Effects of mechanical strain on proliferation and differentiation of bone marrow stromal cell line ST2.
Differentiation of mesenchymal stromal cells into osteoblasts is regulated by many factors including growth factors, cytokines, and hormones. Mechanical stress has been considered to be an important factor in bone modeling and remodeling. However, biological responses of stromal cells to mechanical stimuli are still unknown. To show the correlation between magnitude of mechanical strain and differentiation of stromal cells into osteoblasts, we investigated the proliferation and the expression of osteoblast-related genes in stromal cell line ST2 that is in the process of osteoblastic differentiation by treatment with ascorbic acid and beta-glycerophosphate, under 0.8%-15% elongation using the Flexercell Strain system. The expression of osteoblast-related genes was analyzed by real-time quantitative polymerase chain reaction (PCR). Cell proliferation significantly increased at 5%, 10%, and 15% elongation compared to that of unloaded controls. Alkaline phosphatase (ALPase) activity significantly increased at 0.8% and 5% elongation but decreased at 10% and 15% elongation. At 1 h and 6 h, mRNA level of Cbfa1/Runx2 increased at lower magnitudes of strain (0.8% and 5% elongation) but decreased at higher magnitude of strain (15% elongation). At 24 and 48 h, Cbfa1/Runx2 and osteocalcin mRNAs decreased at 5%, 10%, and 15% elongation, whereas cell proliferation and expression of type I collagen mRNA increased at the same elongation. These results indicate that mechanical strain stimulates osteoblastic differentiation of stromal cells at low magnitudes of strain.
Koike
Mariko
M
Orthodontic Science, Department of Orofacial Development and Function, Division of Oral Health Sciences, Graduate School, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan. mariko.orts@tmd.ac.jp
Shimokawa
Hitoyata
H
Kanno
Zuisei
Z
Ohya
Keiichi
K
Soma
Kunimichi
K
D000469:Alkaline Phosphatase / Q000378:metabolism; D001483:Base Sequence; D001854:Bone Marrow Cells / Q000166:cytology*; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D049109:Cell Proliferation; D050659:Core Binding Factor Alpha 1 Subunit; D005786:Gene Expression Regulation; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D010006:Osteoblasts / Q000737:chemistry; D013314:Stress, Mechanical; D017154:Stromal Cells / Q000166:cytology* / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D050659:Core Binding Factor Alpha 1 Subunit; D009363:Neoplasm Proteins; D014157:Transcription Factors; D000469:Alkaline Phosphatase