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P. R. Fournie, G. M. Gordon, D. G. Dawson, H. F. Edelhauser, M. E. Fini; Correlations of Epithelial Ingrowth in Human Post-LASIK Corneas With Basement Membrane Remodeling at the Flap Margin. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2966.
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We have recently reported immunolocalization of matrix metalloproteinase (MMP)-9 around epithelial cells trapped in the lamellar scar of post-LASIK corneas with epithelial ingrowth. A causal relationship between MMP-9 in the corneal epithelium and basement membrane dissolution has been demonstrated in experimental models. We investigated the hypothesis that epithelial ingrowth in human post-LASIK corneas was correlated with basement membrane remodeling.
Eighteen postmortem corneas from 10 patients with postoperative intervals of 2 to 8 years after LASIK surgery were collected from various eye banks in North America. Unwounded corneas served as control specimens. Corneas were processed for conventional histologic analysis and immunofluorescence with antibodies to MMP-9, laminin, integrin beta 4, mucin 16, and transforming growth factor (TGF)-beta 2. In addition, ultrastructural studies were performed using transmission electron microscopy (TEM) to assess the basement membrane zone of the corneas.
Epithelial ingrowth into the flap margin was observed in 8 of the 18 corneas (44.4%). MMP-9 was immunolocalized around in-grown epithelium in 6 out of these 8 corneas (75%). There was a positive correlation between the presence of MMP-9 at the wound margin and basement membrane discontinuities viewed with immunofluorescence. TGF-beta 2, a key mediator of fibrosis, remained localized to the epithelium in the absence of basement membrane damage but was present into the stroma of some corneas with epithelial ingrowth and interrupted basement membrane. TEM confirmed that the epithelial basement membrane was partly discontinuous along in-grown epithelial cells.
The epithelial basement membrane was shown to be partially disassembled at the flap margin of post-LASIK corneas with epithelial ingrowth. Remodeling of the basement membrane could relate to reduced resistance of some LASIK corneas to shearing trauma, resulting in late flap displacements.
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