RESUMO
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.
RESUMO
Intervertebral disc (IVD) degeneration is considered to be the main cause of low back pain (LBP),however,there are lack of long-lasting and effective methods of clinical treatment.Tissue engineering technique based on stem cells becomes an essential research direction on repair of IVD degeneration at present,and its effectiveness and feasibility have been confirmed,but it is difficult to maintain the sufficiency and vitality of stem cells in IVD.Previous studies showed that stem cells existed naturally in IVD,and stem cells from stem cell niche could migrate to IVD physiologically to maintain the IVD environment balance under the adverse microenvironment.Unfortunately,these behaviors cannot preclude IVD degeneration.Therefore,theoretical basis for the regeneration of nucleus pulposus (NP) in situ can be obtained from studying the mechanism that the endogenous repair failure during IVD degeneration,the cell death and the migration of stem cells in IVD,and the key regulatory targets to sustain the quantity and quality of the stem cells.Although there have been few researches to study the mechanism of the cell death and the migration of stem cells in IVD so far,studies demonstrated that the major inducing factors of IVD degeneration (pressure and hypoxia) could decrease the number of NP cells by autophagy,apoptosis and necroptosis,and chemokines and their receptors played a critical role in the migration of mesenchymal stem cells.These researches provide a clue for studying the mechanism of endogenous repair failure during IVD degeneration.We reviewed the current research situation and progress of the mechanism that endogenous repair failure during IVD degeneration in the following articles.First,we exhibited the potential of IVD stem cells in IVD degeneration repair.Second,the effect of the adverse microenvironment (pressure,hypoxia,etc) on the migration of IVD stem cells was discussed.Third,the mechanism of the stem cell death,autophagy,apoptosis and necroptosis under the adverse (pressure,hypoxia,etc.) microenvironment,and the correlation between the IVD stem cells migration and autophagy,apoptosis and necroptosis was studied.And then tissue engineering of NP was also discussed to achieve the endogenous repair of IVD degeneration.These studies will provide an innovative research direction on endogenous repair and a new strategy of early therapy for IVD degeneration.