280 mT static magnetic field promotes the growth of postpartum condylar cartilage

ABSTRACT

Purpose

Functional appliances made of permanent magnets have been used in jaw orthopedic treatment. However, whether the static magnetic field (SMF) generated by permanent magnets promotes the developmental sequence of condylar cartilage and thus promotes the growth of the mandible remains to be studied. The aim of this study was to investigate the effects of 280 mT SMF on postnatal condylar chondrogenesis and endochondral ossification and the roles of FLRT3, FGF2 and BMP2 signaling in this chondrodevelopmental sequences.

Methods

Forty-eight rats were assigned to two groups (control and SMF). The condyles were collected at the specified time points. The histomorphological changes in the condyle were observed by histological staining. The expression of proteins related to the proliferation and differentiation of the condylar cartilage and the changes in subchondral bone microstructure were analyzed by immunohistochemical staining and micro-CT scanning. FLRT3, FGF2, and BMP2 expression was detected by immunofluorescence staining.

Results

Under SMF stimulation, the cartilage of young rats grew longitudinally and laterally, and the thickness of the cartilage became thinner as it grew. The SMF promoted the proliferation and differentiation of condylar chondrocytes and endochondral ossification and increased subchondral bone mineral density, and BMP2 signaling was involved. Moreover, under SMF loading, the increased expression of FGF2 and FLRT3 were involved in regulating cartilage morphogenesis and growth. In late development, the decreased expression of FGF2/FLRT3 and the increased expression of BMP2 promoted endochondral ossification. The SMF accelerated this opposite expression trend.

Conclusion

FGF2/FLRT3 and BMP2 signals are involved in the regulatory effect of SMF exposure on chondrogenesis and endochondral ossification, which provides a theoretical basis for the clinical use of magnetic appliances to promote condylar growth.

KEYWORDS:

• Static magnetic field
• condylar cartilage
• differentiation
• endochondral ossification
• FGF2/FLRT3 and BMP2 signals

Acknowledgements

We thank the members of the Yunnan Provincial Key Laboratory of Stomatology for their cooperation.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the National Natural Science Foundation of China (81960195 and 82160177), the Reserve interests for young and middle aged academic and technical leaders in Yunnan Province (202205AC160067), the Scientific and Technical Innovation Team of Yunnan Province (202105AE160004), the Scientific and Technological Innovation Team of Kunming Medical University (CXTD202010), and the Graduate Innovation Foundation of Kunming Medical University(2020S112).