Effects Of Pulsed Electromagnetic Fields On Osteoblasts

Objective:Ⅰ. Study the effects of pulsed electromagnetic fields (PEMFs) on osteoblasts of rat. Research the mechanism of PEMFs on osteoporosis treatment. Ⅱ. Study the effects of PEMFs on the major components of hematopoietic stem cell niche---ALCAM+Sca-1-osteoblasts in mouse. Explore the role of PEMFs on hematopoietic stem cell homing.Methods:Ⅰ. Osteoblasts were separated from the calvaria of newly born SD rats and cultured in vitro.The third-generation cells were divided into five groups:1-70group;2-70group;3-70group;4-70group and control group. According to the given dose of each group, treated groups were exprosed to PEMFs, and the control group was given nothing. After these treatments, alkaline phosphatase(ALP) test, core-binding factorα1(cbfα1/RUNX2) staining and mineralized nodules staining were done respectively.Ⅱ.24C57/6mice were randomly divided into two groups:PEMF group and control group. The PEMF group were exprosed to PEMFs at a dose of2mT,70Hz,1h/d, and the control group was given nothing. The process continued for4weeks. After these treatment, the femur and tibia of mice in two groups were separated respectively. Its bone marrow cell were flushed out. Then the bone were minced with scissors and incubated with a collagenase Ⅱ. The dissociated cells were collected and bone-associated mononuclear cells (MNCs) were isolated using density centrifugation with LymphoprepTM. The CD31-CD45-TER119-cells were selected by magnetic bead system, and then ALCAM+Sca-1-osteoblasts cell were sorted by flow cytometry. The ALCAM+Sca-1-osteoblast cells in two groups were identified differentially for gene expression with gene chip.Results:Ⅰ. After exposed to PEMFs, ALP activity was significantly reduced. The cbfal-positive osteoblasts were increased. The number of mineralized nodules was significantly increased. Ⅱ. After exposed to PEMFs, the ALCAM+Sca-1-osteoblast up-regulated the expression of osteoblasts maker genes, hematopoietic stem cell homing--related genes, such as cell adhesion molecule genes, chemokine molecule genes, cytokine genes, etc.Conclusion:Ⅰ. PEMFs could promote osteoblasts differentiation and extracellular matrix maturation. PEMFs could contribute to extracellular matrix mineralization. Ⅱ. PEMFs could promote the major components of the hematopoietic stem cell niche---ALCAM+Sca-1-osteoblasts to up-regulate the expression of hematopoietic stem cell homing-related genes. We can conclude that PEMFs could contribute to hematopoietic stem cell homing and hematopoietic reconstitution function at the gene level.