Of Oestrogens and Sperm: A Review of the Roles of Oestrogens and Oestrogen Receptors in Male Reproduction

Abstract

The crucial role that oestrogens play in male reproduction has been generally accepted; however, the exact mechanism of their action is not entirely clear and there is still much more to be clarified. The oestrogen response is mediated through oestrogen receptors, as well as classical oestrogen receptors’ variants, and their specific co-expression plays a critical role. The importance of oestrogen signalling in male fertility is indicated by the adverse effects of selected oestrogen-like compounds, and their interaction with oestrogen receptors was proven to cause pathologies. The aims of this review are to summarise the current knowledge on oestrogen signalling during spermatogenesis and sperm maturation and discuss the available information on oestrogen receptors and their splice variants. An overview is given of species-specific differences including in humans, along with a detailed summary of the methodology outcome, including all the genetically manipulated models available to date. This review provides coherent information on the recently discovered mechanisms of oestrogens’ and oestrogen receptors’ effects and action in both testicular somatic and germ cells, as well as in mature sperm, available for mammals, including humans.

Missing Information from the Estrogen Receptor Puzzle: Where Are They Localized in Bull Reproductive Tissues and Spermatozoa?

“…Mature sperm cells are considered to be transcriptionally inactive but capable of translating synthesized mRNA [56]; therefore, it can be assumed that estrogens exert non-genomic rapid effects in spermatozoa [3]. In the female reproductive tract, ERs might have an effect on active transport of sperm to the site of fertilization [57].…”

“…The translocation of classical ERs to the plasma membrane is mediated by palmitoylation [16,79]. It has been suggested that the rapid signaling pathway is activated by estrogen through crosstalk between GPER1 and ESR1/2 [3,13,14]. The localization of ESR1, ESR2, and GPER1 within the acrosomal cap of bull spermatozoa seems to be a prerequisite for the possible co-operation between ERs involved in the events of the sperm lifetime.…”

“…Estrogens are steroid hormones that affect a wide range of functions, especially those in reproductive organs [1,2]. Although estrogens were traditionally considered to be female hormones, it is now clear that they also have an important role in the male reproductive tract (reviewed in [3,4]).…”

Immunohistochemical Localization of Estrogen Receptors in Human Spermatozoa

“…Later immunohistochemical and molecular presence of Estrogen Receptors and its mRNA were also reported in spermatozoa [3,18]. Difference can be found in localization and molecular weight in different studies varies between species [22]. Interestingly, one study reported Estrogen receptor  truncated variant of 46 kDa were detected in mature human spermatozoa [23].…”

“…A novel estrogen receptor of smaller size (29kDa) has been identified on the membrane of human spermatozoa that may mediate consequence on human spermatozoa [29]. No further investigation have been studied this in more detail [22].…”