Response of human mature adipocytes to hypoxia-reoxygenation.

Adipocytes are metabolically active cells and have endocrine functions, such as cytokine secretion. Notably, adipocytes are found underneath skin and are thought to be involved in the body's response to ischemia-reperfusion (I-R). I-R injury is an important factor in the pathogenesis of chronic skin wounds. In this study, we investigated the response of human adipocytes to hypoxia-reoxygenation (H-R), the in vitro equivalent of I-R. We cultured human mature adipocytes by enclosing them in hydrogel composed of hyaluronan and collagen and analyzed their proliferation and response to H-R. The average diameter of mature adipocytes isolated from abdominal subcutaneous fat tissue was between 60 and 109 μm, and a positive correlation was found between adipocyte size and body mass index. Hydrogel-enclosed human adipocytes displayed viability in in vitro culture and were capable of expressing foreign genes for at least 1 month. Proliferation analysis revealed 5-bromo-2'-deoxy-uridine labeling and positive Ki67 signaling. vascular endothelial growth factor expression was differentially altered in adipocytes in response to hypoxia and H-R. Adipocyte messenger RNA expression of pro-inflammatory cytokines, such as interleukin-1, interleukin-8 and tumor necrosis factor-α, was upregulated in response to H-R. In addition, the expression of heat shock protein 70, a cytoprotective gene, and inducible nitric oxide synthase, a proapoptotic gene, were both increased in H-R. Survival of hydrogel-enclosed adipocytes was found at 2 months after delivery into athymic mice. These and previous results from our group show that mature adipocytes can be cultured in vitro within a matrix and that they are functionally active cells that respond to environmental changes.