Flow Cytometric Characterization of MSCs and HUVECs

WJ-MSCs and HUVECs, respectively, at the eighth and the sixth passage, were treated with 0.05% trypsin–EDTA and collected; 10⁶ cells per sample were incubated with 1 μg of the specific antibody, conjugated with fluorescein isothiocyanate (FITC), phycoerythrin (PE), allophycocyanin (APC), phycoerythrin-cyanine 5.5 (PE Cy5.5), or Alexa Fluor 488 for 30 min at 4°C in the dark. WJ-MSCs were stained using the following antibodies: anti-CD31, anti-CD73, anti-CD13, anti-CD90, anti-CD117, anti-CD14, anti-CD34, anti-CD105, anti-CD146, anti-CD133, anti-CD144, anti-ESA, anti-HLA-ABC, anti-HLA-DR, anti-CD45 (Becton Dickinson [BD], San Jose, CA), anti-CD29, anti-CD44, and anti-CD166 (Ancell, Bayport, MN). HUVECs were stained with anti-CD146 (BD) and anti-CD144 (Acris Antibodies, San Diego, CA). After incubation, cells were washed and acquired with a flow cytometer (FACS Calibur; BD), collecting 10,000 events per sample. Data were analyzed by the FlowJo software v8.8.6 (TreeStar, Ashland, OR). The mean fluorescence intensity (MFI) ratio values were calculated (i.e., dividing the MFI of positive events by the MFI of negative events).^{22 (link),23 (link)}