Objective:To investigate the effect of icariin on osteogenic differentiation and adipogenic differentiation of rat bone marrow stromal stem cells (rBMSCs). Method: rBMSCs were incubated with final concentrations of 1×10-5 mol·L-1 icariin under the conditions of osteogenic induction culture. The alkalin phosphatase(ALP) activity was determined at day of 3

6

9

12 days and mineralized nodules were stained at the 15th days; Total RNA was isolated and the gene expressions of bone morphogenetic protein 2(BMP-2) and Runx-2 were investgated by Real time PCR. rBMSCs adipogenic differentiation were treatment by icariin with the concentration 1×10-5mol·L-1

triglycerides content was determined at day of 5

10

15 and 20

rathonum red staining was made at day of 21.Total RNA was isolated at 12

24

48 and 72 h to investigate the gene expression of PPARγ and C/EBPα mRNA by Real Time PCR. Result: Icariin significantly enhanced the ALP activity of the rBMSCs and the number of calcified nodules

and increased the gene expression of osteogenic factor BMP-2 and Runx-2.Icariin significantly reduced triglyceride levels and the formation of lipid droplets

and decreased gene expression levels of the adipogenic transcription factors PPARγ and C/EBPα. Conclusion: Icariin can regulate rBMSCs differentiation

and promote rBMSCs osteogenic differentiation and at the same time icariin can exert suppression of rBMSCs adipogenic differentiation.