Alterations of Extracellular Matrix Components and Proteinases in Human Corneal Buttons With INTACS for Post-Laser In Situ Keratomileusis Keratectasia and Keratoconus

Abstract

To perform an immunohistochemical evaluation of corneas with INTACS for post-laser in situ keratomileusis (LASIK) keratectasia and keratoconus, obtained after corneal transplantation. Corneas from 1 patient with INTACS for post-LASIK keratectasia and 2 patients with INTACS for keratoconus were obtained within 3 hours after penetrating keratoplasty, and cryostat sections were analyzed by immunostaining for 35 extracellular matrix (ECM) components and proteinases. In the stroma of all corneas next to an INTACS implant, ECM components typically associated with fibrosis were observed. These included tenascin-C, fibrillin-1, and types III, IV (alpha1/alpha2 chains), and XIV collagen. Also, significant deposition of perlecan, nidogen-2, and cellular fibronectin was revealed in the same locations. The keratoconus cases displayed typical Bowman layer breaks and subepithelial fibrosis with deposition of various ECM components. In all cases, some keratocytes around INTACS were positive for specific proteinases associated with stromal remodeling, including cathepsins F and H, matrix metalloproteinase (MMP)-1, MMP-3, and MMP-10. Staining for MMP-7 was variable; MMP-2 and MMP-9 were mostly negative. Patterns of type IV collagen alpha 3, alpha 4, and alpha 6 chains; types VI and VIII collagen; laminin-332, alpha 4, alpha 5, beta1, beta2, and gamma 1 laminin chains; vitronectin; thrombospondin-1; urokinase; EMMPRIN; and cathepsins B and L were unchanged around INTACS in all 3 cases compared with normal. Abnormal accumulation of fibrotic ECM components and proteinases near INTACS suggests ongoing lysis and remodeling of corneal stroma. Specific changes observed in each case may be related to underlying pathology.