Molecular and morphologic characterization of superficial- and deep-subcutaneous adipose tissue subdivisions in human obesity

Objective Human abdominal subcutaneous white adipose tissue (SAT) is composed of two different subcompartments: a superficial SAT (SSAT), located between the skin and a fibrous-fascia plane; and a deeper SAT, located under this fibrous fascia plane, indicated as deep SAT (DSAT). Design and Methods In order to investigate whether SSAT and DSAT have different molecular and morphological features, paired SSAT/DSAT biopsies were collected from 10 female obese patients and used for microarray and morphologic analysis. The stroma-vascular fraction cells were also isolated from both depots and cultured in vitro to assess the lipid accumulation rate. Results SSAT and DSAT displayed different patterns of gene expression, mainly for metabolic and inflammatory genes, respectively. Detailed gene expression analysis indicated that several metabolic genes, including adiponectin, are preferentially expressed in SSAT, whereas inflammatory genes are over-expressed in DSAT. Despite a similar lipid accumulation rate in vitro, in vivo SSAT showed a significant adipocyte hypertrophy together with a significantly lower inflammatory infiltration and vascular vessel lumen mean size, when compared to DSAT. Conclusions These data show that, SSAT and DSAT are functionally and morphologically different and emphasize the importance of considering independent these two adipose depots when investigating SAT biology and obesity complications.