Is the pre-antral ovarian follicle the 'holy grail'for female fertility preservation?

Fertility preservation is not only a concern for humans with compromised fertility after cancer treatment. The preservation of genetic material from endangered animal species or animals with important genetic traits will also greatly benefit from the development of alternative fertility preservation strategies. In humans, embryo cryopreservation and mature-oocyte cryopreservation are currently the only approved methods for fertility preservation.

Image-guided phenotyping of ovariectomized mice: altered functional connectivity, cognition, myelination, and dopaminergic functionality.

A large proportion of the population suffers from endocrine disruption, e.g., menopausal women, which might result in accelerated aging and a higher risk for developing cognitive disorders.

Effects of vitrification on the viability of alginate encapsulated isolated bovine pre-antral follicles.

Purpose: Individual follicle cryopreservation techniques, without hydrogel support, are labor-intensive and a substantial proportion of isolated follicles are lost during handling and after warming. Therefore, the viability and morphology of isolated bovine (as a model for human) pre-antral follicles after vitrification and warming, when encapsulated in alginate beads, were investigated.

Methods: Bovine pre-antral follicles were mechanically isolated and divided into four different groups: (1) culture in 2% alginate beads (3D system) and vitrification in beads using mesh cups (3DVIT), (2) culture in 2% alginate beads (3DCUL), (3) culture in 96-well plates (2D system) and vitrification using High Security Vitrification straws® (2DVIT), (4) culture in a 2D system (2DCUL).

The effect of a negative energy balance status on β-carotene availability in serum and follicular fluid of nonlactating dairy cows.

Maternal metabolic pressure due to a cow's negative energy balance (NEB) has a negative effect on oocyte quality as a result of increased oxidative stress. In this study, we hypothesized that a NEB status may negatively affect the availability of β-carotene (bC, an antioxidant) in the micro-environment of the oocyte or follicular fluid (FF) and that daily bC supplementation can increase bC availability. We aimed to (1) determine the effect of a nutritionally induced NEB on bC concentrations in serum and FF as well as on the presence of bC metabolites, oxidative stress levels, and follicular growth in a nonlactating dairy cow model, and (2) investigate how this effect could be altered by dietary bC supplementation.

Endometrial transcriptional profiling of a bovine fertility model by Next-Generation Sequencing.

Studying the multitude of molecular networks and pathways that are potentially involved in a complex trait such as fertility requires an equally complex and broad strategy. Here, we used Next-Generation Sequencing for the characterization of the transcriptional signature of the bovine endometrial tissue. Periovulatory endocrine environments were manipulated to generate two distinctly different fertility phenotypes.

Morphometrical analysis of preantral follicular survival of VEGF-treated bovine ovarian cortex tissue following xenotransplantation in an immune deficient mouse model.

The increasing number of cancer survivors the past decades, has sparked the need for fertility preservation strategies. Due to predominantly ethical constraints, human research material is scarce. A bovine in vitro model is a valuable alternative.

The Receptive Endometrial Transcriptomic Signature Indicates an Earlier Shift from Proliferation to Metabolism at Early Diestrus in the Cow.

This study aimed to characterize the endometrial transcriptome and functional pathways overrepresented in the endometrium of cows treated to ovulate larger (≥13 mm) versus smaller (≤12 mm) follicles. Nelore cows were presynchronized prior to receiving cloprostenol (large follicle [LF] group) or not (small follicle [SF] group), along with a progesterone (P4) device on Day (D) -10. Devices were withdrawn and cloprostenol administered 42-60 h (LF) or 30-36 h (SF) before GnRH agonist treatment (D0).

Bovine in vitro reproduction models can contribute to the development of (female) fertility preservation strategies.

