Expression of O-glycosylated oncofetal fibronectin in alternatively activated human macrophages

Macrophage (M phi) polarization is an essential phenomenon for the maintenance of homeostasis and tissue repair, and represents the event by which M phi reach divergent functional phenotypes as a result to specific stimuli and/or microenvironmental signals. M phi can be polarized into two main phenotypes, M1 or classically activated and M2 or alternatively activated. These two categories diverge in many aspects, such as secreted cytokines, markers of cell surface, and biological functions. Over the last 10 years, many potential markers have been proposed for both M1 and M2 human M phi. However, there is scarce information regarding the glycophenotype adopted by these cells. Here, we show that M2- but not M1-polarized M phi expresses high levels of an unusual glycoform of fibronectin (FN), named O-glycosylated oncofetal FN (onf-FN), found in fetal/cancer cells, but not in healthy tissues. The onf-FN expression was confirmed in vitro by Western blot and real-time RT-qPCR in primary and cell line monocyte-derived M phi. onf-FN was induced by IL-4 and IL-13, but not by pro-inflammatory stimuli (LPS and INF-gamma). RNA and protein analysis clearly demonstrated that it is specifically associated with the M2 polarization. In conclusion, we show by the first time that O-glycosylated onf-FN is expressed by M2-polarized M phi.