Endothelial colony-forming cells to study bleeding or vascular malformation disorders - opportunities and limitations.

Hemostasis relies on a balance between procoagulant and anticoagulant factors involving interactions among the vascular endothelium, platelets, and multiple coagulation proteins. Disturbed hemostasis can result in clinical bleeding symptoms. Widely used diagnostic laboratory assays evaluate platelet count, platelet function, and various coagulation factors present in plasma, as typically studied in patients with bleeding, whereas endothelial cell function cannot be studied in this same manner. Measuring vascular endothelium function could indirectly be done using endothelial colony-forming cells (ECFCs), but this is not an assay readily used in diagnostic laboratories. ECFCs are true endothelial progenitor cells that can be isolated from peripheral blood. They exhibit great proliferative potential to form colonies in vitro and actively participate in angiogenesis; therefore, they are an excellent ex vivo model for studying several conditions where the vascular endothelium is involved. In this review, we provide a comprehensive overview of the use of ECFCs as a disease model to study various bleeding and vascular malformation disorders. Additionally, we discuss both advantages and (future) challenges associated with the use of ECFCs.