State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi International Joint Research Center for Oral Diseases, Department of Oral Anatomy and Physiology and TMD, School of Stomatology, the Fourth Military Medical University, Xi'an 710032, China.
Department of Biochemistry, Rush University Medical Center, Chicago, IL 60612, USA.
Int J Mol Sci. 2019 Aug 3;20(15):3797. 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.
颞下颌关节(TMJ)与牙咬合的生物力学有关,常受到骨关节炎(OA)的侵犯。本研究旨在阐明印度刺猬(Ihh)和甲状旁腺激素受体 1(PTH1R)信号在调节牙齿刺激 TMJ 骨关节炎软骨中增强的软骨细胞终末分化中的关系。在体外模型中,我们采用了获得和丧失功能的策略,施加了流体剪切力(FFSS),在体内模型中,采用了单侧前交叉咬合(UAC)刺激。通过用抑制剂/激活剂处理分离的软骨细胞,并通过在 tamoxifen 诱导型模式下删除 ()和/或 基因,调节了 Ihh 和 PTH1R 信号。我们发现,FFSS 和 UAC 刺激均促进深层区软骨细胞进行终末分化,而浅层区的细胞则很活跃。我们证明了 FFSS 和 UAC 促进深层区软骨细胞终末分化的过程是由增强的 Ihh 信号和降低的 PTH1R 表达介导的。FFSS 促进的终末分化可通过施用 Ihh 抑制剂或 PTH1R 激活剂来抑制。在 敲除小鼠中,UAC 促进的软骨细胞终末分化和 OA 样病变得到挽救,但在 敲除小鼠中则增强。重要的是,当也应用 敲除时, 敲除小鼠的缓解作用被减弱。我们的数据表明,抑制 TMJ OA 软骨中的 Ihh 信号具有软骨细胞保护作用,这依赖于 PTH1R 信号。