Runx2 promoter methylation level changes in bone tissue of rats with ovariectomized osteoporosis treated by electroacupuncture

BACKGROUND: Shenshu and Zusanli are commonly used acupuncture acupoints in the treatment of osteoporosis; however, the specific mechanism is still unclear. OBJECTIVE: To explore the therapeutic mechanism of electroacupuncture at Shenshu and Zusanli acupoints in ovariectomized rats with osteoporosis based on the methylation level of Runx2 promoter in bone tissue. METHODS: Fifty Sprague-Dawley rats were randomly divided into sham operation group, model group, electroacupuncture acupoint group, electroacupuncture non-acupoint group and estradiol group (n=10 per group). The model of osteoporosis was established by ovariectomy in all the groups except for sham operation group. Shenshu and Zusanli acupoints were selected for electroacupuncture treatment in the electroacupuncture acupoint group. Nonacupoint electroacupuncture was selected for intervention in the electroacupuncture non-acupoint group, while the other three groups did not receive electroacupuncture intervention. The estradiol group was given estradiol tablets (0.09 mg/kg) by gavage, and the sham operation group and the model group were given 10 mL/kg normal saline. Femoral and vertebral bone mineral density, biomechanical properties of the femur, serum bone calcium, type I tropocollagen n-terminal propeptide (P1NP), bone tissue osteopontin and bone sialoprotein levels, and Runx2 promoter methylation level in bone tissue were determined at 12 weeks after intervention. RESULTS AND CONCLUSION: Bone mineral density levels of the femur and vertebrae decreased significantly in the model group compared with the sham operation group (P < 0.05). The maximum load, stiffness and elastic modulus of the femur, serum calcium, and P1NP levels were significantly decreased in the model group compared with the sham operation group (P < 0.01). The osteopontin and bone sialoprotein levels and expressions of Runx2 promoters CpG1, CpG2, CpG3 and CpG4.5 in bone tissue were significantly increased in the model group compared with the sham operation group (P < 0.01). Compared with the model group, electroacupuncture at acupoints and estradiol significantly improved the above-mentioned indicators (P < 0.01), while the expression of Runx2 promoters CpG1, CpG2, CpG3 and CpG4.5 in the bone tissue of the electroacupuncture non-acupoint group showed no significant decrease (P > 0.05). In addition, the other indicators were all improved in the electroacupuncture non-acupoint group (P < 0.05). Compared with the estradiol group, the level of serum P1NP was significantly increased in the electroacupuncture acupoint group (P < 0.05), while the difference in the other indicators was not statistically significant (P > 0.05). To conclude, electroacupuncture at Shenshu and Zusanli acupoints can enhance bone mineral density and improve the biomechanical properties of the femur by reducing the methylation level of Runx2 promoter in bone tissue, thus effectively preventing and controlling osteoporosis.