Joris van Dongen

67 FAT procedure to obtain SVF for regenerative purposes INTRODUCTION Nowadays, autologous adipose tissue transplantation is frequently used to reduce dermal scarring 1,2 and to restore volume loss 3 as is the case with soft tissue defects, facial fat atrophy 4,5 and ageing of the face. 6 The therapeutic benefit of autologous adipose tissue transplantation in these aforementioned situations is partly ascribed to the presence of precursors of Adipose Derived Stromal Cells (ASC) in this autologous adipose tissue albeit that this awaits formal proof. ASC are progenitor cells that reside in the Stromal Vascular Fraction (SVF) of adipose tissue attached around the vessels as pericytes and periadventitial cells. 7,8 In vitro , these precursors readily adhere to tissue culture plastic after their enzymatic dissociation from other cells in the SVF. During culture, the typical ASC phenotype emerges, e.g. the secretion of a plethora of growth factors, cytokines, matrix proteases and extracellular matrix molecules. 9 Furthermore, these cells are able to differentiate into ectodermal 10 , endodermal 11 or mesenchymal cell-lineages. 12 Therefore, ASC seem to be suitable for cell-based therapy to repair damaged tissue in organs and aged skin. 13 For example, in cardiology ASC are already used for the clinical experimental treatment of ischemic cardiomyopathy 14 to repair heart muscle cells, in orthopedics ASC are used to treat intervertebrate disc degeneration 15 and in cosmetic facial surgeryASC are reported to be beneficial for skin rejuvenation. 16 The SVF of adipose tissue comprises all non-adipocyte cells, e.g. fibroblasts, leukocytes, endothelial cells, and the connecting extracellular matrix (ECM). 17 As a whole, the SVF potentially harbors more therapeutic capacity than the ASC alone: the ECM can augment tissue remodeling, because it acts as a temporary scaffold that also contains matrix remodeling enzymes and because it serves as a slow-release reservoir of growth factors. Moreover, the fragmented microvasculature may augment reperfusion after injection of SVF. 18-21 Therefore, it would be ideal to harvest this SVF fraction as an intact and injectable ‘unit’ to be used in amore specificway such as in cell-based therapy. This SVF can be isolated from adipose tissue either by means of enzymatic dissociation or by means of mechanical dissociation. Most enzymatic techniques used thus far for isolating the SVF from adipose tissue use collagenase. 22 Main disadvantage of all these enzymatic techniques is that they are rather time-consuming and expensive, but also that enzymatic treatment disrupts all communicative connections that exist between the cells as well as between the cells and ECM.Moreover, legislation in several countries does not allow to clinically apply cell-based products that are derived with collagenase. Mechanical dissociation of adipose tissue to isolate the SVF, however, might be more suitable as compared to enzymatic dissociation, because mechanical dissociation of