Spermiation is the culmination of a spermatid’s journey in the seminiferous epithelium, which is regulated by a number of endocrine and paracrine factors. Being one of the most sensitive phases of spermatogenesis means that any adverse effects on spermiation can affect the sperm concentration. Hence it is crucial to understand the mechanism and molecular control to advance our knowledge on the nuances of spermatogenesis and male fertility. This review focuses on the endocrine aspect of spermiation and gives an overview on how different hormones influence the process of spermiation.

Phthalate esters are endocrine disrupters that can affect male gonad and testosterone production in a species-specific manner. This study evaluated the consequences of prenatal exposure to di-n-butyl phthalate (DBP; 100 mg kg⁻¹ day⁻¹ in mineral oil) on testis development in the Mongolian gerbil. Both DBP and mineral oil (vehicle) affected the number of germ cells and plasma testosterone concentrations on Postnatal Day 7, and the mineral oil increased oestrogen concentrations at 28 days by approximately 112%.

The Booroola fecundity gene (FecB) mutation is highly related to ovulation rate and litter size in sheep. Through the clustered regularly interspaced short palindromic repeat (CRISPR) approach, we successfully introduced a defined FecB^B mutation, resulting in single amino acid substitutions in the proteins, as expected, in sheep. This study represents a significant development for improving reproduction traits in sheep, as well as for validating the function of single nucleotide polymorphisms in large animals.

The effects of multiple oestrus synchronisation (ES) treatments on ovarian gene expression of goats remained unknown. RNA sequencing of ovaries from goats subjected to triple ES treatments identified 319 differentially expressed genes including 11 novel genes related to reproductive performance. The results indicated that multiple ES treatments changed gene expression, potentially affected ovarian function, neural regulation and hormone secretion.

Methylation can regulate expression of genes. We observed higher methylation of progesterone receptor isoform A than B gene promoters in bovine corpus luteum (CL) and endometrium. This may indicate that methylation affects isoform A expression, which inhibits activity of isoform B and in this way regulates the effect of progesterone in CL and endometrium.

Multiple genes of the transforming growth factor beta (TGFß) signaling pathway have known variants affecting ovulation rate, including SMAD6 in cattle. Protein levels in follicular fluid of carriers of a SMAD6 mutation were characterized and multiple proteins were found in reduced concentration. Several of these proteins are the product of genes whose expression is known to be stimulated by the TGFß signaling pathway, making underexpression consistent with the inhibitory role of SMAD6 on this pathway.

Proper temporal organisation of luteal regression is crucial for reproductive function. Such temporal regulation may involve the endogenous cellular clock. In this study we investigated whether tumour necrosis factor (TNF)-α, via p55 TNF receptor (TNFRp55), participates in the regulation of circadian rhythms of factors related to luteal regression in the ovary during dioestrus. The findings demonstrate that TNFRp55 is crucial for the sequence of events and temporal relationship between factors that trigger luteal regression. Data from this study highlight the endogenous clock and TNFRp55 signalling as potential novel therapeutic targets for gynaecological disorders.

In mammals, the oviduct is responsible carrying the embryos while they develop before they implant in the uterus. This process is regulated by ovarian hormones, like progesterone. In this study we show that progesterone affects the actions of local neurotransmitters that control ciliary beat frequency and the transport of embryos, observations that allow us to gain an insight into the mechanism associated with hormonal pathophysiological conditions in which fertility is decreased.

Amino acids (AA) are essential for embryo development, and specific transporters are required to transport AA from the maternal side (uterus) to the embryo side (membranes). We investigated the expression of AA transporters in the uterus and embryonic membranes during early horse pregnancy. Many transporters are expressed in the uterus, but a wider range of transporters is present in the membranes, which could ensure adequate nutrient provision.

Given the importance of angiogenesis for the maintenance of pregnancy, we investigated the role of endothelial progenitor cells in the development and maintenance of the vasculature during pregnancy. We found increased concentrations of circulating endothelial progenitor cells in pregnant women with premature rupture of membranes, which could be due to an increased concentration of oestrogen in these women. Endothelial progenitor cells should be considered as an attractive target for the control of this condition.

Progesterone affects embryo growth and survival in early pregnancy. This study demonstrated that the timing of administration of exogenous progesterone during the pre-implantation period was critical to achieving enhanced embryo growth, altered maternal uterine gene expression and increased pregnancy rates. Our results provide additional insights into maternally driven mechanisms that advance embryo growth and survival.

One of the main reasons for female infertility is disrupted endocrinology caused by life stress. This study aimed to clarify whether high levels of insulin and androgen cause epigenetic changes in oocytes. We showed that whole genome DNA methylation status is not altered, but that methylation of some gene loci does occur. This provides a basis for understanding the adverse effect of disrupted endocrinology on fertility.

Next-generation sequencing (NGS) is probably the most advanced way to determine the genetic status of embryos. This study clearly shows the potential of NGS used in preimplantation genetic testing, with an almost twofold increase in the live birth ratio, a significant increase in the implantation ratio and clinical pregnancies and an almost threefold decrease in the pregnancy loss ratio. We believe that NGS preimplantation genetic testing is a powerful, yet still underestimated tool in assisted reproduction.

The developmental competence of oocytes matured in vitro can be enhanced by antioxidant agents. This study describes nuclear and cytoplasmic events associated with the maturation process and early embryo development when the in vitro maturation (IVM) medium is supplemented with α-tocopherol. At 100 μM, α-tocopherol effectively minimised oxidative stress and increased the developmental competence of rabbit oocytes in vitro.

Maturation of mammalian eggs is highly prone to chromosome segregation errors that markedly reduce female fertility. In the present study, we showed that platelet-activating factor acetylhydrolase 1B3 is localised at the meiotic spindle structure and that functional inhibition of this enzyme leads to defective spindle morphology and failure of polar body extrusion. These findings help us to better understand the origin of errors of female meiosis, causing miscarriages and congenital defects.

The overuse of bupropion among adults has been increasing and previous studies showed a relationship between antidepressants and male reproductive system dysfunction. This study investigated the effects of bupropion on mouse testicular function and evaluated offspring development. There was an observed decrease in Sertoli and Leydig cells and in testosterone levels and impaired sperm structure, as well as congenital abnormalities in the offspring.

A receptive endometrium is essential for embryo implantation in mammalian reproduction. This study shows that the circRNA-9119–miR-26a–prostaglandin-endoperoxide synthase 2 pathway may be a potential target to regulate the development of receptive endometrium. The findings of this study may provide essential information to support further research into the development of the endometrium and improve reproductive function and fecundity.

In postpartum dairy cows elevated non-esterified fatty acids (NEFAs) alter reproductive efficiency. The mechanisms by which NEFAs affect bovine endometrial epithelial cells (bEECs) were investigated in vitro. Oleic and palmitic acid decreased the survival of bEEC, increased apoptosis and induced the release of pro-inflammatory cytokines. These changes may alter the uterine environment, especially at the time of implantation, and may affect fertility.

In this study, proteomics based on isobaric tags for relative and absolute quantification (iTRAQ) analysis was used to explore the possible mechanism underlying spermatogenic dysfunction caused by intense exercise. Related proteins, including vimentin, Apolipoprotein A1, collagen α-1(I) chain, fatty acid-binding protein 9 and 40S ribosomal protein S3a, were screened, and ribosome and extracellular matrix–receptor interaction pathways were found to be involved in signal transduction. These results provide new ideas for male infertility research.