PURPOSE Dysregulation of polymorphonuclear neutrophil (PMN) biology is associated with the development of inflammatory complications after trauma, such as acute respiratory distress syndrome (ARDS). It has been demonstrated that intramedullary nailing is both associated with altered pulmonary neutrophil deposition and the occurrence of ARDS. This standardized study aimed to characterize the long-term remote neutrophil response in the lungs in case of a femur fracture and intramedullary nailing. METHODS A standardized rat model including intramedullary nailing and a femur fracture was utilized. Groups were terminated after observation times of three, seven and 14 days. Neutrophils were isolated from lung parenchyma and broncho-alveolar lavage fluid (BALF) and analyzed by flow cytometry. Absolute neutrophil numbers as well as membrane expression levels of CD11b, CD62L, and CD11a were compared. RESULTS Pulmonary neutrophil numbers were increased 3 days after intervention. Membrane expression levels of CD11b (P < 0.01), CD62L (P < 0.01), and CD11a (P = 0.06) on parenchymal PMNs increased as well after 3 days. Thereafter, values restored gradually to physiological levels. Furthermore, neutrophil activation status patterns between parenchymal and BALF neutrophil pools did not correlate. CONCLUSIONS The current study demonstrates that IMN and a femur fracture are associated with transient increased pulmonary PMN deposition, as well as a specific pattern of activation characterized by temporary increased selectin and integrin receptor expression on pulmonary neutrophils. This phenomenon might play an important role in the pathomechanism of ARDS after IMN. Moreover, we found striking differences between parenchymal and BALF-neutrophil populations, demonstrating the limited readout potential of BALF analysis to investigate the entire pulmonary neutrophil pool.

中文翻译：

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髓内钉对啮齿动物肺中性粒细胞池特征的影响。


目的 多形核中性粒细胞 (PMN) 生物学功能失调与创伤后炎症并发症的发生有关，例如急性呼吸窘迫综合征 (ARDS)。已经证明，髓内钉固定与肺中性粒细胞沉积的改变和 ARDS 的发生有关。这项标准化研究旨在表征股骨骨折和髓内钉固定情况下肺部的长期远程中性粒细胞反应。方法 采用包括髓内钉固定和股骨骨折的标准化大鼠模型。观察3天、7天和14天后终止各组。从肺实质和支气管肺泡灌洗液（BALF）中分离出中性粒细胞，并通过流式细胞术进行分析。比较中性粒细胞的绝对数量以及 CD11b、CD62L 和 CD11a 的膜表达水平。结果 干预后 3 天，肺中性粒细胞数量增加。 3天后，实质PMN上的CD11b (P < 0.01)、CD62L (P < 0.01) 和CD11a (P = 0.06) 的膜表达水平也增加。此后，数值逐渐恢复至生理水平。此外，实质和 BALF 中性粒细胞池之间的中性粒细胞激活状态模式不相关。结论 目前的研究表明，IMN 和股骨骨折与肺部 PMN 沉积的短暂增加以及以肺中性粒细胞上选择素和整合素受体表达暂时增加为特征的特定激活模式相关。这种现象可能在IMN后ARDS的病理机制中发挥重要作用。 此外，我们发现肺实质和 BALF 中性粒细胞群之间存在显着差异，这表明 BALF 分析在研究整个肺中性粒细胞库时的读数潜力有限。