The in vitro growth pattern of MSC is shown in Fig. 1 . Human bone marrow-derived MSCs were cultured and expanded. Dur- Table 1 . ing the log phase of growth, cells proliferated with a population doubling time of 30 hr, and this growth period was followed by a confluent growth-arrested phase. Colonies were examined approximately 7 days after initial plating. A morphologically homogeneous population of 90% confluent fibroblast-like cells was obtained after 2 weeks. The cells were replated into culture dishes and cultured for 2 weeks. The replated cells were used for subsequent experiments. The cultured MSCs were positive for SH2 by flow cytometry (Fig. 2) .