Session: 06-05-02: Biomedical Devices, Sensors, and Actuators

Paper Number: 142470

142470 - Comparison of Shear Stress Response on Immortalized Cells to Primary Cells in Stent Analysis 

Vascular stenting is considered a primary method for treating stenosis, although it frequently leads to an undesired post-operative side effect where the expanded vessels experience another constriction/restenosis. One theorized cause of this phenomenon is the inadequacy of endothelial cell (EC) coverage (i.e., inadequate endothelization) on stents. To address this drawback, several studies have proposed to promote endothelization on stent by modifying its surface. However, many of these studies remiss to include the effect of wall shear stress (WSS) when assessing the effect of such stent modifications on endothelization. Even with some studies that consider WSS by introducing flow in the investigation, the short evaluation periods, that is 24 hours, limit the validity of their conclusions. This short duration of experiment is primarily caused from the type of EC used, namely primary ECs which are ECs directly extracted from specific blood vessels. These types of ECs are incapable of surviving in a long-term experiment.

With the existence of immortalized ECs which are more resilient and capable of withstanding long duration of experiment, the potential that such ECs have in extending the flow-based experiment period is considerably high. However, since they are essentially mutated primary ECs, confirming that they respond similarly to WSS as their primary counterpart is crucial. As such, this study aims to confirm the suitability of immortalized ECs as a substitute of primary EC in flow-based stent modification evaluation by comparing their WSS response to that of primary ECs.

To achieve this objective, two batches of cells were used: Human Carotid Artery Endothelial Cell (HCtAEC) and Human Umbilical Vein Endothelial Cell – SV40 transfected (HUVEC-SV40). The former represents the primary ECs while the latter represents the immortalized cells. Both cells were cultured until 80-90% confluent, from which point they would be attached to the base of a flow chamber. Inside the flow chamber, both batches were then exposed to 2 Pa and 3 Pa shear stress. After flow exposure, their behaviors were then observed by fluoroscopy and further compared. Two parameters were chosen and observed to determine the behavioral change: Stress Fiber Orientation and Cell Elongation. Stress fiber orientation is used as an indicator to determine the alignment of the endothelial cell, whereas cell elongation is used as an indicator to determine cell morphological change under the influence of shear stress. To ensure the validity of the result, three samples of ECs were considered for each shear stress condition. In addition to that, both samples of ECs also include control samples. They are samples left in a static environment.

Under the stated conditions, this study reveals that both HUVEC-SV40 and HCtAEC undergo similar behavioral changes under shear stress. To be more precise, both ECs undergo elongation when exposed to shear stresses, while the ones left in a static condition experience no significant morphological changes. A slight disparity was found between the two samples, however, where the nuclear orientation of the HCtAEC tends to align with the flowrate direction as opposed to the randomly oriented HUVEC-SV40 samples. Despite that, observation of the stress fiber on both cells implies alignment of both cells to the flow direction. A normal distribution was found in the histogram considering the EC orientation, where the peak for both types of ECs occurring at the direction parallel to the flow direction. Furthermore, a comparison with previous studies indicates that HUVEC primary cells also align themselves with the flow direction in an analogous manner to the cells used in this study.

Thus, this study finds the immortalized cells to be suitable for flow-based stent surface modification analysis.  

Presenting Author: Hanif Saifurrahman Tohoku University

Presenting Author Biography: Hanif Saifurrahman, B.Eng, M. Eng, is currently a P.hD. candidate affiliated with Tohoku University. He has actively participated in researches on flow chamber and stent analysis ever since his Masters, and has been involved in collaborations with several stent modification researchers ranging from Prof. Naofumi Ohtsu from Kitami Institute of Technology, Japan and Dr. Jedlovszky-Hajdú Angéla (egyetemi docens) from Semmelweis University, Hungary. As a member of Japanese Society of Mechanical Engineering, he also participated in some of their conferences and will be participating in the upcoming ones as well. His attendance ASME is targeted to broaden his horizon on other scopes of research, as well as expanding his network.

Authors:

Hanif Saifurrahman Tohoku University
Zi Wang Institute of Fluid Science, Tohoku University
Kazuyoshi Jin Tohoku University
Naofumi Ohtsu Kitami Institute of Technology
Makoto Ohta Institute of Fluid Science, Tohoku University