Platelet-derived growth factor-BB (PDGF-BB) in tear fluid: a potential modulator of corneal wound healing following photorefractive keratectomy

Abstract

PURPOSE. To measure the pre- and postoperative tear fluid platelet-derived growth factor-BB (PDGF-BB) concentrations of patients undergoing excimer laser photorefractive keratectomy (PRK). METHODS. Tear fluid samples from PRK patients were collected with scaled microcapillary tubes preoperatively (Day 0, N = 23), on the second (Day 2, N = 24) and on the seventh (Day 7, N = 14) postoperative days. The PDGF-BB concentration was measured using a sandwich enzyme immunoassay, and the PDGF-BB release was calculated by multiplying the concentration by the tear fluid flow in the collection capillary. RESULTS. The mean tear fluid flow in the capillary was 17.4 µl/min (range 1.4–55.0) on Day 0, 62.6 µl/min (4.3–125.0, p = 0.0000) on Day 2, and 15.5 µl/min (1.2–50.0, NS) on Day 7. Seventeen percent (4/23) of the Day 0 samples contained detectable concentrations of PDGF-BB (range 95–1330 ng/l). On Day 2 all (24/24) tear samples showed significantly increased concentrations (mean 507 ng/l, range 45–2280 ng, p = 0.0001) and releases (mean 27.6 pg/min, range 1.0–98.0; p = 0.0000). On Day 7 PDGF-BB was still measurable in 9/14 samples (mean concentration 194 ng/l, range < 5–925 ng/l, and mean release 1.9 pg/min, range 0.04–6.8 pg/min). CONCLUSIONS. PDGF-BB is an inducible component of tear fluid. In spite of hypersecretion caused by the corneal wound, PDGF-BB concentrations raised significantly during the initial wound healing. Increased PDGF-BB release during the two postoperative days following PRK suggests a role in corneal wound healing.