Model Construction And Numerical Simulation Of Arterial Remodeling After Stent Implantation With Variations Of Cell Concentration

The mechanism of in-stent restenosis after percutaneous coronary intervention has not yet been elucidated.The difference in molecular concentration will lead to the diffusion of molecules to lower concentrations.Similarly,it can be speculated that the concentration of the cell will also affect the distribution of cell proliferation,thereby affecting the process of vascular remodeling.Therefore,it is necessary to explore the role of cell concentration in vascular remodeling.Methods of building computer models to probe the biomechanical and mechanobiological mechanisms of pathophysiological processes have been widely used.Most of the current research on remodeling models is based on a single injury without taking into account the feedback of stress and geometry.Therefore,we investigated two questions:(1)explored the effect of differences in cell concentration on arterial remodeling;and(2)explored a bidirectional coupled model that can update arterial stress and geometry.For the first problem: We used finite element and agent-based models to simulate the process of smooth muscle cell injury and proliferation induced by stent implantation in coronary arteries.The expansion of the stent in the coronary artery was simulated in the finite element model,and the stent expansion stress on the vessel wall was input into the agent-based model.Then smooth muscle cells underwent stress injury,and proliferated under the regulation of matrix metalloproteinases and extracellular matrix,gradually reduced the level of injury.Smooth muscle cells were randomly distributed within a defined domain,and the number of surrounding cells was used to indicate changes in concentration,cell locations with the least number of surrounding cells proliferated preferentially.Simulations and comparative analyses were carried out for the cases with and without concentration effects,respectively.For the second problem: We built a bidirectional coupling of finite element and agent-based models.The smooth muscle cells in agent based model formed a new intima on the arterial wall after growth,and the shape of the wall changed.Three cross-sectional profiles after vessel growth were extracted,reconstructed to generate3 D solids,and the stress of the vessel wall after growth was recalculated.Took it as a new input to the agent-based model,and then entered a new round of growth simulation,which realized the bidirectional coupling of stress and geometry.Based on this,the stress and lumen changes in the process of arterial remodeling and the formation of arterial homeostasis were simulated and analyzed.The simulation results showed that,after stent implantation,severely damaged smooth muscle cells in the stent-supported area first proliferated and gradually extended toward the lumen until the artery reached a steady state.Compared with no concentration effect,the smooth muscle cells proliferated faster,the number of newly generated smooth muscle cells was more,and the intima formed by the artery was thicker after adding the concentration effect.The bidirectional coupling model showed that the stress value of the arteries after growth decreased,the number of smooth muscle cells satisfying the growth was significantly reduced,and the lumen area was further reduced.Cells could make full use of the lumen space for growth under the influence of concentration,so the effect of concentration is of great significance on arterial remodeling.The bidirectional coupling model could simulate the process of reducing lumen and stress in the artery,and more realistically show the process of arterial remodeling.