Objective   To investigate the effects of pulsed electromagnetic fields (PEMF) on osteogenic differentiation in demineralized bone matrix (DBM)induced human marrow stromal cell

s (hMSCs).    Methods   hMSCs were obtained from iliac crest marrow aspirates of a healthy boy aged 14. Then 1×10

4

hMSCs per well were plated in 8 24-well tissue culture plates

and 1×10

5

hMSCs per well in 2 6-well plates after they were expanded until passage 2. Those 24-well plates and 6-well plates were divided into 4 groups

cell control group (C group)

cell-material group (CD group)

cell-PEMF group (CP group) and cell-material-PEMF group (CDP group). CD group and CDP group were added with one DBM (size of 5 mm×5 mm×3 mm)

CP and CDP groups were exposed to the PEMF (frequency of 15 Hz

intensity of 5 Gs)

and hMSCs were cultivated in subculture medium with full media exchange in every 3 d. Alkaline phosphatase (ALP) activity and osteocalcin (OC) level were performed at 1

7

14 and 21 d

and alizarin red staining and counting of calcium nodules were performed at 21 d.    Results   Significant differences in ALP activity and OC level were observed between cell control group and the other 3 groups in 7 d after treatment (P0.01). ALP activity of CD group was increased significantly than that of CP group only at 14 d (P0.01)

so did the OC level and calcium nodules only at 21 d (P0.01). Compared with CD group and CP group

ALP activity in CDP group was increased significantly at 7 and 14 d (P0.01)

OC level in CDP group was increased significantly at 14 and 21 d (P0.01)

and the number of calcium nodules in CDP group was increased significantly at 21 d (P0.01).    Conclusion   PEMF alone or together with DBM increases the expression of all osteoblast markers and the amount of mineralized matrix during the differentiation phase

but a combined treatment of DBM and PEMF is more effective than themselves alone. Also this effect was synergic on osteoblastic differentiation

suggesting that PEMF enhances the responsiveness of hMSCs to oteogenic factors such as BMPs.