Abstract: Objective　To observe the effects of long-term simulated weightlessness induced by tail suspension on the rat cornea, and to explore the molecular mechanisms underlying corneal injury. Methods　Twenty-four SD rats were randomly divided into control group, 4-week tail suspension group and 8-week tail suspension group, with 8 rats per group. After model establishment, tear secretion was measured by the phenol red thread test. Corneal fluorescein staining was used to observe corneal injury. Hematoxylin-eosin (HE) staining of pathological sections was performed to detect pathological changes of corneal tissue, and TUNEL staining was applied to assess corneal cell apoptosis. Molecular biological techniques were utilized to detect the levels of reactive oxygen species (ROS), malondialdehyde (MDA) and superoxide dismutase (SOD) in corneal tissue, as well as the expression of apoptosis-related proteins and inflammatory cytokines.Results　After 4 weeks of tail suspension, tear secretion volume in rats decreased. Edema was observed in the corneal epithelial and stromal layers, accompanied by disorganized collagen fibers and inflammatory cell infiltration. TUNEL staining revealed obvious apoptosis of corneal epithelial cells, and the expression trend of apoptosis-related proteins detected by Western blot in the cornea was consistent with the TUNEL staining results. The levels of ROS and MDA in rat corneal tissues were significantly higher than those in the control group (P<0.05), while the SOD level was markedly lower. Meanwhile, the expression levels of IL-1β and TNF-α in the corneal tissues of tail suspended rats were upregulated (P<0.05). Furthermore, All corneal pathological lesions were further aggravated after 8 weeks of tail suspension. Compared with the age-matched control group, the indicators including tear secretion, apoptosis-related proteins, oxidative stress markers and pro-inflammatory cytokines in the TS8W group showed extremely significant differences (P<0.01), and statistically significant differences were also observed when compared with the TS4W group (P<0.05).Conclusion Tail suspension simulating weightlessness can jointly mediate pathological damage to rat corneal tissues by inducing corneal oxidative stress imbalance and activating local inflammatory responses, and the severity of lesions increases progressively with the extension of tail suspension intervention duration. This study preliminarily elucidates the pathogenesis of corneal injury under microgravity exposure, and provides potential intervention targets and novel strategies for the prevention and treatment of microgravity-related corneal lesions.

Key words: simulated weightlessness, cornea, oxidative stress, inflammation

摘要： 目的　观察尾部悬吊模拟长期失重对大鼠角膜的影响,并探讨导致角膜损伤的相关分子机制。方法　24只 SD大鼠随机分为对照组、尾部悬吊4周组和尾部悬吊8周组,每组8只,对照组正常饲养,模型组采取30°头低位尾 悬吊4周、8周模拟失重,造模结束后采用酚红棉线检测泪液分泌量,角膜荧光素钠染色观察角膜损伤情况,病理切 片苏木精-伊红染色观察角膜组织病理变化,Tunel染色观察角膜细胞凋亡情况,分子生物学方法检测角膜组织活 性氧(ROS)、丙二醛(MDA)、超氧化物歧化酶(SOD)的表达量及凋亡相关蛋白和炎性因子的表达。结果　尾部悬 吊4周后大鼠泪液分泌量减少,角膜上皮细胞层及基质层出现水肿,胶原纤维排列紊乱,伴有炎性细胞浸润,Tunel 染色观察到角膜上皮细胞凋亡,Western blot检测角膜凋亡相关蛋白表达结果与Tunel染色趋势相一致,大鼠角膜 组织中ROS、MDA含量表达均高于对照组(P<0.05),SOD含量低于对照组,并且尾部悬吊组大鼠角膜组织中IL-1β 和TNF-α表达水平上调(P<0.05),在尾部悬吊8周后角膜损伤更为显著,TS8W组泪液分泌、凋亡相关蛋白、氧化 应激及炎性因子指标与同期对照组相比差异较为显著(P<0.01),且与TS4W组对比存在统计学差异(P<0.05)。 结论　尾部悬吊模拟失重可通过诱导角膜氧化应激紊乱、激活局部炎性反应,共同介导大鼠角膜组织病理性损伤; 且损伤程度随尾吊干预时间延长呈进行性加重。本研究初步阐明了微重力暴露下角膜损伤的发病机制,可为微重 力相关角膜病变的防治提供潜在干预靶点与新思路。

关键词: 模拟失重, 角膜, 氧化应激, 炎性反应