Characterization of Structure and Cellular Components of Aspirated and Excised Adipose Tissue

Background: Adipose tissue is an easily accessible tissue for use as a soft-tissue filler and source of adult multipotent cells, called adipose-derived stem/stromal/progenitor cells. However, many aspects of its anatomy remain unclear because of the fragile structure of adipocytes and adipose tissue. Methods: Aspirated (n = 15) or intact (n = 9) subcutaneous adipose tissue samples were evaluated by (1) whole-mount histology with triple-fluorescence staining for three-dimensional visualization of living adipose tissue, (2) glycerol-3-phosphate dehydrogenase assay, (3) multicolor flow cytometry (CD34, CD31, and CD45), and (4) adherent cell culture of stromal vascular fraction cells for viable adipose-derived stromal cell yield. Results: Whole-mount histology revealed the presence of a capillary network running alongside adipocytes, which was partly disrupted in aspirated adipose tissues. Aspirated adipose tissue also lacked large vasculature structures and showed significantly larger numbers of small lipid droplets (ruptured adipocytes) (p = 0.00016) and dead cells (p = 0.0038) compared with excised adipose tissue. Adipocyte number was less than 20 percent of total cellularity, and vasculature-associated cells, including endothelial cells and adipose-derived stromal cells, constituted over one-half of total cells in both intact and aspirated adipose tissue. Glycerol-3-phosphate dehydrogenase assay suggested that greater than 30 percent and 5 percent of adipocytes were ruptured in aspirated and excised adipose tissue, respectively (p = 0.032). Multicolor flow cytometric analysis indicated a much higher percentage of blood-derived cells (CD45+) contaminated in aspirated adipose tissue (p = 0.0038), and adipose-derived stromal cell yield in aspirated adipose tissue was approximately one-half that in excised tissue (p = 0.011). Conclusion: The authors’ results indicate the differential structure and cellular composition of the two tissues, and significant tissue damage and progenitor yield deficiency in aspirated adipose tissue.