The road to maturation: somatic cell interaction and self-organization of the mammalian oocyte.

Mammalian oocytes go through a long and complex developmental process while acquiring the competencies that are required for fertilization and embryogenesis. Recent advances in molecular genetics and quantitative live imaging reveal new insights into the molecular basis of the communication between the oocyte and ovarian somatic cells as well as the dynamic cytoskeleton-based events that drive each step along the pathway to maturity. Whereas self-organization of microtubules and motor proteins direct meiotic spindle assembly for achieving genome reduction, actin filaments are instrumental for spindle positioning and the establishment of oocyte polarity needed for extrusion of polar bodies. Meiotic chromatin provides key instructive signals while being 'chauffeured' by both cytoskeletal systems.

Use of confocal microscopy and intracytoplasmic sperm injection (ICSI) to assess viability of equine oocytes from young and old mares after vitrification.

BACKGROUND: The impact of vitrification on oocyte developmental competence as a function of donor age remains an important issue in assisted reproductive technologies (ARTs). METHODS: Equine germinal vesicle (GV) or metaphase II (M(II) oocytes were vitrified using the Cryotop® method. Spindle organization and chromosome alignment were evaluated from confocal imaging data sets of in vivo (IVO) or in vitro (IVM) matured oocytes subjected to vitrification or not. Intracytoplasmic sperm injection (ICSI) from the same groups was used to assess developmental potential. RESULTS: An increase in chromosome misalignment was observed in spindles from older mares when compared to those of younger mares (P < 0.05). When MII oocytes subjected to vitrification were examined following warming, there was no difference in the percentage of oocytes displaying chromosome misalignment. Next, GV oocytes, collected from the ovaries of younger and older mares, were compared between fresh IVM and IVM following vitrification and warming. For nonvitrified samples, an age difference was again noted for spindle organization and chromosome alignment, with a higher (P < 0.05) percentage of normal bipolar meiotic spindles with aligned chromosomes observed in nonvitrified oocytes from young versus older mares. Vitrification led to a reduction of spindle length (P < 0.05) for oocytes from old mares, whether vitrified at GV or MII stages, whereas this effect was not observed in oocytes from young mares except those vitrified at GV and subjected to IVM. Oocyte developmental potential after vitrification was evaluated after ICSI of vitrified and warmed MII or GV oocytes from young mares. From 25 MII oocytes, 18 oocytes were injected with sperm, and six blastocysts were produced, which, upon transfer to mares' uteri, resulted in four pregnancies. Immature (GV) oocytes collected from live mares were also vitrified, warmed, and matured in vitro before ICSI. In this group, nonvitrified, control, and vitrified oocytes did not differ (P > 0.05) with respect to the incidence of maturation to MII, cleavage after ICSI, or blastocyst development. CONCLUSION: These findings demonstrate an effect of maternal age in an equine model at the level of meiotic spindle integrity and chromosome positioning that is influenced by both the meiotic stage at which oocytes are vitrified and whether meiotic maturation occurred in vivo or in vitro.

The changing world of IVF: the pros and cons of new business models offering assisted reproductive technologies.

This analysis contrasts traditional not-for-profit academic with new corporate practices of reproductive medicine and offers an assessment of risks to quality of patient care with investors entering the for-profit reproductive medicine market. Large corporate enterprises may have a global impact on access to care while at the same time is putting at risk the training of the next generation of reproductive medicine specialists.

Protecting life in a time of war.

Despite centuries of lessons from history, war endures. Across Earth, during nearly every year from the beginning of the twentieth century to present day, over 30 wars have been fought resulting in 187 million casualties, excluding the most recent conflict, which is the impetus for this essay (Timeline of 20th and 21st century wars). We are, sadly, a war-mongering people. The word "war" word infiltrates our vernacular, e.g., the war on poverty, on drugs, on cancer, on COVID, and, apropos, on terror. How did rational approaches to disagreement and conflict evade the world's progress? Reproductive physicians and scientists are dedicated to safeguard lives and build families. Violence is antithetical to our mission as professionals, and moral integrity as humans. We are deeply concerned for, and stand in unity with, our Ukrainian colleagues-the embryologists, scientists, OBGYN and REI physicians, infertility patients, and all people under siege. Reproductive health services for Ukrainians (as with many other war-torn regions) have collapsed. Deeply disturbing reports have emerged that cite civilian hospitals (including maternity centers) being targeted. Liquid nitrogen supplies are scarce. Pregnant mothers and gestational carriers are at emergent risk of delivering in extremely harsh conditions, cold underground bunkers and refugee queues.

The subcortical maternal complex: emerging roles and novel perspectives.

Since its recent discovery, the subcortical maternal complex (SCMC) is emerging as a maternally inherited and crucial biological structure for the initial stages of embryogenesis in mammals. Uniquely expressed in oocytes and preimplantation embryos, where it localizes to the cell subcortex, this multiprotein complex is essential for early embryo development in the mouse and is functionally conserved across mammalian species, including humans. The complex has been linked to key processes leading the transition from oocyte to embryo, including meiotic spindle formation and positioning, regulation of translation, organelle redistribution, and epigenetic reprogramming. Yet, the underlying molecular mechanisms for these diverse functions are just beginning to be understood, hindered by unresolved interplay of SCMC components and variations in early lethal phenotypes. Here we review recent advances confirming involvement of the SCMC in human infertility, revealing an unexpected relationship with offspring health. Moreover, SCMC organization is being further revealed in terms of novel components and interactions with additional cell constituents. Collectively, this evidence prompts new avenues of investigation into possible roles during the process of oogenesis and the regulation of maternal transcript turnover during the oocyte to embryo transition.

Germ cell nests in adult ovaries and an unusually large ovarian reserve in the naked mole-rat.

