2007 Volume 15 Pages 9-15
Visceral obesity and metabolic syndrome have been recognized to be a leading cause of cardiovascular disease, and chronic inflammation. Adipose tissue remodeling and malfunctioning has been suggested to play a central role in obesity. Adipose tissue contains multiple cell types including stromal cells: adipocytes, macrophages, and endothelial cells, and their interaction is important in obese adipose tissue remodeling including angiogenesis, and adipogenesis, thus leading to a dysfunction at the tissue level. However, little is known about the detailed mechanisms of these cell-cell interactions, because much of the structural and functional integrity of the tissue is lost when it is fixed, processed and sectioned. A visualization technique, based on laser confocal microscopy, was therefore developed that made it possible to precisely evaluate the three-dimensional structures in living tissue, and the cell dynamics in vivo with a high time and spatial resolution. These findings demonstrated a close spatial and temporal interrelationship between blood vessel development and adipogenesis, and both were augmented in animal models of obesity. In obesity, close interactions of activated platelets, leukocytes, and endothelial cells in the vessel walls of adipose tissue was also observed by in vivo imaging. The activating status of the macrophages that infiltrated the adipose tissue was altered, and the expression of adhesion molecules in adipose tissue increased in the macrophages as well as in endothelial cells. Platelets were activated locally in obesity, and the vascular permeability also increased. Such abnormal cell-cell interactions could be a cause of obese adipose tissue remodeling and, as a result, they could be a potentially useful therapeutic target.
