Deep Crypt Secretory Cell Differentiation in the Colonic Epithelium Is Regulated by Sprouty2 and Interleukin 13

Abstract

Background & aims: Deep crypt secretory (DCS) cells are a critical component of the colonic stem cell niche. However, the regulatory mechanisms controlling DCS cell numbers and function are not well understood. Sprouty2 is an inflammation-responsive regulator of intracellular signaling that influences colonic secretory cell numbers in colitis via an epithelial-stromal interleukin (IL)33/IL13 signaling loop. Here, we tested the hypothesis that IL13, induced by epithelial Sprouty2 down-regulation, promotes DCS cell differentiation and function.

Methods: Distal colons from mice with an intestinal epithelial-specific Sprouty2 deletion (Spry2^ΔIE) and littermate controls were analyzed by in situ hybridization for Reg4⁺ DCS cells. Single-cell RNA sequencing and immunostaining were used to identify DCS cell-derived host defense peptides (HDPs) and localization of IL13 and IL13 receptor; bulk RNA sequencing and quantitative polymerase chain reaction were used to quantify changes in expression of identified HDPs. Cytokine-treated colonoids were assessed for DCS cells. A requirement for an IL33/IL13 signaling loop in the regulation of DCS cells was assessed in vivo using IL13 null mice.

Results: Reg4⁺ DCS cell numbers were increased 2-fold in distal colons of Spry2^ΔIE mice with a concomitant overall increase in DCS cell marker expression (Reg4, Spink4, and Agr2). Single-cell transcriptomics showed the HDP Retnlb/Resistin Like Beta (RELMβ) is highly enriched in DCS cells. Retnlb/RELMβ expression was increased in Spry2^ΔIE colons. IL13, but not IL33, induced Reg4 and Retnlb expression in colonic epithelial organoids, and IL33-mediated expansion of the DCS cell population in vivo was dependent on IL13, which was expressed predominantly by type II innate lymphoid cells in the colonic mucosa.

Conclusions: Sprouty2 limits colonic DCS cell differentiation through suppression of IL13 signaling. At homeostasis, DCS cells are marked by high levels of the HDP RELMβ. Loss of epithelial Sprouty2 activates type II innate lymphoid cells to release IL13, promoting expansion of the DCS cell population and increased colonic RELMβ levels.

Keywords: Deep Crypt Secretory Cell; IL13; ILC2; RELMβ.