Influence of Recipient Site on the Function and Survival of Fat Grafts.

[BACKGROUND] Autologous fat grafting has become an increasingly common procedure for soft tissue augmentation throughout the body. However, the long-term outcome is always unpredictable because of inconsistent graft survival. Based on the "law of use and disuse," we speculate that the volume loss of fat grafts will occur when transferred into a site where there is less fat. The purpose of this study is to investigate the cause of high resorption rate from the perspective of fat function after transplantation.

[METHODS] Adipose aspirates obtained from routine liposuction were injected into the dorsal site of athymic mice, which have no subcutaneous fat layer. The fat grafts were explanted at days 7, 15, and 30 after transplantation. Changes in fat function were evaluated by measuring the adipocyte size and the expression level of adipose differentiation-related protein.

[RESULTS] After grafting, adipose tissue was replaced by fibrosis, inflammation, and vacuolar tissues gradually over time. The size of fat cells decreased sharply from day 0 to day 7, increased at day 15, and further declined at day 30. Adipose differentiation-related protein expression experienced a dramatic increase at day 7 and then continuously decreased until day 30.

[CONCLUSIONS] Assuming that the extrinsic factors influencing fat function and distribution remain stable, capabilities of the redistributed fat to handle free fatty acid and store lipid substance are reduced, leading to substantial tissue atrophy and volume decline after grafting.