Functions of Steroid Hormones in the Male Reproductive Tract as Revealed by Mouse Models

Abstract

Steroid hormones are capable of diffusing through cell membranes to bind with intracellular receptors to regulate numerous physiological processes. Three classes of steroid hormones, namely androgens, estrogens and glucocorticoids, contribute to the development of the reproductive system and the maintenance of fertility. During the past 30 years, mouse models have been produced in which the expression of genes encoding steroid hormone receptors has been enhanced, partially compromised or eliminated. These mouse models have revealed many of the physiological processes regulated by androgens, estrogens and to a more limited extent glucocorticoids in the testis and male accessory organs. In this review, advances provided by mouse models that have facilitated a better understanding of the molecular regulation of testis and reproductive tract processes by steroid hormones are discussed.

Keywords: Leydig cell; Sertoli cell; androgen receptor; epididymis; estrogen receptor; glucocorticoid receptor; peritubular myoid cell; prostate; seminal vesicle; testis.

Figure 1

Steroid hormone-mediated signals between testicular cells maintain fertility. Androgen receptor (AR)-mediated actions in Sertoli cells support four major germ cells processes (1–4) required to maintain fertility. AR and glucocorticoid receptor (GR) in Sertoli cells support expansion and maturation of Leydig cells and steroidogenesis. Leydig cells produce testosterone that stimulates AR-mediated processes in Sertoli and peritubular myoid (PTM) cells. AR-dependent actions in PTM cells support the maturation of Leydig cells and their steroidogenesis as well as production of extracellular matrix (ECM), cell–cell interactions, Sertoli localization (positioning on the basement membrane) and AR-mediated mRNA expression in Sertoli cells. BTB, blood–testis barrier, PL, preleptotene; L, leptotene; Z, zygotene; EP, MP, LP; early, mid, late pachytene; II, meiosis II; RB, residual body.