The extracellular matrix is a novel attribute of endothelial progenitors and of hypoxic mature endothelial cells

Extracellular matrix (ECM) production is critical to preserve the function and integrity of mature blood vessels. Toward the engineering of blood vessels, studies have centered on ECM production by supporting cells, whereas few studies implicate endothelial cells (ECs) with ECM synthesis. Here, we elucidate variations between cultured human arterial, venous, and progenitor ECs with respect to ECM deposition assembly, composition, and response to biomolecular and physiological factors. Our studies reveal that progenitor ECs, endothelial colony-forming cells (ECFCs), deposit collagen IV, fibronectin, and laminin that assemble to an organized weblike structure, as confirmed by decellularized cultures. Mature ECs only express these ECM proteins intracellularly. ECFC-derived ECM is abrogated in response to TGF beta signaling inhibition and actin cytoskeleton disruption. Hypoxic (1%) and physiological (5%) O-2 tension stimulate ECM deposition from mature ECs. Interestingly, deposition of collagen I is observed only under 5% O-2 tension. ECM production from all ECs is found to be regulated by hypoxia-inducible factors 1 alpha and 2 alpha but differentially in the different cell lines. Collectively, we suggest that ECM deposition and assembly by ECs is dependent on maturation stage and oxygen supply and that these findings can be harnessed to advance engineered vascular therapeutics.-Kusuma, S., Zhao, S., Gerecht, S. The extracellular matrix is a novel attribute of endothelial progenitors and of hypoxic mature endothelial cells. FASEB J. 26, 4925-4936 (2012). www.fasebj.org