Kim Tae-Im, Pak Jhang Ho, Lee Sun Young, Tchah Hungwon
Department of Ophthalmology, University of Ulsan, College of Medicine, Asan Medical Center, Seoul, Korea.
Invest Ophthalmol Vis Sci. 2004 Sep;45(9):2978-84. doi: 10.1167/iovs.04-0070.
To investigate the effects of mitomycin C (MMC) on the number of keratocytes and the proliferation of fibroblasts after photorefractive keratectomy (PRK) and exposure to ultraviolet B (UV-B) irradiation.
The right eyes of New Zealand White rabbits in Groups 1, 2, and 3 (n = 18 each) underwent PRK to correct -10 diopters with 5 mm optical zone. Sponges soaked with 0.02% MMC were applied to the right eyes of Group 1 rabbits for 2 minutes. Antibiotic ointment was applied daily to all rabbits until the epithelium healed completely, after which 0.02% MMC eye drops were applied twice daily to the right eyes in Group 2 until 4 weeks after PRK. Three weeks after PRK, the right eyes of all the remaining rabbits were exposed to 100 mJ/cm2 C UV-B radiation. Corneal haziness was assessed biomicroscopically using the Fantes scale every 3 weeks. Six eyes of each group were each enucleated 3, 6, and 12 weeks after PRK, and tissue specimens were stained with hematoxylin and eosin and with TUNEL stain. The tissues were evaluated immunohistochemically with antibody to alpha-smooth muscle actin (SMA). Cellular changes in the anterior stroma and epithelial basement membrane were evaluated by electron microscopy.
Corneal haze was observed after PRK and was aggravated by UV-B irradiation. A single intraoperative application of MMC immediately after PRK induced opacity and apoptosis of keratocytes. Twelve weeks after PRK, MMC significantly reduced corneal haze, the number of keratocytes, apoptotic cells, and fibroblasts, even after UV-B irradiation. Relatively large numbers of apoptotic and SMA-positive cells were found only in PRK-treated, non-MMC treated rabbits (Group 3), even after 12 weeks. Three weeks after PRK, dying stromal cells showed cell shrinkage, and chromatin condensation was observed in all treated groups by electron microscopy. Twelve weeks after PRK, fewer keratocytes and inflammatory cells were observed just beneath the epithelial layer in Group 1 than in any of the other groups.
MMC is a potent inhibitor of corneal haze induced by PRK. MMC reduced the number of keratocytes and fibroblasts after PRK and UV-B irradiation. Although MMC would improve the clinical results of PRK, it has significant toxicity on corneal keratocytes, which did not disappear until 3 months after PRK.
研究丝裂霉素C（MMC）对准分子激光屈光性角膜切削术（PRK）后角膜细胞数量以及暴露于紫外线B（UV-B）照射下的成纤维细胞增殖的影响。
第1、2、3组（每组n = 18只）的新西兰白兔右眼接受PRK以矫正-10屈光度，光学区为5 mm。将浸有0.02% MMC的海绵应用于第1组兔子的右眼2分钟。所有兔子每天应用抗生素眼膏，直至上皮完全愈合，之后第2组兔子的右眼每天应用0.02% MMC滴眼液，直至PRK后4周。PRK后3周，将所有剩余兔子的右眼暴露于100 mJ/cm²的UV-B辐射下。每隔3周使用范特斯量表通过生物显微镜评估角膜混浊情况。每组6只眼睛在PRK后3、6和12周分别摘除眼球，组织标本用苏木精-伊红染色和TUNEL染色。用抗α-平滑肌肌动蛋白（SMA）抗体对组织进行免疫组织化学评估。通过电子显微镜评估前基质和上皮基底膜的细胞变化。
PRK后观察到角膜混浊，UV-B照射使其加重。PRK后立即单次术中应用MMC可诱导角膜细胞混浊和凋亡。PRK后12周，即使在UV-B照射后，MMC也显著降低了角膜混浊、角膜细胞数量、凋亡细胞和成纤维细胞数量。即使在12周后，仅在接受PRK治疗但未接受MMC治疗的兔子（第3组）中发现相对大量的凋亡和SMA阳性细胞。PRK后3周，通过电子显微镜观察到所有治疗组中死亡的基质细胞出现细胞收缩和染色质浓缩。PRK后12周，第1组上皮层下方观察到的角膜细胞和炎症细胞比其他任何组都少。
MMC是PRK诱导的角膜混浊的有效抑制剂。MMC减少了PRK和UV-B照射后的角膜细胞和成纤维细胞数量。尽管MMC会改善PRK的临床效果，但它对角膜细胞具有显著毒性，这种毒性直到PRK后3个月才消失。
