Figure 4.

Erythropoietin (EPO) increases ephrinB2-expressing osteoclasts while reducing their functional activity. RAW264.7 cells were cultured in osteoclastogenic medium, with or without EPO. RNA was extracted on day 4, and expressions of ephrinB2 (A), Nfatc1, Mmp9, and Ctsk (B) in RAW264.7 cells were quantified by quantitative reverse transcription polyermerase chain reaction. RAW264.7 cells were cultured with receptor activator of nuclear factor κB ligand (RANKL) and/or EPO. Tartrate-resistant acid phosphatase (TRAP) staining was performed on day 9 and the number of TRAP-positive cells was counted (C). RAW264.7 cells were cultured on bone slices with RANKL and/or EPO. After 14 d, bone resorption lacunae area was delineated, calculated with Image-Pro Plus (IPP) 6.0 software, and normalized to TRAP-positive cells. Data shown are mean ± SD. These assays were repeated 3 times. ^*P < 0.05; ^**P < 0.01.