TY - JOUR Y1 - 2020/01// A1 - McCormack, JJ A1 - Harrison-Lavoie, K A1 - Cutler, DF IS - 1 AV - public JF - Journal of Thrombosis and Haemostasis EP - 254 SN - 1538-7836 N1 - This version is the author accepted manuscript . For information on re-use, please refer to the publisher?s terms and conditions. ID - discovery10082089 VL - 18 N2 - BACKGROUND: The secretory granules of endothelial cells, Weibel-Palade bodies, are released in response to numerous extracellular signals. Their cargo is critical to many vascular functions including haemostasis and inflammation. This presents a fundamental problem; how can these cells initiate tailor-made responses from the release of a single type of organelle, each with similar cargo? Each cell contains Weibel-Palade bodies in a wide range of sizes, and we have shown that experimentally-shortening these organelles disproportionately reduces their ability to initiate haemostasis in vitro, leaving leukocyte recruitment unaffected. Could the production of this range of sizes underpin differential responses? OBJECTIVES: To determine whether different agonists drive the exocytosis of different sizes of Weibel-Palade bodies. METHODS: We used a high-throughput automated unbiased imaging workflow to analyse the sizes of Weibel-Palade bodies within HUVECs before and after agonist activation to determine changes in organelle size distributions. RESULTS: We found that a subset of agonists differentially evoke the release of the longest, most pro-haemostatic organelles. Inhibiting the release of these longest organelles by just 15% gives a fall of 60% in an assay of secreted VWF function. CONCLUSIONS: The size-selection of granules for exocytosis represents a novel layer of control, allowing endothelial cells to provide diverse responses to different signals via the release of a single type of organelle. TI - Human endothelial cells size-select their secretory granules for exocytosis to modulate their functional output KW - Endothelial Cells KW - Exocytosis KW - Organelle Size KW - Weibel-Palade Bodies KW - von Willebrand Factor UR - https://doi.org/10.1111/jth.14634 SP - 243 ER -