Crucial role of estrogen for the mammalian female in regulating semen coagulation and liquefaction in vivo

Abstract

Semen liquefaction changes semen from a gel-like to watery consistency and is required for sperm to gain mobility and swim to the fertilization site in the Fallopian tubes. Kallikrein-related peptidases 3 (KLK3) and other kallikrein-related peptidases from male prostate glands are responsible for semen liquefaction by cleaving gel-forming proteins (semenogelin and collagen). In a physiological context, the liquefaction process occurs within the female reproductive tract. How seminal proteins interact with the female reproductive environment is still largely unexplored. We previously reported that conditional genetic ablation of Esr1 (estrogen receptor α) in the epithelial cells of the female reproductive tract (Wnt7a) causes female infertility, partly due to a drastic reduction in the number of motile sperm entering the oviduct. In this study, we found that post-ejaculated semen from fertile wild-type males was solidified and the sperm were entrapped in Wnt7aCre/+ ;Esr1 f/f uteri, compared to the watery semen (liquefied) found in Esr1 f/f controls. In addition, semenogelin and collagen were not degraded in Wnt7aCre/+ ;Esr1 f/f uteri. Amongst multiple gene families aberrantly expressed in the absence of epithelial ESR1, we have identified that a lack of Klks in the uterus is a potential cause for the liquefaction defect. Pharmacological inhibition of KLKs in the uterus replicated the phenotype observed in Wnt7aCre/+ ;Esr1 f/f uteri, suggesting that loss of uterine and seminal KLK function causes this liquefaction defect. In human cervical cell culture, expression of several KLKs and their inhibitors (SPINKs) was regulated by estrogen in an ESR1-dependent manner. Our study demonstrates that estrogen/ESR1 signaling in the female reproductive tract plays an indispensable role in normal semen liquefaction, providing fundamental evidence that exposure of post-ejaculated semen to the suboptimal microenvironment in the female reproductive tract leads to faulty liquefaction and subsequently causes a fertility defect. Author summarySemen liquefaction has been considered to be solely modulated by prostate-derived kallikrein-related peptidases (KLKs), especially KLK3 (or prostate specific antigen). However, our research demonstrated that female mice lacking estrogen receptor alpha (ERα) in the uterine epithelial cells had a drastic decrease in Klk transcripts and semen from fertile males fails to liquefy within the uteri of these females. Therefore, our results provide a novel aspect that, due to an interplay between semen and female reproductive tract secretions, the physiology of semen liquefaction is more complicated than previously assumed. This information will advance research on semen liquefaction in the female reproductive tract, an area that has never been explored, and could lead to the development of diagnostic tools for unexplained infertility cases and non-invasive contraception technologies.

Estrogen Action in the Epithelial Cells of the Mouse Vagina Regulates Neutrophil Infiltration and Vaginal Tissue Integrity

“…To assess this, we generated a similar model in which ESR1 was deleted in the vaginal epithelium using the Wnt7a cre/+ ( Wnt7a cre/+ ; Esr1 f/f ) 22 . Our Wnt7a cre/+ ; Esr1 f/f females ovulate normally without the need for an exogenous gonadotropins 3 . These Wnt7a cre/+ ; Esr1 f/f females are also receptive to copulation 3 , allowing us to validate the role of ESR1 in maintaining vaginal tissue integrity after physical stress in vivo .…”

“…Our Wnt7a cre/+ ; Esr1 f/f females ovulate normally without the need for an exogenous gonadotropins 3 . These Wnt7a cre/+ ; Esr1 f/f females are also receptive to copulation 3 , allowing us to validate the role of ESR1 in maintaining vaginal tissue integrity after physical stress in vivo . Additionally, we used this model to investigate the role of vaginal epithelial ESR1 for both neutrophil recruitment/infiltration and maintenance of the vaginal microbiota.…”

“…The female reproductive tract is composed of upper (oviduct, uterus, and endocervix) and lower (ectocervix and vagina) sections. Recent studies of the upper female reproductive tract (UFRT) suggest that estrogen receptor α (ESR1) in the epithelial cells is crucial for embryo development and transport in the oviduct 1 , 2 , as well as for semen liquefaction in the uterus 3 . ESR1 is required in epithelial cells of the lower female reproductive tract (LFRT) to regulate the differentiation of vaginal epithelial cells 4 .…”

Structural modeling and mRNA expression of epididymal β‐defensins in GnRH immunized boars: A model for secondary hypogonadism in man

“…The importance of estrogens in epididymal development and function has been extensively studied (Hess, Bunick, & Bahr, ; Hess, Bunick, & Bahr, ; Hess, Zhou et al, ; Joseph et al, ). Comparatively, the boar has elevated estrogens levels in blood and semen (reviewed by Hess ()), which have physiological relevance for spermatogenesis (Carreau, Bouraima‐Lelong, & Delalande, ), epididymal maturation (Hess et al, ) and postejaculatory events (Li, Garcia, Gewiss, & Winuthayanon, ). The impact of anti‐GnRH immunization on luteinizing hormone (LH) and follicle stimulating hormone (FSH) secretion impairs steroidogenesis, reducing estradiol and estrone sulfate plasma levels to 40 pg/ml (Kubale et al, ) and 0.2 ng/ml (Zamaratskaia et al, ), respectively.…”

Deletion of kallikrein 1b5 (Klk1b5) has no impact on fertility in mice

“…In the uterus, the expression of Klk1 and its subfamily members are estrogen (E 2 )-dependent. Accordingly, our previous work showed that Klk1b5 is expressed at the highest level compared to other Klk members in the mouse uterus after E 2 treatment (Li, Garcia, Gewiss, & Winuthayanon, 2017). However, the physiological function of Klk1b5 has never been investigated.…”