Analysis of Fat Graft Metabolic Adaptation and Vascularization Using Positron Emission Tomography–Computed Tomographic Imaging

BACKGROUND: Fat tissue transfer is commonly used for different soft-tissue defects in surgery. The immediate result of these operations is often good, but the long-term result is unfortunately unpredictable. The authors used an experimental model to evaluate the vascularization, survival, and metabolic changes after free fat transfer and the impact of proangiogenic therapy on these processes. METHODS: Fat was collected from the mouse epididymal region and placed into the subcutaneous tissue of the forehead. Fat grafts were treated with proangiogenic vascular endothelial growth factor (VEGF)-A (n = 9) or the control vector (n = 9). Metabolic activity and fat graft volume were investigated by positron emission tomography-computed tomography at 4 weeks and at 12 weeks. Histologic analysis was performed at 12 weeks. RESULTS: The glucose metabolism (fluorodeoxyglucose uptake) of the transferred epididymal fat was higher than in the epididymal fat before transplantation in both study groups (VEGF-A and control) and resembled that of normal subcutaneous fat. VEGF-A therapy enhanced the survival and capillary density of the transferred fat after surgery. CONCLUSIONS: Transfer of the metabolically inactive (epididymal) fat into a new environment modulated the metabolic activity of the fat grafts to resemble the situation in the recipient site. These novel findings support the clinical use of free fat grafts in various anatomical regions and tissue types. Proangiogenic VEGF-A therapy enhanced the vascularization and survival of the free fat grafts.