Altered type VI collagen synthesis by keratoconus keratocytes in vitro.

Type VI collagen and gelatinase A are synthesized by human keratocytes in vitro. Keratoconus is a corneal disease that has increased gelatinase A activity. Normal keratocyte culture media analyzed by Western blotting with polyclonal antibody to type VI collagen showed a single 140 kDa band that increased in intensity after phorbol ester treatment. The same 140 kDa band was absent in media collected from keratoconus keratocytes cultured with or without phorbol ester. We speculate that in keratoconus keratocyte cultures, type VI collagen may be degraded or modified by the increased gelatinase A activity so as not to be recognized by the type VI antibody.