Shift toward Mechanical Isolation of Adipose-derived Stromal Vascular Fraction: Review of Upcoming Techniques

Background: Standard isolation of adipose stromal vascular fraction (SVF) requires the use of collagenase and is considered more than "minimally manipulated" by current good manufacturing practice requirements. Alternatively, nonenzymatic isolation methods have surfaced using physical forces to separate cells from the adipose matrix. The purpose of this study was to review the literature on the use of mechanical isolation protocols and compare the results. The implication for use as a standard procedure in practice is discussed. Methods: A systematic review of the literature was performed on mechanical isolation of SVF with a search of six terms on PubMed and Medline databases. One thousand sixty-six articles were subject to evaluation by predetermined inclusion and exclusion criteria. Results: Two level 2 evidence articles and 7 in vitro studies were selected. SVF was isolated using automated closed systems or by subjecting the lipoaspirate to centrifugation only or by shaking or vortexing followed by centrifugation. Six articles reported isolation in laboratory settings and three inside the operating room. Stromal vascular cells expressed CD34, and CD44, CD73, CD90, and CD105, and differentiated along adipogenic and osteogenic lineages. When compared with enzymatic methods, mechanical isolation required less time but yielded fewer cells. Both case-control studies reported improved volume retention with cell-supplemented fat grafts for breast reconstruction. Conclusions: Mechanical isolation methods are alternatives to circumvent safety issues posed by enzymatic protocols. However, randomized comparative studies with long-term clinical outcomes using mechanically isolated stromal vascular cells are needed to identify their ideal clinical applications.