Thrombomodulin Activity of Fat-Derived Microvascular Endothelial Cells Seeded on Expanded Polytetrafluorethylene

Abstract

Lining the luminal surface of prosthetic vascular grafts with endothelial cells (cell seeding) will lower its thrombogenicity. Commonly used macrovascular human adult endothelial cells (HAEC) require in vitro cultivation before large enough numbers are obtained to cover grafts confluently. Fat-derived microvascular endothelial cells (MVEC) prove to be a good alternative as they can be harvested in much larger numbers while showing similar antithrombotic and fibrinolytic characteristics. An important anticoagulant function of macrovascular endothelial cells is due to the activity of thrombomodulin (TM) on their surface. In this study, the presence and functional activity of TM on fat-derived microvascular cells used in cell seeding was investigated. The expression and localization of TM on MVEC was studied using immunohistochemistry. Functional activity of TM on MVEC was measured by the generation of activated protein C (APC) and was compared to human umbilical vein endothelial cells (HUVEC). TM activity was studied in MVEC seeded on expanded polytetrafluorethylene (ePTFE) vascular prostheses and compared to blank prostheses. We found that TM was expressed on the surface of MVEC, both in vivo and vitro. TM-dependent generation of APC differed significantly between MVEC and HUVEC (3.98 ± 1.2 vs. 3.0 ± 0.7 nM, respectively). After seeding MVEC on vascular prostheses, TM activity did not change. APC generation was significantly higher on MVEC-seeded vascular grafts compared to blank grafts (4.0 ± 0.7 vs. 1.7 ± 0.5 nM, respectively). We conclude that TM is present and highly active on cultured MVEC. When seeded on ePTFE, MVEC retain the possibility to inhibit thrombin coagulant activity and to activate protein C. Therefore, since MVEC are readily available, the anticoagulant properties demonstrated here indicate that this cell type is suitable for cell seeding of vascular prostheses.

The influence of biomaterials on endothelial cell thrombogenicity

“…For example, different levels of ELAM are expressed on HUVEC cultured on knitted versus woven Dacron [151] and different neutrophil adhesion [152], tissue factor and prostacyclin levels have been observed on Dacron grafts versus smooth films [153]. The goal of many of the studies listed [154][155][156][157][158][159][160][161][162][163] was to compare particular vascular graft materials, with or without different ECM coatings, to TCPS, and thus differences can potentially be attributed to topography rather than surface chemistry. EC function has also been shown to depend on cell density and level of confluence [140].…”

Effect of streptavidin–biotin on endothelial vasoregulation and leukocyte adhesion

“…thromboplastin, selectins, cell adhesion molecules) [3,9]. The biochemistry and function of ECs in the lumen of vascular grafts have been examined [17][18][19][20][21][22]. In general, seeded EC exhibit elevated production of PGI 2 , tPA, and PAI-1, and reduced levels of thrombin activity and fibrin formation.…”

Porcine Endothelial Cells Cocultured with Smooth Muscle Cells Became ProcoagulantIn Vitro

“…4 There is some evidence suggesting that the seeded ECs display normal function by the presence of TM and reduced thrombogeneity. 5,6 However, other lines of evidence suggest the opposite; human ECs seeded on expanded polytetrafluoroethylene vascular graft have been reported to release growth factors, plateletderived growth factor, and basic fibroblast growth factor, which cause smooth muscle cell (SMC) proliferation, neointimal fibrous hyperplasia, and graft failure. 7 Human umbilical vein ECs (HUVECs) seeded on Dacron (polyethylene terephthalate) showed less-effective adherence 8 and increased Eselectin expression that favors leukocyte adhesion.…”