Inhibition of gap junction intercellular communication by extremely low‐frequency electromagnetic fields in osteoblast‐like models is dependent on cell differentiation

Abstract

Electromagnetic fields have been used to augment the healing of fractures because of its ability to increase new bone formation. The mechanism of how electromagnetic fields can promote new bone formation is unknown, although the interaction of electromagnetic fields with components of the plasma membrane of cells has been hypothesized to occur in bone cells. Gap junctions occur among bone forming cells, the osteoblasts, and have been hypothesized to play a role in new bone formation. Thus it was investigated whether extremely low-frequency (ELF) magnetic fields alter gap junction intercellular communication in the pre-osteoblastic model, MC3T3-E1, and the well-differentiated osteoblastic model, ROS 17/2.8. ELF magnetic field exposure systems were designed to be used for an inverted microscope stage and for a tissue culture incubator. Using these systems, it was found that magnetic fields over a frequency range from 30 to 120 Hz and field intensities up to 12.5 G dose dependently decreased gap junction intercellular communication in MC3T3-E1 cells during their proliferative phase of development. The total amount of connexin 43 protein and the distribution of connexin 43 gap junction protein between cytoplasmic and plasma membrane pools were unaltered by treatment with ELF magnetic fields. Cytosolic calcium ([Ca(2+)](i)) which can inhibit gap junction communication, was not altered by magnetic field exposure. Identical exposure conditions did not affect gap junction communication in the ROS 17/2.8 cell line and when MC3T3-E1 cells were more differentiated. Thus ELF magnetic fields may affect only less differentiated or pre-osteoblasts and not fully differentiated osteoblasts. Consequently, electromagnetic fields may aid in the repair of bone by effects exerted only on osteoprogenitor or pre-osteoblasts.

Effects of Sinusoidal Electromagnetic Field on Structure and Function of Different Kinds of Cell Lines

“…Moreover, distribution of Cx43 between the cytoplasm and plasma membrane was unaffected. This result was dependent on the differentiation state of the cells in culture, since it was observed only in preconfluent, proliferating MC-3T3-E1, but not after the cells had become more differentiated, nor was it observed in ROS 17/2.8 cells 19,40. In this study, the expression of Cx43 was analyzed to assess the GJIC in hFOB 1.19 cells.…”

Effects of Different Extremely Low-Frequency Electromagnetic Fields on Osteoblasts

“…Despite the clinical application of EMF, its mechanism is still obscure. Previous studies suggested that bioeffects of EMF were related to the cells used (Lohmann et al, 2000(Lohmann et al, , 2003Santini et al, 2003;Sollazzo et al, 1997), their maturation (Aaron and Ciombor, 1996;Diniz et al, 2002;Yamaguchi et al, 2002), and the percentage of fetal calf serum in the culture medium (De Mattei et al, 2005;Sollazzo et al, 1997). The physical parameters of the exposure unit are very crucial (Aaron et al, 1999;Fitzsimmons et al, 1989;Katsir et al, 1998), but there are little comparative results between different EMF signals.…”

Use of laptop computers connected to internet through Wi-Fi decreases human sperm motility and increases sperm DNA fragmentation

“…Extremely low frequency magnetic fields can initiate a number of biochemical and physiological alterations in biological systems of different species (8)(9)(10)(11)(12). Many of these effects have been associated with free-radical production (13,14).…”