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Differential Secretomes Of Processed Adipose Grafts, The Stromal Vascular Fraction And Adipose-derived Stem Cells
Summer E. Hanson, MD PhD1, Malke Asaad1, Yewen Wu, MS1, Qixu Zhang, MD PhD1, Cynthia Branch-Brooks1, Charles Butler, MD1, Peiman Hematti, MD2.
1The University of Texas MD Anderson Cancer Center, Houston, TX, USA, 2The University of Wisconsin, Madison, WI, USA.

Purpose: Autologous fat grafting (AFG) is a widely accepted technique for soft tissue replacement or augmentation; however, graft take or retention remains unpredictable. To address this, there have been numerous variations in the processing technique, including the addition of progenitor cells known as adipose derived stem cells (ASCs) or other cells from the stromal vascular fraction (SVF). The objective of this study was to compare cytokine, chemokine and other protein expression in adipose grafts, the heterogenous SVF and a pure population of ASCs.
Methods: Adipose grafts were harvested from healthy female donors and processed via three commonly used techniques: centrifugation (C), an active filtration device (AF, Revolve) or a passive filtration system (PF, Puregraft). Each resulting graft was further processed to isolate the SVF and protein for analysis. A pure population of ASCs expanded from each donor to passage 4 were used for comparison.
Results: When comparing cytokine expression between the graft, SVF cells and pure ASCs, we found variations both across the three processing techniques and among the sample components (ie, ASCs, SVF or fat). There were similar concentrations of adipogenic markers among all three grafts with minimal concentrations in the ASCs or SVF. Angiogenin, CD31 and vascular endothelial growth factor (VEGF) were used as markers of vasculogenesis. CD31 expression was similar among all samples. VEGF and angiogenin values were higher in the graft samples processed with the AF system compared to PF or centrifugation. Markers of inflammation had the greatest variability. For example, C-reactive protein (CRP) was not expressed in the pure ASC samples but similarly found in the SVF and grafts across all three techniques. Conversely, IL-8 was minimal in the grafts, and comparable in the SVF and ASC samples. CD14 concentration was negligible in the pure ASC populations, and comparable in the SVF and grafts processed by active or passive filtration; however, there was nearly two-fold higher concentration in the graft processed by centrifugation and minimal expression in the SVF. Markers important in tissue regeneration, hepatocyte growth factor (HGF), fibroblast growth factor (FGF) and matrix metalloproteinase 9 (MMP9), were similarly variable. FGF was comparable among all samples and all techniques. HGF was similar in the SVF and grafts resulting from filtration devices (AF and PF) but negligible in the SVF and grafts from centrifugation. MMP9 was highest in the SVF from all processing techniques compared to ASCs and fat.
Conclusions: This study compares secretomes of the adipose tissue grafts, SVF and ASCs resulting from three different processing techniques. While there were many similarities, there are differences in cytokine expression both in the graft and the associated SVF, particularly in inflammation and wound healing. These secretomes may impact graft retention and fat necrosis in the clinical setting or have implications in cell-assisted lipotransfer. Outcomes studies are underway to correlate these findings.


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