Abstract
The objective of this study was to develop and validate a flow system capable of simulating in vitro the pulsatile-flow waveform, pressures, and degree of oxygenation of physiological arterial circulation in vivo. We used this model to accurately determine endothelial cell adhesiveness on seeded vascular grafts exposed to physiological shear stress. The system consisted of a pulsatile-flow phantom capable of reproducing physiological arterial flow-including a reverse-flow component-which was filled with a nutritive, oxygenated solution that was of the same viscosity as whole blood. Real-time monitoring of all flow variables allowed continual adjustment of parameters and maintenance of physiological shear stress. To assess cell retention, human umbilical vein endothelial cells were radiolabeled with111indium, seeded onto compliant polyurethane vascular graft segments at a density of 1.8×106 cells/cm2, mounted in series with the flow circuit, and exposed to arterial shear stress for an 8-h period (n=6). Dynamic scintigraphy images were acquired in real time using a nuclear medicine gamma camera system during the 8-h perfusion period. The perfusion medium was tested for cytotoxicity, and the viability of seeded cells was assessed by Alamar Blue assay and scanning electron microscopy. Using the model, the shear stress and flow waveforms of human femoral arterial circulation were successfully simulated. The perfusate (viscosity 0.035 poise) was determined to be noncytotoxic. Postperfusion examination by scanning electron microscopy for known morphological indicators and Alamar Blue colorimetric assay for metabolic activity demonstrated normal cell appearance and activity. This system allows complete simulation of the hemodynamic variables encountered at the luminal surface of the femoral artery, while providing a nontoxic supportive milieu. Investigation of the behavior of seeded endothelial cells can be reliably and accurately undertaken with this system.
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