Paracrine regulation of angiogenesis and adipocyte differentiation during in vivo adipogenesis

With an increasing incidence of obesity worldwide, rational strategies are needed to control adipogenesis. Growth of any tissue requires the formation of a functional and mature vasculature. To gain mechanistic insight into the link between active adipogenesis and angiogenesis, we developed a model to visualize noninvasively and in real time both angiogenesis and adipogenesis using intravital microscopy. Implanted murine preadipocytes induced vigorous angiogenesis and formed fat pads in a mouse dorsal skin-fold chamber. The newly formed vessels subsequently remodeled into a mature network consisting of arterioles, capillaries, and venules, whereas the preadipocytes differentiated into adipocytes as confirmed by increased aP2 expression. Inhibition of adipocyte differentiation by transfection of preadipocytes with a peroxisome proliferator-activated receptor gamma dominant-negative construct not only abrogated fat tissue formation but also reduced angiogenesis. Surprisingly, inhibition of angiogenesis by vascular endothelial growth factor receptor-2 (VEGFR2) blocking antibody not only reduced angiogenesis and tissue growth but also inhibited preadipocyte differentiation. We found that part of this inhibition stems from the paracrine interaction between endothelial cells and preadipocytes and that VEGF-VEGFR2 signaling in endothelial cells, but not preadipocytes, mediates this process. These findings reveal a reciprocal regulation of adipogenesis and angiogenesis, and suggest that blockade of VEGF signaling can inhibit in vivo adipose tissue formation.