Epidermal growth factor mediates spermatogonial proliferation in newt testis.

Keisuke Abé,Ko Eto,Shin-Ichi Abé

doi:10.1186/1477-7827-6-7

Keisuke Abé, Ko Eto + Show 1 more

Open Access

https://doi.org/10.1186/1477-7827-6-7

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Abstract

The complex processes of spermatogenesis are regulated by various factors. The aim of the current study is to determine the effect of epidermal growth factor (EGF) on spermatogonial proliferation and clarify the mechanism causing the proliferation in newt testis. In the organ culture, EGF stimulated spermatogonial proliferation, but not their differentiation into spermatocytes. cDNA cloning identified 3 members of the EGF receptors, ErbB1, ErbB2, and ErbB4, in the testis. RT-PCR showed that all the receptors cloned were expressed in both Sertoli and germ cells at the spermatogonial stage. In the organ cultures with inhibitors for the EGF receptors, mitogen-activated protein kinase (MAPK), and phosphoinositide 3-kinase (PI3K), the EGF-induced spermatogonial proliferation was suppressed. Furthermore, when the organ culture was exposed to EGF, the expressions of stem cell factor (SCF), immunoglobulin-like domain containing neuregulin1 (Ig-NRG1), and ErbB4 mRNA were increased. These results suggested that, since the spermatogonia are sequestered within cysts by the blood-testis barrier consisted of Sertoli cells, EGF possibly mediates spermatogonial proliferation in an endocrine manner through the receptors including ErbB1, ErbB2, and ErbB4 expressed on Sertoli cells via activation of MAPK cascade or/and PI3K cascade by elevating the expressions of SCF, Ig-NRG1, and ErbB4.

Highlights

Spermatogenesis is a complex process consisting of sequential and highly organized steps of germ cell proliferation and differentiation, resulting in the generation of functional spermatozoa, in the testis [1]
Effect of epidermal growth factor (EGF) on the proliferation and differentiation of spermatogonia in the testis To examine whether EGF is able to stimulate the proliferation of spermatogonia dose-dependently in an endocrine manner in the testis, the testicular fragments containing only spermatogonial stage were cultured for 1 week in the absence or presence of folliclestimulating hormone (FSH) or EGF and subjected to BrdU incorporation assay
Expressions of mRNA for stem cell factor (SCF), c-kit, 3 members of the EGF receptor, ErbB1, ErbB2, and ErbB4, and 2 isoforms of neuregulin1, immunoglobulin-like domain containing neuregulin1 (Ig-NRG1) and CRD-NRG1, at the early spermatogonial, late spermatogonial, and spermatocyte stage, and in the spermatogonia and Sertoli cells were analyzed by reverse transcription and polymerase chain reaction (RT-PCR)

Summary

Introduction

Spermatogenesis is a complex process consisting of sequential and highly organized steps of germ cell proliferation and differentiation, resulting in the generation of functional spermatozoa, in the testis [1]. Sertoli cells have essential roles in the spermatogenic function of the testis: they produce and secrete local factors to germ cells, and represent the only cellular component of the blood-testis barrier [3]. The germ cells are in close contact with Sertoli cells in a cyst, the smallest unit of the testis, and the testis consists of lobules in successive zones arranged along a cephalo-caudal axis, in which spermatogenesis proceeds synchronously [4,5]. We have demonstrated with the organ culture that the functional blood-testis barrier with size (page number not for citation purposes)

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