Li Ying, Ryan Johannah, Xu Fei, Vostal Jaroslav G
Laboratory of Cellular Hematology, Division of Blood Components and Devices, Office of Blood Research and Review, Food and Drug Administration, Silver Spring, MD, United States.
Front Med (Lausanne). 2019 Dec 17;6:300. doi: 10.3389/fmed.2019.00300. eCollection 2019.
Sepsis is often accompanied with thrombocytopenia partly due to platelet sequestration in the lung and liver. The spleen can store up to one-third of circulating platelets and can also significantly affect platelet transfusion outcomes by accumulating platelets. However, in sepsis, it is not clear whether there are platelet changes in the spleen which could contribute to sepsis-associated thrombocytopenia and also influence platelet transfusion outcomes. By using confocal microscopy, we examined endogenous rat platelets and infused human platelets in the spleen of severe combined immune deficient Rag2 KO rats which were injected intraperitoneally with lipopolysaccharide (LPS). LPS-injected Rag2 KO rats developed sepsis as indicated by increased TNFa, IL-6, IL-1b, and IL-10 levels and thrombocytopenia. Large platelet aggregates were observed in the spleen with majority located in the marginal zone and closely associated with CD169+ macrophages. Depletion of macrophages by clodrosome resulted in reduction of LPS-induced cytokine generation and alleviated LPS-induced thrombocytopenia. Macrophage depletion also remarkedly diminished large platelet aggregate formation in the splenic marginal zone but had less effect on those in red pulp. Infusion of human platelets into LPS-injected rats failed to raise platelet counts in the peripheral blood. In LPS-injected rat spleen, human platelets interacted with aggregated rat platelets in the marginal zone. In contrast, human platelets infused into control rats were located outside of splenic marginal zone. This study provides morphological evidence of platelet aggregates in the splenic marginal zone in sepsis which can interact with infused platelets and thus can contribute to platelet infusion refractoriness in sepsis. It indicates that macrophages play an important role in LPS-associated thrombocytopenia. It also suggests that CD169+ macrophages support platelet aggregate formation in the splenic marginal zone.
脓毒症常伴有血小板减少，部分原因是血小板在肺和肝脏中被隔离。脾脏可储存多达三分之一的循环血小板，并且还可通过积聚血小板显著影响血小板输注结果。然而，在脓毒症中，尚不清楚脾脏中是否存在血小板变化，这些变化可能导致脓毒症相关的血小板减少，并影响血小板输注结果。通过共聚焦显微镜，我们检查了严重联合免疫缺陷Rag2基因敲除大鼠脾脏中的内源性大鼠血小板和输注的人血小板，这些大鼠经腹腔注射脂多糖（LPS）。注射LPS的Rag2基因敲除大鼠出现脓毒症，表现为TNFα、IL-6、IL-1β和IL-10水平升高以及血小板减少。在脾脏中观察到大的血小板聚集体，大多数位于边缘区并与CD169+巨噬细胞密切相关。用氯膦酸盐清除巨噬细胞可减少LPS诱导的细胞因子生成，并减轻LPS诱导的血小板减少。巨噬细胞清除还显著减少了脾边缘区大的血小板聚集体形成，但对红髓中的聚集体影响较小。将人血小板输注到注射LPS的大鼠中未能提高外周血中的血小板计数。在注射LPS的大鼠脾脏中，人血小板与边缘区聚集的大鼠血小板相互作用。相比之下，输注到对照大鼠中的人血小板位于脾边缘区之外。本研究提供了脓毒症中脾边缘区血小板聚集体的形态学证据，其可与输注的血小板相互作用，从而导致脓毒症中血小板输注无效。这表明巨噬细胞在LPS相关的血小板减少中起重要作用。这也提示CD169+巨噬细胞支持脾边缘区血小板聚集体的形成。
