Recombinant human uteroglobin/CC10 inhibits the adhesion and migration of primary human endothelial cells via specific and saturable binding to fibronectin

Uteroglobin (UG) or Clara Cell 10 kDa protein (CC10) is a small, stable, epithelial secretory anti-inflammatory protein. Uteroglobin has been shown to inhibit neointimal formation in vivo after balloon angioplasty through an unknown mechanism. An interaction between UG and plasma fibronectin (Fn) has been demonstrated in mice. Since Fn plays a key role in endothelial cell (EC) migration and angiogenesis, we investigated whether recombinant human UG (rhUG) affects EC migration via Fn binding. In this report, we show a saturable binding of rhUG to Fn depending on Fn conformation and that rhUG is covalently cross-linked to Fn by transglutaminase (TGase). Additionally, our study highlights that rhUG can also bind to exogenously added or self-secreted Fn on the membrane of human primary microvascular endothelial cells (HMVEC), although these complexes are weakly associated with the plasmalemma. Upon the interaction with Fn in solid phase, rhUG strongly inhibits HMVEC attachment on Fn, but not on other ECM proteins. Consequently, rhUG also inhibits cell migration in a dose dependent fashion (I.C.50 = 65 nM) and hinders the "wound healing" in vitro. The small size, stability and human tolerability of rhUG suggest that rhUG in slow-release form or genetically delivered could be used in humans to modulate cell/Fn interactions in the context of tumor microenvironment or in the context of inflammation and fibrosis.