Recent increases in the number of successful cancer treatments have stimulated interest in fertility preservation strategies in women of reproductive age and in prepubertal girls. However, research on the application of such programs under clinical conditions suffers from the scarce availability of human tissue for research purposes and from concurrent relevant ethical issues. To partly address this problem, this review focuses on the possibilities of ruminant in vitro models providing additional insights into several aspects of fertility preservation, ranging from preantral follicle collection to oocyte and follicle cryopreservation, to noninvasive quality assessment, and to follicle culture.

Morphologic characterization of isolated bovine early preantral follicles during short-term individual in vitro culture.

To provide new insights in the molecular mechanism controlling preantral follicular development and to unravel the needs to support in vitro follicular development of early-stage preantral follicles (PAFs), there is a need for alternative in vitro bovine follicle culture methods. In this study, we aimed to characterize follicular dynamics using an IVC system of isolated and individually cultured bovine early PAFs during 10 days to generate individual follicle follow-up data. Preantral follicles (<50 μm) were isolated from slaughterhouse ovaries and cultured individually for 10 days.

Effects of neutral red assisted viability assessment on the cryotolerance of isolated bovine preantral follicles.

Purpose: Fertility preservation strategies warrant non-invasive viability assessment of preantral follicles (PAF) such as staining with Neutral Red (NR) that is incorporated by viable follicles. To optimize the procedure, we firstly determined the lowest concentration and shortest exposure time needed for optimal viability screening of isolated bovine PAF. Secondly, we combined this protocol to a vitrification procedure to assess cryotolerance of the stained follicles.

Characterization of freshly retrieved preantral follicles using a low-invasive, mechanical isolation method extended to different ruminant species.

Due to the increased interest in preantral follicular physiology, non-invasive retrieval and morphological classification are crucial. Therefore, this study aimed: (1) to standardize a minimally invasive isolation protocol, applicable to three ruminant species; (2) to morphologically classify preantral follicles upon retrieval; and (3) to describe morphological features of freshly retrieved follicles compared with follicle characteristics using invasive methods. Bovine, caprine and ovine ovarian cortex strips were retrieved from slaughterhouse ovaries and dispersed.

Monitoring preantral follicle survival and growth in bovine ovarian biopsies by repeated use of neutral red and cultured in vitro under low and high oxygen tension.

The development and optimization of preantral follicle culture methods are crucial in fertility preservation strategies. As preantral follicle dynamics are usually assessed by various invasive techniques, the need for alternative noninvasive evaluation tools exists. Recently, neutral red (NR) was put forward to visualize preantral follicles in situ within ovarian cortical fragments.

Effects of parity and periconceptional metabolic state of Holstein-Friesian dams on the glucose metabolism and conformation in their newborn calves.

The metabolic state of pregnant mammals influences the offspring's development and risk of metabolic disease in postnatal life. The metabolic state in a lactating dairy cow differs immensely from that in a non-lactating heifer around the time of conception, but consequences for their calves are poorly understood. The hypothesis of this study was that differences in metabolic state between non-lactating heifers and lactating cows during early pregnancy would affect insulin-dependent glucose metabolism and development in their neonatal calves.

Unravelling the needs of singly in vitro-produced bovine embryos: from cumulus cell co-culture to semi-defined, oil-free culture conditions.

Producing bovine in vitro embryos individually is a challenge as it generally leads to impaired embryo development. Earlier research optimised a single embryo in vitro production (IVP) protocol using serum, cumulus cells and oil during culture. As some of these factors are undesirable in certain circumstances, the present study investigated their necessity and possible interactions, and defined their role during single-embryo culture.

Xenotransplantation in immunodeficient mice to study ovarian follicular development in domestic animals.

Nowadays, in vitro study of follicular dynamics of primordial and primary follicular stages is limited because in vitro culture systems for these follicles are lacking, both in domestic animal species and in human. Therefore, additional insights might be generated by grafting ovarian tissue into immunodeficient mice to study activation and maturation of early follicular stages. A considerable amount of data has already been gathered in laboratory animals and through clinical application of human assisted reproduction technologies where live births were reported recently after the use of (cryopreserved) ovarian grafts.