To measure the expression of surface antigens in MSC-TK(A168H) or MSCs, FACS analysis was performed as described previously (Park et al., 2013 (link)). Briefly, cells were stained for 15 min at 25℃ with fluorochrome-conjugated antibodies against CD29 (Cat. No. 303003; BioLegend, USA), CD90 (Cat. No. 559869; BD Biosciences, USA), CD105 (Cat. No. 323205; BioLegend), CD34 (Cat. No. 343505; BioLegend), CD45 (Cat. No. 304011; BioLegend), HLA-DR (Cat. No. 560896; BD PharmingenTM, USA), and isotype control. The cells were washed with PBS and suspended in flow cytometry staining buffer. Cells were analyzed using an Attune NxT Acoustic Focusing Cytometer (Thermo Fisher Scientific) with AttuneTM NxT software.