Estrogen in the adult male reproductive tract: A review

Abstract

Testosterone and estrogen are no longer considered male only and female only hormones. Both hormones are important in both sexes. It was known as early as the 1930's that developmental exposure to a high dose of estrogen causes malformation of the male reproductive tract, but the early formative years of reproductive biology as a discipline did not recognize the importance of estrogen in regulating the normal function of the adult male reproductive tract. In the adult testis, estrogen is synthesized by Leydig cells and the germ cells, producing a relatively high concentration in rete testis fluid. Estrogen receptors are present in the testis, efferent ductules and epididymis of most species. However, estrogen receptor-α is reported absent in the testis of a few species, including man. Estrogen receptors are abundant in the efferent ductule epithelium, where their primary function is to regulate the expression of proteins involved in fluid reabsorption. Disruption of the α-receptor, either in the knockout (αERKO) or by treatment with a pure antiestrogen, results in dilution of cauda epididymal sperm, disruption of sperm morphology, inhibition of sodium transport and subsequent water reabsorption, increased secretion of Cl-, and eventual decreased fertility. In addition to this primary regulation of luminal fluid and ion transport, estrogen is also responsible for maintaining a differentiated epithelial morphology. Thus, we conclude that estrogen or its α-receptor is an absolute necessity for fertility in the male.

E2f4 and E2f5 are essential for the development of the male reproductive system

“…It is also possible that the stirring or mixing function of efferent ductule cilia is essential for homogenous reabsorption of fluid by the nonciliated cells, as previously predicted. [45][46][47] Additionally we speculate that the near absence of sperm from the epididymis could be caused by impaired fluid flow, an occlusion or a defect in smooth muscle contraction, which may rely upon signaling from the efferent ducts. Irrespective of the contribution of the multiciliogenesis defect, we believe that the primary problem is an accumulation of luminal fluid that reflects both impaired absorption and excess secretion.…”

Oestrogens and spermatogenesis

“…(b) Testicular oestrogens in mammals As abundantly documented in the literature, it is difficult to find a tissue completely devoid of aromatase gene expression (Simpson et al 1994); indeed, it is now well established that the mammalian testis is able to produce oestrogens (table 1; Hess 2003;Carreau et al 2006). Early in the study of testicular aromatase, it was thought that its expression was in Sertoli cells during development in the rodent species, but then only in Leydig cells in the adult testis (see reviews of Carreau et al 2007b).…”

“…Aromatase, which is the last step in the steroidogenesis pathway leading to the formation of oestrogens from androgens, is localized in the cellular endoplasmic reticulum of numerous tissues. The role of oestrogens in the physiology of male reproductive tract of mammals has for a long time been a subject of debate, even though more and more evidence suggests that oestrogens are involved via their specific receptors (see reviews of O'Donnell et al 2001;Hess 2003;Carreau et al 2008). Indeed, 70 years ago, Zondek (1934) discovered an oestrogenic hormone in stallion urine; but at the beginning, oestrogen production by testicular tissues was more a curiosity and it was only 30 years later that several publications provided evidence that testes are able to synthesize and secrete oestrogens.…”

Actin-binding protein drebrin E is involved in junction dynamics during spermatogenesis

“…[1][2][3][4][5][6][7][8][9][10] In the seminiferous tubules, a unique ultrastructure known as the blood-testis barrier (BTB), which is created by coexisting tight junctions (TJ), basal ectoplasmic specializations (basal ES), desmosomes and the actin-based cytoskeleton plays a critical role in the seminiferous epithelium during spermatogenesis by conferring cell shape, adhesion, structural support and cell polarity to both Sertoli and developing germ cells, which are essential for spermatogonial stem cell renewal, maintenance of the stem cell niche, cell cycle progression, mitosis, meiosis, spermiogenesis and spermiation. However, few functional studies are found in the literature, which explore the functional significance of actin dynamics in these events.…”