Single-cell RNA-Seq profiling of the mouse anorectal junction before, during, and after acute colitis

We have identified a squamous epithelium that repairs the distal colon of mice after injury and colitis. Lineage tracing studies demonstrate that this squamous epithelium is derived from a small zone of transitional cells located at the squamocolumnar junction of the rectum and anus. To characterize the molecular properties of this junctional epithelium in homeostasis, colitis, and regeneration, we profiled the distal colon and anus of mice using single-cell RNA-Seq. We found that junctional cells in this transition zone express high levels of Krt7 and, at baseline, co-express markers of both colonic epithelium and squamous epithelium. These cells thus represent a specialized reserve epithelial population capable of striking plasticity in their generation of a hybrid tissue type to mediate colonic repair. Wildtype C57Bl/6 mice were exposed to the DSS colitis model for 6 d. They were dissected and their anorectal junctions analyzed via single-cell RNA-Seq at experimental day (exp d) 0 (unchallenged mice), exp d 7 (highly colitic mice), and exp d 42 (recovered mice).

本研究鉴定出一种可在损伤及结肠炎发生后修复小鼠远端结肠的鳞状上皮。谱系示踪（lineage tracing）实验证实，该鳞状上皮起源于位于直肠与肛管鳞柱交界的一小片过渡细胞区域。为解析该交界上皮在稳态、结肠炎及再生过程中的分子特征，我们通过单细胞RNA测序（single-cell RNA-Seq）对小鼠远端结肠及肛管开展了测序分析。研究发现，该过渡区域的交界细胞高表达角蛋白7（Krt7），且在基础状态下共表达结肠上皮与鳞状上皮的标志物。因此，这类细胞代表一类特化的储备上皮细胞群，可通过生成混合组织表型展现出显著的细胞可塑性，以介导结肠修复。我们将野生型C57Bl/6小鼠暴露于葡聚糖硫酸钠（DSS）结肠炎模型中造模6天，分别在实验第0天（未造模小鼠）、实验第7天（重症结肠炎小鼠）及实验第42天（已恢复小鼠）剖杀小鼠，对其肛管直肠交界组织进行单细胞RNA测序分析。