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Context: Declining fertility is an issue in multiple mammalian species. As the site of fertilisation and early embryo development, the oviduct plays a critical role in embryo survival, yet there is a paucity of information on how the oviduct regulates this process. Aims: We hypothesised that differences in steroid hormone signalling and/or immune function would be observed in a model of poor embryo survival, the peripubertal ewe. Methods: We examined expression of steroid hormones in systemic circulation, oviductal expression of oestrogen receptor α and genes important in steroid hormone signalling, and immune function in pregnant and cyclic peripubertal and adult ewes on day 3 after oestrus. Key results: Concentrations of progesterone, but not oestradiol, were decreased in the peripubertal ewe compared to the adult ewe. Oestrogen receptor α protein expression was increased in the peripubertal ewe, but pathway analysis of gene expression revealed downregulation of the oestrogen signalling pathway compared to the adult ewe. Differential expression of several genes involved in immune function between the peripubertal and adult ewe was consistent with an unfavourable oviductal environment in the peripubertal ewe lamb. Oestradiol concentration was positively correlated with the expression of multiple genes involved in the regulation of immune function. Conclusions: Differences in the immune environment of the oviduct, potentially linked to differential modulation by steroid hormones, may partially underly the poor fertilisation and early embryo survival observed in the peripubertal ewe. Implications: A unfavourable oviductal environment may play an important role in limiting reproductive success. Declining fertility is an issue in multiple mammalian species, with around 15% of couples experiencing infertility. Differential expression of genes involved in inflammation, linked with altered steroid signalling in the oviduct, was observed in peripubertal ewes, a model of poor fertility. Ensuring that the oviductal environment does not become hostile to fertilisation and early embryo development may provide a novel approach to improve fertility, particularly in conditions associated with chronic low-grade inflammation. Photograph by Jenny Juengel. [ABSTRACT FROM AUTHOR]

Context. Mating of ewe lambs can increase farm profitability, although uptake is limited by low reproductive success. Reproductive loss to Day 35 of pregnancy in peripubertal ewe lambs is greater than in adult ewes; however, the precise timing of this loss is unknown. Aim. We aimed to define more clearly early embryo development and key times of loss in peripubertal ewes. Methods. Health and development of embryos from naturally cycling crossbred ewes ~8 months of age were recorded. Following mating across 2 years, ewes were assigned to three groups (n = 80-87 per group): assessed on Day 3 of pregnancy, on Day 14, or between Day 35 and birth. For Day 3 and Day 14 groups, ewes were humanely killed, and embryos were assessed by microscope following recovery from the reproductive tract. Ultrasonography at around Days 35 and 70, and lambing data, were used to assess loss in the third group. Key results. By Day 3 of pregnancy, 22.9% of ova released were not present as healthy embryos (P < 0.05). Embryo survival on Day 14 tended (P < 0.10) to decrease further, with 34.0% (±4.5%) of ova released not present as healthy embryos. No decrease was detected between Days 14 and 35, whereas between Day 35 and birth, an additional 6.8% reproductive loss occurred (P < 0.05). Attainment of puberty prior to introduction of the fertile ram did not affect reproductive loss. Structures collected on Day 3 ranged from one cell to 12 cells: 11% (13/120) being one cell; 49% (59/120) two to four cells; and the remainder (48/120) at least five or six cells. Conceptus length at Day 14 ranged from 5.3 to 200.0 mm, with large variation between and within animals; within-ewe variation was 67% of between-ewe variation. Concentration of progesterone at time of collection was associated (P < 0.001) with developmental stage on Day 3, but not Day 14, of pregnancy. Conclusions. Reproductive loss in peripubertal ewes primarily occurred prior to Day 14, with much of this loss before Day 3. Implications. Improving oocyte and oviduct quality is important to supporting normal fertilisation and early embryo development in peripubertal ewe lambs, thus improving reproductive success. [ABSTRACT FROM AUTHOR]

