Inhibition of Ihh Reverses Temporomandibular Joint Osteoarthritis via a PTH1R Signaling Dependent Mechanism

• Published in: International journal of molecular sciences 2019-08, Vol.20 (15), p.3797
• Main Authors: Yang, Hongxu, Zhang, Mian, Liu, Qian, Zhang, Hongyun, Zhang, Jing, Lu, Lei, Xie, Mianjiao, Chen, Di, Wang, Meiqing
• Format: Article
• Language: English
• Subjects: Animals; Arthritis; Biomechanics; Biomedical materials; Cartilage; Cartilage diseases; Cartilage, Articular - growth & development; Cartilage, Articular - metabolism; Cell culture; Cell Differentiation - genetics; Chondrocytes; Chondrocytes - metabolism; Chondrocytes - pathology; Chondrogenesis; Chondrogenesis - genetics; Collagen Type II - genetics; Dental Occlusion; Differentiation; Feedback loops; Gene expression; Growth plate; Hedgehog protein; Hedgehog Proteins - genetics; Humans; Hypertrophy; Ligands; Mice; Mice, Knockout; Osteoarthritis; Osteoarthritis - genetics; Osteoarthritis - pathology; Parathyroid; Parathyroid hormone; Parathyroid hormone-related protein; Protein expression; Proteins; Receptor, Parathyroid Hormone, Type 1 - genetics; Signal Transduction - genetics; Smoothened Receptor - genetics; Stress, Mechanical; Temporomandibular joint; Temporomandibular Joint - growth & development; Temporomandibular Joint - metabolism
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms20153797

The temporomandibular joint (TMJ), which is biomechanically related to dental occlusion, is often insulted by osteoarthritis (OA). This study was conducted to clarify the relationship between Indian hedgehog (Ihh) and parathyroid hormone receptor 1 (PTH1R) signaling in modulating the enhanced chondrocyte terminal differentiation in dental stimulated TMJ osteoarthritic cartilage. A gain- and loss-of-function strategy was used in an in vitro model in which fluid flow shear stress (FFSS) was applied, and in an in vivo model in which the unilateral anterior cross-bite (UAC) stimulation was adopted. Ihh and PTH1R signaling was modulated through treating the isolated chondrocytes with inhibitor/activator and via deleting ( ) and/or genes in mice with the promoter gene of type 2 collagen ( ) in the tamoxifen-inducible pattern. We found that both FFSS and UAC stimulation promoted the deep zone chondrocytes to undergo terminal differentiation, while cells in the superficial zone were robust. We demonstrated that the terminal differentiation process in deep zone chondrocytes promoted by FFSS and UAC was mediated by the enhanced Ihh signaling and declined PTH1R expression. The FFSS-promoted terminal differentiation was suppressed by administration of the Ihh inhibitor or PTH1R activator. The UAC-promoted chondrocytes terminal differentiation and OA-like lesions were rescued in knockout, but were enhanced in knockout mice. Importantly, the relieving effect of knockout mice was attenuated when knockout was also applied. Our data suggest a chondrocyte protective effect of suppressing Ihh signaling in TMJ OA cartilage which is dependent on PTH1R signaling.