青光眼是以视网膜神经节细胞（RGCs）凋亡为特征的神经退行性疾病，研究发现青光眼与小胶质细胞稳态失衡有关，而衰老会加重其极性失调，进一步损害RGCs。课题组前期研究发现骨髓中Sca-1+干细胞（BMC-Sca-1+）具有更强的修复视网膜损伤能力。但异体干细胞治疗存在免疫排斥反应，应用受到限制；而外泌体作为BMCs旁分泌的重要物质，与BMC具有相似的组织保护作用。本项目将在前期基础上拟对年轻优质BMC-Sca-1+进行富集培养，提取优质Sca-1+功能性外泌体，分析其活性成分；在体外和体内模型中观察Sca-1+外泌体对衰老视网膜高眼压损伤修复能力和对视功能的改善；分析BMC-Sca-1+外泌体调控小胶质细胞极化和FGF2等相关信号通路在促视网膜损伤修复中的机制；本课题利用优质功能性外泌体作为替代干细胞治疗的载体，为青光眼等视网膜损伤及神经退行性眼病的“无细胞”治疗提供新方法和新思路。

Glaucoma is a disorder that leads to retinal ganglion cells apoptosis and optic nerve degeneration, as well as visual field loss, and, eventually, blindness. The cell death is irreversible and the retinal ganglion cells have very limited ability to regenerate their axons after injury. The prevalence of glaucoma is correlated with aging and increased risk of developing a visual impairment. Aging induces a para-inflammatory response in the retina elicited by robust microglial activation. The imbalance in microglia polarization disturbs retinal homeostasis and aggravates neurodegeneration. Recent efforts have allowed the possibilities of pluripotent bone marrow (BM) stem cell-based regeneration of retinal cells and repair of neurodegenerative diseases. However, aging is associated with an impairment of endogenous stem and progenitor cells, including BM progenitor cells, which may contribute to the limited regenerative capacity for the retina. Previously we identified the stem cell antigen 1 (Sca-1+) cell as the young BM cell type with the greatest ability to restore retina progenitors and improve healing of the aged retina after injury. However, the mechanisms involved in the protective effects of BM Sca-1+ cells on aged retina remain unclear. Furthermore, the allogenic-origin of the young stem cells may bring the concern of immuno-rejection. Recent research has shown that exosomes secreted from BM stem cells can be used as a direct therapeutic agent for tissue repair. Furthermore, studies have demonstrated that exosomes are an important part of the cell component and regulate the polarization of microglia. However, the biologic capacities of BM stem cell-derived exosomes in repairing the damage retina are unknown. The present proposal is designated to explore the therapeutic potentials of BM Sca-1+ cell-derived exosomes against aged retinal injury by glaucoma. We hypothesized that young BM Sca-1+ cell-derived exosomes protect the aged retina from ocular hypertension injury through regulating microglia polarization. In the present study, we will isolate BM Sca-1+ subset stem cells and their exosomes from the culture medium in conjunction with the model of ocular hypertensive glaucoma to identify the regulation on microglia polarization and the neuroprotective effects on aged retinal explant in vitro and on BM reconstituted chimeric retina in vivo. We believe that the young BM Sca-1+ cell exerts its beneficial actions on the aged retina by releasing biologically active exosomes. Furthermore, we will identify the important factors such as FGF2 and the underlying signal pathway involved in BM Sca-1+ cell-derived exosome-mediated neuroprotection of the aged retina. We will evaluate the possible attenuation of retinal inflammation by BM Sca-1+ cell-derived exosomes through regulating the polarization of microglia. We will also evaluate the therapeutic potential of direct using novel factors identified in this study instead of using stem cell-exosomes for the treatment of aged retinal injury. It will provide a more effective approach for the treatment of ocular diseases and glaucoma among aged population in the future. We believe that the current proposal will provide a new strategy of stem cell derived-exosome therapy for ocular diseases and identify the most efficient “cell free” therapy for ophthalmological treatment in aged population.