B7-H3 promoted proliferation of mouse spermatogonial stem cells via the PI3K signaling pathway.

Xuedong Wei,Miao Li,Jinxing Lv,Guangbo Zhang,Kai Li,Jianquan Hou,Hexing Yuan,Jinxian Pu,Caibin Fan,Yuhua Huang,Lun Zhao

doi:10.18632/oncotarget.23457

Abstract

ObjectiveWe found seminal B7-H3 was associated with human sperm concentration. However, the mechanism is unclear. The purpose of this study was to investigate the expression of B7-H3 in mouse testis and determine the effects of B7-H3 on the proliferation of mouse spermatogonial stem cells (SSCs) and the underlying mechanisms.MethodsB7-H3 expression in the testis of mice at different ages (3 weeks, 8 weeks, 4 months and 9 months) was detected by western blot and immunohistochemistry. CCK-8 were used to measure mouse SSCs proliferation after incubation with different concentrations of B7-H3 for 1-72 h in vitro. Flow cytometry was used to analyze the cell cycle of mouse SSCs after incubation with different concentrations of B7-H3 for 48 and 72 h. The signaling pathways involved were assessed by western blot.ResultsFour-month-old mice had the highest expression of B7-H3 in the testis, while 3-week-old mice had the lowest expression of B7-H3. B7-H3 was predominantly detected on the membrane and in the cytoplasm of Sertoli cells. Furthermore, B7-H3 promoted mouse SSCs proliferation and increased the percentage of cells in S+G2/M phase in a time- and dose-dependent manner in vitro. These effects were inhibited by LY294002, indicating the involvement of the phosphoinositide 3-kinase signaling pathway.ConclusionsThe expression of B7-H3 in mouse testis, especially Sertoli cells, was associated with mouse age. In vitro, B7-H3 promoted the proliferation and accelerated the cell cycle of mouse SSCs via the PI3K pathway, indicating a critical role of B7-H3 expressed by Sertoli cells in mouse spermatogenesis.

Highlights

Spermatogenesis is a continuous, productive and strictly controlled process [1, 2] that is supported by the self-renewal and differentiation of spermatogonial stem cells (SSCs) in the microenvironment of the seminiferous tubules [3]
The expression levels of B7-H3 in the mouse testes of the 3 w, 8 w and 9 m groups were 22.76%±1.31%, 64.40%±6.25% and 65.36%±4.20%, respectively, compared to those of the 4 m mice (Figure 1E and 1F). These data demonstrated that the expression of B7-H3 in testis was increased during the process of maturation to an adult, after which it decreased
Because SSC proliferation is a critical step in spermatogenesis, we investigated the effect of soluble B7H3 on the proliferation and cell cycle of mouse SSCs

Summary

Introduction

Spermatogenesis is a continuous, productive and strictly controlled process [1, 2] that is supported by the self-renewal and differentiation of spermatogonial stem cells (SSCs) in the microenvironment of the seminiferous tubules [3]. The only somatic cell type in the tubules, control the proliferation and differentiation of SSCs by direct interaction and secretion of specific factors [4]. We previously reported that soluble B7-H3 was detected in expressed prostatic secretions [7]. The original study reported that B7- H3 could activate T cells and increase T cell www.impactjournals.com/oncotarget proliferation as well as interferon-γ (IFN-γ) production [5]. Several subsequent studies found that B7H3 inhibited T cell function [9,10,11,12]. The underlying mechanisms and the biological functions of B7-H3 in this process are still unknown

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Results

Conclusion