Joris van Dongen

331 General discussion and future perspectives extracellular matrix isolated from FAT procedure-obtained SVF plays an important role in binding and releasing growth factors released fromASCs in a controlled fashion. Moreover, these factors are still biologically active over a long release time e.g. stimulate angiogenesis as well as fibroblast proliferation and migration. 16 In contrast to the FAT procedure, many mechanical isolation procedures focus only on the cellular fraction of SVF trying to eliminate extracellular matrix in order to improve injectability. 10,13,17 Probably a significant part of the regenerative capacity of SVF is thereby reduced by reducing the extracellular matrix with pericytes and supra-adventitial cells attached around vessels. To date, the definition of SVF comprising both enzymatic and mechanical isolated SVF should be redefined. According to definitions by pathologists and histologists, stromal tissue is the connective and structural component of every organ throughout the human body. Connective tissue consists of cells and extracellular matrix containing proteins embedded in ground substance. 18 After enzymatic digestion of adipose tissue, all connective tissue i.e. stromal tissue including vascular structures are resolved leaving just the cellular component. To our opinion, mechanically isolated SVF should therefore be named tissue SVF (tSVF) whereas enzymatically isolated SVF should be named cellular SVF (cSVF). 12 In 2006, Coleman was the first to mention regenerative effects of lipofilling. 19 Coleman described less wrinkles and an increased skin quality of the ageing face e.g. reduced pigmentation and reduced number of pores after autologous lipofilling. Though, no formal scientific proof was given because of a lack of statistics and objective validated measurement outcomes. Besides, the addition of subcutaneous volume by autologous lipofilling causes wrinkles to disappear. Since 2006, multiple case series as well as retrospective and prospective studies have investigated the effects of autologous lipofilling to ageing facial skin showing positive results. 20-25 In comparison with Coleman’s first report, most of these studies lack a good study design with validated measurement outcomes as well as a control group. In contrast, in this thesis, two well- designed prospective randomized placebo-controlled double-blinded clinical trials showed that lipofilling with and without additives i.e. tSVF or platelet rich plasma (PRP) does not improve skin elasticity of ageing facial skin nor patient satisfaction. 26,27 On the other hand, the addition of PRP to lipofilling reduced postoperative recovery time. A possible explanation for the reduced recovery time is that lipofilling is an invasive procedure causing many minor (sub)cutaneous traumas. Recovery from these iatrogenic traumas e.g. small wounds might benefit from released growth factors from additional platelets.