Pterygial derived fibroblasts express functionally active histamine and epidermal growth factor receptors

Pterygia are characterised by a fleshy outgrowth of altered conjunctival tissue over the cornea and are most common in tropical regions. Pterygial fibroblasts are characteristically distinct from normal conjunctival fibroblasts, and therefore the aim of this study was to determine the presence and functional significance of histamine and epidermal growth factor (EGF) receptors in these cells. Pterygial specimens were cultured in vitro and cellular outgrowths were phenotypically characterised as fibroblasts using vimentin and cytokeratin staining. Intracellular calcium mobilization was used to characterise the functional activity of histamine receptors on these cells. Maximal response was obtained with 100 microM histamine. However, lower concentrations of histamine also caused mobilization of calcium that were totally abolished by pre-incubation with H1 but not H2 or H3 receptor antagonists. EGF receptor was diffusely expressed over the cell surfaces. EGF stimulated receptor internalization, ERK protein phosphorylation and intracellular calcium mobilization. Therefore, fibroblasts derived from human pterygia express functionally active histamine and epidermal growth factor receptors. Controlled modification of either the receptors or the appropriate ligands could have beneficial effects in pterygia treatment.