Male Seminal Relaxin Contributes to Induction of the Post-mating Cytokine Response in the Female Mouse Uterus

Abstract

The hormone relaxin is important in female reproduction for embryo implantation, cardiovascular function, and during labor and lactation. Relaxin is also synthesized in males by organs of the male tract. We hypothesized that relaxin might be one component of seminal plasma responsible for eliciting the female cytokine response induced in the uterus at mating. When recombinant relaxin was injected into the uterus of wild-type (Rln +/+ ) mice at estrus, it evoked the production of Cxcl1 mRNA and its secreted protein product CXCL1 in four of eight animals. Mating experiments were then conducted using mice with a null mutation in the relaxin gene (Rln −/− mice). qRT-PCR analysis of mRNA expression in wild-type females showed diminished uterine expression of several cytokine and chemokine genes in the absence of male relaxin. Similar differences were also noted comparing Rln −/− and Rln +/+ females mated to wild-type males. Quantification of uterine luminal fluid cytokine content confirmed that male relaxin provokes the production of CXCL10 and CSF3 in Rln +/+ females. Differences were also seen comparing Rln −/− and Rln +/+ females mated with Rln −/− males for CXCL1, CSF3, and CCL5, implying that endogenous relaxin in females might prime the uterus to respond appropriately to seminal fluid at coitus. Finally, pan-leukocyte CD45 mRNA was increased in wild-type matings compared to other combinations, implying that male and female relaxin may trigger leukocyte expansion in the uterus. We conclude that male and/or female relaxin may be important in activating the uterine cytokine/chemokine network required to initiate maternal immune adaptation to pregnancy.

Mating to Intact, but Not Vasectomized, Males Elicits Changes in the Endometrial Transcriptome: Insights From the Bovine Model

“…Growing evidence exists for a role of SP in the modulation of cellular and molecular events in the maternal tract of several species during early pregnancy ( Gangnuss et al, 2004 ; O’Leary et al, 2004 , 2006 ; Bromfeld, 2016 ; Song et al, 2016 ; Glynn et al, 2017 ; Morgan and Watkins, 2020 ). However, most of the in vivo evidence comes from pigs and mice, species in which SP reaches the uterus ( Gangnuss et al, 2004 ; O’Leary et al, 2004 , 2006 ; Bromfield et al, 2014 ; Song et al, 2016 ; Glynn et al, 2017 ). Because of the relatively low volume of ejaculate in men (an average of 3.7 mL, Cooper et al, 2009 ) and bulls (around 5 mL), and the fact that the ejaculate is deposited in the vagina, it is questionable whether any SP reaches the uterus.…”

“…Most of these losses occur before implantation, highlighting the importance of this period that encompasses such critical events as the first embryonic cleavage divisions; embryonic genome activation; blastocyst formation and hatching; conceptus development; and the preparation of the endometrium to interact with the embryonic trophectoderm ( Diskin and Morris, 2008 ; Niakan et al, 2012 ; Sandra et al, 2017 ). Many factors are involved in implantation failure, but in mice and pigs there is growing evidence of a role for the maternal immune system and its regulation by seminal plasma (SP) ( Gangnuss et al, 2004 ; O’Leary et al, 2004 , 2006 ; Song et al, 2016 ; Glynn et al, 2017 ).…”

“…However, mounting evidence demonstrates an emerging role for SP components in the modulation of the endometrial and oviductal environment, which results in improved fertility and embryo survival and development (reviewed in Bromfeld, 2016 ; Morgan and Watkins, 2020 ). Exposure to SP in mice ( Schjenken et al, 2015 ; Song et al, 2016 ; Glynn et al, 2017 ), as well as in pigs ( O’Leary et al, 2004 , 2006 ) and mares ( Tunon et al, 2000 ; Palm et al, 2008 ; Fedorka et al, 2017 ), induces the expression of several endometrial cytokines, leading to leukocyte recruitment to the uterus. This migration of immune cells was thought to solely serve the purpose of clearing microorganisms and excess sperm ( Pandya and Cohen, 1985 ; Thompson et al, 1992 ).…”

Perspective: Re-defining “Pheromone” in a Mammalian Context to Encompass Seminal Fluid

“…In addition to the immunological effects and the ovulatory response, seminal fluid affects the ovary where as-yet unidentified components facilitate luteal development and progesterone secretion ( 37 ), after being delivered by unique counter-current exchange mechanisms where small molecules are transferred to the ovarian artery from the uterine vein ( 38 ). One candidate, relaxin, is known to be carried by seminal plasma in rodents ( 39 ) and has been shown to promote ovulation through connective tissue remodeling in the follicle wall ( 40 ).…”

Sperm exposure to accessory gland secretions alters the transcriptomic response of the endometrium in cattle

“…In addition to affecting sperm function, SP has been proposed to regulate the maternal environment. In mammals, including humans 11 , mice [12][13][14] , and livestock species such as horses 15 , pigs 16 , and sheep 17 , exposure to semen induces an inflammatory response in the female reproductive tract. It has been suggested that SP components are responsible for this modulation of the maternal immune response, creating an immune tolerogenic environment 18,19 which can lead to improved embryo development and fertility.…”