Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL, 60612, USA.
Research Center for Human Tissues and Organs Degeneration, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055, China.
Int J Oral Sci. 2020 Sep 29;12(1):26. doi: 10.1038/s41368-020-00095-0.
Orofacial pain or tenderness is a primary symptom associated with temporomandibular joint (TMJ) disorders (TMDs). To understand the pathological mechanisms underlying TMDs, several mouse models have been developed, including mechanical stimulus-induced TMD and genetic mouse models. However, a lack of feasible approaches for assessing TMD-related nociceptive behaviours in the orofacial region of mice has hindered the in-depth study of TMD-associated mechanisms. This study aimed to explore modifications of three existing methods to analyse nociceptive behaviours using two TMD mouse models: (1) mechanical allodynia was tested using von Frey filaments in the mouse TMJ region by placing mice in specially designed chambers; (2) bite force was measured using the Economical Load and Force (ELF) system; and (3) spontaneous feeding behaviour tests, including eating duration and frequency, were analysed using the Laboratory Animal Behaviour Observation Registration and Analysis System (LABORAS). We successfully assessed changes in nociceptive behaviours in two TMD mouse models, a unilateral anterior crossbite (UAC)-induced TMD mouse model and a β-catenin conditional activation mouse model. We found that the UAC model and β-catenin conditional activation mouse model were significantly associated with signs of increased mechanical allodynia, lower bite force, and decreased spontaneous feeding behaviour, indicating manifestations of TMD. These behavioural changes were consistent with the cartilage degradation phenotype observed in these mouse models. Our studies have shown reliable methods to analyse nociceptive behaviours in mice and may indicate that these methods are valid to assess signs of TMD in mice.
口颌面部疼痛或压痛是颞下颌关节（TMJ）紊乱（TMD）的主要症状。为了了解 TMD 的病理机制，已经开发了几种小鼠模型，包括机械刺激诱导的 TMD 和遗传小鼠模型。然而，缺乏可行的方法来评估小鼠口颌区域与 TMD 相关的伤害感受行为，这阻碍了对 TMD 相关机制的深入研究。本研究旨在探讨三种现有方法的改进，以分析两种 TMD 小鼠模型的伤害感受行为：（1）通过将小鼠放置在特制的腔室内，使用 von Frey 纤维在小鼠 TMJ 区域测试机械性超敏反应；（2）使用经济负荷和力（ELF）系统测量咬合力；（3）使用实验室动物行为观察登记和分析系统（LABORAS）分析自发进食行为测试，包括进食持续时间和频率。我们成功评估了两种 TMD 小鼠模型，即单侧前交叉咬合（UAC）诱导的 TMD 小鼠模型和β-连环蛋白条件激活小鼠模型中的伤害感受行为变化。我们发现，UAC 模型和β-连环蛋白条件激活小鼠模型与机械性超敏反应增加、咬合力降低和自发进食行为减少的迹象显著相关，表明 TMD 的表现。这些行为变化与这些小鼠模型中观察到的软骨降解表型一致。我们的研究表明了分析小鼠伤害感受行为的可靠方法，并且可能表明这些方法可用于评估小鼠 TMD 的迹象。
