Pulsed Electromagnetic Fields Partially Preserve Bone Mass, Microarchitecture, and Strength by Promoting Bone Formation in Hindlimb-Suspended Rats.

Abstract
A large body of evidence indicates that pulsed electromagnetic fields (PEMF), as a safe and noninvasive method, could promote in vivo and in vitro osteogenesis. Thus far, the effects and underlying mechanisms of PEMF on disuse osteopenia/osteoporosis remain poorly understood. Herein the efficiency of PEMF on osteoporotic bone microarchitecture, bone strength and bone metabolism together with its associated signaling pathway mechanism was systematically investigated in hindlimb-unloaded (HU) rats. Thirty three-month-old young mature male Sprague-Dawley rats were equally assigned to the Control, HU and HU + PEMF groups. The HU + PEMF group was subjected to daily 2-hour PEMF exposure with 15 Hz, 2.4 mT. After 4 weeks, MicroCT results showed that PEMF ameliorated the deterioration of trabecular and cortical bone microarchitecture. Three-point bending test demonstrated PEMF mitigated HU-induced reduction in femoral mechanical properties, including maximum load, stiffness and elastic modulus. Moreover, PEMF increased serum bone formation markers, including osteocalcin (OC) and N-terminal propeptide of type 1 procollagen (P1NP); nevertheless PEMF exerted minor inhibitory effects on bone resorption markers, including C-terminal crosslinked telopeptides of type I collagen (CTX-I) and tartrate-resistant acid phosphatase 5b (TRAcP5b). Bone histomorphometric analysis demonstrated that PEMF increased mineral apposition rate, bone formation rate and osteoblast numbers in cancellous bone, whereas induced no obvious changes on osteoclast numbers. Real-time PCR showed that PEMF promoted tibial gene expressions of Wnt1, LRP5, β-catenin, OPG and OC, but did not alter RANKL, RANK or Sost mRNA levels. Moreover, the inhibitory effects of PEMF on disuse-induced osteopenia were further confirmed in eight-month-old mature adult HU rats. Together, these results demonstrate that PEMF alleviated disuse-induced bone loss by promoting skeletal anabolic activities, and imply that PEMF might become a potential biophysical treatment modality for disuse osteoporosis. © 2014 American Society for Bone and Mineral Research.
© 2014 American Society for Bone and Mineral Research.
KEYWORDS:
Pulsed electromagnetic fields, Wnt/Lrp5/β-catenin signaling, bone turnover, disuse, hindlimb unloading, three-point bending test

PMID: 24753111