Abstrakt: |
Background: With aging and atherosclerosis plaque development, endothelial permeability increases leading to blood and platelets (PLT) infiltration into the vascular wall. In the media, vascular smoothmuscle cells (VSMCs) are crucial for clearance of infiltrated molecules and cells including senescent red blood cells (1). Moreover, blood has a high concentration of macromolecules making it a macromolecularly crowded environment (MMC). The objective is to decipher the clearance mechanisms of PLT by VSMCs and the influence of MMC on it. Methods: Human VSMCs were cultured with either human: (i) fresh PLT, (ii) ADP-activated PLT, (iii) senescent PLT. PLT and VSMCs were stained with fluorescent tracers prior their co-culture. We also cultured VSMC in media supplemented with crowders to mimic MMC. Results: After three or seven days of co-culture, we observed that activated and/or senescent PLT, which are characterized by phosphatidylserine exposure, were localized within VSMCs. In contrast to fresh red blood cells that are not phagocytosed by VSMCs, fresh PLT were also entrapped within VSMCs. We then stained VSMCs with phalloidin, an actin filament dye, revealing that PLT are surrounded by an actin shell within the VSMC. In addition, we observed that MMC modified the deposition of extracellular matrix (fibronectin, laminin and sugar moieties) by VSMCs. Conclusions: VSMCs engulf PLT with an actin-dependent endocytosis process and MMC modifies the secretory phenotype of VSMC. PLT engulfment could be an inducible pathogenic event that is responsible for VSMC phenotypic switching in atherosclerosis and their procoagulant status. [ABSTRACT FROM AUTHOR] |