Embryos experience stress when they are grown in the laboratory, and this is believed to be detrimental to the embryo later in life. This article reviews the effects of in vitro conditions on the embryo and the mechanisms involved. By having a greater understanding of the mechanisms, we can potentially prevent stress during embryo growth in vitro.

Oxygen is a key component of the environment during oocyte maturation, in vivo and in vitro. Expression of target genes of the hypoxia-inducible factors was increased in cumulus cells from mouse cumulus–oocyte complexes matured in vitro at 2% or 5%, compared with 20% oxygen. Oxygen-regulated gene expression is identified as a potential mechanism through which oxygen could influence cumulus cell function.

Ezh2 controls the fate of mouse embryos at an early stage. We investigated Ezh2 expression during preimplantation and found that lacking Ezh2 results in mouse embryos with severe development defects. Our results showed that Ezh2 affect mouse embryo development through the regulation of epigenetic modification, gene expression and apoptosis.

A novel direct bovine embryo-tagging system has been developed using polysilicon barcodes. This system allows the collective culture of embryos from different origins whilst preserving their pedigree, and facilitates the production of embryos from live animals of high genetic merit.

Oocyte cryopreservation is important for assisted reproductive technologies (ART) in both human and animals. This study showed that ovine oocytes vitrified at GV stages using cryoloop have the ability to be matured, fertilised and subsequently develop in vitro and produce good quality blastocysts at comparable trends like those seen in fresh control groups. The vitrification protocols used here may be a promising tool for the establishment of oocyte cryobanks.

The regulation of uterine function is a complex multifactorial process, considered paramount for equine fertility. The present study investigated the presence of cytokines (tumour necrosis factor (TNF)-α, interferon-γ, Fas ligand) and their receptors in the mare endometrium and the ability of TNF-α, together with steroid hormones and oxytocin, to modulate endometrial physiology. A coordinated action between cytokines and ovarian hormones may regulate secretory, vascular and proliferative functions in the equine endometrium.

It has been known for some time that, despite of their compact chromatin, spermatozoa contain mRNA. It has been suggested that this mRNA could be a candidate marker for the evaluation of sperm quality. In the present study, we confirm the relationship between early embryo development and the abundance of mRNA in spermatozoa to suggest its use as a marker of sperm quality in the pig. These results could help in the development of a new diagnostic method to evaluate sperm quality.

The ovary, with its predictable cycles of growth and regression of new blood vessels, has been used to identify and study key molecular pathways involved in angiogenesis. This review describes the potential for the therapeutic manipulation of ovarian angiogenesis and the translation of these findings into the clinic. Some treatments are already in clinical use and there is real potential for the development of additional therapies in the future.

The corpus luteum (CL) is a transient endocrine organ that produces progesterone to achieve pregnancy. It grows rapidly from the site of ovulation with extremely active angiogenesis, like a ‘transitory tumour’. The exquisite balance between angiogenesis and the differentiation of steroidogenic cells is regulated by timely recruitment of immune cells. Neutrophils and macrophages are novel pivotal regulators not only of innate immunity, but also the success of pregnancy by accelerating angiogenesis to build up the CL.

The seasonal infertility period in sows is the most economically important reproductive problem for pig producers. Significantly, there is an increase in pregnancy loss during this time. This review summarises recent advancements made in our understanding of the mechanisms that contribute to this reduced fertility. With emphasis on seasonal variation in ovarian function and its influence on subsequent fertility, there is clear evidence that reduced oocyte developmental competence contributes to seasonal infertility. With this new information in mind, researchers and producers can now devise strategies to overcome the seasonal infertility phenomenon.

Vitrification is a crypreservation technique enabling to freeze spermatozoa in a fast and simplified fashion. However, the use of vitrified spermatozoa in assisted reproduction has been limited, and no live births have been reported to date. We report the birth of two healthy babies following ICSI using motile spermatozoa vitrified without permeable cryoprotectants, suggesting that this technique can be successfully applied to achieve normal pregnancy and birth.