An Annulus of Collagen Fibrils in Mouse Cornea and Structural Matrix Alterations in a Murine-Specific Keratopathy

Abstract

Abstract: : Purpose: Mouse corneas were investigated to see whether a limbal annulus of corneal collagen exists as in humans. Mice with corneas predisposed to topographical changes (the SKC strain) were also examined to establish the size and spacing of stromal collagen fibrils and the integrity of the annulus. Methods: X-ray diffraction was used to measure collagen fibril spacing and diameter in normal (the BALB/c strain; 4 male, 2 female) and SKC (6 male and 6 female) corneas, and to identify the degree of preferred collagen orientation at 200 µ m intervals across two BALB/c and four SKC corneas. Results: Average collagen fibril diameter measured 35.5 nm in 3-month-old BALB/c corneas, and 37.0 nm in corneas of age-matched male and female SKC mice. In male and female SKC corneas, average collagen interfibrillar spacings were significantly higher (62 nm and 57 nm, respectively) than in corneas of BALB/c mice (48 nm). Circumferentially aligned collagen, indicative of a limbal annulus of fibrillar collagen 2.2 mm in diameter, was identified in mouse cornea. On occasion, this was disturbed in the SKC phenotype. Conclusions: Collagen fibrils are marginally larger in the corneas of SKC mice than in the corneas of BALB/c mice, and are considerably more widely spaced. An annulus of fibrillar collagen likely exists near the limbus of the normal mouse cornea, and this may help promote biomechanical stability and maintain corneal shape. A loss of structural integrity in the annulus of some SKC mice might predispose the corneas to biomechanical instability and shape changes.

Keywords: cornea: stroma and keratocytes • extracellular matrix • keratoconus