Novel Vascular Roles of Human Endoglin in Pathophysiology

Endoglin, alias CD105, is a human membrane glycoprotein highly expressed in vascular endothelial cells. It is involved in angiogenesis and in angiogenesis-related diseases, including the rare vascular pathology known as hereditary hemorrhagic telangectasia type 1. Although endoglin acts as an accessory receptor for members of the transforming growth factor-β (TGF-β) family, in recent years emerging evidences have shown a novel functional role for this protein beyond the TGF-β system. In fact, endoglin has been found to be an integrin counter-receptor involved in endothelial cell adhesion processes during pathological-inflammatory conditions and primary haemostasis. Furthermore, a circulating form of endoglin (sEng) whose levels are abnormality increased in different pathological conditions like preeclampsia, seems to act as an antagonist of membrane-bound endoglin and as a competitor of the fibrinogen-integrin interaction in platelet-dependent thrombus formation. These studies suggest that membrane-bound endoglin and circulating endoglin are important components involved in vascular homeostasis and in hemostasis.