Pro-haemostatic effect of DDAVP is partially derived through non-classical (CD14dim /CD16++ ) monocytes residing the spleen

The splenic endothelial Weibel-palade bodies are one of the most important candidate organelles to release von Willebrand factor upon stimulation with desmopressin. However, the presence of functional desmopressin-specific receptor has not yet been demonstrated on endothelial cells. Experimental evidences are in favour of an indirect pro-haemostatic effect of desmopressin, but the exact mediator and its cellular origin are largely elusive. Here, we report partially hampered desmopressin response in a splenectomised severe haemophilia A/Beta Thalassemia patient without any genetic variant relevant to his incomplete desmopressin response. To further investigate the role of the spleen in this phenomenon, the release of VWF from desmopressin-treated human splenic endothelial cells was assessed in vitro. As a result, desmopressin induced the release of VWF from endothelial cells when the cells were co-cultured with non-classical (CD14^dim /CD16⁺⁺ ), but not other subtypes of monocytes or PBMCs. This in vitro study which resembles close proximity of endothelial cells of sinusoids to monocyte reservoir reside in parenchyma of subcapsular red pulp of the spleen sheds a light upon the role of this highly vascularized VWF-producing organ in driving indirect effect of desmopressin.

Pure ultra-fine carbon particles do not exert pro-coagulation and inflammatory effects on microvascular endothelial cells

Pro-thrombotic and inflammatory changes play an important role in cardiovascular morbidity and mortality, resulting from short-term exposure to fine particulate air-pollution. Part of those effects has been attributed to the ultra-fine particles (UFPs) that pass through the lung and directly contact blood-exposed and circulating cells. Despite UFP-induced platelet activation, it is unclear whether the penetrated particles exert any direct effect on endothelial cells. While exposure levels are boosting as a result of world-wide increases in economic development and desertification, which create more air-polluted regions, as well as increase in demands for synthetic UFPs in medicine and various industries, further studies on the health effects of these particles are required. In this study, human pulmonary and cardiac microvascular endothelial cells (MECs) have been exposed to 0.1, 1, 10, and 100 μg/ml suspensions of either a natural (carbon black) or a synthetic (multi-walled carbon nano-tubes) type of UFPs, in vitro. As a result, no changes in the levels of coagulation factor VIII, Von Willebrand factor, Interleukin 8, and P-selectin measured in the cells' supernatant were observed prior to and 6, 12, and 24 h after exposure. In parallel, the spatio-temporal effect of UFPs on cardiac MECs was evaluated by Transmission Electron Microscopy. Despite phagocytic uptake of pure UFPs observed on cellular sections of the treated cells, Weibel-Palade bodies remained intact in shape and similar in number when compared with the untreated cells. Our work shows that carbon itself is a non-toxic carrier for endothelial cells.