Department of Neurosurgery, Xijing Hospital, Airforce Military Medical University (Fourth Military Medical University), Xi'an, 710032, China.
Department of Neurosurgery, PLA 422nd Hospital, Zhanjiang, 524005, China.
Neurochem Res. 2019 Apr;44(4):811-828. doi: 10.1007/s11064-018-02714-z. Epub 2019 Jan 9.
MicroRNA-124 (miR-124) is a brain specific miRNA that is highly expressed in microglia. The upregulation of miR-124 contributes to M2 polarization of microglia, which is beneficial to neurogenesis. Exosomes are lipid membrane vesicles that can deliver miR-124 into the brain. However, whether miR-124 enriched exosomes (Exo-miR-124) can regulate the polarization of microglia and affect hippocampus neurogenesis after traumatic brain injury (TBI) is unknown. To clarify this, the Exo-miR-124 was first constructed, and then was intravenously administrated into rats via tail vein with the dose of 3 × 10 particles/each rat at 24 h post TBI. The polarization of microglia in hippocampus was evaluated through measuring the signature genes and cytokines of M1/M2 phenotype by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immune sorbent assay (ELISA) at 7/14/21/28 days after TBI. Hippocampus neurogenesis was evaluated through detecting the proliferation marker BrdU/SOX2 and differentiation marker BrdU/NeuN by immunofluorescence (IF) at 7 and 28 days after TBI respectively. Neurological function was evaluated by neurological severity score (NSS) and morris water maze (MWM) at 7/14/21/28 and 24-28 days after TBI respectively. To explore the underlying mechanisms, the mRNA expression of TLR4 pathway molecules in hippocampus were measured by RT-PCR, and the polarization of microglia and the activation of TLR4 pathway in BV2 cells were measured after exosome treatment as well. Results demonstrated that Exo-miR-124 treatment promoted the M2 polarization of microglia, enhanced neurogenesis in hippocampus, and improved function recovery after TBI. The M2 polarization effect of Exo-miR-124 was produced through inhibiting TLR4 pathway, which was verified in hippocampus and BV2 microglia. In conclusion, Exo-miR-124 treatment promoted M2 polarization of microglia and improved hippocampal neurogenesis and functional recovery after brain injury, which might be a strategy to improve the outcome of TBI.
微小 RNA-124（miR-124）是一种脑特异性 miRNA，在小胶质细胞中高度表达。miR-124 的上调有助于小胶质细胞的 M2 极化，这有利于神经发生。外泌体是脂质膜囊泡，可以将 miR-124 递送至大脑。然而，富含 miR-124 的外泌体（Exo-miR-124）是否可以调节小胶质细胞的极化并影响创伤性脑损伤（TBI）后的海马神经发生尚不清楚。为了阐明这一点，首先构建了 Exo-miR-124，然后通过尾静脉在 TBI 后 24 小时内以每个大鼠 3×10 个颗粒的剂量静脉内给予大鼠。通过逆转录聚合酶链反应（RT-PCR）和酶联免疫吸附测定（ELISA）测量 TBI 后 7/14/21/28 天海马中小胶质细胞的特征基因和 M1/M2 表型细胞因子来评估小胶质细胞的极化。通过免疫荧光（IF）分别在 TBI 后 7 和 28 天检测增殖标志物 BrdU/SOX2 和分化标志物 BrdU/NeuN 来评估海马神经发生。通过神经学严重程度评分（NSS）和 Morris 水迷宫（MWM）分别在 TBI 后 7/14/21/28 和 24-28 天评估神经功能。为了探索潜在机制，通过 RT-PCR 测量海马中 TLR4 途径分子的 mRNA 表达，并在 Exo 处理后测量小胶质细胞的极化和 TLR4 途径的激活。结果表明，Exo-miR-124 治疗促进了小胶质细胞的 M2 极化，增强了海马中的神经发生，并改善了 TBI 后的功能恢复。Exo-miR-124 的 M2 极化作用是通过抑制 TLR4 途径产生的，这在海马和 BV2 小胶质细胞中得到了验证。总之，Exo-miR-124 治疗促进了小胶质细胞的 M2 极化，改善了脑损伤后的海马神经发生和功能恢复，这可能是改善 TBI 结果的一种策略。
