Flow cytometry was performed to determine MSCs positive for SH2. Cells were permeabilized with ice cold 75% methanol in PBS for 30 min at 4°C, and washed three times. A FITC-conjugated SH2 antibody (DiNonA), diluted 1:500 in PBS, was then added, and cells were incubated for 1 hr at 4°C. Cells were analyzed within 2 hr of staining using a flow cytometer (FACScali-bur, Becton Dickinson, Bedford, MA, USA). A total of 1 × 10 6 cells were collected for each measurement. Negative control samples were stained with an isotype-matched irrelevant mAb.