Within MSCs, CD200⁺ population inhibits osteoclast formation.

<p>PBMC adherent cells were co-cultured with MSCs in presence of M-CSF for 48 hr. RANKL was added after 48 hr and half of the medium was changed every 3 days. (A) After 21 days of culture, actin rings were stained with phalloidin-Alexa 540 and nuclei with DAPI. (B) Osteoclast precursors were cultivated with MSCs, CD200⁺ MSCs or CD200^– MSCs for 21 days. Tartrate-resistant acid phosphatase (TRAP) assay was performed and area of TRAP-positive cells was measured. Data are mean±SD. *, P<0.05. (C) Effect of MSCs on bone resorption activity of osteoclasts. White arrows represent bone resorption pits. The results of 1 experiment out of 3 are presented.