Joris van Dongen

91 FAT procedure with a disposable one-hole fractionator INTRODUCTION Adipose tissue has been widely used in regenerative- and reconstructive surgery for its therapeutic potential in the treatment of osteoarthritis, as anti-scarring treatment, to improve wound healing and to compensate for volume loss. 1-4 The therapeutic potential of adipose tissue is often ascribed to the presence of adipose tissue-derived stromal cells (ASCs) in stromal vascular fraction (SVF). 5 SVF of adipose tissue consist of all non-parenchymal i.e. non-adipocyte cell types such as ASCs, fibroblasts, vascular cells, immune cells as well as extracellular matrix (ECM). 6-10 Upon culturing, ASCs develop from their in vivo precursors i.e. pericytes or supra-adventitial cells. 11,12 Cultured ASCs secrete a plethora of growth factors and exosomes that are pro- regenerative and stimulate angiogenesis, promote proliferation of parenchymal cells, suppress apoptosis and modulate immune responses in vivo. 1,13,14 In addition, ASCs secrete ECM components as well as ECM degrading enzymes, which are relevant for tissue remodeling. ASCs are readily isolated from lipoaspirates in high numbers by both enzymatic and mechanical procedures. 15 However, enzymatic isolation is rather costly and time-consuming, because of reagents used such as collagenase that are of non-human origin. 14 Enzymatic isolation procedures result in a single cell suspension of SVF (cSVF) that lacks cell-cell and cell-matrix connections, whereas mechanical isolation procedures result in a tissue-like SVF (tSVF) containing ECM as well as all cell-cell and cell-matrix connections. 15,16 In tSVF, ECM functions as a scaffold for SVF cells and prevents cells from diffusion after injection and therefore might enhances tissue regeneration. Additionally, ECM functions as a slow release reservoir of growth factors. 8,9,17 The interaction between cells and growth factors in tSVF is postulated to increase the regenerative potential as compared to the use of cSVF. One of the recently published mechanical isolation procedures is the ‘Fractionation of Adipose Tissue’ (FAT) procedure, which is a fast and low cost intraoperative procedure to obtain tSVF from adipose tissue. 18 It appeared that the original FAT device and procedure would benefit from improvements for several reasons. Firstly, the original fractionator contains an internal disk with three off-centered holes of 1.4 mm. In our experience, the absence of a central hole in the original fractionator leads to congestion in the device, which makes the FAT procedure less practical. Secondly, the original fractionator is a non-disposable device. In view of patient safety, however, sterile disposable devices are preferred over non-disposable devices. For all the aforementioned reasons, a new disposable one-hole fractionator was developed. The purpose of this study is to compare the one-hole fractionator with the original reusable three-hole fractionator based on the composition of the isolated tSVF.