Growth factors in cystic fibrosis - when more is not enough.

In the airways of patients with cystic fibrosis, repeated cycles of infection and inflammation are responsible for bronchial wall thickening, a major determinant of loss of FEV(1) and progressive damage to the small and large airways. Proteolytic degradation of elastin, collagen and fibronectin fibrils in the tissue matrix leads to the loss of normal tissue architecture and the development of bronchiectasis, the most commonly observed morphological change on high-resolution computed tomography examination. We have reviewed the evidence for increased expression of growth factors (TGF, HGF, FGF, EGF, VEGF) and activation of tissue repair processes in cystic fibrosis. Significantly higher concentrations of the growth factors compared with normal do not appear to prevent or reverse structural remodelling in the airways. The reasons why this process appears to be ineffective are discussed and we speculate on alternative strategies that might have a significant impact on the observed structural changes.