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BASIC FIBROBLAST GROWTH FACTOR INDUCES ADIPOGENESIS IN ORBITAL FIBROBLASTS; IMPLICATION FOR THE PATHOGENESIS OF GRAVES' ORBITOPATHY.

Thyroid 2019, vol. 29, issue 3

PURPOSE

Basic fibroblast growth factor (bFGF) has been implicated in the pathogenesis of Graves' orbitopathy (GO). It stimulates several processes, including hyaluronan synthesis, involved in orbital tissue volume expansion and may act synergistically with platelet derived growth factor (PDGF)-BB. PDGF-BB is known to stimulate adipogenesis in orbital fibroblasts, but the effect of bFGF on adipogenesis in orbital fibroblasts is so far unknown. This study was conducted to determine: 1) whether bFGF induces adipogenesis in orbital fibroblasts, 2) whether bFGF and PDGF-BB together exert an additive or synergistic effect on adipogenesis and 3) to study whether treatment directed at bFGF- and PDGF-BB signaling may potentially be of interest for the treatment of GO.

METHODS

Orbital fibroblasts from GO patients and controls were cultured in adipocyte differentiation medium with or without bFGF and/or PDGF-BB at different concentrations. Adipogenesis was determined by Oil-Red-O (ORO) staining and messenger RNA expression of the late adipocyte differentiation markers cell death inducing DFFA like effector C (CIDEC) and adiponectin (ADIPOQ). To demonstrate involvement of FGF-receptor and PDGF-receptor signaling, experiments were also conducted in the presence of dasatinib (inhibitor of PDGF-receptor) or nintedanib (inhibitor of PDGF-receptor and FGF-receptor).

RESULTS

bFGF significantly stimulated adipogenesis by orbital fibroblasts as shown by increased ORO staining and CIDEC and ADIPOQ expression after 14 days of differentiation. Furthermore an additive effect of bFGF/PDGF-BB co-stimulation on adipogenesis was observed at the lowest concentration (12.5 ng/ml) of these growth factors tested. Nintedanib completely inhibited bFGF, PDGF-BB and bFGF/PDGF-BB induced adipogenesis, while dasatinib only fully abrogated PDGF-BB induced adipogenesis.

CONCLUSION

bFGF induces adipogenesis in orbital fibroblasts and as such may contribute to GO. The additive effect of bFGF and PDGF-BB on adipogenesis along with the observed inhibitory effects of dasatinib and nintedanib point at independent receptor mediated effects. This supports the hypothesis that multitarget directed therapy might be more efficient in the treatment of GO.

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