Adipose-derived stem cells (ASCs) are the mesenchymal stem cell (MSC) population found in the stromal vascular fraction (SVF) of adipose tissue. ASCs are selected from stromal vascular fraction cells by their adhesion to plastic. ASC suspensions can be differentiated from SVF cells by their significantly lower levels of CD45. Adipose-derived stem cells are characterized by positive expression (>90%) of CD73, CD90 and CD13, and negative expression (<2%) of hematopoietic markers, such as CD11b and CD45. In addition, in contrast to bone marrow-derived mesenchymal stem cells, adipose-derived stem cells do not express CD106 but are positive for CD36. CD34 expression varies in accordance with culture conditions; it can be expressed during the early passages of culture and later decrease. Additional adipose-derived stem cell-specific markers include: positive expression of CD10, CD26, CD49d, CD49e, CD146 and negative or negligible expression (<2%) of CD3, CD11b, CD49f and PODXL. Adipose-derived stem cell populations may display heterogeneity for additional surface antigens.
The relative abundance of and ease of accessibility to adipose tissue, render adipose-derived mesenchymal stem cells more advantageous than mesenchymal stem cells derived from bone marrow.
The multi-lineage differentiation capacity and unique immunobiological properties of adipose-derived stem cells render them an attractive candidate for regenerative medicine. ASCs are immunoprivileged cells, which secrete immunomodulatory, angiogenic, anti-apoptotic and haematopoietic factors that facilitate tissue repair.