Infertility affects about 15% of the population and male factors only are responsible for ~25–30% of cases of infertility. Currently, the etiology of suboptimal semen quality is poorly understood, and many environmental and genetic factors, including oxidative stress, have been implicated. Oxidative stress is an imbalance between the production of free radicals, or reactive oxygen species (ROS), and the capacity of the body to counteract their harmful effects through neutralization by antioxidants. The purpose of this review, by employing the joint expertise of international researchers specialized in nutrition and male fertility areas, is to update the knowledge about the reproductive consequences of excessive ROS concentrations and oxidative stress on the semen quality and Assisted Reproduction Techniques (ART) clinical outcomes, to discuss the role of antioxidants in fertility outcomes, and finally to discuss why foods and dietary patterns are more innocuous long term solution for ameliorating oxidative stress and therefore semen quality results and ART fertility outcomes. Since this is a narrative review and not a systematic/meta-analysis, the summarized information in the present study should be considered cautiously.

Declining reproductive health and fertility are global public health issues affecting an estimated 15% of reproductive-aged couples worldwide. The reasons for declining fertility are complex. However, a male contribution is thought to occur in ∼50% of infertile couples. Deficits in sperm number and/or function are undeniably a major cause of infertility, but compelling evidence suggests that additional factors in the male ejaculate also play an influential and underappreciated role. In this review, we focus specifically on extracellular vesicles within human seminal plasma and explore their emerging roles in reproduction and fertility. These seminal extracellular vesicles (SEVs) are nano-sized membrane structures secreted by various cell lineages in virtually all regions of the male reproductive tract and exert key roles in intercellular communication. Consideration is given to the well-characterized effects of SEVs in supporting sperm as they transit through the female reproductive tract and their ability to modulate the immune environment within the female reproductive tract. Building on these important roles, we also detail the emerging links between dysregulated SEV production and male fertility status, and highlight the potential utility of leveraging these vesicles to improve fertility and reproductive outcomes in infertile couples. Altogether, this review highlights how expanding knowledge of SEVs provides a new perspective on the complexity of seminal fluid physiology and the underlying aetiology of male infertility.

Kinetochores are complex protein assemblies at centromeres that direct and regulate chromosome segregation1. During gamete formation by meiosis, kinetochore specialisations drive two sequential and distinct segregation events to partition half the genome to the offspring2,3. Age-dependent segregation errors in human oocytes are a major cause of reproductive failure and are linked to kinetochore dysfunction4-6, however the molecular composition and function of mammalian meiotic centromeric chromatin and kinetochores remains poorly defined. Here, we reconstitute vertebrate meiosis I and II centromeric chromatin using meiosis I and II endogenous proteins to uncover conserved regulators of chromosome segregation in mammalian meiosis. We find that, in addition to canonical kinetochore proteins, a specific subset of chromatin regulators is enriched on meiotic centromeric chromatin. We discover previously unrecognized kinetochore proteins conserved from frogs to mouse and humans and demonstrate their localisation at mammalian oocyte centromeres. Among these, we show that the newly identified centromeric protein HSPBAP1, is required to maintain chromosome integrity and ensure faithful segregation in both mouse and human oocytes. These findings define the composition of vertebrate meiotic kinetochores and uncover conserved factors that safeguard mammalian meiotic chromosome segregation, a highly error-prone process and major cause of aneuploidy and reproductive failure in humans7.