Fat tissue, Harvesting techniques and processing of fat graft
Adipose tissue is remarkably complex and has a profound role in nutrient
homeostasis and is, due to adipose-derived serum factors like adipsin,
TNF-α and leptin seen as a separate endocrine organ(21). Fat tissue
further has a necessary role in thermogenesis and insulation and
protects important organs like the eyes mechanically (22). Fat tissue
therefore contains a high quantity of cell types. Adipose-derived stem
cells (ASCs) can differentiate into adipocytes, fibroblasts, neurons,
muscles or endothelial cells (8). Zuk et al found regenerative and stem
cells in the stromal vascular fraction (SVF) of fat (23). SVFcells have been shown to have regenerative effects, like angiogenesis
and reduction of inflammation in facial aesthetics. There are reports on
regenerative effects on elastin and collagen fibers and an elevation of
capillary density (24).
Every step in the process of AFG from the choice of the donor
site, donor site preparation, to harvesting over processing to injection
has the potential to influence graft outcome and volume retention (19).
Tuin et al analysed 35 studies to identify the optimal processing
technique. Their outcome was adipocyte viability, ASC survival and
growth factors in vitro, volume of the graft in animal studies and
volume retention in human studies. They discovered no superior
processing technique could be identified based on clinical outcome (25).
Lee et al found no differences in histology and weight with high versus
low aspiration pressure in lipoaspirates injected in nude mice. Shear
stress had a high impact on graft viability, therefore slowly injected
fat grafts outperformed injection with high shear stress (26).