Platelet-derived growth factor: receptor expression in corneas and effects on corneal cells.

Purpose: Platelet-derived growth factor (PDGF), a major mitogen and chemoattractant, is a dimeric molecule of disulfide-bonded A and/or B polypeptide chains (PDGF-AA/AB/BB). Two PDGF receptors (PDGFR) exist, alpha and beta, which dimerize after ligand exposure. The alpha-receptor binds both A- and B-chains, whereas the beta-receptor preferentially binds the B-chain. Whether PDGFR are present on, and whether PDGF is mitogenic for, corneal cells was investigated.

Methods: For receptor determination, a two-step immunoperoxidase technique with monoclonal antibodies against both alpha- and beta-receptors was applied on frozen sections of human and bovine corneas. To test the mitogenic activity of PDGF-BB, two proliferation assays, the DNA synthesis assay (3H-thymidine incorporation) and the colorimetric MTT assay, were used for cultured bovine corneal endothelial cells (BCEC) and human corneal fibroblast (HCF).

Results: Both receptors were present on epithelial cells, stromal fibroblasts, and endothelial cells, the beta-receptor being most abundant. In BCEC, minimal and maximal effects on DNA synthesis occurred at 10 ng/ml and 50-100 ng/ml PDGF, respectively. For HCF, the minimal and maximal effective doses were 1 ng/ml and 25-100 ng/ml of PDGF, respectively. The MTT assay, carried out in BCEC only, showed a minimal and maximal cell activity at 1 ng/ml and 10-100 ng/ml of PDGF, respectively.

Conclusions: The presence of PDGFR in human corneal epithelium, fibroblasts, and endothelium and the mitogenic effects of PDGF on corneal cells indicate that PDGF may play a role in corneal wound healing.