Expressions of parathyroid hormone-related protein (PTHrP) and parathyroid hormone receptor-1 (PTH1R) in the condylar cartilage of temporomandibular joint modulated by occlusal elevation

Qianzhi Zhuang; Bing Li; Xiuping Wu

doi:10.1016/j.jds.2022.08.001

Expressions of parathyroid hormone-related protein (PTHrP) and parathyroid hormone receptor-1 (PTH1R) in the condylar cartilage of temporomandibular joint modulated by occlusal elevation

J Dent Sci. 2023 Apr;18(2):626-635. doi: 10.1016/j.jds.2022.08.001. Epub 2022 Aug 30.

Authors

Qianzhi Zhuang^{1

2}, Bing Li¹, Xiuping Wu¹

Affiliations

¹ Shanxi Province Key Laboratory of Oral Diseases Prevention and New Materials, School and Hospital of Stomatology, Shanxi Medical University, Taiyuan, Shanxi, PR China.
² Department of Stomatology, Weifang Hospital of Traditional Chinese Medicine, Weifang, Shandong, PR China.

Abstract

Background/purpose: Parathyroid hormone-related protein (PTHrP) is an important regulatory factor in the growth, development and remodeling of bone or cartilage, and acts through its sole receptor, parathyroid hormone receptor-1 (PTH1R). The present study aimed to research the expression changes of PTHrP, PTH1R and other relevant factors in condylar cartilage during the progress of temporomandibular joint osteoarthritis (TMJOA).

Materials and methods: The animal model of TMJOA was constructed by the "resin-modified method", and Sprague Dawley (SD) rats were euthanized at 2 weeks, 4 weeks, 6 weeks and 8 weeks after occlusal elevation. The histological changes of condylar cartilage were observed by X-ray, hematoxylin-eosin (HE) and safranine O-fast green (SO-FG) staining. The expressions of PTHrP, PTH1R, Ki67, Collagen II (Col II), Collagen X (Col X) and Caspase 3 in each group were detected by quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemistry (IHC).

Results: TMJOA progression was time-dependent. In the experimental group, PTHrP expression was unimodal with a peak at 4 weeks, but PTH1R expression showed a decreasing trend. From 2 weeks to 8 weeks in the experimental group, Col X expression rather than Caspase 3 expression was negatively related to PTHrP's, which has no positive relation to Ki67 or Col II. These results demonstrated abnormal occlusal load may be an important pathogenic factor of TMJOA.

Conclusion: It may be one of the reasons of TMJOA progression that PTHrP can't play an effective role due to the low expression of PTH1R. PTHrP may be a direct factor regulating the hypertrophic differentiation of chondrocytes, but it does not directly regulate the proliferation and apoptosis of chondrocytes, and the realization of both regulatory effects may depend on the inhibition of hypertrophic differentiation.

Keywords: Condylar cartilage; Occlusal elevation; PTH1R; PTHrP; Temporomandibular joint osteoarthritis.