环角膜缘缝合与激光光凝模型:两种慢性高眼压模型的比较

Circumlimbal suture and laser burns:Comparison between two different chronic glaucoma models

目的:青光眼是一种多因素相关的视神经病变,致盲率高,其发病机制复杂,目前尚未明确。高眼压是目前唯一可调控的、与青光眼的发病密切相关的危险因素。本研究通过运用环角膜缘缝合与小梁网联合巩膜静脉激光光凝2种不同的方法建立慢性高眼压大鼠模型,比较2种模型的眼压升高程度和高眼压持续时间,视网膜形态损伤和视网膜神经节细胞(retinal ganglion cells,RGCs)损伤程度,以及超微结构改变等。方法:建立2种慢性高眼压模型,分为环角膜缘缝合组(缝合组,用10/0尼龙线沿角巩膜缘缝合)和激光光凝组(激光组,激光灼烧小梁网联合巩膜外静脉),并以其对侧眼作为对照组。观察并定期规律监测2组大鼠的眼压变化。采用大鼠视网膜切片HE染色观察2种慢性高眼压模型对视网膜和视神经病理学的影响,透射电镜(transmission electron microscope,TEM)观察慢性高眼压模型超微结构中线粒体形态的变化,大鼠视网膜铺片Brn3b抗体免疫荧光染色特异性标记RGCs并计数,蛋白质印迹法检测凋亡相关蛋白caspase-3的表达以明确RGCs的凋亡情况。结果:与对照组相比,缝合组与激光组大鼠眼压均明显升高(均P<0.05),其中缝合组的眼压最高升高1.5倍,眼压显著升高持续8周;激光组的眼压最高达对照组的2倍,持续12周。2组都会导致RGCs丢失,与Brn3b染色的结果相符,2组caspase-3表达水平均升高(均P<0.05)。而在TEM下,2组RGCs中的线粒体形态均变为碎片化,从正常的长条形变小、变圆。与激光组相比,缝合组视网膜形态学的病理变化较轻微。结论:环角膜缘缝合可建立有效的慢性高眼压模型,诱导与激光光凝模型相似的青光眼性病理改变,但病理改变较激光光凝轻微。相较于激光光凝建模,环角膜缘缝合法对于设备要求和操作能力要求更低。

Objective:Glaucoma is a multifactorial optic neuropathy with a high rate of irreversible visual loss,and its pathogenesis is complex and still unclear.Elevated intraocular pressure(IOP)is well recognized as the sole modifiable risk factor for the development of glaucoma in the majority of cases.This study aims to compare 2 different methods of inducing chronic ocular hypertension by circumlimbal suture or by laser burns in degree and lasting time of the IOP,different status of the retina and retinal ganglion cells(RGCs),and changes of the microstructure of neurons.Methods:The chronic ocular hypertension models were induced by 2 different ways.One kind of the models was built by unilateral circumlimbal suture(10/0)implantation(suture group),another kind of model was built by laser burns at trabecular meshwork and episcleral veins(laser group).The untreated contralateral eye served as the control group.Changes in IOP were observed and regularly monitored in the 2 groups of rats.HE staining was applied to observe the retinal and optic nerve pathology.Transmission electron microscope(TEM)was used to observe the mitochondrial morphology.RGCs were specifically labeled with Brn3b antibody and counted.The expression of caspase-3 was detected by Western blotting to clarify the apoptosis of RGCs.Results:Compared with the control group,IOP were significantly increased in the suture group and the laser group(both P<0.05).The suture group induced a 1.5-fold elevation of IOP,and sustained for 8 weeks.The laser group induced a 2-fold elevation of IOP for 12 weeks.Both methods could cause RGCs loss(both P<0.05),which were verified by pathology and immune staining of Brn3b.The expressions of caspase-3 were also increased(both P<0.05).The mitochondrial morphology became more fragment,which changed from long shape to round and small one under TEM in 2 models.For comparison,the pathology changes of retinal structure in suture group were not obviously than those in the laser group.Conclusion:Circumlimbal suture can build an effective model of chronic elevated IOP and induce glaucomatous pathologic changes similar to those in the laser photocoagulation,but the pathologic changes are milder than those in laser photocoagulation.Compare with translimbal laser photocoagulation,equipment and skill demand for circumlimbal suture is less.