Expression of the Receptor Genes of FSH, Estrogen- α, β, Androgen, IGF I and TGF-β During Fetal and Pre-Pubertal Testicular Development in Mouse

Abstract

Objectives: Gonadotrophins (FSH and LH) secreted from pituitary and operate directly or indirectly on the differentiation and proliferation of Sertoli cells and Leydig cells in fetal testis. Sertoli cells and Leydig cells regulate the differentiation, maturation, and proliferation of germ cells. However, in the early stage before the accomplishment of testicular differentiation, it was not clear what was the expression pattern of gonadotropin receptor, steroid hormone receptor and growth factor receptor and the role of them in testicular development. The aim of this study was to elucidate the location and initiation of gene expression of these receptors involved in the regulation of testicular development. Design: The expression receptor gene of FSH, steroid hormone and growth factors were investigated in mouse testis during fetal and neonatal development. Materials and Methods: Fetal and postnatal testicular tissues were collected at 10, 11, 12, 14, 16 and 18 days gestation, 1, 4, 7, 10, 12, 15, and 21 day after birth and adult in ICR mice. The testis tissues were sliced and fixed using 2% glutaradehyde for electron microscopy study, and 4% paraformaldehyde for PCR in situ hybridization. Total RNA for RT-PCR was isolated using RNeasy prep kit. Expression of the receptor of FSH, estrogen-α, β, androgen, IGF I, TGF β and LIF were analyzed by RT-PCR and localized by using PCR in situ hybridization. Results: The transcripts of FSH receptor were highly expressed at 18 days gestation. The expression of them was maintained constantly after this stage throughout testicular development. Estrogen-α receptor and growth factors (IGFI and TGF-β) receptor were also expressed in the same stage with FSH receptor. However, estrogen-β receptor and androgen receptor were expressed at a later stage (neonatal 4 days) than estrogen-α receptor. In ultrastructure study of testis, Sertoli cells were differentiated at 16–18 days gestation, and the spermatogenic differentiation of germ cells was started at neonatal 4 days. As results of PCR in situ hybridization, FSH receptor transcripts were detected in Sertoli cells and spermatogonia, whereas the receptors of IGFI, TGF-β and androgen were detected in spermatogonia, primary spermatocyte and secondary spermatocyte. Conclusion: It can be suggested that FSH receptor was expressed after differentiation of Sertoli cells. The expression of FSH receptor triggers the expression of other receptor (estrogen-α, IGFI receptor, TGF-β receptor) in germ cell. Therefore, receptor genes of FSH, estrogen-α, β, androgen, IGFI and TGF-β were expressed stage specifically depending on testicular histogenesis during fetal and pre-pubertal testicular development in mouse.