Donati Guy, Kapetanios Anastasios, Dubois-Dauphin Michel, Pournaras Constantin Jean
Department of Ophthalmology, Vitreo-retinal Unit, University Hospitals of Geneva, Geneva, Switzerland.
Acta Ophthalmol. 2008 May;86(3):302-6. doi: 10.1111/j.600-0420.2007.01044.x.
Acute brain ischaemia (stroke) causes a central area of coagulation necrosis. Peripheral to it and after a few hours, apoptosis causes neurons throughout the entire area to die progressively. However, this sequence of events is related to the reperfusion of regenerated capillaries or collateral circulation, and is considered to be potentially salvageable. Similar findings have been reported in the retina after ischaemia-reperfusion injury in rats. In the present study, we intended to investigate whether delayed cell death is involved in neuronal injuries to the inner retina during chronic retinal ischaemia.
Experimental branch retinal vein occlusion (BRVO) was induced in miniature pigs using indirect argon laser. The eyes were prelevated at 4, 24 and 48 hours and at 1 and 3 weeks following BRVO. The caspase inhibitor Z-VAD was injected intravitreally 24 hours after BRVO. Affected retinas were examined 24 hours later for any protective effect from apoptotic cell death. Histological examination with cresyl violet staining and TUNEL (TdT-mediated dUTP-biotin nick-end labelling) was performed on the samples.
A progressive oedema of the nerve fibre, ganglion cell and inner plexiform layers, related to a widely diffused cell necrosis, was observed in the affected territory within 4-24 hours after BRVO. This was followed by a wave of apoptosis localized at the periphery of the affected territory, which peaked approximately 48 hours after BRVO and was associated with a diffuse oedema of the inner nuclear layer. A progressive atrophy of the inner retina was observed 1-3 weeks after BRVO. Injection of the caspase inhibitor Z-VAD (24 hours after BRVO) decreased the amount of apoptotic cell bodies 48 hours after BRVO.
This study shows that although necrosis is the predominant form of neuronal death in the early phase, massive delayed neuronal cell death caused by apoptosis occurs on a widespread basis as a result of chronic ischaemia after BRVO in the retina. Further studies are needed to evaluate the possibility of rescuing retinal neurons from death by neuroprotective treatments.
急性脑缺血（中风）会导致中心区域的凝固性坏死。在其周边且数小时后，凋亡会使整个区域的神经元逐渐死亡。然而，这一系列事件与再生毛细血管的再灌注或侧支循环有关，被认为具有潜在的挽救可能性。在大鼠缺血再灌注损伤后的视网膜中也报道了类似的发现。在本研究中，我们旨在调查慢性视网膜缺血期间延迟性细胞死亡是否参与了视网膜内层的神经元损伤。
使用间接氩激光诱导小型猪发生实验性视网膜分支静脉阻塞（BRVO）。在BRVO后4小时、24小时、48小时以及1周和3周时摘除眼球。在BRVO后24小时经玻璃体注射半胱天冬酶抑制剂Z-VAD。24小时后检查受影响的视网膜，观察其对凋亡性细胞死亡的任何保护作用。对样本进行甲酚紫染色和TUNEL（末端脱氧核苷酸转移酶介导的dUTP生物素缺口末端标记）组织学检查。
在BRVO后4 - 24小时内，在受影响区域观察到神经纤维层、神经节细胞层和内网层逐渐出现水肿，这与广泛扩散的细胞坏死有关。随后，在受影响区域周边出现一波凋亡，在BRVO后约48小时达到峰值，并与内核层的弥漫性水肿相关。在BRVO后1 - 3周观察到视网膜内层逐渐萎缩。在BRVO后24小时注射半胱天冬酶抑制剂Z-VAD，可减少BRVO后48小时凋亡细胞体的数量。
本研究表明，尽管坏死是早期神经元死亡的主要形式，但在视网膜BRVO后的慢性缺血过程中，凋亡导致的大量延迟性神经元细胞死亡广泛发生。需要进一步研究以评估通过神经保护治疗挽救视网膜神经元免于死亡的可能性。
