Growth factors during proliferation of the middle ear mucosa

The presence of growth factors during otitis media with effusion (OME), induced by antigenic stimulation of the middle ear, was explored in guinea pigs. There was a significant increase in heparin-binding proliferative activity detected in mucosal tissue. This heparin-binding activity was identified as basic fibroblast growth factor (FGF) using several criteria. First, the majority of this activity was eluted from heparin-Sepharose gels with 1.3-1.8 M NaCl, consistent with basic FGF. Second, these fractions are potent stimulators of endothelial cell proliferation, characteristic of basic FGF. Third, the fractions contain basic FGF-like immunoreactivity based on radioimmunoassay. Finally, Western blotting of tissue extracts reveals the presence of an 18 kDa protein that is indistinguishable from basic FGF. We conclude that basic FGF plays a major role in the proliferation of the middle ear mucosa during OME.