Vemuganti G K, Sharma S, Athmanathan S, Garg P
Ophthalmic Pathology Service, L.V. Prasad Eye Institute, L.V. Prasad Marg, Banjara Hills, Hyderabad-500 034, India.
Indian J Ophthalmol. 2000 Dec;48(4):291-4.
Pathogenesis of Acanthamoeba keratitis involves breakdown of epithelial barrier, stromal invasion by Acanthamoeba, loss of keratocytes, inflammatory response and finally stromal necrosis. The loss of keratocytes, believed to be due to the phagocytic activity of the parasite, occurs disproportionate to and independent of the parasite load, thereby suggesting additional modes of cell loss. To test our hypothesis that the loss of keratocytes in Acanthamoeba keratitis is due to apoptosis, we did both histology and histochemistry on the corneal tissues.
Routine Haematoxylin and Eosin, Gomori's Methenamine Silver and Periodic acid Schiff stained sections of five corneal tissues from penetrating keratoplasty and eviscerated eyes were reviewed. TUNEL staining was done for morphological detection of apoptosis in three cases, using formalin-fixed, paraffin-processed tissues.
Histological changes were epithelial ulceration, loss of keratocytes in all layers, inflammation in anterior two-thirds of the stroma with necrosis, and deeper quiet stroma. Acanthamoeba trophozoites were found in the anterior stroma while the cysts were more in the deeper stroma, with minimal or no inflammatory response. TUNEL staining was positive in keratocytic nuclei in all layers.
This study demonstrates that one of the modes of keratocyte loss in Acanthamoeba keratitis is by apoptosis, possibly in addition to the necrotic process and phagocytic activity of the parasite. The death of inflammatory cells also appears to be mediated by apoptosis.
棘阿米巴角膜炎的发病机制包括上皮屏障破坏、棘阿米巴侵袭基质、角膜细胞丢失、炎症反应，最终导致基质坏死。角膜细胞的丢失被认为是由于寄生虫的吞噬活性所致，其发生与寄生虫负荷不成比例且独立于寄生虫负荷，从而提示存在其他细胞丢失模式。为了验证我们关于棘阿米巴角膜炎中角膜细胞丢失是由于细胞凋亡的假设，我们对角膜组织进行了组织学和组织化学研究。
回顾了穿透性角膜移植术和眼球摘除术后五只角膜组织经苏木精和伊红、Gomori 六胺银和过碘酸希夫染色的常规切片。使用福尔马林固定、石蜡处理的组织对三例进行 TUNEL 染色，以形态学检测细胞凋亡。
组织学变化包括上皮溃疡、各层角膜细胞丢失、基质前三分之二处伴有坏死的炎症以及较深的静止基质。在前基质中发现了棘阿米巴滋养体，而囊肿在较深基质中更多，炎症反应轻微或无炎症反应。TUNEL 染色在各层角膜细胞核中均呈阳性。
本研究表明，棘阿米巴角膜炎中角膜细胞丢失的模式之一是通过细胞凋亡，可能除了寄生虫的坏死过程和吞噬活性外。炎症细胞的死亡似乎也由细胞凋亡介导。
