Objective       To determine the effect of platelet-derived growth factor-D (PDGF-D) on the differentiation and maturation of osteoclasts (OCs) from peripheral blood mononuclear cells (PBMCs) in vitro.       Met

hods       After PBMCs were gathered and isolated from the fresh blood

and then were treated with receptor activator of nuclear factor-kappa B ligand (RANKL) and macrophage colony stimulating factor (M-CSF) as positive control cells

and with PDGF-D as experimental cells. The cells cultured in normal culture medium served as negative control. After treatment for 15 d

the mRNA levels of tartate-resistant acid phosphatase (TRAP)

matrix metalloproteinases-9 (MMP-9) and Cathepsin K were detected by real-time PCR. The differentiation and maturation of OCs were observed by TRAP staining. The expression of Cathepsin K were detected by Western blotting

and the protein level of MMP-9 in the supernatant was detected by ELISA.       Results       The OC-like cells positive to TRAP were observed in both positive control and experimental cells

but there was no such cell in negative control (

P

0.05). The mRNA levels of TRAP

MMP-9 and Cathepsin K at day 15 were significantly higher in positive control and experimental cells than those in the negative control (

P

0.05)

but there was no difference between the former 2 groups of cells （

P

0.05）. As the same as the mRNA results

the protein levels of MMP-9 (ELISA) and Cathepsin K (Western blotting ) were significantly higher in positive control and experimental cells than those in the negative control

P

0.05).       Conclusion        PDGF-D

not combination of RANKL and M-CSF

induces PBMCs to differentiate into OC-like cells in vitro.