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Type: Thesis
Title: Regulators of seminal fluid signalling and their impact on gene expression during the peri-implantation period of pregnancy
Author: Chan, Hon Yeung
Issue Date: 2020
School/Discipline: Adelaide Medical School
Abstract: Seminal fluid is no longer viewed as merely a medium for the delivery and survival of sperm in the female reproductive tract. Molecules in seminal fluid can interact with the female tract to elicit cellular responses that drive fetomaternal immune adaptation to prevent inappropriate immune responses towards the fetus. Several signalling molecules within the seminal plasma fraction that drive immune adaptation have been characterised, but there are other, as yet unidentified factors that contribute to seminal fluid signalling capacity. Although it has been suggested that seminal fluid contributes to healthy pregnancy and long-term offspring health, the underlying molecular mechanisms are not well understood. Hence, the aims of this thesis are to (1) identify factors that influence and mediate seminal fluid signalling potential, and to (2) expand knowledge on the cellular mechanisms regulated by seminal fluid in the uterus during the peri-implantation period. Using microRNA-146a-null (miR-146a-/-) mice, we investigated the contribution of paternal miR-146a to seminal fluid signalling capacity, and pregnancy outcomes. miR-146a is involved in regulation of the inflammatory response and has been postulated to contribute to male reproductive function. miR-146a-/- males exhibited poor sperm quality and seminal fluid from these males exhibited reduced capacity to induce female expression of Cxcl2 and Il6 at 8 hours (h) post-coitum (pc). Despite reduced reproductive parameters, miR-146a-/- males sired litters with more viable pups on day (D) 17.5 pc and the allocation of reproductive resources appeared to be altered. However at birth, this increase in litter size was no longer evident compared to litters sired by miR-146a+/+ males. This corresponds to a loss of viable offspring in the late gestation/early neonatal period in miR-146a-/- males-sired litters. These findings suggest paternal miR-146a may influence the female response to impact female ‘quality control’ of embryo implantation and development. We then investigated the contribution of maternal TLR4 to the female post-mating cytokine response and the subsequent pregnancy outcomes using TLR4-null (Tlr4-/-) mice. In mated Tlr4-/- females, a reduction in neutrophil recruiting factors Il6, Cxcl2 and microRNA-223 (miR-223) expression, and in neutrophil recruitment to the endometrium was evident at 8h pc. In addition, we showed that sperm may further induce Il6, Cxcl2 and miR-223 in the endometrium via TLR4 activation. On D17.5pc, there were less viable fetuses in litters carried by Tlr4-/- females, with smaller viable fetuses and increased placental size. These results suggest that maternal TLR4 plays a key role in fetal outcomes potentially by modulating uterine immune environment during early pregnancy. RNA-sequencing was employed to assess gene expression and cellular responses regulated by components of seminal fluid in the pre-implantation endometrium (D3.5pc). We identified a number of genes induced by seminal fluid including Cd8a and Tcrg-C1, with T cell receptor (TCR) signalling pathway amongst the top 10 pathways regulated by seminal fluid. Small RNA-sequencing identified microRNA-155 (miR-155), a factor that is key to regulatory T cell functions, to be highly regulated by seminal fluid on D3.5pc. These results are consistent with existing data that seminal fluid regulates T cell populations in the uterus, and suggest that TCRγδ+ T cells are an hitherto unstudied population requiring further investigation in the female tract at peri-implantation. These data collectively build the understanding of factors that regulate seminal fluid signalling and the effect of seminal fluid on endometrial gene expression during peri-implantation, which may help elucidate new factors that contribute to infertility, and ultimately be useful in leading to new treatments to alleviate conditions in infertile/subfertile patients.
Advisor: Robertson, Sarah
Schjenken, John
Dissertation Note: Thesis (Ph.D.) -- University of Adelaide, Adelaide Medical School, 2020
Keywords: Seminal fluid
Provenance: This thesis is currently under Embargo and not available.
Appears in Collections:Research Theses

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