Adipose stem cell side population in the mouse.

Adipose tissue has become a reliable source of adult stem cells, which appear to possess a yet-undetermined degree of plasticity. With the difficulties associated with harvesting adult bone marrow stem cells, adipose tissue may represent a valuable and easily acquired source of stem cells. Stem cells have been identified using the DNA binding dye Hoechst 33342 and flow cytometry in various tissues known as the side population (SP). The present study shows, for the first time, the presence of side population stem cells in adult adipose tissues. Flow cytometric identification and isolation of this subpopulation of stem cells revealed that in the mouse there are 2.5% of adipose SP cells within the stromal vascular fraction of adipose tissue. In culture, mouse adipose SP cells showed the capacity to undergo in vitro differentiation into osteogenic, chondrogenic and adipogenic lineages. In NOD/SCID mice, freshly sorted mouse adipose SP cells were able to engraft and assist in wound healing. This animal model study showed that adipose SP cells were able to regenerate epithelial layers and connective tissue with minor scar formation. The ability of this novel cell population within adipose tissue to undergo directional differentiation in vitro and to regenerate skin in vivo has potential impact for uses in surgical dermal applications.