Electric fields modulate bone cell function in a density-dependent manner

Abstract

The influence of an extremely low frequency (ELF) electric field stimulus (30 Hz at 6 microV/cm rms), known to promote bone formation in vivo, was evaluated for its ability to affect bone cell function in vitro. To accomplish this, we developed an apparatus for the exposure of monolayer cell systems to electric fields in a manner that provides relatively uniform electric field exposure of multiple cell samples as well as a rigorous sham exposure. We show that field exposure significantly limits the normal increase in osteoblastic cell number and enhances alkaline phosphatase activity compared to sham-exposed samples. Moreover, these alterations are shown to occur in a cell density-dependent manner. Samples plated at 6 x 10(3) cells/cm2 show no effect of field exposure. In samples plated at 30 x 10(3) cells/cm2, 72 h of field exposure resulted in 25% fewer cells in the exposed samples, and a doubling of alkaline phosphatase activity in those cells compared to sham exposure. Experiments using a 12 h exposure to preclude significant changes in cell number during the exposure show this density-dependent response to be biphasic. Sparse cultures (< 50 x 10(3) cells/cm2) were not found to be affected by the field exposure, but increases in alkaline phosphatase activity occurred in cultures at densities of 50-200 x 10(3) and 200-350 x 10(3) cells/cm2 and no effect on alkaline phosphatase activity was seen in confluent cell cultures of greater than 350 x 10(3) cells/cm2.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of pulsed electromagnetic field on the proliferation and differentiation potential of human bone marrow mesenchymal stem cells

“…However, the mechanism by which PEMF stimulation induces cellular proliferation and bone regeneration remains unclear. PEMF stimulation affects not only proliferation of osteoblasts, but also apoptosis of osteoclasts [Luben, 1991;McLeod et al, 1993;Chang et al, 2004aChang et al, , 2006. In addition, different characteristics of PEMF signals can reduce or enhance osteoclastogenesis of bone marrow cells [Chang et al, 2004a[Chang et al, , 2005.…”

“…Under specific electromagnetic fields, it has been observed that the proliferation of osteoblasts is limited and that alkaline phosphatase (ALP) activity is elevated [McLeod et al, 1993]. Recent research on the MG-63, ROS 17/2.8, and MLO-Y4 cell lines has shown that PEMF treatment either causes no effect or has a negative effect on cell proliferation [Sollazzo et al, 1997;Lohmann et al, 2000Lohmann et al, , 2003.…”

Effects of pulsed electromagnetic fields on the mRNA expression of CAII and RANK in ovariectomized rats

“…It has been shown that PEMFs are capable of preventing bone loss in the animal models of disuse osteoporosis [26], tail-suspension osteoporosis [27], and ovariectomy-induced osteoporosis [28][29][30]. PEMF can directly aVect not only osteoblasts, but also osteoclasts [31][32][33]. It is possible that eVects of PEMFs stimulation on osteoclastogenesis might be responsible for the modulation of bone resorption.…”

Gap Junctions and Biophysical Regulation of Bone Cells

“…These diverse biophysical signals affect the level or activity of various markers of bone cell activity and differentiation. These factors include alkaline phosphatase in the case of electric fields [65], cytosolic Ca 2+ mobilization, NF-κB activation, Cx protein expression and phosphorylation, osteopontin mRNA expression, and prostaglandin E2 (PGE 2 ) production in the case of fluid flow [66–69], and osteopontin mRNA expression during substrate stretch [70]. In the presence of fluid flow and electric fields, the effects are more pronounced in cells displaying relatively more abundant GJIC.…”