Pulsed electromagnetic fields improve bone microstructure and strength in ovariectomized rats through a Wnt/Lrp5/β-catenin signaling-associated mechanism

PLoS One. 2013 Nov 14;8(11):e79377. doi: 10.1371/journal.pone.0079377. eCollection 2013.

Abstract

Growing evidence has demonstrated that pulsed electromagnetic field (PEMF), as an alternative noninvasive method, could promote remarkable in vivo and in vitro osteogenesis. However, the exact mechanism of PEMF on osteopenia/osteoporosis is still poorly understood, which further limits the extensive clinical application of PEMF. In the present study, the efficiency of PEMF on osteoporotic bone microarchitecture and bone quality together with its associated signaling pathway mechanisms was systematically investigated in ovariectomized (OVX) rats. Thirty rats were equally assigned to the Control, OVX and OVX+PEMF groups. The OVX+PEMF group was subjected to daily 8-hour PEMF exposure with 15 Hz, 2.4 mT (peak value). After 10 weeks, the OVX+PEMF group exhibited significantly improved bone mass and bone architecture, evidenced by increased BMD, Tb.N, Tb.Th and BV/TV, and suppressed Tb.Sp and SMI levels in the MicroCT analysis. Three-point bending test suggests that PEMF attenuated the biomechanical strength deterioration of the OVX rat femora, evidenced by increased maximum load and elastic modulus. RT-PCR analysis demonstrated that PEMF exposure significantly promoted the overall gene expressions of Wnt1, LRP5 and β-catenin in the canonical Wnt signaling, but did not exhibit obvious impact on either RANKL or RANK gene expressions. Together, our present findings highlight that PEMF attenuated OVX-induced deterioration of bone microarchitecture and strength in rats by promoting the activation of Wnt/LRP5/β-catenin signaling rather than by inhibiting RANKL-RANK signaling. This study enriches our basic knowledge to the osteogenetic activity of PEMF, and may lead to more efficient and scientific clinical application of PEMF in inhibiting osteopenia/osteoporosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biomechanical Phenomena
  • Body Weight / radiation effects
  • Bone and Bones / diagnostic imaging
  • Bone and Bones / metabolism*
  • Bone and Bones / radiation effects*
  • Electromagnetic Fields*
  • Female
  • Gene Expression Regulation / radiation effects
  • Low Density Lipoprotein Receptor-Related Protein-5 / metabolism*
  • Osteogenesis / physiology*
  • Osteogenesis / radiation effects*
  • Ovariectomy
  • Rats
  • Wnt Proteins / metabolism*
  • Wnt Signaling Pathway*
  • X-Ray Microtomography
  • beta Catenin*

Substances

  • Low Density Lipoprotein Receptor-Related Protein-5
  • Wnt Proteins
  • beta Catenin

Grant support

The authors acknowledge support from the National Natural Science Foundation of China (grant numbers 50377044, 51077128, and 31000381) and the Doctoral Thesis Foundation of the Fourth Military Medical University (number 2012D01). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.