Investigating the effects of ejiao on joint health and wnt signalling pathway in ovariectomised rats with osteoarthritis induced with monosodium iodoacetate

Abstract

Osteoarthritis is a degenerative disease of the joint which affects a significant proportion of the elderly population worldwide. It is characterised by functional, structural and biochemical changes in the joint, affecting the quality of life of the patients. Despite the prevalence, an effective preventive agent for osteoarthritis is lacking. Ejiao is a traditional Chinese medicine derived from donkey hide to promote blood formation. Despite the lack of experimental data, Ejiao is believed to possess joint protective effects because (i) it is a collagen-rich product which provides building blocks for cartilage; (ii) anti-osteoporotic medications generally protect subchondral bone and improve joint health; (iii) it is shown to modulate Wnt signalling which regulates progression of osteoarthritis. However, this belief lacks experimental support. Thus, this study aims to determine the effects of Ejiao on joint health and Wnt signalling in ovariectomised female Sprague-Dawley rats (12 weeks old) with osteoarthritis induced with monosodium iodoacetate. In this study, 36 rats were ovariectomised and randomly assigned to 2 arms, namely sham (n=6) and osteoarthritis arms (n=30). Osteoarthritis was induced with monosodium iodoacetate on the right knee one month after ovariectomy. Supplementation was initiated a day after osteoarthritis induction. Sham and osteoarthritis control (n=6) received distilled water. The rest of the rats with osteoarthritis received glucosamine sulphate (positive control, 250 m/kg/day, n=6) and Ejiao at low- (0.26 mg/kg/day, n=6), medium- (0.53 mg/kg/day, n=6), and high-dose (1.06 mg/kg/day, n=6) via oral gavage for 5 weeks. During this period, the body weight, joint width, and grip strength of the rats were monitored weekly. At the end of the study period, the rats were euthanised, and their right tibial and femur bones were harvested for analysis. The results show that body weight and joint width increased, while grip strength decreased with the induction of osteoarthritis and improved gradually without treatment. Medium-dose Ejiao accelerated the improvement in body weight, joint width and grip strength in rats with osteoarthritis. Mankin’s scores for cartilage histology increased significantly in the osteoarthritis control but reduced with medium dose Ejiao. No significant subchondral bone changes were observed with osteoarthritis induction, but low dose Ejiao showed increased bone volume, trabecular number, separation and mineral apposition rate. Subchondral bone cellular indices showed decreased osteoid surface and volume but increased osteoclast surface. All treatments reduced the increase in osteoclast number. Gene expression results revealed a significant reduction in Il-1b, Mmp9, and Mmp13 at the cartilage with osteoarthritis induction, suggesting cellular exhaustion. These changes were reversed by medium- and high-dose Ejiao. Western blot analysis revealed no significant changes in Sost, Dkk1, total Ctnnb and phosphorylated Ctnnb levels with osteoarthritis, but medium dose Ejiao significantly increased phosphorylated Ctnnb levels. In conclusion, Ejiao demonstrates potential osteoarthritis preventive effects by reversing functional, structural and biochemical changes due to osteoarthritis in ovariectomised rats, mimicking postmenopausal women. Further investigations should look into testing the effects of Ejiao in a more representative osteoarthritis model and its mechanistic effects, prior to its use in patients with osteoarthritis.