Fig. 3.

Characterization of module thrombogenicity using whole-blood studies. (a) Clot formation times. The presence of HUVEC on the modules significantly increased the time to clot formation (P = 1.4 × 10⁻⁵) of slightly heparinized whole blood (0.75 units/ml) in a clotting test. In some cases, clot formation never actually occurred, and the test was terminated between 4,500 and 5,400 s; in these instances, the recorded time was the test termination time. Mean clot time is represented by the thick central line within the box. Open circles and stars represent outliers and extreme outliers, respectively. (b) Fresh whole blood (0.75 units/ml heparin) perfused through a HUVEC-covered modular construct (filled circles) maintains platelet levels no different from those measured in the absence of modules (open circles, flow circuit blank; includes polypropylene mesh required to keep modules in place). Blood perfusion through a control modular construct in which HUVEC have been removed by dispase–collagenase action (open squares), however, results in significant reductions in platelet number, indicating platelet activation and the thrombogenic response that occurs in the absence of HUVEC. Error bars indicate SEM (n = 3, 4, and 7 for background, dispase-treated modular constructs, and HUVEC-covered modular constructs, respectively).