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E. W. Lee, N. A. Tucker; Comparison of Orbital Fat and Subcutaneous Body Fat. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1340.
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The use of autologous fat to restore volume deficiencies in the periorbital region has been well-described in the literature. Various techniques have been reported, such as fat injection using body fat, and fat repositioning using orbital fat. However, it is not known whether one source is superior. We hypothesize that orbital fat is superior due to structural differences on a cellular level compared to subcutaneous body fat.We investigated the histologic, structural, and immunohistochemical differences between orbital fat and subcutaneous body fat.
A prospective study was conducted with IRB approval comparing 6 samples of orbital fat, and 6 samples of subcutaneous body fat (age- and gender-matched) which were obtained intraoperatively. Digital microscopy image analysis (Automated Cellular Imaging System; Clarient Inc., Aliso Viejo, CA) was used to determine the proportion of stromal composition and amount of nuclear staining present in hematoxylin-eosin stained sections of orbital and subcutaneous fat samples. Immunohistochemical staining for peroxisome proliferator-activated receptor-gamma (PPAR-gamma), a known marker of adipogenesis, was also performed for each sample of orbital and subcutaneous body fat.
The mean percentage of stromal staining in the orbital fat group was 13.75±3.37% (mean±std dev) compared to subcutaneous body fat group, 7.96±2.62% (p-value 0.008). The mean percentage of nuclear staining in the orbital fat group was 1.65±1.02% compared to the subcutaneous fat group, 1.09±0.45% (p-value 0.251). The mean percentage of PPAR-gamma positive nuclei in the orbital fat group was 19.3% compared to 30.1% in the subcutaneous body fat group (p-value 0.08).
The amount of stromal composition was significantly higher in the orbital fat group compared to the subcutaneous fat group. This may be explained by the fact that orbital fat appears to be organized into smaller lobules compared to subcutaneous body fat resulting in a greater proportion of interlobular stroma per given volume of fat. This may explain why orbital fat is grossly softer and more compliant than body fat. The amount of nuclear staining was not significantly different between the two groups suggesting that the actual number of cells per given volume are similar between the two groups.The proportion of PPAR-gamma positive nuclei was greater in the body fat group, although this was not statistically significant. This may reflect a higher turnover of adipocytes in body fat compared to orbital fat.
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