Efficacy of a standardized Centella asiatica (ECa 233) extract against allodynia in a mouse model of temporomandibular osteoarthritis

Abstract

Prolonged inflammation causing tissue injury can induce chronic pain hypersensitivity (allodynia and hyperalgesia). Osteoarthritis of the temporomandibular joint (TMJ-OA) is a common cause of chronic allodynia encountered in dental practice, but many currently available treatments induce intolerable side effects. In this study, we investigated the potential efficacy of a standardized Centella asiatica extract (ECa 233) on allodynia in a TMJ-OA mouse model established by an injection of complete Freund’s adjuvant (CFA) into the TMJ. After CFA injection, animals daily received oral administration of vehicle, 0.14 g/kg ibuprofen (positive control), 30 mg/kg ECa 233, or 100 mg/kg ECa 233. Behavioral pain responses were examined by air-puff tests before and after CFA injection on days 3, 7, 14, 21, and 28. On day 28, TMJ-OA pathology was assessed by changes in articular cartilage thickness and graded according to the Osteoarthritis Cartilage Histopathology Assessment (OCHA) system. In the CFA + vehicle group, pain response scores increased gradually, reaching statistical significance compared to untreated Sham controls on days 14, 21, and 28. On day 28, OCHA grade score was 3.5 ± 0.35, and articular cartilage thickness was reduced compared to the Sham group. Both ECa 233 doses significantly attenuated pain response scores and also slowed degeneration of the TMJ with efficacy comparable to ibuprofen. We conclude that ECa 233 can protect against mechanical allodynia and cartilage degeneration in a mouse model of TMJ-OA.