Glycosaminoglycans in prenatal and adult human cornea

Abstract

Collagenolytic activities have been detected in the culture media from an eye bank cornea and in media from corneal tissues biopsied at the time of surgery. The eye bank cornea was not pathological but was not used for corneal grafting because of the donor age (77). The corneal biopsies were from keratoplasty patients with no history of corneal ulceration. Enzymes from both sources cleave tropocollagen at the same site as do tadpole-tail collagenase and rabbit corneal collagenases, and, because of the restricted cleavage, belong to the class of enzymes known as “tissue collagenases”. The human corneal collagenase activities also degrade reconstituted collagen fibrils. The collagenase activity(ies) from human keratoplasty tissues is inhibited by Calcium-EDTA and N-acetyl-l-cysteine, both of which have been found previously to prevent ulceration in the alkali-burned rabbit cornea and to inhibit collagenases produced by the ulcerating rabbit cornea. The serum antiprotease, α2-Macroglobulin, has also been found to inhibit the collagenase(s) from keratoplasty tissues, an observation which supports the ophthalmologist's sometime contention that serum inhibits corneal ulceration. It is hoped that the human corneal collagenase(s) produced by the culture of keratoplasty tissues and of eye bank corneas judged unfit for corneal grafting will facilitate the discovery of effective inhibitors of corneal ulceration.