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

Abstract

Electromagnetic fields (EMFs) have emerged as a versatile means for osteoporosis treatment and prevention. However, its optimal application parameters are still elusive.Here, we optimized the frequency parameter first by cell culture screening and then by animal experiment validation. Osteoblasts isolated from newborn rats (ROBs) were exposed 90 min/day to 1.8 mT SEMFs at different frequencies (ranging from 10 to 100 Hz, interval of 10 Hz). SEMFs of 1.8 mT inhibited ROB proliferation at 30, 40, 50, 60 Hz, but increased proliferation at 10, 70, 80 Hz. SEMFs of 10, 50, and 70 Hz promoted ROB osteogenic differentiation and mineralization as shown by alkaline phosphatase (ALP) activity, calcium content, and osteogenesis-related molecule expression analyses, with 50 Hz showing greater effects than 10 and 70 Hz. Treatment of young rats with 1.8 mT SEMFs at 10, 50, or 100 Hz for 2 months significantly increased whole-body bone mineral density (BMD) and femur microarchitecture, with the 50 Hz group showing the greatest effect. Furthermore, 1.8 mT SEMFs extended primary cilia lengths of ROBs and increased protein kinase A (PKA) activation also in a frequency-dependent manner, again with 50 Hz SEMFs showing the greatest effect. Pretreatment of ROBs with the PKA inhibitor KT5720 abolished the effects of SEMFs to increase primary cilia length and promote osteogenic differentiation/mineralization. These results indicate that 1.8 mT SEMFs have a frequency window effect in promoting osteogenic differentiation/mineralization in ROBs and bone formation in growing rats, which involve osteoblast primary cilia length extension and PKA activation.

Exposure of primary osteoblasts to combined magnetic and electric fields induced spatiotemporal endochondral ossification characteristic gene- and protein expression profiles

“…Similar effects have been observed for mesenchymal stem cells exposed in vitro to an alternating electric current of 5-40 μA at a frequency between 5 and 10 Hz (EF) [10,42,55]. Zhou described a PKA-driven optimal effect of electromagnetic fields with 50 Hz and 1.8 mT on osteogenic differentiation and mineralization in an animal model [60]. Considering the outcomes of previous studies, in the present study, we investigated the potential effect of combined specified electric and magnetic field (EFMF) exposure on primary human osteoblasts to modify cellular and molecular biological pathways in vitro and the parameters that may support and stimulate the biological processes of bone fracture healing in vivo.…”

“…These previously described cellular mechanisms and principles of the potential mode of action of electromagnetic field exposure are supported by a recent study by Zhou 2021, who applied inductively coupled electromagnetic fields (IC) in a rat osteoblast system. These authors showed, also that exposure to sinusoidal electromagnetic fields promotes osteogenic differentiation and bone formation through activation of protein kinase A [60]. In this context it is important to mention, that Rodemann applied inductively coupled electromagnetic fields (IC), which are an integrative part of the combination of alternating magnetic and electric fields (CS), we used in our experiments and were also used by Darwiche [12] in a sucessful animal study.…”

Angelica sinensis polysaccharide promotes the proliferation and osteogenic differentiation of human dental pulp stem cells (hDPSCs) by activating the wnt/β-catenin pathway

“…myocardial fibrosis and oxidative stress in the heart of hypertensive rats (He et al, 2021). ASP could antagonize 5-FU-induced oxidative stress injury to suppress apoptosis in the liver.…”

“…Cells treated with ASP were subjected to calcium deposition detection by ARS. @, P < 0.05; @@, P < 0.01; @@@, P < 0.001. more and more attention due to the ease of availability, less immune rejection, and avoidance of ethics (Zhou et al, 2021). Therefore, hDPSCs are suitable sources of tissue repair not only in dentine generation but also in regeneration-related diseases, such as diseases related to dental pulp (Liu et al, 2020;Zhou et al, 2019).…”

“…hDPSCs have attracted increasing attention due to their advantages, such as ease of availability, less immune rejection, and avoidance of ethics (Zhou et al, 2019). These excellent functions make hDPSCs suitable sources of tissue repair not only in dentine generation but also in regeneration-related diseases (Zhang et al, 2021;Zhou et al, 2021). Although the research of hDPSCs has made great progress, the study on…”