Department of Mechanical and Industrial Engineering, New Jersey Institute of Technology, Newark, New Jersey, USA.
J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, Florida, USA.
Microcirculation. 2024 Oct;31(7):e12875. doi: 10.1111/micc.12875. Epub 2024 Jul 11.
Tortuous microvessels are characteristic of microvascular remodeling associated with numerous physiological and pathological scenarios. Three-dimensional (3D) hemodynamics in tortuous microvessels influenced by red blood cells (RBCs), however, are largely unknown, and important questions remain. Is blood viscosity influenced by vessel tortuosity? How do RBC dynamics affect wall shear stress (WSS) patterns and the near-wall cell-free layer (CFL) over a range of conditions? The objective of this work was to parameterize hemodynamic characteristics unique to a tortuous microvessel.
RBC-resolved simulations were performed using an immersed boundary method-based 3D fluid dynamics solver. A representative tortuous microvessel was selected from a stimulated angiogenic network obtained from imaging of the rat mesentery and digitally reconstructed for the simulations. The representative microvessel was a venule with a diameter of approximately 20 μm. The model assumes a constant diameter along the vessel length and does not consider variations due to endothelial cell shapes or the endothelial surface layer.
Microvessel tortuosity was observed to increase blood apparent viscosity compared to a straight tube by up to 26%. WSS spatial variations in high curvature regions reached 23.6 dyne/cm over the vessel cross-section. The magnitudes of WSS and CFL thickness variations due to tortuosity were strongly influenced by shear rate and negligibly influenced by tube hematocrit levels.
New findings from this work reveal unique tortuosity-dependent hemodynamic characteristics over a range of conditions. The results provide new thought-provoking information to better understand the contribution of tortuous vessels in physiological and pathological processes and help improve reduced-order models.
迂曲的微血管是与许多生理和病理情况相关的微血管重构的特征。然而，由红细胞（RBC）引起的迂曲微血管中的三维（3D）血液动力学在很大程度上是未知的，并且存在重要问题。血管迂曲会影响血液粘度吗？在一系列条件下，RBC 动力学如何影响壁面切应力（WSS）模式和近壁无细胞层（CFL）？这项工作的目的是参数化迂曲微血管特有的血液动力学特征。
使用基于浸入边界法的 3D 流体动力学求解器进行 RBC 分辨模拟。从大鼠肠系膜成像中获得的刺激血管生成网络中选择了一个代表性的迂曲微血管，并对其进行了数字重建以进行模拟。代表性的微血管是直径约为 20μm 的小静脉。该模型假设血管长度内的直径恒定，并且不考虑由于内皮细胞形状或内皮表面层而导致的变化。
与直管相比，微血管迂曲度观察到使血液表观粘度增加了高达 26%。在整个血管横截面上，高曲率区域的 WSS 空间变化达到 23.6 达因/厘米。由于迂曲度引起的 WSS 和 CFL 厚度变化的幅度强烈受到剪切率的影响，而受管血细胞比容水平的影响可以忽略不计。
这项工作的新发现揭示了在一系列条件下独特的迂曲依赖性血液动力学特征。结果提供了新的发人深省的信息，有助于更好地理解迂曲血管在生理和病理过程中的贡献，并有助于改进降阶模型。
