Joris van Dongen

54 Chapter 2 known that increased centrifugal forces have a harmful effect on the viability of fat grafts 86,87 . However, the use of centrifuged adipose tissue is necessary to determine the actual cell yield after an isolation procedure. Furthermore, cell viability of tSVF should be determined directly on tSVF, instead of using an extra non-intraoperative isolation protocol which possibly results in more cell damage. However, the proposed adjusted standardized endpoints and methods by IFATS and ICTS are time-consuming and expensive since it requires culturedASCs. In order to quicklyverify isolation procedures intraoperatively during clinical trials, the end product of non-enzymatic intraoperative isolation procedures should be centrifuged to separate the oily fraction from the tSVF and pellet fraction based on density. For enzymatic intraoperative isolation procedures, microscopy can be used to visualize single cells. In this way, isolation procedures can be quickly evaluated during clinical trials. Alargenumberof SVFisolationprocedureswithout applyinga fullverificationaccording to the IFATS and ICTS guidelines is available 14 . Oberbauer et al. presented a narrative overview of enzymatic and non-enzymatic intraoperative SVF isolation procedures 14 . In twenty-one out of thirty (both enzymatic as well as non-enzymatic) intraoperative isolation procedures reported in their study, there was a lack of verification data. In two studies intraoperative isolation procedures without scientific evidence e.g. viability of SVF, flow cytometry of SVF cells and ASCs, were used to treat patients. One study used SVF obtained by ultrasonic cavitation to treat patients with migraine and tension headache 88 . Another study used SVF in combination with platelet rich plasma for meniscus repair 89 . Hence, it cannot be guaranteed that the isolation procedures indeed isolate SVF, which is clinical safe for use. It seems that the use of most SVF isolation procedures with its concomitant clinical application is far ahead of a sound scientific base upon which these procedures should be used. Moreover, the clinical safetyof isolated SVForASCs is not clearyet, especially regarding clinical use in patients with any kind of malignancy. It is demonstrated, in vitro , that ASCs influence growth, progression and metastasis of cancer cell lines through e.g. promoting angiogenesis and differentiation of ASCs into carcinoma-associated fibroblasts 90 . Zimmerlin et al. showed in vitro that ASCs influence growth of active malign cell lines, but this is not seen in latent cancer cell lines 91 . Clinical data suggest that the use of isolated SVF orASCs is safe in patients without an oncological history 92 . In vitro studies often use higher concentrations of ASCs as compared to clinical studies and this might be the cause of differences found between in vitro and in vivo studies 92 . However, to test clinical safety it is important to reach scientific validation of the commercially available procedures at an acceptable level. In this review it become clear