Opposing Wnt signals regulate cervical squamocolumnar homeostasis and emergence of metaplasia

The transition zones (TZs) of the squamous and columnar epithelium constitute hotspots for the emergence of cancers, often preceded by metaplasia, where one epithelial type is replaced by cells of another type. Yet, it remains uncertain how the spatial organization of the epithelia is maintained and how the TZ niche is remodeled during metaplasia. Here, we used single-cell RNA-sequencing to characterize subpopulations of the epithelium as well as the underlying stromal compartment of endo and ectocervix, encompassing the TZ. Mouse lineage tracing, organoid culture and smRNA-ISH revealed that the two epithelia derive from two separate cervix-resident lineage-specific stem cell populations that are regulated by opposing WNT signals from the stroma. Using a mouse model of cervical metaplasia, we further show that the endocervical stroma undergoes remodeling and increased expression of WNT signaling inhibitor Dickkopf-2 (DKK2), promoting the outgrowth of ectocervical stem cells. Thus, homeostasis at the TZ results from divergent stromal signals, driving the differential proliferation of resident epithelial lineages.

鳞状上皮与柱状上皮的过渡区（transition zones, TZs）是癌症发生的热点区域，该区域癌变前常伴随化生过程——即一种上皮类型被另一种类型的细胞所替代。然而目前学界仍未明确上皮的空间组织结构如何维持，以及化生过程中TZs微环境（niche）如何被重塑。本研究借助单细胞RNA测序（single-cell RNA-sequencing）技术，对涵盖该过渡区的子宫内颈与外颈的上皮亚群及其下方的间质室进行了表征分析。小鼠谱系示踪、类器官培养以及单分子RNA原位杂交（smRNA-ISH）实验结果显示，两种上皮分别起源于宫颈内的两种独立驻留谱系特异性干细胞群，且这两类干细胞受到来自间质的相互拮抗的WNT信号的调控。借助宫颈化生小鼠模型，本研究进一步证实，内颈间质会发生重塑，且其WNT信号抑制剂Dickkopf-2（DKK2）的表达水平显著上调，进而促进外颈干细胞的增殖扩增。综上，该过渡区的上皮稳态由差异化的间质信号所维持，这些信号驱动了驻留上皮谱系的差异性增殖。