Sinusoidal Electromagnetic Fields Increase Peak Bone Mass in Rats by Activating Wnt10b/β-Catenin in Primary Cilia of Osteoblasts

Abstract

Extremely low‐frequency electromagnetic fields have been considered a potential candidate for the prevention and treatment of osteoporosis; however, their action mechanism and optimal magnetic flux density (intensity) parameter are still elusive. The present study found that 50‐Hz sinusoidal electromagnetic fields (SEMFs) at 1.8 mT increased the peak bone mass of young rats by increasing bone formation. Gene array expression studies with femoral bone samples showed that SEMFs increased the expression levels of collagen‐1α1 and Wnt10b, a critical ligand of the osteogenic Wnt/β‐catenin pathway. Consistently, SEMFs promoted osteogenic differentiation and maturation of rat calvarial osteoblasts (ROBs) in vitro through activating the Wnt10b/β‐catenin pathway. This osteogenesis‐promoting effect of SEMFs via Wnt10b/β‐catenin signaling was found to depend on the functional integrity of primary cilia in osteoblasts. When the primary cilia were abrogated by small interfering RNA (siRNA) targeting IFT88, the ability of SEMFs to promote the osteogenic differentiation of ROBs through activating Wnt10b/β‐catenin signaling was blocked. Although the knockdown of Wnt10b expression with RNA interference had no effect on primary cilia, it significantly suppressed the promoting effect of SEMFs on osteoblastic differentiation/maturation. Wnt10b was normally localized at the bases of primary cilia, but it disappeared (or was released) from the cilia upon SEMF treatment. Interestingly, primary cilia were elongated to different degrees by different intensities of 50‐Hz SEMFs, with the window effect observed at 1.8 mT, and the expression level of Wnt10b increased in accord with the lengths of primary cilia. These results indicate that 50‐Hz 1.8‐mT SEMFs increase the peak bone mass of growing rats by promoting osteogenic differentiation/maturation of osteoblasts, which is mediated, at least in part, by Wnt10b at the primary cilia and the subsequent activation of Wnt/β‐catenin signaling. © 2019 American Society for Bone and Mineral Research.

The frequency window effect of sinusoidal electromagnetic fields in promoting osteogenic differentiation and bone formation involves extension of osteoblastic primary cilia and activation of protein kinase A

“…Furthermore, animal studies found that EMFs prevented ovariectomy-induced OP, attenuated microgravity-induced bone loss, and increased the peak bone mass in growing young rats (Lei et al, 2018;Li et al, 2018; Y. Y. Zhou et al, 2019;.…”

“…Therefore, there is still no consensus about the efficacy of EMF treatment for the prevention and treatment of OP. This may have resulted from the lack of a set of standard operating procedures in selecting EMF parameters for various studies, and the fact that EMFs have a strict window of bioactivity (Bagnato et al, 2016;Funk et al, 2009; C. Markos, 2005;Zhou et al, 2019Zhou et al, , 2011Zhou et al, , 2014S. Zhu et al, 2017).…”

Characterization of Primary Cilia in Osteoblasts Isolated From Patients With ADPKD and CKD

“…Cells were treated with LiCl as it induces cilia elongation in mice osteoblasts. ( 45 ) Notably, LiCl activates canonical Wnt signaling, a pathway previously implicated in cyst expansion of polycystic disease in animal models, through the inhibition of glycogen synthase kinase 3. ( 45 ) Following serum starvation, cells were treated with either 10mM or 25mM LiCl for 24 hours and processed for immunofluorescence analyses.…”

“…( 45 ) Notably, LiCl activates canonical Wnt signaling, a pathway previously implicated in cyst expansion of polycystic disease in animal models, through the inhibition of glycogen synthase kinase 3. ( 45 ) Following serum starvation, cells were treated with either 10mM or 25mM LiCl for 24 hours and processed for immunofluorescence analyses. Cilia length was measured using pericentrin to mark the cilium base acetylated α‐tubulin as microtubules extend to the tip of the organelle.…”

Expression profiles and prognostic significance of WNT family members in glioma via bioinformatic analysis

“…Then, GO analysis predicted that WNT5A regulated molecular functions including GTPase activity, biological processes such as signal translation, and biological pathways such as EGFR-dependent signaling events in glioma; differently, WNT10B regulated molecular functions including GTPase activity, biological processes such as signal translation, and biological pathways such as development biology in glioma. Finally, KEGG pathway analysis showed that WNT5A is primarily through the WNT/Ca+ pathway, also activates the canonical pathway [20,[48][49][50] and WNT10B has been only reported in the canonical WNT signaling pathway [51][52][53][54]. KEGG pathway analysis also showed that the neighbor genes of WNT5A were widely distributed in multiple pathways in the de novo pathways of glioma occurrence, in which crucial oncogenes (EGFR and MDM2) and 2 important tumor suppressors (PTEN and IKN4a/ARF) were closely correlated with WNT5A.…”