Altered corneal stromal matrix organization is associated with mucopolysaccharidosis I, III and VI

The presence of cloudy corneas is a prominent feature of mucopolysaccharido sis (MPS) types I and VI, but not MPS IIIA or IIIB. The cause of corneal cl oudiness in MPS I and VI is speculative. Transparency of the cornea is depe ndent on the uniform diameter and the regular spacing and arrangement of th e collagen fibrils within the stroma. Alterations in the spacing of collage n fibrils in a variety of conditions including corneal edema, scars, and ma cular corneal dystrophy is clinically manifested as corneal opacity. The pu rpose of this study was to compare the structural organization of the strom al extracellular matrix of normal corneas with that of MPS corneas. The siz e and arrangement of collagen fibrils in cloudy corneas from patients with MPS I were examined. The alterations observed were an increased mean fibril diameter with a broader distribution in the MPS corneas. The MPS I corneas also had altered fibril spacing and more irregular packing compared with n ormal control corneas. The clear corneas of patients with MPS IIIA and IIIB also showed increases in mean fibril diameter and fibril spacing. However, there was less variation indicating more regularity than seen in MPS I. In addition, corneas from cat models of certain MPS were compared to the huma n corneas. Cats with MPS I and VI, as well as normal control cats, were exa mined. Structural alterations comparable to those seen in human MPS corneas were seen in MPS I and VI cats relative to normal clear corneas. The findi ngs suggest that cloudy corneas in MPS I and VI are in part a consequence o f structural alterations in the corneal stroma, including abnormal spacing, size, and arrangement of collagen fibrils. (C) 1999 Academic Press.