Oviduct: roles in fertilization and early embryo development

Prolonged in vivo functional assessment of the mouse oviduct using optical coherence tomography through a dorsal imaging window

The oviduct (or fallopian tube) serves as an environment for gamete transport, fertilization and preimplantation embryo development in mammals. Although there has been increasing evidence linking infertility with disrupted oviduct function, the specific roles that the oviduct plays in both normal and impaired reproductive processes remain unclear. The mouse is an important mammalian model to study human reproduction. However, most of the current analyses of the mouse oviduct rely on static histology or 2D visualization, and are unable to provide dynamic and volumetric characterization of this organ. The lack of imaging access prevents longitudinal live analysis of the oviduct and its associated reproductive events, limiting the understanding of mechanistic aspects of fertilization and preimplantation pregnancy. To address this limitation, we report a 3D imaging approach that enables prolonged functional assessment of the mouse oviduct in vivo. By combining optical coherence tomography with a dorsal imaging window, this method allows for extended volumetric visualization of the oviduct dynamics, which was previously not achievable. The approach is used for quantitative analysis of oviduct contraction, spatiotemporal characterization of cilia beat frequency and longitudinal imaging. This new approach is a useful in vivo imaging platform for a variety of live studies in mammalian reproduction.

Sex Steroid-Mediated Control of Oviductal Function in Cattle

In cattle, the oviduct is a tubular organ that connects the ovary and the uterus. The oviduct lumen stages a dynamic set of cellular and molecular interactions to fulfill the noble role of generating a new individual. Specific anatomical niches along the oviduct lumen provide the appropriate microenvironment for final sperm capacitation, oocyte capture and fertilization, and early embryo development and transport. To accomplish such complex tasks, the oviduct undergoes spatially and temporally-regulated morphological, biochemical, and physiological changes that are associated with endocrine events of the estrous cycle. Specifically, elevated periovulatory concentrations of estradiol (E2) and progesterone (P4) influence gene expression and morphological changes that have been associated positively to fertility in beef cattle. In this review, we explore how E2 and P4 influence oviductal function in the beginning of the estrous cycle, and prepare the oviductal lumen for interactions with gametes and embryos.

Metabolomic profiling of bovine oviductal fluid across the oestrous cycle using proton nuclear magnetic resonance spectroscopy

In the present study we tested whether regulation of the metabolome in bovine oviductal fluid depended on the stage of the oestrous cycle, the side relative to ovulation and local concentrations of steroid hormones. Luminal fluid samples from both oviducts were collected in the preovulatory, postovulatory, mid- and late luteal phases, from cyclic cows at a local abattoir (18–27 cows per stage and side). The metabolomes were assessed by proton nuclear magnetic resonance spectroscopy (H-NMR). In all, 39 metabolites were identified, among which the amino acid glycine and the energy substrates lactate and myoinositol were the most abundant at all stages. The concentrations of 14 metabolites varied according to the stage of the oestrous cycle in at least one side relative to ovulation, of which four (choline, glucose-1-phosphate, glycine and pyruvate) were correlated with intraoviductal progesterone or oestradiol concentrations. Glucose-1-phosphate was most affected by the stage of the cycle, with four- to sixfold higher levels in luteal than periovulatory stages. These results provide new knowledge on the regulation of secretory activity in the oviduct and may help optimise culture media for gamete maturation, IVF and embryo production.

In Vivo Imaging of the Mouse Reproductive Organs, Embryo Transfer, and Oviduct Cilia Dynamics Using Optical Coherence Tomography

The oviduct (or fallopian tube) serves as the site where a number of major reproductive events occur for the start of a new life in mammals. Understanding the oviduct physiology is essential to uncover hidden mechanisms of the human reproduction and its disorders, yet the current analysis of the oviduct that is largely limited to in vitro imaging is a significant technical hurdle. To overcome this barrier, we have recently developed in vivo approaches based on optical coherence tomography for structural and functional imaging of the mouse oviduct. In this chapter, we describe the details of such live imaging methods that allow for three-dimensional visualization of the oviduct wall morphology, microscale mapping of the oviduct cilia beat frequency, and high-resolution observation of the cumulus-oocyte complex at the cellular level. We expect this set of imaging tools will enable novel studies toward a comprehensive knowledge of the mammalian reproduction.

Introduction: A Brief Guide to the Periconception Environment

Definition of the periconception period is not an exact science and is probably somewhat arbitrary. One can define it as spanning the period from the final stages of gamete maturation until formation of the embryo and the stages of embryonic development and implantation. Hence, the periconception period includes periods when spermatozoa are in the female reproductive tract, oocytes are matured and ovulated into the oviduct, fertilization occurs and the embryo undergoes development. By definition the implantation process and the early stages of placenta formation are also regarded as a part of the periconception period. In this article we highlight a few of the major advances which have transformed this topic over the last two decades. It is now clear that the fitness and wellbeing of developing mammalian embryos, including the human, are highly dependent on the health status, diet and habits of both parents especially in the months and weeks that precede the formation of oocytes and spermatozoa.

Natural and environmental oestrogens induce TGFB1 synthesis in oviduct cells

Autocrine/paracrine factors generated in response to 17β-oestradiol (E2), within the oviduct, facilitate early embryo development for implantation. Since transforming growth factor beta 1 (TGFB1) plays a key role in embryo implantation, regulation of its synthesis by E2 may be of biological/pathophysiological relevance. Here, we investigated whether oviduct cells synthesize TGFB1 and whether E2 and environmental oestrogens (EOEs; xenoestrogens and phytoestrogens) modulate its synthesis. Under basal conditions, bovine oviduct cells (OCs; oviduct epithelial cells and oviduct fibroblasts; 1:1 ratio) synthesized TGFB1. E2 concentration-dependent induced TGFB1 levels in OCs and these effects were mimicked by some, but not all EOEs (genistein, biochanin A and 4-hydroxy-2',4',6'-trichlorobiphenyl, 4-hydroxy-2',4',6'-dichlorobiphenyl); moreover, EOEs enhanced (P < 0.05) the stimulatory effects of E2 on TGFB1 synthesis. The OCs expressed oestrogen receptors alpha and beta and aryl hydrocarbon; moreover, co-treatment with ER antagonist ICI182780 blocked the stimulatory effects of E2 and EOEs on TGFB1 synthesis. Treatment with non-permeable E2-BSA failed to induce TGFB1, thereby ruling out the involvement of membrane ERs. Cycloheximide (protein synthesis inhibitor) blocked E2-induced TGFB1 synthesis providing evidence for de novo synthesis. The stimulatory effects of E2 and EOEs, were inhibited (P < 0.05) by MAPK inhibitor (PD98059), whereas intracellular-Ca²⁺ chelator (BAPTA-AM) and adenylyl cyclase inhibitor (SQ22536) abrogated the effects of E2, but not EOEs, suggesting that post-ER effects of E2 and EOEs involve different pathways. Our results provide the first evidence that in OCs, E2 and EOEs stimulate TGFB1 synthesis via an ER-dependent pathway. Exposure of the oviduct to EOEs may result in continuous/sustained induction of TGFB1 levels in a non-cyclic fashion and may induce deleterious effects on reproduction.