In vitro adipocytic conversion in Meckel's chondrocytes in response to a fatty acid-containing medium.

Chick serum (CKS) contains factors that stimulate adipocytes in Meckel's chondrocytes in vitro. In the present study, we analyzed levels of fatty acids in CKS, and further examined whether these had the potential to convert chondrocytes to adipocytes. Phenotypic changes were evaluated by light and electron microscopies, bromodeoxyuridine (BrdU) incorporation, triglyceride assays, and immunocytochemistry. We showed that CKS contained high levels of fatty acids, and a mixed medium containing 5 particular fatty acids inhibited DNA synthesis and the proliferation of chondrocytes as it facilitated their differentiation into adipocytes. The adipocytes produced were sudan-positive multilocular cells that morphologically and histochemically resembled adipocytes induced by the CKS-containing medium. Almost all lipid droplet-containing cells were positive for leptin and alpha-glycerophosphate dehydrogenase (GPDH), as evaluated by immunoperoxidase staining, and their triglyceride concentrations markedly increased during 4 to 6 days of culture. These results suggested that specific fatty acids in CKS are involved in the adipocytic conversion of Meckel's chondrocytes.