Differentiation of human adipose stromal cells in vitro into insulin-sensitive adipocytes

Adipose tissue-related diseases such as obesity and type 2 diabetes are worldwide epidemics. In order to develop adipose tissue cultures in vitro that mimic more faithfully the in vivo physiology, new well-characterized and publicly accepted differentiation methods of human adipose stem cells are needed. The aims of this study are (1) to improve the existing natural adipose tissue extract (ATE)-based induction method and (2) to study the effects of a differentiation method on insulin responsiveness of the resulting adipocytes. Different induction media were applied on human adipose stromal cell (hASC) monocultures to study the differentiation capacity of the induction media and the functionality of the differentiated adipocytes. Cells were differentiated for 14 days to assess triglyceride accumulation per cell and adipocyte-specific gene expression (PPARγ, adiponectin, AP2, leptin, Glut4, Prdm16, CIDEA, PGC1-α, RIP140, UCP and ADCY5). Insulin response was studied by measuring glucose uptake and inhibition of lipolysis after incubation with 100 or 500 nM insulin. The selected differentiation method included a 3-day induction with ATE, 6 days in serum-free medium supplemented with 1.15 μM insulin and 9.06 μM Troglitazone, followed by 4 days in a defined serum- and insulin-free stimulation medium. This protocol induced prominent general adipocyte gene expression, including markers for both brown and white adipocytes and triglyceride accumulation. Moreover, the cells were sensitive to insulin as observed from increased glucose uptake and inhibition of lipolysis. This differentiation protocol provides a promising approach for the induction of hASC adipogenesis to obtain functional and mature human adipocytes.