Differential effects of insulin-like growth factors on scratch wound repair in respiratory epithelial cells

Background: Insulin-like growth factors (IGFs) I and II, being potent promoters of cellular growth and differentiation, were investigated for their effectiveness in improving the rate of scratch closure in human respiratory epithelium in vitro. Methods: Human epithelial cell lines from the nasal, bronchial, and tracheal regions were analyzed for their response to IGF-I and IGF-II, in a confluent monolayer scratch assay. IGF-binding proteins (IGFBPs) produced by certain cells are able to reduce the effectiveness of the IGFs. Consequently, the analogues LongR3 IGF-I, Des1-3 IGF-I and Arg3 IGF-I were investigated also because of their lower affinity for the IGFBPs, while still retaining unaffected affinity for the IGF-I receptor. Results: All growth factors that were analyzed significantly improved the rate of scratch closure in bronchial and tracheal epithelial cells (p <= 0.05). In comparison, scratch closure was markedly slower in nasal epithelial cells and IGF-I was the most effective growth factor a effecting scratch closure in these cells. The IGF-I analogues did not significantly improve scratch closure compared with IGF-1, despite the presence of IGFBP-3 in nasal, bronchial, and tracheal epithelial cells. Conclusion: Addition of IGF-I to wounded nasal epithelial cells increases the rate of scratch closure and therefore may have potential for improving the healing of the nasal mucosa.