deletion of the muscarinic receptor 1 (M1R) in OPCs. The clemastine treatment or M1R deletion significantly increased new OL generation in the aged ONs and consequently preserved visual function and retinal integrity. Together, our data indicate that dynamic OL turnover in ONs is required for axon survival and visual function, and enhancing new OL generation represents a potential approach to reversing age-related declines of visual function.SIGNIFICANCE STATEMENT:Oligodendrocyte (OL) turnover has been reported in adult optic nerves (ONs), but the longitudinal change and functional significance of OL turnover during aging remain largely unknown. Using cell-lineage tracing and oligodendroglia-specific manipulation, this study reported that OL generation was active in adult ONs and the efficiency decreased in an age-dependent manner. Genetically dampening OL generation by Olig2 ablation resulted in significant axon loss and retinal degeneration, along with delayed visual signal transmission. Conversely, pro-myelination approaches significantly increased new myelin generation in aging ONs, and consequently preserved retinal integrity and visual function. Our findings indicate that promoting OL generation might be a promising strategy to preserve visual function from age-related decline.

Visual impairment in diabetes is a growing public health concern. Apart from the well‐defined diabetic retinopathy, disturbed optic nerve function, which is dependent on the myelin sheath, has recently been recognized as an early feature of visual impairment in diabetes. However, the underlying cellular mechanisms remain unclear. Using a streptozotocin‐induced diabetic mouse model, we observed a myelin deficiency along with a disturbed composition of oligodendroglial lineage cells in diabetic optic nerve. We found that new myelin deposition, a continuous process that lasts throughout adulthood, was diminished during pathogenesis. Genetically dampening newly generated myelin by conditionally deleting olig2 in oligodendrocyte precursor cells within this short time window extensively delayed the signal transmission of the adult optic nerve. In addition, clemastine, an antimuscarinic compound that enhances myelination, significantly restored oligodendroglia, and promoted the functional recovery of the optic nerve in diabetic mice. Together, our results point to the role of new myelin deposition in optic neuropathy under diabetic insult and provide a promising therapeutic target for restoring visual function.