Effects of sinusoidal electromagnetic fields on the osteogenic differentiation of bone marrow mesenchymal stem cells / 中华物理医学与康复杂志

ABSTRACT

Objective To explore in vitro the best time window for using sinusoidal electromagnetic fields to promote the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs).Methods BMSCs were isolated and cultured from 4-week-old Sprague-Dawley rats (male and female,80-120g).The BMSCs (from passage 3) were exposed 0,1,4 or 8h/d for 7d,14,or 28d,respectively,to 15Hz sinusoidal electromagnetic fields with a maximum amplitude of lmT.Those exposed 0h/d served as the control.The relative expressions of runt related gene-2 (RUNX2),bone sialoprotein (BSP) and osteopontin (OPN) were determined using real-time,quantitative reverse transcription-polymerase chain reactions (RT-PCRs).The level of RUNX2 protein was determined by Western blotting after 14d.Alizarin red staining was used to compare calcium distribution in each group.Results Obvious promotion of differentiation to osteoblasts was observed after 7 days of exposure to the15 Hz sinusoidal electromagnetic fields,most obviously manifested by an outstanding increase of the early osteogenic index RUNX2 in those exposed 4h/d.After 14 days of intervention,the 1h/d exposure showed to be most effective,especially in inducing the changes of the late osteogenic index OPN.The trends of changes in RUNX2 protein were similar in all groups.After stimulating 1h/d for 14 and 28days,calcium deposition increased to the greatest extent.Conclusions Exposure to sinusoidal electromagnetic fields induces osteogenic differentiation to osteoblasts in rat BMSCs in vitro.There is an apparent window effect.The best results are observed with more days of exposure and shorter exposure time (1h) every day.