DIFFERENTIATION OF EMBRYONIC STEM-CELLS INTO ADIPOCYTES IN-VITRO

Embryonic stem cells, derived from the inner cell mass of murine blast ocysts, can be maintained in a totipotent state in vitro, In appropria te conditions embryonic stem cells have been shown to differentiate in vitro into various derivatives of all three primary germ layers, We d escribe in this paper conditions to induce differentiation of embryoni c stem cells reliably and at high efficiency into adipocytes. A prereq uisite is to treat early developing embryonic stem cell-derived embryo id bodies with retinoic acid for a precise period of time, Retinoic ac id could not be substituted by adipogenic hormones nor by potent activ ators of peroxisome proliferator-activated receptors. Treatment with r etinoic acid resulted in the subsequent appearance of large clusters o f mature adipocytes in embryoid body outgrowths, Lipogenic and lipolyt ic activities as well as high level expression of adipocyte specific g enes could be detected in these cultures. Analysis of expression of po tential adipogenic genes, such as peroxisome proliferator-activated re ceptors gamma and delta and CCAAT/enhancer binding protein beta, durin g differentiation of retinoic acid-treated embryoid bodies has been pe rformed, The temporal pattern of expression of genes encoding these nu clear factors resembled that found during mouse embryogenesis. The dif ferentiation of embryonic stem cells into adipocytes will provide an i nvaluable model for the characterisation of the role of genes expresse d during the adipocyte development programme and for the identificatio n of new adipogenic regulatory genes.