Traumatic brain injury (TBI) is a chronic, life threatening injury for which few effective interventions are available. Evidence in animal models suggests un-checked immune activation may contribute to the pathophysiology. Changes in regional density of active brain microglia can be quantified in vivo with positron emission topography (PET) with the relatively selective radiotracer, peripheral benzodiazepine receptor 28 (11 C-PBR28). Phenotypic assessment (activated vs resting) can subsequently be assessed (ex vivo) using morphological techniques. To elucidate the mechanistic contribution of immune cells in due to TBI, we employed a hybrid approach involving both in vivo (11 C-PBR28 PET) and ex vivo (morphology) to elucidate the role of immune cells in a controlled cortical impact (CCI), a rodent model for TBI. Density of activated brain microglia/macrophages was quantified 120 hours after injury using the standardized uptake value (SUV) approach. Ex vivo morphological analysis from specific brain regions using IBA-1 antibodies differentiated ramified (resting) from amoeboid (activated) immune cells. Additional immunostaining of PBRs facilitated co-localization of PBRs with IBA-1 staining to further validate PET data. Injured animals displayed greater PBR28suv when compared to sham animals. Immunohistochemistry demonstrated elevated density of amoeboid microglia/macrophages in the ipsilateral dentate gyrus, corpus callosum, thalami and injury penumbra of injured animals compared to sham animals. PBR co-stained with amoeboid microglia/macrophages in the injury penumbra and not with astrocytes. These data suggest the technologies evaluated may serve as bio-signatures of neuroinflammation following severe brain injury in small animals, potentially enabling in vivo tracking of neuroinflammation following TBI and cellular-based therapies.

创伤性脑损伤 (TBI) 是一种慢性、危及生命的损伤，几乎没有有效的干预措施。动物模型中的证据表明，未经检查的免疫激活可能有助于病理生理学。活性脑小胶质细胞区域密度的变化可以通过正电子发射形貌 (PET) 与相对选择性的放射性示踪剂、外周苯二氮卓受体 28 (11 C-PBR28) 在体内量化。随后可以使用形态学技术评估表型评估（激活与静止）（离体）。为了阐明免疫细胞在 TBI 中的机制贡献，我们采用了一种涉及体内（11 C-PBR28 PET）和体外（形态学）的混合方法来阐明免疫细胞在受控皮质影响 (CCI) 中的作用，一种用于 TBI 的啮齿动物模型。使用标准化摄取值 (SUV) 方法在受伤后 120 小时量化活化的脑小胶质细胞/巨噬细胞的密度。使用 IBA-1 抗体对特定大脑区域进行离体形态学分析，从变形虫（激活）免疫细胞分化出分支（静止）。PBR 的额外免疫染色促进了 PBR 与 IBA-1 染色的共定位，以进一步验证 PET 数据。与假动物相比，受伤的动物表现出更大的 PBR28suv。免疫组织化学表明，与假手术动物相比，受伤动物的同侧齿状回、胼胝体、丘脑和损伤半暗带中变形虫小胶质细胞/巨噬细胞的密度升高。PBR 与损伤半暗带中的变形虫小胶质细胞/巨噬细胞共染色，而不与星形胶质细胞共染色。