Abstract Background Recently, several members of the transforming growth factor-beta (TGF-beta) superfamily have been shown to be essential for regulating the growth and differentiation of ovarian follicles and thus fertility. Methods Ovaries of neonatal and adult sheep were examined for expression of the TGF-betas 1–3 and their receptors (RI and RII) by in situ hybridization using ovine cDNAs. The effects of TGF-beta 1 and 2 on proliferation and differentiation of ovine granulosa cells in vitro were also studied. Results The expression patterns of TGF-beta 1 and 2 were similar in that both mRNAs were first observed in thecal cells of type 3 (small pre-antral) follicles. Expression of both mRNAs continued to be observed in the theca of larger follicles and was also present in cells within the stroma and associated with the vascular system of the ovary. There was no evidence for expression in granulosa cells or oocytes. Expression of TGF-beta 3 mRNA was limited to cells associated with the vascular system within the ovary. TGFbetaRI mRNA was observed in oocytes from the type 1 (primordial) to type 5 (antral) stages of follicular growth and granulosa and thecal cells expressed this mRNA at the type 3 (small pre-antral) and subsequent stages of development. The TGFbetaRI signal was also observed in the ovarian stroma and vascular cells. In ovarian follicles, mRNA encoding TGFbetaRII was restricted to thecal cells of type 3 (small pre-antral) and larger follicles. In addition, expression was also observed in some cells of the surface epithelium and in some stromal cells. In granulosa cells cultured for 6 days, both TGF-beta 1 and 2 decreased, in a dose dependent manner, both the amount of DNA and concentration of progesterone. Conclusion In summary, mRNA encoding both TGF-beta 1 and 2 were synthesized by ovarian theca, stroma and cells of the vascular system whereas TGF-beta 3 mRNA was synthesized by vascular cells. Luteinizing granulosa cells also responded to both TGF-beta 1 and beta 2 in vitro. These findings in sheep are consistent with TGF-beta potentially being an important autocrine regulator of thecal cell function and possibly a paracrine regulator of ovarian cell function at various development stages.

I. INTRODUCTION A. Historical Perspective Corpora (bodies) lutea (yellow) were named by Marcello Malpighi (1628--1694) and first accurately described by Regnier de Graaf (1641--1673) who noted that after coitus 'globular [...]

The ability of an oocyte to undergo successful cytoplasmic and nuclear maturation, fertilization and embryo development is referred to as the oocyte's quality or developmental competence. Quality is dependent on the accumulation of organelles, metabolites and maternal RNAs during the growth and maturation of the oocyte. Various models of good and poor oocyte quality have been used to understand the essential contributors to developmental success. This review covers the current knowledge of how oocyte organelle quantity, distribution and morphology differ between good and poor quality oocytes. The models of oocyte quality are also described and their usefulness for studying the intrinsic quality of an oocyte discussed. Understanding the key critical features of cytoplasmic organelles and metabolites driving oocyte quality will lead to methods for identifying high quality oocytes and improving oocyte competence, both in vitro and in vivo. [ABSTRACT FROM AUTHOR]

The oocyte-derived growth factor bone morphogenetic protein (BMP) 15 plays important roles in fertility, but its mechanism of action differs between species. Generation of BMP15-binding molecules, as an essential investigation tool, would be helpful to provide valuable insight into the underlying biological features of BMP15. The BMP15-binding molecules could be antibodies or aptamers. Aptamers have many advantages over antibodies as macromolecular ligands for target proteins. DNA aptamers can be obtained by a method of Systematic Evolution of Ligands by EXponential enrichment (SELEX) beginning with a pool of random sequences. However, the success of this technique cannot be guaranteed if the initial pool lacks candidate sequences. Herein, we report on the creation of DNA aptamers by means of modified SELEX. The modification included enhanced mutation and progressive selection during an in vitro evolutionary process. As a proof-of-principle, we started from a single sequence instead of a multiple-sequence pool. Functional aptamers against the recombinant BMP15 were successfully created and identified. [ABSTRACT FROM AUTHOR]