Mature adipocytes observed to undergo reproliferation and polyploidy

Lipid-filled mature adipocytes are important for the study of lipid metabolism and in the development of obesity, but whether they are capable of reproliferation is still controversial. Here, we monitored lipid droplet dynamics and adipocyte reproliferation in live, differentiated 3T3-L1 cells using a phase-contrast microscope in real time. Phase-contrast microscopy achieves a similar visual effect in situ to that obtained using traditional dyes such as Oil Red O and BODIPY in vitro. Using this method, we captured the process that lipid droplets use for dynamic fusion in living cells. Unexpectedly, we acquired images of the moment that differentiated 3T3-L1 cells containing lipid droplets entered mitosis. In addition, we observed some binucleated mature adipocytes. This information provides a better understanding of the adipocyte differentiation process.