Identification and Characterization of Stem Cells in Mammalian Esophageal Stratified Squamous Epithelia

Abstract

Somatic stem cells are essential for maintenance of cell proliferation-differentiation homeostasis in organs. Despite the importance, how the esophageal epithelium that executes its self-renewal and maintenance remains elusive. In this study, using 5-bromo-2-deoxyuridine (BrdU) label-chase in rat and rat esophageal keratinocyte cell line-derived organoids together with genome-wide DNA methylation profiling and single-cell RNA sequencing (scRNA-seq), we identify slow cycling/quiescent stem cell population that contain high levels of hemidesmosome (HD)s and low levels of Wnt signaling localized spatially and randomly at the basal layer of the esophageal epithelium. Pseudo-time cell trajectory from scRNA-seq indicates that cell fates begin from quiescent basal cells (the stem cells) of the basal layer that produce proliferating and/or differentiating cells in the basal layer, which, in turn, progress into differentiating cells in the suprabasal layer, ultimately transforming into differentiated keratinocytes in the differentiated layer. Perturbations of HD component expressions and/or Wnt signaling reduce stem cell in the basal layer of esophageal keratinocyte organoids, resulting in alterations of organoid formation rate, size, morphogenesis and proliferation-differentiation homeostasis. Furthermore, we show that not only high levels of HDs and low levels of Wnt signaling but also an interplay between HD and Wnt signaling defined stem cells of the basal layer in the esophageal squamous epithelium. Hence, HDs and Wnt signaling are the critical determinants for defining stem cells of the basal layer required for proliferation-differentiation homeostasis and maintenance in the mammalian esophageal squamous epithelium.