Fat Cell Progenitors: Origins and Plasticity

A pool of adipocyte progenitors remains present in adipose tissue during adult life. This pool is responsible for regeneration of adipocytes and for the potential of this tissue to expand in response to chronic energy overload. However, the factors controlling proliferation and differentiation of human adipocyte progenitors are largely unknown. We will present stem cells derived from human adipose tissue, termed (hMADS) cells, as an appropriate cell model for studying proliferation and differentiation of adipocyte progenitors. We will describe the plasticity of hMADS cells and will show, in this chapter, that FGF2 and activin A are key regulators of their self-renewal. The developmental origin of adipocytes has been largely disregarded until now. We report recent observations emerging from adipocyte differentiation of mouse embryonic stem cells and from in vivo lineage tracing studies that have revealed two origins for adipocytes. We also discuss the differentiation of human induced pluripotent stem cells into adipocytes. This novel model might be a powerful tool to investigate the earliest developmental events of human adipogenesis.