White HM, Acton AJ, Kamocka MM, Considine RV. Hepatocyte growth factor regulates neovascularization in developing fat pads. Am J Physiol Endocrinol Metab 306: E189 -E196, 2014. First published December 3, 2013 doi:10.1152/ajpendo.00394.2013In this study, we used lentiviral-delivered shRNA to generate a clonal line of 3T3-F442A preadipocytes with stable silencing of hepatocyte growth factor (HGF) expression and examined the long-term consequence of this modification on fat pad development. HGF mRNA expression was reduced 94%, and HGF secretion 79% (P Ͻ 0.01), compared with preadipocytes treated with nontargeting shRNA. Fat pads derived from HGF knockdown preadipocytes were significantly smaller (P Ͻ 0.01) than control pads beginning at 3 days postinjection (0.022 Ϯ 0.003 vs. 0.037 Ϯ 0.004 g), and further decreased in size at day 7 (0.015 Ϯ 0.004 vs. 0.037 Ϯ 0.003 g) and day 14 (0.008 Ϯ 0.002 vs. 0.045 Ϯ 0.007 g). Expression of the endothelial cell genes TIE1 and PECAM1 increased over time in control fat pads (1.6 Ϯ 0.4 vs. 11.4 Ϯ 1.7 relative units at day 3 and 14, respectively; P Ͻ 0.05) but not in HGF knockdown fat pads (1.1 Ϯ 0.5 vs. 5.9 Ϯ 2.2 relative units at day 3 and 14). Contiguous vascular structures were observed in control fat pads but were much less developed in HGF knockdown fat pads. Differentiation of preadipocytes to mature adipocytes was significantly attenuated in HGF knockdown fat pads. Fat pads derived from preadipocytes with knockdown of the HGF receptor c-MET were smaller than control pads at day 3 postinjection (0.034 Ϯ 0.002 vs. 0.049 Ϯ 0.004 g; P Ͻ 0.05), and remained the same size through day 14. c-MET knockdown fat pads developed a robust vasculature, and preadipocytes differentiated to mature adipocytes. Overall these data suggest that preadipocyte-secreted HGF is an important regulator of neovascularization in developing fat pads. neovascularization; 3T3-F442A; TIE-1; PECAM-1; peroxisome proliferator-activated receptor-␥; lipoprotein lipase THERE IS INTENSE INTEREST in understanding the function of the adipose tissue vasculature in health and disease. It is known that angiogenesis is required to support the substantial growth potential of adipose tissue and that angiogenesis plays a critical role in the development of obesity (8,20,31). On the other hand, a number of studies have suggested that in obesity the adipose tissue is hypoxic, either due to rarefaction or insufficient blood flow, and that adipose tissue hypoxia is a root cause of the chronic inflammation characteristic of obesity (28, 31). In related areas of inquiry, studies to understand adipocyteregulated vascular growth are expected to provide novel insight into the mechanisms responsible for the greater risk of cancer in obese subjects (27), and there continues to be an active interest in targeting the adipose tissue vasculature as a means of treating and/or preventing obesity (5, 13, 34).Our laboratory is investigating the role of hepatocyte growth factor (HGF), a potent angiogenic and mitogenic factor, in the regulati...