Phenotypic overlap between hematopoietic cells with suggested angioblastic potential and vascular endothelial cells.
The existence of angioblast-like circulating endothelial progenitor cells (EPC) in adult humans has been suggested recently. Their role in postnatal angiogenesis is under intensive investigation. Discrimination between the supposed angioblasts (AC133(+)/FLK-1(+)/CD34(+)) and mature endothelial cells (ECs) is complicated by the fact that subsets of hematopoietic cells express markers similar to those of ECs. Among these, monocytes/macrophages and monocyte-derived dendritic cells (DCs) are more differentiated hematopoietic cell populations. They show a wide phenotypic overlap with particularly sinusoidal and microvascular ECs. Furthermore, under local angiogenic growth conditions, monocytes or monocyte precursors or immature DCs may differentiate into endothelial-like cells (ELC). Initial evidence suggests an endothelium-independent revascularization potential carried by macrophages. These macrophages have been shown to form "tunnel-like structures" in ischemic regions. Future studies will need to address the question of whether monocyte-/dendritic cell-derived ELC can develop a similar functional behavior in vasoregulation, coagulation, and fibrinolysis, as described for vascular ECs, and thus may contribute to neoangiogenesis by a direct vessel-forming role.
Schmeisser
Alexander
A
Department of Cardiology, Medical Clinic II, Technical University Dresden, Fetscherstrasse 76, D-01307 Dresden, Germany. AlexanderSchmeis@t-online.de
Strasser
Ruth H
RH
D000954:Antigens, Surface; D002454:Cell Differentiation; D019070:Cell Lineage; D004730:Endothelium, Vascular / Q000166:cytology* / Q000276:immunology; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000276:immunology / Q000502:physiology; D006801:Humans; D016130:Immunophenotyping; D008264:Macrophages / Q000166:cytology / Q000276:immunology / Q000502:physiology; D009000:Monocytes / Q000166:cytology / Q000276:immunology / Q000502:physiology; D018919:Neovascularization, Physiologic / Q000276:immunology
D000954:Antigens, Surface