Cytochemical studies on the fibroblast-preadipocyte relationships in cultured fibroblast cell lines

The theoretical basis of adipogenesis has always been a matter of debate. O ne concept suggests that all types of adipocytes are derived from undiffere ntiated connective tissue cells, whereas another concept suggests that adip ocytes develop from specialized cells only that are able to accumulate fat. Many conflicting data have been published with respect to the transition o f fibroblasts into preadipocytes. For example, this transition has been dec lared as impossible for dermal and perimysial fibroblasts. The present stud y analysed spontaneous accumulation of fat in various types of fibroblasts from different origin (retroocular, skin, NIH/3T3, and L929). It was found that intense Oil Red O-positive triglyceride-containing droplets accumulate d in practically all types of fibroblasts provided that the cells were cult ured on glass surface. When the cells were cultured on plastic surfaces, li pid staining was inhibited in a variable manner: inhibition was virtually c omplete in skin fibroblasts, whereas in other types of fibroblasts, inhibit ion was only partial. It is concluded that all types of fibroblasts can acc umulate fat spontaneously, and thus can be considered as preadipocytes. The refore, interpretations of data obtained with cultures of fibroblasts with respect to adipogenesis have to be reconsidered.