ABSTRACT
We use an in-vitro osteoblast cell culture model to investigate the effects of low-frequency (7.5 Hz) pulsed electromagnetic field (PEMF) stimulation on osteoblast population, cytokines (prostaglandin E(2) (PGE(2)), transforming growth factor beta1(TGFbeta1), and alkaline phosphatase (ALP) activity to find the optimal intensity of PEMF for osteoblast growth. The results demonstrate that PEMF can stimulate osteoblast growth, release of TGFbeta1, and, in addition, an increase of ALP activity. The synthesis and release of PGE(2) in the culture medium are reduced with increasing numbers of cells. Higher intensity does not necessarily mean increased osteoblast growth, and the most efficient intensity is about 2 mV/cm in this case. Although the lower intensities of the PEMF are yet to be determined, the results of this study can shed light on the mechanisms of PEMF stimulation on non union fracture therapy and osteoporosis prevention in the future.
Subject(s)
Cytokines/metabolism , Osteoblasts/physiology , Osteoblasts/radiation effects , Animals , Animals, Newborn , Cell Proliferation/radiation effects , Cell Survival/radiation effects , Cells, Cultured , Dose-Response Relationship, Radiation , Electromagnetic Fields , Gene Expression/physiology , Gene Expression/radiation effects , Radiation Dosage , Rats , Rats, WistarABSTRACT
This study compares the mechanisms of ultrasound (US) on osteoblast proliferation with those of pulsed electromagnetic field (PEMF), by different signal transduction pathway inhibitors. The cells were stimulated for 15 min under US or for 2 h under PEMF exposure. Twenty-four h after the beginning of stimulation, the cells were harvested and used for mitochondrial activity test (MTT) analysis. The results showed that there are different transduction pathways for US and PEMF stimulation that lead to an upgrade of osteoblast proliferation, although their pathways all lead to an increase in cytocolic Ca2+ and activation of calmodulin. These findings offer a biochemical mechanism to support the process of ultrasound and PEMF-induced enhanced healing of bone fractures.
Subject(s)
Electromagnetic Fields , Osteoblasts/cytology , Ultrasonic Therapy , Animals , Calcium/metabolism , Calmodulin/metabolism , Cell Division/physiology , Cell Division/radiation effects , Cell Survival/physiology , Cell Survival/radiation effects , Mitochondria/physiology , Mitochondria/radiation effects , Nitric Oxide Synthase/physiology , Osteoblasts/metabolism , Osteoblasts/radiation effects , Rats , Rats, Wistar , Signal Transduction/physiology , Signal Transduction/radiation effectsABSTRACT
This study compared the effects of different intensity ultrasound (US) on osteoblasts in the far-field model with effects of the near-field model from the literature, to understand the relations between prostaglandin E(2) (PGE(2)) and osteoblast growth. We used an in vitro model to investigate the effects of 1-MHz, pulsed 1:4, and five different spatial-average temporal-peak intensity (150, 300, 600, 1200 and 2400 mW/cm(2)) US stimulations in far-field exposure (240 mm) on osteoblasts for 15 min. Optimum intensity in this study was 600 mW/cm(2), and cell density and PGE(2) secretion could be significantly stimulated at this intensity. This research may indicate that the growth of osteoblasts by US stimulation was, at least partly, due to increases in the synthesis and secretion of PGE(2). This well-controlled model can lead to further research on the biologic mechanisms for US.
