Role of the TGF-β pathway in dedifferentiation of human mature adipocytes.

Dedifferentiation of adipocytes contributes to the generation of a proliferative cell population that could be useful in cellular therapy or tissue engineering. Adipocytes can dedifferentiate into precursor cells to acquire a fibroblast-like phenotype using ceiling culture, in which the buoyancy of fat cells is exploited to allow them to adhere to the inner surface of a container. Ceiling culture is usually performed in flasks, which limits the ability to test various culture conditions. Using a new six-well plate ceiling culture approach, we examined the relevance of TGF-β signaling during dedifferentiation. Adipose tissue samples from patients undergoing bariatric surgery were digested with collagenase, and cell suspensions were used for ceiling cultures. Using the six-well plate approach, cells were treated with SB431542 (an inhibitor of TGF-β receptor ALK5) or human TGF-β1 during dedifferentiation. Gene expression was measured in these cultures and in whole adipose tissue, the stromal-vascular fraction (SVF), mature adipocytes, and dedifferentiated fat (DFAT) cells. TGF-β1 and collagen type I alpha 1 (COL1A1) gene expression was significantly higher in DFAT cells compared to whole adipose tissue samples and SVF cells. TGF-β1, COL1A1, and COL6A3 gene expression was significantly higher at day 12 of dedifferentiation compared to day 0. In the six-well plate model, treatment with TGF-β1 or SB431542, respectively, stimulated and inhibited the TGF-β pathway as shown by increased TGF-β1, TGF-β2, COL1A1, and COL6A3 gene expression and decreased expression of TGF-β1, COL1A1, COL1A2, and COL6A3, respectively. Treatment of DFAT cells with TGF-β1 increased the phosphorylation level of SMAD 2 and SMAD 3. Thus, a new six-well plate model for ceiling culture allowed us to demonstrate a role for TGF-β in modulating collagen gene expression during dedifferentiation of mature adipocytes.