模拟失重对成年小鼠闪光视网膜电图和视网膜微循环的影响

目的:小鼠通过悬尾来模拟失重状态下体液头向重分布,然后观察视网膜电图(ERG)和视网膜微循环的变化。方法:正常成年雄性C57BL/6J小鼠随机分到3个实验组和3个对照组,最终每组6只。具体分组如下:实验1组(尾悬15d),实验2组(尾悬30d),实验3组(悬吊30d后恢复体位30d);对照1组(正常饲养15d),对照2组(正常饲养30d),对照3组(正常饲养60d)。时间满足后马上检测暗适应闪光ERG,记录混合反应和振荡电位(OPs),并进行荧光素眼底血管造影(FFA)。然后提取视网膜组织,用免疫组化法检测感光细胞视色素或视蛋白的表达,用TUNEL试剂盒检测视网膜组织细胞的凋亡情况。结果:悬吊15d组,暗适应ERG的混合反应,b波较大而OPs振幅明显降低,后者第二个子波(O 2)幅值197±33μV,15d未悬吊组336±47μV(t=-5.938,P<0.001)。悬吊30d组,小鼠ERG恢复,O 2幅值264±39μV,与30d未悬吊组308±41μV无差异(t=-1.887,P>0.05)。悬吊15d组FFA,视网膜微血管较对照组更密集,呈迂曲扩张的表现,其他实验组基本正常。各实验组感光细胞视色素或视蛋白的表达未见明显异常,视网膜未见凋亡阳性细胞。结论:模拟失重状态下体液头向重分布,短期内小鼠ERG和视网膜微循环可能受到影响,但未对视网膜产生明显的永久性损伤。

Impact of simulated microgravity on flash electroretinogram and retinal microcirculation in adult mice

AIM:To observe changes in the flash electroretinogram(ERG)and retinal microcirculation in mice suspended by their tails,an animal model that simulates cephalad movement of bodily fluids under conditions of microgravity.METHODS:Thirty-six adult male C57BL/6J mice(36 eyes)were randomly divided into three experimental groups and three control groups.Mice in the experimental groups were tail-suspended for 15d(Group one),tail-suspended for 30d(Group two),or tail-suspended followed by returning to normal position for 30d(Group three).Three control groups were similarly fixed with a harness but kept in the normal position for corresponding periods of 15,30,and 60d.The mice were immediately examined using scotopic ERG(including oscillatory potentialsOPs])and fundus fluorescein angiography(FFA)in vivo,and subsequently sacrificed to analyze the retinal histology(methods including immunohistochemistry and TUNEL staining)in vitro.Independent sample t-test was used for data comparison between the same time-point groups.RESULTS:Following 15-days’tail-suspension,scotopic ERG showed a decline in OPs,but not in the b-wave;the second OP(O 2)showed an amplitude of 197±33μV,which was about 60%of the control level(t=-5.938,P<0.001).Following 30-days’tail-suspension,ERG recovered,with O 2 showing an average value of 264±39μV;when compared to the corresponding control group(308±41μV),no significant difference was observed(t=-1.887,P>0.05).Morphologically,only the 15-days’tail-suspended mice showed FFA with microvascular dilation and tortuosity.Rhodopsin and cone-opsin were almost normal and no apoptotic-positive signals were detected in the retinas of the three tail-suspended groups.CONCLUSION:Simulating cephalad shifting of bodily fluids as under microgravity,using short-term tail-suspension can affect rodent ERG and retinal microcirculation;however,the change is reversible with no obvious permanent injury observed in the retinas.