Objective To observe the effect of electroacupuncture(EA)on histopathological changes of cartilage and subchondral bone and osteoprotegerin(OPG)

receptor activator of nuclear factor-κB(RANK)

and RANK ligand(RANKL)(OPG/RANK/RANKL)signaling and the expression of matrix metalloproteinase-13(MMP-13)in ovariectomized(OVX)rats

so as to explore its mechanism underlying improvement of osteoporosis.Methods Three-month female SD rats were randomly divided into sham operation

model and EA groups(n=8 in each group).The ovoariectomy model was established by resection of bilateral ovaries.Rats of the sham group were treated by simple removal of a piece of adipose tissue around the bilateral ovaries.EA(3 Hz/15 Hz

1 mA)was applied to bilateral"Sanyinjiao"(SP 6)

"Yanglingquan"(GB 34)

"Yinlingquan"(SP 9)and"Zusanli"(ST 36)for 30 min

once daily(except the weekends)for 12 weeks.The histopathological changes of the subchondral bone of the right knee-joint were observed after Saffron O dyeing and evaluated by Mankins score

and its anatomical structure including the bone volume fraction(bone volume/tissue volume

BV/TV)

trabecular bone number(Tb.N)and trabecular thickness(Tb.Th)

trabecular separation(Tb.Sp)was observed by using Micro CT imaging.The urine C-terminal cross-linking telopeptide of typeⅠcollagen(CTX-Ⅰ)

CTX-Ⅱ(two bone resorption markers)and serum estrogen(E 2)contents were assayed by ELISA

and the expression levels of OPG

RANKL and MMP-13 mRNAs in the cartilage tissue of the left knee-joint were detected by quantitative RT-PCR.Results Following modeling

the BV/TV

Tb.N and Tb.Th levels were significantly decreased(P<0.01)and Tb.Sp and Mankin's score obviously increased in the model group compared with the sham group(P<0.01)

suggesting a formation of osteoporosis and degeneration of the cartilage tissue.The serum E 2 content and OPG mRNA level in the cartilagetissue were significantly down-regulated(P<0.01)

and urine CTX-Ⅰ and CTX-Ⅱcontents and RANKL mRNA and MMP-13 mRNA expression levels cartilagetissue were considerably up-regulated in the model group relevant to the sham group(P<0.01).After EA intervention

modeling-induced decrease of BV/TV

Tb.N

Tb.Th

E 2 and OPG mRNA levels and OVX-induced increase of Tb.Sp

Mankin's score

CTX-Ⅰ

CTX-Ⅱ

RANKL mRNA and MMP-13 mRNA levels were all completely reversed in the EA group relevant to the model group(P<0.01

P<0.05).Conclusion EA intervention can inhibit subchondral bone osteoporosis and articular cartilage degeneration of knee-joint in OVX rats

which is closely associated with its effects in inhibiting the downregulation of serum E 2 and OPG mRNA expression and up-regulation of CTX-Ⅰ

CTX-Ⅱ

RANKL mRNA and MMP-13 mRNA levels

including adjusting OPG/RANK/RANKL signaling.