The effects of elevated fibroblast growth factor 23 on mandibular growth in rats.

Objective: The aim of this study is to elucidate the local effects of fibroblast growth factor 23 (FGF23) in on mandibular condylar growth in growing rats.

Design: Growing Sprague-Dawley rats received intra-temporomandibular joint injections of phosphate buffer solution (PBS), adenovirus-mediated green fluorescent protein (Ad-GFP) or adenovirus-mediated fibroblast growth factor 23 (Ad-FGF23), which were marked as groups A, B, and C, respectively. In vitro, we treated rat mandibular cartilage chondrocytes with PBS, Ad-GFP, and Ad-FGF23.

Results: The mandibular condyles in group C grew smaller sizes than those in the other control groups due to significant differences among the experimental and control groups with the value of C-D, Q-R (P ≤ 0.05), accompanied by diminished bone mass of sub-cartilage condyles via micro CT analysis. Histologically, the length of the hypertrophic zone was diminished and was associated with decreasing chondrocyte proliferation in group C. Quantitative real-time PCR indicated significant decreases in the expression of chondrogenesis marker genes, including Type X collagen (Col X) and SRY-type box 9 (Sox 9). Moreover, elevated Ad-FGF23 suppressed chondrocyte proliferation and the expression of the chondrogenic differentiation markers Col X and Sox 9 of in vitro.

Conclusions: Local injection of FGF23 suppressed the development and decreased the bone mass of condyles through the decreasing the formation of condylar cartilage, specifically by regulating condylar cartilage cell viability and chondrogenesis expression.