Giasson Claude J, Bouchard Cindy, Boisjoly Hélène, Germain Lucie
Ecole d'Optométrie, Université de Montréal, CP 6128, Succursale Centre-ville, Montréal, Québec, J1H 5N4 Canada.
Med Sci (Paris). 2006 Jun-Jul;22(6-7):639-44. doi: 10.1051/medsci/20062267639.
The amniotic membrane, the most internal placental membrane, has various properties useful in ophthalmology. Collected on delivery by elective Caesarean section, the amnion is prepared under sterile conditions, and, usually, cryopreserved until its use as a biological bandage or as a substrate for epithelial growth in the management of various ocular surface conditions. Specifically, the amnion is used to : (1) limit formation of adhesive bands between eyelids and eyeball (symblepharon) or the progression of a fibrovascular outgrowth towards the cornea (pterygium) or to (2) facilitate the healing of corneal ulcers, bullous keratopathy, and corneal stem cell deficiency. In this last condition, either hereditary or acquired after a thermal or a chemical burn, corneal stem cells, located at a transitional zone between the cornea and conjunctiva, are lost. These cells are essential for renewal of corneal epithelium in normal and in diseased states. The loss of these cells leaves the corneal surface free for invasion by conjunctival epithelium. Not only, does conjunctival epithelium support the development of vascularisation on the normally avascular cornea, but some conjunctival cells differentiate into mucus secreting goblet cells. Such a change in phenotype leads to loss of corneal transparency and visual disability. The removal of this fibro-vascular outgrowth in combination with transplantation of both amniotic membrane and corneal stem cells are used to treat this condition. The amnion stimulates the proliferation of less differentiated cells which have the potential to reconstruct the cornea. This potential is at the origin of the hypothesis that the amnion may provide an alternative niche for limbal stem cells of the corneal epithelium. It abounds in cytokines and has antalgic, anti-bacterial, anti-inflammatory and anti-immunogenic properties, in addition to allowing, like fetal skin does, wound healing with minimal scar formation. These desirable properties are responsible for the increasing use of amniotic membrane in ophthalmology. The complete understanding of the mechanisms of action of amniotic membrane for ocular surface diseases has yet to be understood. Once revealed by research, they may provide new pharmacological avenues to treat ocular surface diseases.
羊膜是胎盘最内层的膜，具有多种在眼科有用的特性。通过选择性剖宫产在分娩时采集羊膜，在无菌条件下制备，通常冷冻保存，直到用作生物绷带或作为上皮生长的基质用于治疗各种眼表疾病。具体而言，羊膜用于：（1）限制眼睑与眼球之间粘连带（睑球粘连）的形成或纤维血管增生向角膜（翼状胬肉）的进展，或（2）促进角膜溃疡、大疱性角膜病变和角膜干细胞缺乏的愈合。在最后这种情况下，无论是遗传性的还是在热烧伤或化学烧伤后获得性的，位于角膜和结膜之间过渡区的角膜干细胞都会丢失。这些细胞在正常和患病状态下对角膜上皮的更新至关重要。这些细胞的丢失使角膜表面容易受到结膜上皮的侵袭。结膜上皮不仅支持正常无血管角膜上血管化的发展，而且一些结膜细胞会分化为分泌黏液的杯状细胞。这种表型变化会导致角膜透明度丧失和视力残疾。去除这种纤维血管增生并结合羊膜和角膜干细胞移植用于治疗这种疾病。羊膜刺激具有重建角膜潜力的低分化细胞的增殖。这种潜力是羊膜可能为角膜上皮的角膜缘干细胞提供替代微环境这一假说的起源。它富含细胞因子，具有止痛、抗菌、抗炎和抗免疫原性特性，此外，像胎儿皮肤一样，能使伤口愈合且瘢痕形成最小。这些理想特性导致羊膜在眼科的使用越来越多。对羊膜治疗眼表疾病作用机制的全面理解还有待探索。一旦通过研究揭示，它们可能为治疗眼表疾病提供新的药理学途径。
