ABSTRACT

Small extracellular vesicles (sEVs) are important mediators of cell–cell communication with respect to diverse physiological processes. To further understand their physiological roles, understanding blood sEV homoeostasis in a quantitative manner is desired. In this study, we propose novel kinetic approaches to estimate the secretion and clearance of mouse plasma–derived sEVs (MP-sEVs) based on the hypothesis that blood sEV concentrations are determined by a balance between the secretion and clearance of sEVs. Using our specific and sensitive sEV labelling technology, we succeeded in analysing MP-sEV clearance from the blood after intravenous administration into mice. This revealed the rapid disappearance of MP-sEVs with a half-life of approximately 7 min. Moreover, the plasma sEV secretion rate, which is presently impossible to directly evaluate, was calculated as 18 μg/min in mice based on pharmacokinetic (PK) analysis. Next, macrophage-depleted mice were prepared as a model of disrupted sEV homoeostasis with retarded sEV clearance. MP-sEV concentrations were increased in macrophage-depleted mice, which probably reflected a shift in the balance of secretion and clearance. Moreover, the increased MP-sEV concentration in macrophage-depleted mice was successfully simulated using calculated clearance rate constant, secretion rate constant and volume of distribution, suggesting the validity of our PK approaches. These results demonstrate that blood sEV concentration homoeostasis can be explained by the dynamics of rapid secretion/clearance.

抽象的

小细胞外囊泡（sEVs）是有关多种生理过程的细胞间通讯的重要介体。为了进一步了解它们的生理作用，需要以定量的方式了解血液sEV的同源性。在这项研究中，我们提出了一种新的动力学方法来估计小鼠血浆来源的sEV（MP-sEVs）的分泌和清除，该假设是血液sEV的浓度取决于sEV的分泌和清除之间的平衡。使用我们特有的敏感sEV标记技术，我们成功地分析了静脉内注射给小鼠后MP-sEV从血液中的清除率。这揭示了MP-sEV的快速消失，其半衰期约为7分钟。此外，目前尚无法直接评估的血浆sEV分泌率，根据药代动力学（PK）分析，小鼠体内的TNF-α被计算为18μg/ min。接下来，将巨噬细胞耗竭的小鼠制备为具有sEV清除延迟的破坏的sEV同质化的模型。巨噬细胞耗竭小鼠中MP-sEV浓度增加，这可能反映了分泌和清除平衡的变化。此外，使用计算的清除率常数，分泌率常数和分布体积成功地模拟了巨噬细胞耗竭小鼠中MP-sEV浓度的增加，这表明我们PK方法的有效性。这些结果表明，血液sEV浓度的稳态可以通过快速分泌/清除的动力学来解释。制备了巨噬细胞耗竭小鼠，将其作为sEV清除受阻的sEV均质破坏模型。MP-sEV浓度在巨噬细胞耗竭的小鼠中增加，这可能反映了分泌和清除的平衡发生了变化。此外，使用计算的清除率常数，分泌率常数和分布体积成功地模拟了巨噬细胞耗竭小鼠中MP-sEV浓度的增加，这表明我们PK方法的有效性。这些结果表明，血液sEV浓度的稳态可以通过快速分泌/清除的动力学来解释。制备了巨噬细胞耗竭小鼠，将其作为sEV清除受阻的sEV均质破坏模型。巨噬细胞耗竭小鼠中MP-sEV浓度增加，这可能反映了分泌和清除平衡的变化。此外，使用计算的清除率常数，分泌率常数和分布体积成功地模拟了巨噬细胞耗竭小鼠中MP-sEV浓度的增加，这表明我们PK方法的有效性。这些结果表明，血液sEV浓度的稳态可以通过快速分泌/清除的动力学来解释。使用计算的清除率常数，分泌率常数和分布体积成功地模拟了巨噬细胞耗竭小鼠中MP-sEV浓度的增加，这表明我们PK方法的有效性。这些结果表明，血液sEV浓度的稳态可以通过快速分泌/清除的动力学来解释。使用计算的清除率常数，分泌率常数和分布体积成功地模拟了巨噬细胞耗竭小鼠中MP-sEV浓度的增加，这表明我们PK方法的有效性。这些结果表明，血液sEV浓度的稳态可以通过快速分泌/清除的动力学来解释。