Corneal endothelium in mucopolysaccharide storage disorders. Morphologic studies in animal models.

In the systemic mucopolysaccharidoses (MPS) in animals, corneal clouding resulted from storage of glycosaminoglycans (GAG) in stromal keratocytes. The corneal epithelium was normal (MPS VI and VII) or minimally affected (MPS I), and stromal edema was not a feature even though the corneal endothelium demonstrated variable pathology. The MPS I (cat) cornea showed endothelial cells with large numbers of secondary lysosomal inclusions that were vacuolated or had a granular matrix. The endothelium was uniformly affected, but was not markedly hypertrophied. In contrast, the MPS VI (cat) cornea showed no endothelial cell disease. The MPS VII (dog) cornea had the most significant and dramatic endothelial pathology. The cells were massively hypertrophied and contained large numbers of vacuolated lysosomal inclusions. Regardless of the severity of the morphologic disease, the endothelial cells in these animal models functioned normally in maintaining the relative dehydration of the cornea. The corneal clouding was the result of storage in stromal keratocytes rather than corneal edema from endothelial dysfunction.