Fibroblast growth factors (FGF-1, FGF-2) promote migration and neurite growth of mouse cochlear ganglion cells in vitro: immunohistochemistry and antibody perturbation.

To study the effect of FGF in the early development of the sensory neurons of the auditory system, we established a culture preparation of ganglionic neuroblasts engaged in migration and process outgrowth. The presumed anlage of the cochlear ganglion was dissected from E11 otocysts, just as the neuronal precursors were migrating. The cultures were divided into 4 groups and supplemented for 7-9 days with either hrFGF-1 or hrFGF-2 or both or with defined medium only (control group). Measurements of the increase in explant growth, neuroblast migration, and neurite outgrowth were made by time-lapse imaging techniques in living cultures. Either FGF-1 or FGF-2 alone stimulated early migration and outgrowth of the ganglion cells by 5-10x. The effect of combining FGF-1 and FGF-2 was greater than either alone, but less than additive, consistent with a shared receptor. BrdU labeling confirmed that the effect was on migration, not on proliferation. Adding a neutralizing antibody for FGF-2 to the cultures inhibited migration and neurite outgrowth, suggesting an endogenous FGF-2 activity in these functions. Immunocytochemical observations in vitro and in situ with antibodies to FGF-1, FGF-2, or FGF receptor (R1) demonstrated immunopositive staining of the migrating ganglionic neuroblasts, their processes, and growth cones at corresponding stages (E13). Also non-neuronal cells, hair cells, and Schwann cells (in situ) expressed FGF-1 and FGF-2. Evidently both FGF-1 and FGF-2 play important roles in the migration and initial differentiation of cochlear ganglion neurons in the mouse. Copyright 2000 Wiley-Liss, Inc.