Human White Adipocytes Convert Into "Rainbow" Adipocytes In Vitro

White adipocytes are plastic cells able to reversibly transdifferentiate into brown adipocytes and into epithelial glandular cells under physiologic stimuli in vivo. These plastic properties could be used in future for regenerative medicine, but are incompletely explored in their details. Here, we focused on plastic properties of human mature adipocytes (MA) combining gene expression profile through microarray analysis with morphologic data obtained by electron and time lapse microscopy. Primary MA showed the classic morphology and gene expression profile of functional mature adipocytes. Notably, despite their committed status, MA expressed high levels of reprogramming genes. MA from ceiling cultures underwent transdifferentiation toward fibroblast-like cells with a well-differentiated morphology and maintaining stem cell gene signatures. The main morphologic aspect of the transdifferentiation process was the secretion of large lipid droplets and the development of organelles necessary for exocrine secretion further supported the liposecretion process. Of note, electron microscope findings suggesting liposecretion phenomena were found also in explants of human fat and rarely in vivo in fat biopsies from obese patients. In conclusion, both MA and post-liposecretion adipocytes show a well-differentiated phenotype with stem cell properties in line with the extraordinary plasticity of adipocytes in vivo.