Medical Scientist Training Program, University of Iowa, Iowa City, IA, USA.
Iowa Institute of Human Genetics, Bioinformatics Division, University of Iowa, Iowa City, IA, USA.
J Neuroinflammation. 2021 Jul 5;18(1):151. doi: 10.1186/s12974-021-02197-w.
Traumatic brain injury (TBI) is a leading cause of death and disability that lacks neuroprotective therapies. Following a TBI, secondary injury response pathways are activated and contribute to ongoing neurodegeneration. Microglia and astrocytes are critical neuroimmune modulators with early and persistent reactivity following a TBI. Although histologic glial reactivity is well established, a precise understanding of microglia and astrocyte function following trauma remains unknown.
Adult male C57BL/6J mice underwent either fluid percussion or sham injury. RNA sequencing of concurrently isolated microglia and astrocytes was conducted 7 days post-injury to evaluate cell-type-specific transcriptional responses to TBI. Dual in situ hybridization and immunofluorescence were used to validate the TBI-induced gene expression changes in microglia and astrocytes and to identify spatial orientation of cells expressing these genes. Comparative analysis was performed between our glial transcriptomes and those from prior reports in mild TBI and other neurologic diseases to determine if severe TBI induces unique states of microglial and astrocyte activation.
Our findings revealed sustained, lineage-specific transcriptional changes in both microglia and astrocytes, with microglia showing a greater transcriptional response than astrocytes at this subacute time point. Microglia and astrocytes showed overlapping enrichment for genes related to type I interferon signaling and MHC class I antigen presentation. The microglia and astrocyte transcriptional response to severe TBI was distinct from prior reports in mild TBI and other neurodegenerative and neuroinflammatory diseases.
Concurrent lineage-specific analysis revealed novel TBI-specific transcriptional changes; these findings highlight the importance of cell-type-specific analysis of glial reactivity following TBI and may assist with the identification of novel, targeted therapies.
创伤性脑损伤（TBI）是导致死亡和残疾的主要原因，目前缺乏神经保护疗法。TBI 后，继发性损伤反应途径被激活，导致持续的神经退行性变。小胶质细胞和星形胶质细胞是关键的神经免疫调节剂，在 TBI 后具有早期和持续的反应性。尽管组织学上的神经胶质反应已经得到很好的证实，但对于创伤后小胶质细胞和星形胶质细胞的功能仍缺乏精确的了解。
成年雄性 C57BL/6J 小鼠接受液压冲击或假手术。伤后 7 天，同时分离小胶质细胞和星形胶质细胞进行 RNA 测序，以评估细胞类型特异性转录反应对 TBI 的影响。双重原位杂交和免疫荧光用于验证 TBI 诱导的小胶质细胞和星形胶质细胞基因表达变化，并确定表达这些基因的细胞的空间取向。将我们的神经胶质转录组与轻度 TBI 和其他神经疾病的先前报告进行比较分析，以确定严重 TBI 是否诱导小胶质细胞和星形胶质细胞激活的独特状态。
我们的研究结果表明，小胶质细胞和星形胶质细胞均表现出持续的、谱系特异性的转录变化，在这个亚急性时间点，小胶质细胞的转录反应大于星形胶质细胞。小胶质细胞和星形胶质细胞均富集与 I 型干扰素信号和 MHC Ⅰ类抗原呈递相关的基因。严重 TBI 对小胶质细胞和星形胶质细胞的转录反应与轻度 TBI 和其他神经退行性和神经炎症性疾病的先前报告不同。
同时进行的谱系特异性分析揭示了新的 TBI 特异性转录变化；这些发现强调了 TBI 后神经胶质反应的细胞类型特异性分析的重要性，并可能有助于鉴定新的、有针对性的治疗方法。
