Basic fibroblast growth factor and fibroblast growth factor receptors in adult olfactory epithelium

Basic fibroblast growth factor (FGF2) stimulates proliferation of the globo se basal cells, the neuron:ll precursor in the olfactory epithelium. The pr esent study investigates the expression of basic fibroblast growth factor a nd fibroblast growth factor receptors in the adult olfactory epithelium. FG F2 immunoreactivity was expressed widely in the olfactory epithelium, with the highest density of immunoreactivity in the supporting cells. In contras t, most cells in the epithelium expressed FGF2 mRNA. Fibroblast growth fact or receptor-1 (FGFr1) immunoreactivity was densest in the basal cell and ne uronal layers of the olfactory epithelium and on the apical surface of supp orting cells. In the lamina propria FGF2 immunoreactivity and mRNA were den sest in cells close to the olfactory nerve bundles. FGFr1 immunoreactivity was heaviest on the olfactory ensheathing cells. Using reverse transcriptas e-polymerase chain reaction analysis, the olfactory epithelium was shown to express only three receptor splice variants, including one (FGFr1c) with w hich basic fibroblast growth factor has high affinity. Other receptor splic e variants were present in the lamina propria. Taken together, these observ ations indicate endogenous sources of FGF? within the olfactory epithelium and lamina propria and suggest autocrine and paracrine pathways via which F GF2 might regulate olfactory neurogenesis. The observation of only three re ceptor splice variants in the olfactory epithelium limits the members of th e fibroblast growth factor family which could act in the olfactory epitheli um. The widespread distribution of receptors suggests that fibroblast growt h factors may have roles other than proliferation of globose basal cells. ( C) 2001 Published by Elsevier Science B.V.