Cell Type-Dependent Nonspecific Fibroblast Growth Factor Signaling in Apert Syndrome.

Apert Syndrome (AS) is one of the most severe forms of craniosynostosis. It is caused by gain-of-function mutations in the receptor fibroblast growth factor receptor 2 (FGFR2), which leads to ligand-receptor promiscuity. Here, we aimed to better understand the behavior of mesenchymal stem cells (MSCs) and of fibroblastoid cells, cellular populations that are part of the suture complex, when stimulated with different fibroblast growth factors (FGFs). We also aimed to verify whether FGFR2 specificity loss due to AS mutations would change their signaling behavior. We tested this hypothesis through cell proliferation and differentiation assays and through gene expression profiling. We found that FGF19 and FGF10 increase proliferation of fibroblastoid cells harboring the FGFR2 p.S252W mutation, but not of mutant MSCs. FGF19 and FGF10 were associated with different expression profiles in p.S252W cells. Further, in accordance to our gene expression microarray data, FGF19 decreases bone differentiation rate of mutant fibroblastoid cells and increases bone differentiation rate of MSCs. This effect in osteogenesis appears to be mediated by BMP signaling. The present data indicate that non-natural FGFR2 ligands, such as FGF10 and FGF19, are important factors in the pathophysiology of AS. Further research is needed to determine the role of modulation of MSC proliferation or use of FGF19 or anti-BMP2 as inhibitors of osteogenesis in AS subjects' cells, and whether these findings can be used in the clinical management of AS.