Adhesion structures of amniotic membranes integrated into human corneas

PURPOSE. The aim of this study was to investigate the structural relationship between integrated amniotic membrane ( AM) and corneal tissues in various integration patterns, focusing on adhesion structures along the interface. METHODS. Fourteen eyes of 14 patients ( age, 65.8 +/- 13.5 years) underwent penetrating keratoplasty (PKP) 19.3 +/- 20.7 weeks after cryopreserved human AM transplantation ( AMT). The corneal buttons ( after PKP) and the corresponding original AM ( before AMT) were examined with the use of transmission electron microscopy ( TEM) and immunohistochemistry for integrin beta 4, type VII collagen, and laminin. Main outcome measures included thickness of the corneal epithelium and AM, density of the epithelial desmosomes and hemidesmosomes, continuity, and thickness of the epithelial basement membrane. RESULTS. Integrated AM was found by slit lamp in only 2 of 14 patients, but histology and TEM revealed AM integration in 11 of 14 patients up to 77 weeks after AMT. No amniotic epithelial cell was detected in any cornea with integrated AM stroma. Three basic patterns of integration could be described: subepithelial, intraepithelial, and intrastromal. Hemidesmosomes anchored the corneal epithelial cells to the AM at a density up to 165.3 +/- 22.9 per 100 mu m cell membrane length. Discontinuous basement membrane segments 17.2 +/- 4.9 nm thick could be detected. Desmosomes among recovered corneal epithelial cells were found at a density of 21.2 +/- 5.3 per 10 mu m cell membrane length. CONCLUSIONS. The AM stroma can integrate into the host corneal tissue. Integration is associated with the formation of adhesion structures such as hemidesmosomes and desmosomes, which provide anchoring and stability of the regenerating corneal epithelium. The presence of integrated AM and adhesion structures with host corneal tissue supports the clinical experience obtained with AMT in ocular surface disease.