Primary cultures of unilocular fat cells: characteristics of growth in vitro and changes in differentiation properties.

Mature white fat tissue consists primarily of unilocular fat cells. Clearly, the study of the biology of these cells would be most helpful for the elucidation of the mechanism of obesity. We describe a new method termed 'ceiling culture' for culturing in vitro unilocular fat cells obtained from humans and rats. These cells can be maintained in culture for long periods of time and, under such conditions, continue to exhibit specific functions such as lipogenesis and lipolysis. Under the culture conditions described, unilocular fat cells change into multilocular fat cells or cells with a fibroblast-like appearance. These cells then proliferate, form a cell monolayer attached to the substratum, and after becoming confluent, exhibit accumulations of intracytoplasmic lipid droplets. These attached dedifferentiated cells continue to exhibit lipogenesis and lipolysis.