Effect of growth factors on collagen lattice contraction by human keratocytes.

A three-dimensional gel contraction model was used to evaluate interactions between human keratocytes and different kinds of collagen in the presence or absence of various growth factors. Bovine collagen type I or human placental copolymerized collagen type I/III was used to create the lattices. Normal keratocytes from neonatal, aged, and insulin-dependent diabetic donors, as well as abnormal keratocytes from a donor with macular corneal dystrophy, were cultured. Growth factors included epidermal growth factor (EGF), basic fibroblastic growth factor (FGF), insulin-like growth factor (IGF-I), and platelet-derived growth factor homodimer beta beta (PDGF). Gel area and optical transmittance were determined from computerized measurements. Dose-response experiments (0.01-100 ng/ml) demonstrated that PDGF at 10 ng/ml (P less than 0.005) and EGF at 1 and 10 ng/ml (P less than 0.0001) were the most effective in promoting gel contraction, compared to IGF-I and FGF. Comparison of cell strains revealed different dose-response profiles. Cells from insulin-dependent diabetics and cells from a donor with macular dystrophy contracted lattices more rapidly than cells from normal neonates (P less than 0.0001). Lattices of copolymerized human collagen type III/I demonstrated significantly reduced contraction rates (P less than 0.0001) and increased optical transmittance, compared to bovine collagen type I lattices. Ultrastructural studies revealed that keratocytes extend processes to form a network within the collagen lattice. Specialized intercellular junctional complexes were observed by transmission electron microscopy. This model provides a useful in vitro corneal stroma-equivalent for the study of keratocyte, extracellular matrix, and growth factor interactions.