Characterisation of young, old and old repopulating microglia in spinal cord and brain of C57BL/6 wild type male mice

To address whether, after depletion by Csf1r inhibition, microglia repopulating the CNS revert to a “younger” phenotype, we treated a group of 23 months old mice with the Csf1r inhibitor for 5 days and let microglia repopulate the central nervous system for 7 days. Young (3 months old) and old (23 months old) mice were included as controls. After the repopulation time, whole spinal cord samples and Fluorescence Activated Sorting (FACS)-sorted microglia cells from brain tissue were collected to perform bulk transcriptome (RNAseq) analysis. Analysis of whole spinal cord suggested that repopulating microglia tend to re-acquire its original aged phenotype. Gene expression in FACS-sorted microglia was then analyzed to better characterize its intrinsic phenotype after repopulation. In contrast to the whole spinal cord samples, old and old-treated replicates separated in Principal Component Analysis, suggesting that repopulating microglia displayed a different phenotype compared to old microglia.

为探究经Csf1r抑制剂清除后，中枢神经系统（CNS）内的小胶质细胞在再生定植后是否可恢复至“更年轻”的表型，本研究对23月龄小鼠施以Csf1r抑制剂处理5天，随后使小胶质细胞在中枢神经系统内完成7天的再生定植过程。本研究设置3月龄青年小鼠与23月龄老年小鼠作为对照。待定植周期结束后，我们采集全脊髓样本与脑组织经荧光激活细胞分选（Fluorescence Activated Sorting, FACS）得到的小胶质细胞样本，开展批量转录组（bulk transcriptome，RNA测序（RNAseq））分析。对全脊髓样本的分析结果显示，再生定植的小胶质细胞倾向于恢复其原本的衰老表型。随后我们对经FACS分选得到的小胶质细胞的基因表达情况进行分析，以更精准地表征其再生定植后的内在表型。与全脊髓样本的分析结果不同的是，老年小鼠组与老年给药组的生物学重复样本在主成分分析（Principal Component Analysis, PCA）中呈现分离趋势，这表明再生定植的小胶质细胞与天然老年小胶质细胞的表型存在显著差异。