Dynamic actin remodeling mediates lipid droplet secretion during adipocyte dedifferentiation

Abstract

Adipocyte plasticity is an important aspect of adipose tissue remodeling in response to changing metabolic demands. Adipocyte dedifferentiation has recently received attention as a mechanism underlying adipocyte plasticity. However, the absence of adequate experimental platforms for studying the cellular mechanisms of adipocyte dedifferentiation has been a constraint. Here, we developed a microscope-mountable ceiling culture chip that enables long-term, high-resolution imaging of adipocytes within a tunable microenvironment. Using this platform, we identified Hippo, Hedgehog, and PPARγ signaling pathways to be potent regulators of adipocyte dedifferentiation via pharmacological or genetic manipulation. Live imaging revealed that dedifferentiating adipocytes undergo dynamic actin remodeling to promote lipid droplet (LD) secretion. An expanding hole in the actin shell surrounding the LD was followed by contraction of the condensed actin shell, resulting in LD extrusion. Unexpectedly, we discovered bidirectional intercellular LD exchange between dedifferentiating adipocytes. Our findings shed light on previously unrecognized molecular and cellular processes that underlie adipocyte dedifferentiation.