Human adipose tissue as a source of Flk-1+ cells: new method of differentiation and expansion.

OBJECTIVE: The low number of postnatal endothelial progenitor cells (EPC) in the circulation limits their therapeutic application in cardiovascular medicine. Processed lipoaspirate (PLA) cells differentiate into osteoid, adipose, muscle, and cartilaginous cells. This study examines the potential of PLA cells as a source of EPCs.
METHODS: PLA cells obtained from human lipoaspirates were cultured for 1 week in serum-depleted medium to form three-dimensional cell clusters (3DCC). The phenotype of 3DCC-derived cells was assessed by immunofluorescence staining and FACS analysis.
RESULTS: Flow cytometry showed that 45+/-5% of cells derived from the 3DCC expressed Flk-1, a marker of early EPC, whilst only 4+/-0.5% of freshly isolated PLA were Flk-1+. The proportion of Flk-1+ cells increased to 98+/-2% during culture in hematopoietic stem cell medium. When cultured in an endothelial cell (EC)-specific medium, Flk-1+ cells also expressed Ve-cadherin, von Willebrand's factor (vW), and a lectin receptor, and took up low-density lipoprotein. Incorporation into an endothelial cell tubular network confirmed their functional activity.
CONCLUSION: This report describes the first isolation and culture of Flk-1+ cells from human adipose tissue. The feasibility of the extraction and culture of these cells in increased numbers suggests that such autologous cells will be useful for applications ranging from basic research to cell-based therapies.