Physical stress by magnetic force accelerates differentiation of human osteoblasts.
We examined the effect of magnetic force on differentiation of cultured human osteoblasts. Magnetic microparticles (MPs) were introduced into the cytoplasm of a human osteoblast cell line and the cells were cultured in a magnetic field (MF) in group MP-MF. Three groups of controls were used: cells without MPs were cultured out of MF (group C), cells without MPs were cultured in MF (group MF), and cells with MPs were cultured out of MF (group MP). The cells in group MP-MF became larger and were elongated along the axis of the magnetic poles. Appearance of alkaline phosphatase (AlPase) activity, formation of bone nodules, and calcium deposition were accelerated depending on the intensity of the magnetic field. It takes longer culture in the other three groups to exhibit these changes. Core-binding factor A1 (Cbfa1: transcription factor for osteoblast differentiation) and osteocalcin (a bone-matrix protein involved in controlling osteogenesis) were expressed earlier or stronger in group MP-MF than the other groups. Then we compared phosphorylation of mitogen-activated protein kinase (MAPK) between group MP-MF and group C. Phosphorylation of p38(MAPK) (p38) was increased in group MP-MF, while total p38 as well as total and phosphorylated forms of MAPK/ERK 1/2 and SAPK/JNK were not changed between the two groups. When a p38 inhibitor, SB 203580, was added to the culture medium in group C, AlPase activity, formation of bone nodules, and calcium deposits were completely inhibited. On the other hand, they were inhibited only partially by a MAPK/ERK 1/2 inhibitor, U-0126. Based on these results, it is concluded that (1) osteoblast differentiation is accelerated by a magnetic force, (2) this acceleration is mainly attributed to the activation of p38 phosphorylation, and (3) the stimulus induced by a magnetic field offers a new approach to osteoblast differentiation.
Institute of Health Sciences, Faculty of Medicine, Graduate School of Biomedical Sciences, Hiroshima University, Japan. ryuge@hiroshima-u.ac.jp
Louis
L
Yuge
Astuko
A
Okubo
Takashi
T
Miyashita
Takanori
T
Kumagai
Takeshi
T
Nikawa
Sin'ichi
S
Takeda
Masamoto
M
Kanno
Yukio
Y
Urabe
Masanori
M
Sugiyama
Katsuko
K
Kataoka
D002113:Calcification, Physiologic / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D050659:Core Binding Factor Alpha 1 Subunit; D050660:Core Binding Factors; D006801:Humans; D008280:Magnetics; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D008846:Micromanipulation / Q000379:methods; D008863:Microspheres; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009363:Neoplasm Proteins; D010006:Osteoblasts / Q000166:cytology* / Q000502:physiology*; D015675:Osteocalcin / Q000378:metabolism; D010012:Osteogenesis / Q000502:physiology*; D010766:Phosphorylation; D010812:Physical Stimulation / Q000379:methods; D013314:Stress, Mechanical; D014157:Transcription Factors / Q000378:metabolism; D016474:Weight-Bearing / Q000502:physiology*; D048051:p38 Mitogen-Activated Protein Kinases
D050659:Core Binding Factor Alpha 1 Subunit; D050660:Core Binding Factors; D009363:Neoplasm Proteins; D014157:Transcription Factors; D015675:Osteocalcin; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases