Claudin-9 constitutes tight junctions of folliculo-stellate cells in the anterior pituitary gland

Atsuko Y Higashi,Hideki Chiba,Kana Ozeki,Tomohito Higashi,Mikio Furuse,Kyoko Furuse

doi:10.1038/s41598-021-01004-z

Abstract

The anterior pituitary gland regulates growth, metabolism, and reproduction by secreting hormones. Folliculo-stellate (FS) cells are non-endocrine cells located among hormone-producing cells in the anterior pituitary glands. They form follicular lumens, which are sealed by tight junctions (TJs). Although FS cells are hypothesized to contribute to fine-tuning of endocrine cells, little is known about the exact roles of FS cells. Here, we investigated the molecular composition of TJs in FS cells. We demonstrated that occludin is a good marker for TJs in the pituitary gland and examined the structure of the lumens surrounded by FS cells. We also found that claudin-9 is a major component of TJs in the FS cells. In immunoelectron microscopy, claudin-9 was specifically localized at TJs of the FS cells. The expression of claudin-9 was gradually increased in the pituitary gland after birth, suggesting that claudin-9 is developmentally regulated and performs some specific functions on the paracellular barrier of follicles in the pituitary gland. Furthermore, we found that angulin-1, angulin-2, and tricellulin are localized at the tricellular contacts of the FS cells. Our findings provide a first comprehensive molecular profile of TJs in the FS cells, and may lead us towards unveiling the FS cell functions.

Highlights

The anterior pituitary gland regulates growth, metabolism, and reproduction by secreting hormones
We investigated the molecular composition of tight junctions (TJs) and tight junctions (tTJs) in FS cells by the quantitative reverse transcriptase-polymerase chain reaction, immunostaining, immunoprecipitation and immunoelectron microscopy, and found that claudin-9 is localized at the TJs of FS cells
Since it has been reported that occludin is expressed in the endothelial TJs in the central nervous system[33], we examined whether the occludin-positive cells include endothelial cells of blood vessels

Summary

Introduction

The anterior pituitary gland regulates growth, metabolism, and reproduction by secreting hormones. Folliculo-stellate (FS) cells are non-endocrine cells located among hormone-producing cells in the anterior pituitary glands. They form follicular lumens, which are sealed by tight junctions (TJs). The anterior pituitary gland ( known as adenohypophysis) is an endocrine organ that secretes several hormones to regulate growth, metabolism, reproduction, and stress responses. It is believed that the combination of expressed claudins determines the physiological characteristics of paracellular permeability of the tissues Another four-transmembrane domain protein occludin[33] and the cytoplasmic plaque protein ZO-134 are major components of TJs in epithelial cells. We investigated the molecular composition of TJs and tTJs in FS cells by the quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR), immunostaining, immunoprecipitation and immunoelectron microscopy, and found that claudin-9 is localized at the TJs of FS cells

Methods

Results

Conclusion