Joris van Dongen

98 Chapter 4 colonies, indicating the colony forming function has not been disturbed by both systems. However, only low number of donors were used for experiments which might causes a larger standard deviation of the results and is thus a limitation of this study. Characterization of the composition of cell types in the isolated tSVF can be done by surface marker analysis. In adipose tissue, cells can be divided into two major subpopulations: adipose derived cells (CD45-) and blood derived cells (CD45+). 21 Adipose derived cell populations can be further divided into two main subpopulations: endothelial like cell types (CD31+) and stromal like cell types (CD31-). 21 Three important cell types within the stromal like cell subpopulation (CD45-; CD31-) are the ASCs (CD34+; CD90+; CD105low) and ASCs precursor cells: pericytes (CD34+/- ; CD146+) and supra-adventitial cells (CD34+; CD146-). 11,21-23 However, controversy remains about the ASCs precursor cell types and CD surface marker combinations to identify different adipose tissue cell subpopulations. 11,12,23,24 ASCs and its precursor cells are important cell types because of the secretion of many regenerative growth factors and cytokines. 1,13,14 In comparison to several other mechanical and enzymatic isolation procedures e.g. Automated isolation system, CHA Biotech Station, Lipokit Medikhan System, PNC’s Multistation, Fastem and Lipogems, both types of FAT procedures isolate more stromal cells. 25-28 Enzymatic isolation procedures e.g. Cytori, Tissue Genesis Cell Isolation System, Sepax System showed comparable stromal cell populations. 26,29,30 However, differences in cell subpopulations of cSVF and tSVF could be caused by donor dependent variations and different use of CD surface markers and thus comparisons between studies are difficult. 18-21 The use of the one-hole fractionator seems to offer several advantages over the non- disposable three-hole fractionator. Firstly, any re-usable device could bring a potential risk of contamination and biofilms to grow after sterilization, in particular in the difficult-to-clean small holes. 15,31 Using a disposable fractionator largely eliminates the risk of contamination and thus complies with the most restricted regulations on sterility. Yet, the potential increased risk of contamination in reusable devices in comparison with disposable devices is solely hypothetical instead of based on sterility data, which is another limitation of this study. To even further reduce the risk of contamination during the isolation procedure, a completely closed system could be designed to promote safe clinical use (which has been manufactured in the meantime (ACA-kit, Arthex GmbH, USA). Secondly, in the one-hole fractionator, the opening in the internal disk is situated in the center of the disk resulting in significant fewer blockages. In the original three-hole fractionator, the internal disk contains three holes without a hole in the center of the disk. The tip of the 10 mL syringe faces the center of the three-hole disk in the middle of the fractionator. In this way, blockage of the three-