Department of Mechanical and Aerospace Engineering, Rutgers, The State University of New Jersey, Piscataway, New Jersey.
Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania.
Biophys J. 2014 Jun 3;106(11):2529-40. doi: 10.1016/j.bpj.2014.04.028.
A high-fidelity computational model using a 3D immersed boundary method is used to study platelet dynamics in whole blood. We focus on the 3D effects of the platelet-red blood cell (RBC) interaction on platelet margination and near-wall dynamics in a shear flow. We find that the RBC distribution in whole blood becomes naturally anisotropic and creates local clusters and cavities. A platelet can enter a cavity and use it as an express lane for a fast margination toward the wall. Once near the wall, the 3D nature of the platelet-RBC interaction results in a significant platelet movement in the transverse (vorticity) direction and leads to anisotropic platelet diffusion within the RBC-depleted zone or cell-free layer (CFL). We find that the anisotropy in platelet motion further leads to the formation of platelet clusters, even in the absence of any platelet-platelet adhesion. The transverse motion, and the size and number of the platelet clusters are observed to increase with decreasing CFL thickness. The 3D nature of the platelet-RBC collision also induces fluctuations in off-shear plane orientation and, hence, a rotational diffusion of the platelets. Although most marginated platelets are observed to tumble just outside the RBC-rich zone, platelets further inside the CFL are observed to flow with an intermittent dynamics that alters between sliding and tumbling, as a result of the off-shear plane rotational diffusion, bringing them even closer to the wall. To our knowledge, these new findings are based on the fundamentally 3D nature of the platelet-RBC interaction, and they underscore the importance of using cellular-scale 3D models of whole blood to understand platelet margination and near-wall platelet dynamics.
使用三维浸入边界方法的高保真计算模型用于研究全血中的血小板动力学。我们专注于血小板-红细胞（RBC）相互作用的 3D 效应对剪切流中血小板靠边和近壁动力学的影响。我们发现全血中的 RBC 分布自然呈现各向异性，并形成局部簇和空腔。血小板可以进入空腔，并将其用作快速靠边到壁的快速通道。一旦靠近壁，血小板-RBC 相互作用的 3D 性质导致血小板在横向（涡度）方向上发生显著运动，并导致在 RBC 耗尽区或无细胞层（CFL）内的血小板扩散出现各向异性。我们发现血小板运动的各向异性进一步导致血小板簇的形成，即使在没有任何血小板-血小板粘附的情况下也是如此。横向运动以及血小板簇的大小和数量被观察到随着 CFL 厚度的减小而增加。血小板-RBC 碰撞的 3D 性质还会引起离切平面取向的波动，从而导致血小板的旋转扩散。尽管观察到大多数靠边的血小板在 RBC 丰富区外翻滚，但在 CFL 内部更远的血小板被观察到以间歇性的流动方式流动，在这种流动方式中，滑动和翻滚之间交替，这是由于离切平面的旋转扩散，使它们更接近壁。据我们所知，这些新发现基于血小板-RBC 相互作用的基本 3D 性质，它们强调了使用全血细胞尺度的 3D 模型来理解血小板靠边和近壁血小板动力学的重要性。
