Comparative characterization of CD271+ and CD271- subpopulations of CD34+ human adipose-derived stromal cells.

Adipose-derived stromal/stem cells (ASCs) are promising candidates for cell-based therapies. However, the lack of markers able to unequivocally identify these cells, the differential expression of cell surface molecules among stromal progenitors from different tissues and cellular alterations caused by culture are phenomena that need to be comprehensively addressed in order to improve ASC purification and consequently refine our knowledge about their function and therapeutic efficiency. In this study, we investigated the potential of CD271, a marker used for purification of bone marrow-derived mesenchymal stem cells, on enriching ASCs from CD34+ stromal cells of human adipose tissue. Putative ASC populations were sorted based on CD271 expression (CD45- CD31- CD34+ CD271+ and CD45- CD31- CD34+ CD271- cells) and compared regarding their clonogenic efficiency, proliferation, immunophenotypic profile, and multilineage potential. To shed light on their native identity, we also interrogated the expression of key perivascular cell markers in freshly isolated cells. CD271- cells displayed twofold higher clonogenic efficiency than CD271+ cells. Upon culture, the progeny of both populations displayed similar immunophenotypic profile and in vitro adipogenic and chondrogenic potentials, while CD271+ cells produced more calcified extracellular matrix. Interestingly, uncultured freshly isolated CD271+ cells displayed higher expression of pericyte-associated markers than CD271- cells and localized in the inner region of the perivascular wall. Our results demonstrate that cells with in vitro ASC traits can be obtained from both CD271+ and CD271- stromal populations of human adipose tissue. In addition, gene expression profiling and in situ localization analyses indicate that the CD271+ population displays a pericytic phenotype.