[The role of transient receptor potential vanilloid 1 expression in rat MIA-induced temporomandibular joint osteoarthritis].

Objective: Exploring the changes in the expression of transient receptor potential vanilloid 1 (TRPV1) in the peripheral and central nervous system in rats temporomandibular joint osteoarthritis (TMJOA) and its relationship with TMJOA pain. Methods: From February 2024 to April 2025, 48 healthy male Sprague Dawley rats were randomly divided into a control group and an experimental group, with 24 rats in each group. Each group is further divided into three groups (2-week, 4-week, and 6-week groups) using a random number table method, with 8 animals in each group. After bilateral injection of sodium iodoacetate (MIA) into the temporomandibular joint (TMJ) cavity to establish a TMJOA model, the TMJ condyle, trigeminal ganglion (TG), trigeminal nucleus caudate (TNC), and hippocampal tissue were collected. Pain threshold detector von Frey silk was used to evaluate the head withdrawal threshold (HWT) of rats, and HE staining and Micro CT scanning were used to observe the histological changes of TMJ. Immunohistochemical staining was used to detect the expression of TRPV1 in TG and hippocampal tissues, as well as the expression of glial fibrillar acidic protein (GFAP) in TNC. Results: On the first day after modeling, the HWT of rats significantly decreased and then gradually increased. From day 7 to day 14, HWT decreased again, and after day 14, HWT gradually increased (P<0.001). HE staining and Micro CT revealed that in the second week after modeling, the arrangement of condylar bone trabeculae was disordered, the trabeculae became thinner, the bone marrow cavity became larger, and then the trabeculae became thicker and the bone marrow cavity became smaller. The number of TRPV1 positive cells in TG of TMJOA rats reached its peak in the second week of modeling, and then gradually decreased in the fourth and sixth weeks (P<0.001), with no statistically significant difference in the control group (P=0.941). The number of GFAP positive cells in TNCs of TMJOA rats significantly increased, reaching its peak in the second week of modeling and gradually decreasing in the fourth and sixth weeks (P<0.001). There was no statistically significant difference between the control group (P=0.720). The number of TRPV1 positive cells in the hippocampus of TMJOA rats significantly increased. The number of TRPV1 positive cells reached its peak in the second week of modeling, and then gradually decreased in the fourth and sixth weeks (P<0.001). There was no statistically significant difference between the control group (P=0.776). Conclusions: In the MIA induced rat TMJOA model, the expression of TRPV1 in TG and hippocampal tissue, as well as the expression of GFAP in TNC, were upregulated, which may be involved in the occurrence and development of TMJOA pain and related to the development of TMJOA lesions.