Enteroendocrine Cells Are Specifically Marked by Cell Surface Expression of Claudin-4 in Mouse Small Intestine

Takahiro Nagatake,Harumi Fujita,Nagahiro Minato,Yoko Hamazaki,Michael Koval

doi:10.1371/journal.pone.0090638

Abstract

Enteroendocrine cells are solitary epithelial cells scattered throughout the gastrointestinal tract and produce various types of hormones, constituting one of the largest endocrine systems in the body. The study of these rare epithelial cells has been hampered by the difficulty in isolating them because of the lack of specific cell surface markers. Here, we report that enteroendocrine cells selectively express a tight junction membrane protein, claudin-4 (Cld4), and are efficiently isolated with the use of an antibody specific for the Cld4 extracellular domain and flow cytometry. Sorted Cld4+ epithelial cells in the small intestine exclusively expressed a chromogranin A gene (Chga) and other enteroendocrine cell–related genes (Ffar1, Ffar4, Gpr119), and the population was divided into two subpopulations based on the activity of binding to Ulex europaeus agglutinin-1 (UEA-1). A Cld4+UEA-1− cell population almost exclusively expressed glucose-dependent insulinotropic polypeptide gene (Gip), thus representing K cells, whereas a Cld4+UEA-1+ cell population expressed other gut hormone genes, including glucagon-like peptide 1 (Gcg), pancreatic polypeptide–like peptide with N-terminal tyrosine amide (Pyy), cholecystokinin (Cck), secretin (Sct), and tryptophan hydroxylase 1 (Tph1). In addition, we found that orally administered luminal antigens were taken up by the solitary Cld4+ cells in the small intestinal villi, raising the possibility that enteroendocrine cells might also play a role in initiation of mucosal immunity. Our results provide a useful tool for the cellular and functional characterization of enteroendocrine cells.

Highlights

The intestinal epithelial cell layer consists of functionally heterogeneous cell populations, including absorptive epithelial cells, goblet cells, paneth cells, M cells, cup cells, tuft cells, and enteroendocrine cells, all of which are derived from Lgr5+ crypt base columnar stem cells [1,2,3]
Enteroendocrine cells comprise a very small population of gut epithelial cells that are scattered solitarily throughout the gastrointestinal tract, and the physical isolation of these cells has been hampered by the lack of specific cell surface markers
We found that chromogranin A (CgA)+ enteroendocrine cells in small intestine rather express a Cld family member, Cld4, diffusely and strongly on the cell surface as revealed by immunostaining

Summary

Introduction

The intestinal epithelial cell layer consists of functionally heterogeneous cell populations, including absorptive epithelial cells, goblet cells, paneth cells, M cells, cup cells, tuft cells, and enteroendocrine cells, all of which are derived from Lgr5+ crypt base columnar stem cells [1,2,3]. Enteroendocrine cells include more than 10 different cell types producing distinct hormones or hormone-like substances, such as serotonin, secretin, glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide 1 (GLP-1), pancreatic polypeptide–like peptide with Nterminal tyrosine amide, and cholecystokinin [4]. Those producing GIP and GLP-1 are called K cells and L cells [5,6], respectively, and are responsible for ‘‘incretin effects’’ regulating postprandial insulin secretion [7,8,9,10,11]. General cell surface markers for the enteroendocrine cell population have not been identified

Methods

Results

Conclusion