Growth factors and collagen distribution in vernal keratoconjunctivitis

PURPOSE. To study the extracellular composition of giant papillae in vernal keratoconjunctivitis (VKC) and the expression of growth factors that may s timulate fibrosis. METHODS. Upper conjunctival specimens were obtained by biopsy in 9 patients affected by active tarsal VKC (14 eyes) and 10 normal control subjects. Im munohistochemistry was performed on tissue sections using monoclonal antibo dies (mAbs) for collagens I, III, and VII; tumor necrosis factor (TNF)-alph a; transforming growth factor (TGF)-beta1; basic fibroblast growth factor ( bFGF); and platelet-derived growth factor (PDGF). The mAbs anti-tryptase, a nti-CD4, anti-CD68, and anti-EG2 were used as markers for mast cells, T-hel per lymphocytes, macrophages, and eosinophils, respectively. Immunofluoresc ent double-staining for growth factors and cell markers was performed in VK C tissues. RESULTS. Immunostaining was highly positive for collagens I, III, and VII i n the subepithelium of VKC conjunctiva. Image analysis showed a significant increase of staining per tissue area for both collagens I and VII and incr eased basal membrane length. The number of cells positive for TNF-alpha, TG F-beta, bFGF, or PDGF was significantly higher in VKC tissue than in contro l samples. Double staining showed that eosinophils and macrophages were the main sources of PDGF and that FGF was expressed by 46% of mast cells. Sign ificant PDGF and FGF staining was observed in the conjunctival epithelium a nd vascular endothelium of all VKC tissues. CONCLUSIONS. In giant papillae of VKC, the extracellular matrix is characte rized by overproduction of collagens. Expression of growth factors in the c onjunctiva by resident cells (mast cells, epithelial cells, endothelial cel ls) and inflammatory cells (macrophages, eosinophils) may contribute to pap illae formation and fibrosis evolution in chronic ocular allergic diseases.