Preterm birth is an important cause of perinatal brain injury (PBI). Neurological injury in extremely preterm infants often begins in utero with chorioamnionitis (CHORIO) or inflammation/infection of the placenta and concomitant placental insufficiency. Studies in humans have shown dysregulated inflammatory signaling throughout the placental-fetal brain axis and altered peripheral immune responses in children born preterm with cerebral palsy (CP). We hypothesized that peripheral immune responses would be altered in our well-established rat model of CP. Specifically, we proposed that isolated peripheral blood mononuclear cells (PBMCs) would be hyperresponsive to a second hit of inflammation throughout an extended postnatal time course. Pregnant Sprague-Dawley dams underwent a laparotomy on embryonic day 18 (E18) with occlusion of the uterine arteries (for 60 min) followed by intra-amniotic injection of lipopolysaccharide (LPS, 4 μg/sac) to induce injury in utero. Shams underwent laparotomy only, with equivalent duration of anesthesia. Laparotomies were then closed, and the rat pups were born at E22. PBMCs were isolated from pups on postnatal day 7 (P7) and P21, and subsequently stimulated in vitro with LPS for 3 or 24 h. A secreted inflammatory profile analysis of conditioned media was performed using multiplex electrochemiluminescent immunoassays, and the composition of inflammatory cells was assayed with flow cytometry (FC). Results indicate that CHORIO PBMCs challenged with LPS are hyperreactive and secrete significantly more tumor necrosis factor α (TNFα) and C-X-C chemokine ligand 1 at P7. FC confirmed increased intracellular TNFα in CHORIO pups at P7 following LPS stimulation, in addition to increased numbers of CD11b/c immunopositive myeloid cells. Notably, TNFα secretion was sustained until P21, with increased interleukin 6, concomitant with increased expression of integrin β1, suggesting both sustained peripheral immune hyperreactivity and a heightened activation state. Taken together, these data indicate that in utero injury primes the immune system and augments enhanced inflammatory signaling. The insidious effects of primed peripheral immune cells may compound PBI secondary to CHORIO and/or placental insufficiency, and thereby render the brain susceptible to future chronic neurological disease. Further understanding of inflammatory mechanisms in PBI may yield clinically important biomarkers and facilitate individualized repair strategies and treatments.

中文翻译：

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大鼠绒毛膜羊膜炎会导致产后炎症淋巴细胞高反应性延长。


早产是围产期脑损伤（PBI）的重要原因。极早产儿的神经损伤通常在子宫内开始，伴有绒毛膜羊膜炎 (CHORIO) 或胎盘炎症/感染以及伴随的胎盘功能不全。对人类的研究表明，整个胎盘-胎儿脑轴的炎症信号失调，并改变了早产脑瘫（CP）儿童的外周免疫反应。我们假设，在我们完善的 CP 大鼠模型中，外周免疫反应会发生改变。具体来说，我们提出，在较长的产后时间过程中，分离的外周血单核细胞（PBMC）会对第二次炎症反应过度反应。怀孕的 Sprague-Dawley 母鼠在胚胎第 18 天（E18）接受剖腹手术，闭塞子宫动脉（60 分钟），然后羊膜内注射脂多糖（LPS，4 μg/sac）以诱导子宫损伤。沙姆斯仅接受剖腹手术，麻醉时间相同。然后关闭剖腹手术，幼鼠在 E22 出生。在出生后第 7 天 (P7) 和 P21 从幼崽中分离 PBMC，随后用 LPS 在体外刺激 3 或 24 小时。使用多重电化学发光免疫测定法对条件培养基的分泌炎症谱进行分析，并使用流式细胞术（FC）测定炎症细胞的组成。结果表明，用 LPS 攻击的 CHORIO PBMC 在 P7 时反应过度，并分泌显着更多的肿瘤坏死因子 α (TNFα) 和 CXC 趋化因子配体 1。 FC 证实，除了 CD11b/c 免疫阳性骨髓细胞数量增加外，LPS 刺激后第 7 代的 CHORIO 幼崽的细胞内 TNFα 也增加。 值得注意的是，TNFα 分泌持续到 P21，白细胞介素 6 增加，同时整合素 β1 表达增加，表明持续的外周免疫高反应性和增强的激活状态。综上所述，这些数据表明，子宫内损伤会启动免疫系统并增强炎症信号传导。已启动的外周免疫细胞的潜在影响可能会加剧继发于 CHORIO 和/或胎盘功能不全的 PBI，从而使大脑容易患上未来的慢性神经系统疾病。进一步了解 PBI 中的炎症机制可能会产生临床上重要的生物标志物，并促进个体化的修复策略和治疗。