Background: Facial lipoatrophy, a common alteration among HIV-1-infected, antiretroviral-treated patients, is often corrected using autologous transplantation. In some cases, especially when enlarged adipose tissue from the dorso-cervical area (that is, a 'buffalo hump') is used as a source of fat for transplantation, the transplanted fat develops progressive hypertrophy. To gain insight into the molecular basis of this phenomenon, we evaluated the cell morphology and gene expression in this hypertrophied facial fat.
Methods: Quantitative real-time PCR was used to examine the expression of various marker genes in a sample of facial fat that underwent hypertrophy after autologous transplantation. The results were compared with gene expression data from 'buffalo hump' fat and subcutaneous fat from healthy controls. Optical and electron microscopic analyses were used to determine cell morphology.
Results: The enlarged facial adipose tissue did not exhibit the overt microscopic morphology of brown adipose tissue but (similar to 'buffalo hump' fat) it contained adipocytes heterogeneous in size. The enlarged facial fat retained the partial molecular signature of a distorted brown-to-white adipocyte phenotype, including expression of uncoupling protein-1 (UCP1) transcript, and showed unaltered adipogenesis and inflammation that are characteristic of 'buffalo hump' fat.
Conclusions: Despite being implanted in a former lipoatrophic area, facially grafted 'buffalo hump' tissue appears to retain the altered phenotype of dorso-cervical adipose cells, thus accounting for its progressive enlargement. These results argue that caution should be exercised when considering 'buffalo hump' fat depots as a fat source for autologous transplantation.