A role for preadipocytes as macrophage-like cells

Several lines of evidence have supported a link betweeen adipose tissue and immunocompetent cells. This link is illustrated in obesity, where excess a diposity and impaired immune function have been described in both humans an d genetically obese rodents. In addition, numerous factors involved in infl ammatory response are secreted by both preadipocytes and macrophages. Here we show that proliferating preadipocytes in cell lines and primary cultures , develop phagocytic activity toward microorganisms. This is demonstrated b y phagocytosis assays and confocal microscopy. This function disappears whe n preadipocytes stop proliferating and differentiate into adipocytes. After phagocytosis, preadipocytes show microbicide activity via an oxygen-depend ent mechanism. In addition, preadipocytes as well as adipocytes are stained with MOMA-2, a marker of monocyte-macrophage lineage, but are negative for specific mature macrophage markers (F4/80 and Mac-1). These results sugges t that preadipocytes could function as macrophage-like cells and raise the possibility of a potential direct involvement of adipose tissue in inflamma tory processes.