Regulation of Osteoblast Differentiation and Iron Content in MC3T3-E1 Cells by Static Magnetic Field with Different Intensities

Jiancheng Yang,Chong Ding,Dandan Dong,Peng Shang,Jian Zhang

doi:10.1007/s12011-017-1161-5

Abstract

Many studies have indicated that static magnetic fields (SMFs) have positive effects on bone tissue, including bone formation and bone healing process. Evaluating the effects of SMFs on bone cell (especially osteoblast) function and exploring the mechanism, which is critical for understanding the possible risks or benefits from SMFs to the balance of bone remodeling. Iron and magnetic fields have the natural relationship, and iron is an essential element for normal bone metabolism. Iron overload or deficiency can cause severe bone disorders including osteoporosis. However, there are few reports regarding the role of iron in the regulation of bone formation under SMFs. In this study, hypomagnetic field (HyMF) of 500 nT, moderate SMF (MMF) of 0.2 T, and high SMF (HiMF) of 16 T were used to investigate how osteoblast (MC3T3-E1) responses to SMFs and iron metabolism of osteoblast under SMFs. The results showed that SMFs did not pose severe toxic effects on osteoblast growth. During cell proliferation, iron content of osteoblast MC3T3-E1 cells was decreased in HyMF, but was increased in MMF and HiMF after exposure for 48 h. Compared to untreated control (i.e., geomagnetic field, GMF), HyMF and MMF exerted deleterious effects on osteoblast differentiation by simultaneously retarding alkaline phosphatase (ALP) activity, mineralization and calcium deposition. However, when exposed to HiMF of 16 T, the differentiation potential showed the opposite tendency with enhanced mineralization. Iron level was increased in HyMF, constant in MMF and decreased in HiMF during cell differentiation. In addition, the mRNA expression of transferrin receptor 1 (TFR1) was promoted by HyMF but was inhibited by HiMF. At the same time, HiMF of 16 T and MMF of 0.2 T increased the expression of ferroportin 1 (FPN1). In conclusion, these results indicated that osteoblast differentiation can be regulated by altering the strength of the SMF, and iron is possibly involved in this process.

Highlights

All the organisms on the Earth are continuously exposed to intrinsic geomagnetic field (GMF, 25-65 μT), which plays an essential role in living
This indicated that MC3T3-E1 cells could grow well regardless of whether they were treated with static magnetic fields (SMFs) including hypomagnetic field (HyMF), moderate SMF (MMF), and high SMF (HiMF) or not
Cell morphology demonstrated that SMFs did not result in distinct modifications of cell shape, but osteoblasts showed an increase in spread area under HyMF

Summary

Introduction

All the organisms on the Earth are continuously exposed to intrinsic geomagnetic field (GMF, 25-65 μT), which plays an essential role in living. Besides GMF, chances for human exposed to various static magnetic fields (SMF) have increased a lot with rapid development in science and technology, such as magnetic resonance imaging (MRI), overhead cables with high-voltage direct current, and some transportation systems based on magnetic levitation. (i.e., hypomagnetic field, HyMF) has adverse impacts on many functional states of organisms (reviewed in [1]). There is no convincing evidence that moderate SMF (MMF) or HiMF would induce any adverse effects [2]. It is necessary to systematically elucidate the biological effects and mechanisms of SMFs ranging from hypomagnetic field (HyMF, < 5 μT), weak SMF (WMF, 5 μT–1 mT), moderate (MMF, 1 mT– 1 T) to high (HiMF, > 1 T)

Methods

Results

Conclusion