Posttraumatic Osteoarthritis of Temporomandibular Joint in Miniature Pigs

The present study investigated the changes in Indian hedgehog (Ihh), periarticular cell-derived parathyroid hormone-related protein (PTHrP), and runt-related transcription factor 2 (Runx2) in the temporomandibular joint (TMJ) cartilage with posttraumatic osteoarthritis (PTOA). The miniature pigs were randomly divided into two groups: the experimental group (EG) (n=8) and the control group (CG) (n=4). The left side of EG had type B intracapsular fractures with anterior disc displacement (ICF+DD), while the right side only had type B intracapsular fractures (ICF), and the CG was a blank control. The production of Ihh, PTHrP, and Runx2 was detected by immunohistochemistry staining and real-time polymerase chain reaction (PCR) at weeks 4 and 12 post-surgery. The expression of Ihh, PTHLH /PTHrP, and Runx2 in the EG was significantly lower than that in the CG at 4 and 12 weeks after the operation (P<0.05). Moreover, significant differences were detected between ICF+DD and ICF (P<0.05). Ihh, PTHHL/PTHrP, and Runx2 proteins affect the endochondral osteogenesis of TMJ and play a significant role in PTOA. Our findings suggested that the interaction mechanism among Ihh, PTHLH/PTHrP, and Runx2 is activated when posttraumatic osteoarthritis (PTOA) occurs, but how they regulate each other remains to be investigated.