LS-14-P-2122 The role of an allosteric modulator of a fibroblast growth factor receptor in neurogenesis

Introduction: The synthetic peptide Fibroblast Growth Loop (FGL) is an allosteric modulator of a Fibroblast Growth Factor Receptor (FGFR) mimicking the Neural Cell Adhesion Molecule (NCAM). FGL reduces glial activation, promotes neurite outgrowth and synaptogenesis and supports the survival of different neuronal types in cell cultures [1-3]; however its effect on neurogenesis in vivo has not yet been fully determined. A recent study showed that FGL increases doublecortin immunoreactivity (a marker of neuronal precursors and immature neurons) in the dentate gyrus [4]. In this experiment we focused on the influence of short-term application of FGL on cell proliferation, survival and expression of a marker of mature neurons NeuN (neuronal nuclei).

Methods: 22 adult male Wistar rats (300±20g) were included in this experiment. Half of the animals received 4 doses of FGL (80mg/kg s.c.) during 4 consecutive days (= FGL group), the 2nd half received saline (= SAL group). On the 4th day all of the animals were injected with the S-phase marker 5-bromo-2-deoxyuridine (BrdU, 3x 50mg/kg i.p). One day after the BrdU injections, 6 animals from each treatment group (= proliferation group) were transcardially perfused. The remaining animals were transcardially perfused on the 21st day after the BrdU injections (= survival group). The rat brains were sliced (40μm) and immunohistochemically stained with mouse anti-NeuN (1:250, Millipore) and/or rat anti-BrdU (1:500, AbD Serotec). BrdU+ cells were counted in the dentate gyrus in every 12th section under a fluorescence microscope (Zeiss Axio Imager Z1). BrdU+/NeuN+ cells in the survival group were quantified using a confocal laser scanning microscope (Leica SPE). Image analysis was performed using ImageJ software and a LOCI tools plug-in. Statistical analysis (Mann-Whitney U test) was performed in the program Statistica 9.0 (Statsoft).

Results: The average number of BrdU+ cells in the SAL-proliferation group did not significantly differ from the FGL-proliferation group and in the SAL-survival group from the FGL-survival group. Three weeks from BrdU application ~80% of the BrdU+ cells survived in both the SAL group and the FGL group. The percentage of NeuN+ cells was higher in the FGL-survival group (88%) than in the SAL-survival group (78%).

Conclusion: Short-term application of FGL did not increase cell proliferation or survival in the dentate gyrus. The higher ratio of cells that differentiated into neurons might be attributed to the FGL-mediated suppressing effect on the glial cells.

References:

[1] Cambon K et al. (2004) J Neurosci. 24(17): 197-204.

[2] Neiiendam JL et al. (2004) J Neurochem. 91(4):920-35.

[3] Ojo B et al. (2011) Exp Neurol. 232(2):318-28.

[4] Ojo B et al. (2013) Neurochem Res. 38(6):1208-18