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Stromal vascular cells' characterization following enzymatic digestion or mechanical processing of aspirated adipose tissue.
Alexandra Condé-Green, MD1, Ricardo L. Rodriguez, MD2, Brunna G. Ivo, JD3, Devinder P. Singh, MD1, Nelson H. Goldberg, MD1, Sheri Slezak, MD1, John C. McLenithan, PhD3
1University of Maryland Medical Center / Plastic Surgery, Baltimore, MD, USA, 2CosmeticSurg, Baltimore, MD, USA, 3University of Maryland, School of Medicine, Baltimore, MD, USA
BACKGROUND: Adipose tissue derived from human lipoaspirates contains a putative population of stem cells, termed adipose-derived stem cells (ADSCs) which display extensive proliferative capacity and multilineage potential. These cells reside within the stromal vascular fraction (SVF) of harvested adipose tissue and can be isolated by numerous procedures, including enzymatic methods the most popular, and mechanical methods. The aim of our study was to characterize the population of regenerative cells named Stromal Vascular Cells (SVCs) issued from these different methods of SVF isolation and compare the yield of these cells in freshly obtained lipoaspirates.
METHODS: A prospective study was conducted in 9 healthy adult patients aged 21-55 years, with a mean BMI of 28, undergoing aesthetic liposuction after obtaining informed consent and institutional review board approval for the study. Subcutaneous adipose tissue (300 ml) harvested with vacuum assisted liposuction at -400 mmHg, was separated into three equal parts, and processed by centrifugation, vortexing or collagenase digestion. After red blood cell lysis, each processed and freshly obtained stromal vascular fraction was analyzed to determine the viability and number of the whole population of cells. Each sample was also analyzed by multicolor flow cytometry for identification and characterization of the SVCs. The relative percentages of adipose-derived mesenchymal stem cells (ADMSCs) (CD45- CD73+ CD90+), endothelial cells (CD45-CD31+) and monocytes/macrophages (CD45+ CD14+) were quantified.
RESULTS: Despite the major differences between enzymatic and mechanical methods, similar populations of cells have been isolated. However, SVC yields were different: the highest yield obtained from enzymatic isolation was 2.3 X105 cells/ml lipoaspirate, there were fewer cells obtained from centrifugation and even less following vortexing. Cell viability estimated by trypan blue exclusion was similar between the methods (80-90%). Collagenase digested SVF contained fewer cells of hematopoietic origin (32%) than mechanically isolated SVF (70-85%) and greater numbers of ADMSCs and endothelial cells than mechanically isolated SVF. Additionally, collagenase digested SVF contained fewer inflammatory cells (monocytes/macrophages) than mechanically isolated SVF.
CONCLUSIONS: Although regenerative cells were isolated from all three methods, the varying cellular yields and composition of SVF obtained from these methods may have an effect on its regenerative capabilities when added to fat grafting.
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