Efficacy of pulsed electromagnetic fields and electromagnetic fields tuned to the ion cyclotron resonance frequency of Ca2+ on chondrogenic differentiation.

Previous studies provide strong evidence for the therapeutic effect of electromagnetic fields (EMFs) on different tissues including cartilage. Diverse exposure parameters applied in scientific reports and the unknown interacting mechanism of EMF with biological systems make EMF studies challenging. In 1985, Liboff proposed that when magnetic fields are tuned to the cyclotron resonance frequencies of critical ions, the motion of ions through cell membranes is enhanced, and thus biological effects appear. Such exposure system consists of a weak alternating magnetic field (B1 ) in the presence of a static magnetic field (B0 ) and depends on the relationship between the magnitudes of B0 and B1 and the angular frequency Ω. The purpose of the present study is to determine the chondrogenic potential of EMF with regards to pulsed EMF (PEMF) and the ion cyclotron resonance (ICR) theory. We used different stimulating systems to generate EMFs in which cells are either stimulated with ubiquitous PEMF parameters, frequently reported, or parameters tuned to satisfy the ICR for Ca2+ (including negative and positive control groups). Chondrogenesis was analysed after 3 weeks of treatment. Cell stimulation under the ICR condition showed positive results in the context of glycosaminoglycans and type II collagen synthesis. In contrast, the other electromagnetically stimulated groups showed no changes compared with the control groups. Furthermore, gene expression assays revealed an increase in the expression of chondrogenic markers (COL2A1, SOX9, and ACAN) in the ICR group. These results suggest that the Ca2+ ICR condition can be an effective factor in inducing chondrogenesis.