Abstract：
Barrier-forming olfactory glia cells, termed sustentacular cells, play important roles for immune defense of the olfactory mucosa, for example as entry sites for SARS-CoV-2 and subsequent development of inflammation-induced smell loss. Here we demonstrate that sustentacular cells express ACKR3, a chemokine receptor that functions both as a scavenger of the chemokine CXCL12 and as an activator of alternative signaling pathways. Differential gene expression analysis of bulk RNA sequencing data obtained from WT and ACKR3 conditional knockout mice revealed upregulation of genes involved in immune defense. To map the regulated genes to the different cell types of the olfactory mucosa, we employed biocomputational methods utilizing a single-cell reference atlas. Transcriptome analysis, PCR and immunofluorescence identified up-regulation of NF-κB-related genes, known to amplify inflammatory signaling and to facilitate leukocyte transmigration, in the gliogenic lineage. Accordingly, we found a marked increase in leukocyte-expressed genes and confirmed leukocyte infiltration into the olfactory mucosa. In addition, lack of ACKR3 led to enhanced expression and secretion of early mediators of immune defense by Bowman\'s glands. As a result, the number of apoptotic cells in the epithelium was decreased. In conclusion, our research underlines the importance of sustentacular cells in immune defense of the olfactory mucosa. Moreover, it identifies ACKR3, a druggable G protein-coupled receptor, as a promising target for modulation of inflammation-associated anosmia.
摘要：
形成屏障的嗅觉神经胶质细胞，称为软骨细胞，在嗅觉粘膜的免疫防御中起重要作用，例如作为SARS-CoV-2的进入部位和随后的炎症诱导的嗅觉丧失的发展。在这里，我们证明了sustentacular细胞表达ACKR3，一种趋化因子受体，作为趋化因子CXCL12的清除剂和替代信号通路的激活剂。从WT和ACKR3条件性敲除小鼠获得的大量RNA测序数据的差异基因表达分析揭示了参与免疫防御的基因上调。为了将调节基因定位到嗅觉粘膜的不同细胞类型，我们采用了利用单细胞参考图谱的生物计算方法。转录组分析，PCR和免疫荧光鉴定了NF-κB相关基因的上调，已知可以放大炎症信号并促进白细胞迁移，在胶质细胞谱系中。因此，我们发现白细胞表达的基因显著增加，并证实白细胞浸润到嗅觉粘膜中。此外,缺乏ACKR3导致Bowman腺体早期免疫防御介质的表达和分泌增强。因此,上皮中凋亡细胞的数量减少。总之,我们的研究强调了软骨细胞在嗅觉粘膜免疫防御中的重要性。此外，它鉴定了ACKR3，一种可药用的G蛋白偶联受体，作为调节炎症相关嗅觉缺失的有希望的目标。
