Effect and mechanism of acupotomy tendon-sparing and knot-dissolving technique in inhibiting bone destruction in rats with rheumatoid arthritis based on the PI3K/AKT/NFATc1 pathway.

Objectives: To observe the effect of acupotomy tendon-sparing and knot-dissolving technique on bone destruction and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/nuclear factor of activated T cells c1 (NFATc1) pathway in rats with rheumatoid arthritis (RA), so as to investigate the underlying mechanism.

Methods: Forty SD rats were randomly divided into normal, model, medication (tripterygium wilfordii), and acupotomy groups, with 10 rats in each group. Except for the normal group, the rest of the rats were injected with bovine type II collagen emulsion at the base of tails to establish a collagen-induced RA model. The acupotomy group was treated with acupotomy tendon-sparing and knot-dissolving technique, once every 3 days, with a continuous intervention for 9 times. The medication group was given tripterygium wilfordii polyglycoside suspension (8 mg·kg^-1) by gavage, once a day for 28 days continuously. The swelling degree of the ankle joint and the arthritis index score of the rats were observed. Micro-CT scanning was used to observe the degree of bone destruction in the left ankle joint. HE staining and ferruben-solid green staining were used to observe the pathological morphological changes of synovial and cartilage tissue respectively. ELISA was used to detect the contents of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6 and IL-17 in synovial tissue. Tartrate-resistant acid phosphatase (TRAP) staining was used to observe the number of osteoclasts in the left ankle joint. Western blot was used to detect the expression levels of NFATc1, p-PI3K and p-AKT proteins in synovial tissue. Immunohistochemistry was used to detect the positive expressions of matrix metalloproteinase-9 (MMP9), cathepsin K (CTSK) and TNF receptor-associated factor 6 (TRAF6) in the synovial tissue of the ankle joint.

Results: In comparison with the normal group, the bones of the ankle joint and toes of rats were severely eroded, with an uneven surface in the model group; there was a large number of inflammatory cell infiltrations in the synovial tissue, obvious damage to the articular cartilage, and disordered arrangement of synovial cells; the cartilage matrix was damaged, the cartilage layer was rough, and the subchondral bone structure was disordered. In comparison with the model group, the above histopathological changes in the medication group and the acupotomy group were alleviated. Compared with the normal group, the joint swelling degree, arthritis index, the ratio of bone surface area to bone volume (BS/BV), trabecular number (Tb.N), trabecular separation (Tb.Sp), the contents of TNF-α, IL-1β, IL-6 and IL-17 in synovial tissue, the number of osteoclasts in the joint, the expressions or ratios of NFATc1, p-PI3K/PI3K, p-AKT/AKT proteins in synovial tissue, and the positive expressions of TRAF6, CTSK and MMP9 proteins in synovial tissue in the model group were significantly increased (P<0.01), while the bone mineral density (BMD), bone volume fraction (BV/TV) and trabecular thickness (Tb.Th) were significantly decreased (P<0.01). Compared with the model group, the joint swelling degree, arthritis index, BS/BV, Tb.Sp, the contents of TNF-α, IL-1β, IL-6 and IL-17 in synovial tissue, the number of osteoclasts, the expressions or ratios of NFATc1, p-PI3K/PI3K, p-AKT/AKT proteins in synovial tissue, and the positive expressions of TRAF6, CTSK and MMP9 proteins in synovial tissue in the medication group and the acupotomy group were significantly decreased (P<0.01, P<0.05), while BMD, BV/TV and Tb.Th were significantly increased (P<0.01, P<0.05), and Tb.N in the acupotomy group was significantly decreased (P<0.01).

Conclusions: Acupotomy tendon-sparing and knot-dissolving technique can effectively reduce the inflammatory response, relieve the pathological damage of joint tissues and inhibit bone destruction in RA rats, and its mechanism may be related to inhibiting the activation of the PI3K/AKT/NFATc1 pathway.