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Abstract QS26: Differential Secretomes Of Processed Adipose Grafts, The Stromal Vascular Fraction And Adipose-derived Stem Cells

Purpose: Limb-sparing procedures are replacing amputations in patients with limb soft-tissue malignancies. Autologous reconstruction restores limb function while improving quality of life. However, nationwide studies comparing types of flap are lacking. Herein, we conduct a nationwide short-term outcomes analysis of limb-preserving autologous reconstruction in patients undergoing resection of soft-tissue malignant neoplasm.

Purpose: Limb-sparing procedures are replacing amputations in patients with limb soft-tissue malignancies. Autologous reconstruction restores limb function while improving quality of life. However, nationwide studies comparing types of flap are lacking. Herein, we conduct a nationwide short-term outcomes analysis of limb-preserving autologous reconstruction in patients undergoing resection of soft-tissue malignant neoplasm.

Methods:
Patients who underwent limb-preserving autologous reconstruction after soft-tissue malignant neoplasm resection between 2005-2017 were identified using Current Procedural Terminology Codes for the excision/resection and their concurrent reconstruction in the ACS-NSQIP database. Demographics, operative characteristics, and surgical outcomes were assessed. Comparisons between type of flap and extremity were performed.
Results: 468 cases were identified: 392 pedicled(121 upper and 271 lower extremities) and 76 free flaps(28 upper and 48 lower extremities). Overall mean age and BMI were 60.1 years and 29.4 kg/m2, respectively. Patient demographics were not statistically different between free and pedicled flap groups. The free flap group had a higher risk of unplanned reoperations(adjustedOR 3.6, 95%CI 1.6-8.3). The lower extremity group showed a higher risk of surgical-site infections(SSI) (adjustedOR 3.5, 95%CI 1.5-8.5). Overall, patients with an operative time above the median (3.4 hours) were associated with a higher risk of SSI, bleeding requiring transfusion, and unplanned reoperation (p<0.004).

Conclusion:
Autologous reconstruction is a powerful option for limb preservation after soft-tissue malignant neoplasm resection. Based on ACS-NSQIP data, free flap reconstruction and lengthier operative time were associated with higher risk of complications. The therapeutic approach should be considered on an individual basis contemplating the risks and benefits of each type of flap. 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.