Intermittent Exposure to a 16 Hz Extremely Low Frequency Pulsed Electromagnetic Field Promotes Osteogenesis In Vitro through Activating Piezo 1-Induced Ca2+ Influx in Osteoprogenitor Cells

Abstract

Exposure to extremely low frequency pulsed electromagnetic fields (ELF-PEMF) is supposed to simulate local EMF generated during mechanical stimulation of bone and may therefore be used to improve bone regeneration. This study aimed at optimizing the exposure strategy and investigating the underlying mechanisms of a 16 Hz ELF-PEMF, previously reported to boost osteoblast function. Comparing influences of daily continuous (30 min every 24 h) and intermittent (10 min every 8 h) exposure to the 16 Hz ELF-PEMF on osteoprogenitor cells revealed that the intermittent exposure strategy enhanced the 16 Hz ELF-PEMF effects regarding cell numbers and osteogenic function. Gene expression of piezo 1 and related Ca2+ influx were significantly increased in SCP-1 cells with the daily intermittent exposure. Pharmacological inhibition of piezo 1 with Dooku 1 largely abolished the positive effect of the 16 Hz ELF-PEMF exposure on osteogenic maturation of SCP-1 cells. In summary, the intermittent exposure strategy enhanced the positive effects of 16 Hz continuous ELF-PEMF exposure in terms of cell viability and osteogenesis. This effect was shown to be mediated by an increased expression of piezo 1 and related Ca2+ influx. Thus, the intermittent exposure strategy is a promising way to further optimize the therapeutic effects of the 16 Hz ELF-PEMF regarding fracture healing or osteoporosis.