Tissue-engineered microvessels on three-dimensional biodegradable scaffolds using human endothelial progenitor cells

Abstract

Tissue engineering may offer patients new options when replacement or repair of an organ is needed. However, most tissues will require a microvascular network to supply oxygen and nutrients. One strategy for creating a microvascular network would be promotion of vasculogenesis in situ by seeding vascular progenitor cells within the biopolymeric construct. To pursue this strategy, we isolated CD34(+)/CD133(+) endothelial progenitor cells (EPC) from human umbilical cord blood and expanded the cells ex vivo as EPC-derived endothelial cells (EC). The EPC lost expression of the stem cell marker CD133 but continued to express the endothelial markers KDR/VEGF-R2, VE-cadherin, CD31, von Willebrand factor, and E-selectin. The cells were also shown to mediate calcium-dependent adhesion of HL-60 cells, a human promyelocytic leukemia cell line, providing evidence for a proinflammatory endothelial phenotype. The EPC-derived EC maintained this endothelial phenotype when expanded in roller bottles and subsequently seeded on polyglycolic acid-poly-l-lactic acid (PGA-PLLA) scaffolds, but microvessel formation was not observed. In contrast, EPC-derived EC seeded with human smooth muscle cells formed capillary-like structures throughout the scaffold (76.5 +/- 35 microvessels/mm(2)). These results indicate that 1) EPC-derived EC can be expanded in vitro and seeded on biodegradable scaffolds with preservation of endothelial phenotype and 2) EPC-derived EC seeded with human smooth muscle cells form microvessels on porous PGA-PLLA scaffolds. These properties indicate that EPC may be well suited for creating microvascular networks within tissue-engineered constructs.

Review:Ex VivoEngineering of Living Tissues with Adult Stem Cells

“…A second, more recently described, source of multipotent cells is processed lipoaspirate cells from adipose tissue. 16 Aspirates from either source can be harvested during routine elective medical procedures 16,31 and, because of their mesenchymal origin, have been used to engineer such tissues as cartilage, 32 bone, 33 adipose, 34 and blood vessels, 35 as described in Table 1. One difference between adipose tissue-and marrow-derived multipotent cells is their expression of adhesion molecules.…”

“…113 Instead of directly seeding EPCs into a scaffold, the cells can be differentiated before inoculation, as in the case EPC-derived endothelial cells seeded onto preformed tubular scaffolds of polyglycolic-acid and polyurethane. 114 Coculture 35 A vascularized tracheal implant has been constructed ex vivo using porcine chondrocytes, respiratory epithelial cells, smooth muscle cells, and EPCs seeded onto a scaffold of acellularized porcine small intestine. Three weeks after inoculation, EPCs uniformly re-endothelialized the vascular network within the scaffold.…”

Endothelial progenitor cells from infantile hemangioma and umbilical cord blood display unique cellular responses to endostatin

“…Hence, HemEPCs were so designated based on expression of the stem-cell marker CD133, which is downregulated quickly as the cells are cultured in vitro. 15 Human dermal microvascular ECs (HDMECs) and cord-blood EPCs (cbEPCs) were isolated, as described previously, but cultured in EBM-2/ 20% FBS as noted above. 14,15 In addition, cbEPCs were isolated by a non-CD133-dependent modification described by Lin et al, 16 which takes advantage of the high proliferative potential of EPCs.…”

The Role of Synthetic Extracellular Matrices in Endothelial Progenitor Cell Homing for Treatment of Vascular Disease

“…One vascular tissue engineering strategy is to create blood vessels and primitive vascular networks within biodegradable scaffolds ex vivo for subsequent implantation in vivo. 86 This approach typically involves seeding and culturing the cells on an appropriate scaffold that stimulates cell growth/differentiation and blood vessel formation in vitro. The rationale for this approach is that engineered microvessels might readily form anastomoses with existing vessels in the host and thus accelerate vascularization and improve construct viability.…”

“…The rationale for this approach is that engineered microvessels might readily form anastomoses with existing vessels in the host and thus accelerate vascularization and improve construct viability. 86 However, although cellularized vessels grown and cultured within biomaterial scaffolds have been shown to have strong mechanical properties in vitro, they often lead to thrombosis shortly after implantation in vivo. 34 Hydrogels are a useful class of cell delivery vehicles as they can be delivered in a minimally invasive manner and used to fill irregularly shaped defects, as opposed to scaffold transplantation.…”