The Optimal Layer for Breast Augmentation in an Autologous Fat Grafting Murine Model.

BACKGROUND: Fat grafting is an effective procedure for breast augmentation, but the variations in this technique result in unpredictable fat retention. Therefore, animal models are needed to simulate the operation and the optimal layer for fat retention. OBJECTIVES: An autologous fat grafting murine model for breast augmentation was built to detect a new layer for fat grafting in the chest. METHODS: The left side of the female rat inguinal fat flap was harvested, dissected into small pieces, and autotransplanted into 3 different layers of the breast. Retention rate and hematoxylin and eosin (H&E) staining were measured at 1, 4, 8 12, and 16 weeks. Immunofluorescence staining was utilized to detect adipocytes and endothelial cells, and immunohistochemistry was conducted to evaluate the expression of integrins ß1 and α6. RESULTS: The volume of fat grafts slightly grew in the intramuscular and submuscular layers at Week 4. Retention rates in the subcutaneous layer and submuscular layer were significantly higher than the intramuscular layer at Week 16. H&E staining showed that oil cysts existed in the subcutaneous layer throughout the 16 weeks. At the terminal time point, well-vascularized mature adipose structures were observed in intramuscular and submuscular layers, with smaller adipocytes in intramuscular layers. Immunohistochemistry analysis showed that integrin ß1 was identically expressed in every adipocyte in all the layers, whereas integrin α6 selectively expressed in bigger adipocytes in the intramuscular layer. The expression intensities of integrin ß1 and α6 were significantly higher in the intramuscular layer than in the subcutaneous and submuscular layers. CONCLUSIONS: The angiogenic and moderate mechanical environment makes the submuscular layer the optimal layer for fat retention.