羊膜移植术在碱烧伤急性期重建结膜表面的实验研究

目的:(1)研究羊膜移植在治疗兔眼大面积结膜碱烧伤,重建健康结膜表面中的作用.(2)探讨碱烧伤急性期施行羊膜移植术的可行性.方法:选用30只家兔,制作角膜缘上方球结膜至穹隆部的碱烧伤的动物模型.实验组于碱烧伤后1wk时(急性期)行保存的人羊膜移植术及穹隆成形术.术后1,2,3,4,8,12wk时做光镜观察移植部位的结膜上皮生长情况,并于术后1,4,8wk时取移植区结膜做电镜观察其超微结构,同时与碱烧伤后行结膜下注射维生素C及应用抗生素眼药水点眼治疗的对照组结膜作对照观察.并在上述相应时期摄眼外观像、做上角膜缘至上方穹隆部宽度的测量.结果:(1)羊膜移植术后1wk时,光镜、电镜可见羊膜上有结膜上皮细胞长入,4wk时,含有杯状细胞的结膜上皮完全覆盖羊膜,接近于正常的结膜组织,12wk时,羊膜上结膜上皮细胞排列整齐,穹隆部结膜上皮下纤维结缔组织较为疏松,无增生.而对照组1wk时见结膜上皮细胞坏死脱落,未见有含杯状细胞的结膜上皮长入,4～8 wk时所见为大量纤维结缔组织增生,伴炎性细胞浸润.12wk时,穹隆部纤维结缔组织增生明显,未见有正常结膜上皮覆盖.(2)外观眼表可见,12wk时实验组移植区结膜光滑无瘢痕,上穹隆形成良好,穹隆深达7.6～8.2 mm,接近正常穹隆深度8.0～8.5 mm.而对照组结膜表面不光滑,有结膜肉芽肿形成,瘢痕增生明显,上方穹隆明显变浅,穹隆深度为1.0～4.5 mm.结论:以甘油保存的羊膜可作为一种底物载体,提供健康的基底膜,有利于周围正常结膜上皮的粘附、移行和分化,进而重建正常结膜表面.结膜碱烧伤后早期行羊膜移植可重建正常结膜表面,有效地防止睑球粘连的发生.

The effect of amniotic membrane transplantation on rabbit conjunctival surface reconstruction at the recovering stage of alkali burn

AIM: (1) To investigate the effect of amniotic membrane transplantation (AMT) on rabbit conjunctival surface reconstruction with severe alkali burns. (2) To evaluate the possibility of AMT treatment for ocular alkali burns during recovering stage.METHODS: Animal models were established on 30 eyes of rabbits by creating severe alkali burns on the conjunctiva from the upper corneal limbus to the upper conjunctival fornix.Preserved human amniotic membrane transplantations and reconstruction of conjunctival fornix were performed at one week after injury (recovering stage). Epithelium growth of burned area after transplantation was observed using light microscope at 1, 2, 3, 4, and 8 weeks. Conjunctival tissue in transplantation area was collected at 1, 4 and 8 weeks. The ultrastructure of the collected tissue was studied by electron microscope. The results were compared with control group,which received only vitamin C subconjunctival injection and antibiotic eye drops as treatment for alkali burn. Exterior eye pictures were also taken at the end of the observation, the width from upper corneal limbus to the edge of upper fornix was measured. Data was analyzed statistically.RESULTS: 1) Tn the transplant group, conjunctival epithelium growth was observed in the area of AMT under both light and electron microscope 1 week after surgery. At 4weeks, conjunctival epithelium with goblet cells that resembled normal conjunctival tissues was observed in the whole amniotic membrane area. At 12 weeks, the conjunctival epithelium on the amniotic membrane was well formed, and the connective tissue under the epithelium was loose at the fornix. No fibrosis was identified. In contrast, conjunctival epithelium necrosis was observed in the control group at 2weeks after alkali burns. Re-epithelization did not occur through the 12-week observation. Severe fibrosis with inflammatory cells infiltration was observed between 4 to 8weeks. At 12 weeks, fibrosis of the connective tissue at the fornix developed and there were no conjunctival epithelium covering the burned area. 2) In the transplant group, the conjunctiva in transplanted area had no scarring and appeared smooth at 12 weeks. Upper fornix was reconstructed. The depth of fornix was 7.9±0.3mm (7.6-8.2mm), which was approximate to the normal depth 8.2±0.2mm (8.0-8.4 mm,P＞.05). While in the control group, the burned area appeared rough with granuloma formation and severe scarring. Upper fornix became shallow. The depth of fornix was 3.1±1.7mm(1.0 to 4.5mm.), and significant difference was found between control and transplant group (P＜0.01).CONCLUSION: Human amniotic membrane preserved in glycerin can promote cell adhering, migrating and differentiating of normal conjunctival epithelium.Reconstruction of conjunctival surface in early stage of alkali burn can be achieved by AMT. AMT can effectively prevent symblepharon formation.