TEAR HEPATOCYTE GROWTH-FACTOR (HGF) AVAILABILITY INCREASES MARKEDLY AFTER EXCIMER-LASER SURFACE ABLATION

Tear cytokines and growth factors are likely to modulate the wound hea ling process following corneal epithelial injury. Hepatocyte growth fa ctor (HGF) is a paracrine mediator of epithelial proliferation, motili ty, and differentiation that is produced by keratocytes and the lacrim al gland. Tear samples were collected preoperatively and one, two, and seven days postoperatively in eyes undergoing excimer laser surface a blation [photorefractive keratoplasty (PRK) or phototherapeutic kerato plasty (PTK)]. Tear HGF concentration was measured with a sensitive EL ISA assay, Tear HGF production was calculated using the tear flaw rate in the collection capillary and HGF concentration. Although the insta ntaneous concentration of HGF in tears decreased significantly in the days following PRK, a large increase in tear flow resulted in a marked increase in HGF bioavailability. The heparin-binding characteristics of HGF would result in increased binding to glycosaminoglycans and oth er heparin-like matrix components and, therefore, increased growth fac tor availability to the cognate receptor. This is the first report doc umenting changes in tear him HGF production. HGF may have an important function in maintenance and wound healing of the ocular surface epith elium since HGF is present in the normal tear film and the HGF secreti on rate increases markedly in parallel with aqueous tear production fo llowing corneal surgical injury. (C) 1997 Academic Press Limited.