Functional Implications of CD34 Expression in Human Adipose-Derived Stem/Progenitor Cells

CD34 is frequently used as a marker of adipose-derived stem/stromal/progenitor cells (ASCs). However, CD34 expression in human ASCs (hASCs) decreases over time in culture, and the implications of this remain unclear. In this study, we sorted shortly-cultured hASCs into CD34+ and CD34- fractions and compared their biological functions. Results indicated that CD34+ hASCs were more proliferative and had a greater ability to form colonies. In contrast, CD34-cells showed a greater ability for differentiation into adipogenic and osteogenic lineages. Both CD34+ and CD34-cells showed similar abilities in migration and capillary formation in response to growth factors. Expression levels of endothelial progenitor markers (Flk-1, FLT1, and Tie-2) were higher in CD34+ cells, whereas those of pericyte markers (CD146, NG2, and alpha-smooth muscle actin) were higher in CD34- cells. Both CD34+ and CD34-cells showed similar expression levels of vascular endothelial growth factor and hepatocyte growth factor, although hypoxia affected the expression levels. Together these results suggest that CD34 expression in hASCs may correlate with replicative capacity, differentiation potentials, expression profiles of angiogenesis-related genes, and immaturity or stemness of the cells. Loss of CD34 expression may be related to the physiological process of commitment and/or differentiation from immature status into specific lineages such as adipose, bone, or smooth muscle.