The naked mole-rat (NMR, Heterocephalus glaber) is renowned for its eusociality and exceptionally long lifespan (> 30 y) relative to its small body size (35-40 g). A NMR phenomenon that has received far less attention is that females show no decline in fertility or fecundity into their third decade of life. The age of onset of reproductive decline in many mammalian species is closely associated with the number of germ cells remaining at the age of sexual maturity. We quantified ovarian reserve size in NMRs at the youngest age (6 months) when subordinate females can begin to ovulate after removal from the queen's suppression. We then compared the NMR ovarian reserve size to values for 19 other mammalian species that were previously reported. The NMR ovarian reserve at 6 months of age is exceptionally large at 108,588 ± 69,890 primordial follicles, which is more than 10-fold larger than in mammals of a comparable size. We also observed germ cell nests in ovaries from 6-month-old NMRs, which is highly unusual since breakdown of germ cell nests and the formation of primordial follicles is generally complete by early postnatal life in other mammals. Additionally, we found germ cell nests in young adult NMRs between 1.25 and 3.75 years of age, in both reproductively activated and suppressed females. The unusually large NMR ovarian reserve provides one mechanism to account for this species' protracted fertility. Whether germ cell nests in adult ovaries contribute to the NMR's long reproductive lifespan remains to be determined.

The slippery slope antedating syngamy: pronuclear activity in preparation for the first cleavage.

Nucleolus precursor bodies (NPB) are aggregations of intrapronuclear material observed in the pronuclei of fertilized human eggs. They derive from and evolve into nucleoli of the growing oocyte and the early embryo, respectively. Decades-old observations suggest that the patterns of their distribution represent a morphological marker of embryo developmental competence. Recent time-lapse microscopy (TLM) data now indicate that the vectorial characteristics of NPB movement can predict blastocyst formation, euploidy, and implantation. Since distributions of NPB and chromatin coincide, chromatin rearrangement in preparation for the first mitotic cleavage is emerging as a crucial process of early development.

Perspectives on the development and future of oocyte IVM in clinical practice.

Oocyte in vitro maturation (IVM) is an assisted reproductive technology designed to obtain mature oocytes following culture of immature cumulus-oocyte complexes collected from antral follicles. Although IVM has been practiced for decades and is no longer considered experimental, the uptake of IVM in clinical practice is currently limited. The purpose of this review is to ensure reproductive medicine professionals understand the appropriate use of IVM drawn from the best available evidence supporting its clinical potential and safety in selected patient groups. This group of scientists and fertility specialists, with expertise in IVM in the ART laboratory and/or clinic, explore here the development of IVM towards acquisition of a non-experimental status and, in addition, critically appraise the current and future role of IVM in human ART.

Correction to: Dealing with loss of life across the spectrum of humankind.

The references of the original version of this article unfortunately were missing.

Euploid miscarriage is associated with elevated serum C-reactive protein levels in infertile women: a pilot study.

PURPOSE: Increased serum C-protein (CRP) levels reduce fecundity in healthy eumenorrheic women with 1-2 pregnancy losses. Subclinical systemic inflammation may impede maternal immune tolerance toward the fetal semi-allograft, compromising implantation and early embryonic development. Some miscarriages with normal karyotypes could, therefore, be caused by inflammation. Whether pre-pregnancy CRP relates to karyotypes of spontaneously aborted products of conception (POCs) was investigated. METHODS: A study cohort of 100 infertile women with missed abortions who underwent vacuum aspirations followed by cytogenetic analysis of their products of conception tissue was evaluated at an academically affiliated fertility center. Since a normal female fetus cannot be differentiated from maternal cell contamination (MCC) in conventional chromosomal analyses, POC testing was performed by chromosomal microarray analysis. MCC cases and incomplete data were excluded. Associations of elevated CRP with first trimester pregnancy loss in the presence of a normal fetal karyotype were investigated. RESULTS: Mean patients' age was 39.9 ± 5.8 years; they demonstrated a BMI of 23.9 ± 4.6 kg/m2 and antiMullerian hormone (AMH) of 1.7 ± 2.4 ng/mL; 21.3% were parous, 19.1% reported no prior pregnancy losses, 36.2% 1-2 and 6.4% ≥ 3 losses. Karyotypes were normal in 34% and abnormal in 66%. Adjusted for BMI, women with elevated CRP were more likely to experience euploid pregnancy loss (p = 0.03). This relationship persisted when controlled for female age and AMH. CONCLUSIONS: Women with elevated CRP levels were more likely to experience first trimester miscarriage with normal fetal karyotype. This relationship suggests an association between subclinical inflammation and miscarriage.

Prospects for new oocyte-based assisted reproduction in animals and humans.

Procuring high-quality oocytes is the rate-limiting step for assisted reproduction technologies intended for embryo production. Although much is known about the intraovarian processes that dictate oocyte growth and maturation, subtleties in the process of oogenesis have yet to be replicated in invitro systems. In contrast with the mouse, in which functional oocytes have been derived from stem cells under ex vivo conditions, the generation of developmentally competent oocytes in other species has yet to be achieved. This paper reviews the principles and practices based on stem cell and organ culture strategies that hold promise for developing a technological base upon which future efforts to recapitulate or augment oogenesis in mammals could be realised.

Older women using their own eggs? Issue framed with two oldest reported IVF pregnancies and a live birth.

RESEARCH QUESTION: What level of IVF pregnancy success is currently possible in women of extremely advanced age? DESIGN: This study reports on outcomes in women aged 43-51 years at the Centre for Human Reproduction, an academically affiliated private clinical fertility and research centre in New York City. RESULTS: During the study years of 2014-2016, 16 pregnancies were established, all through day 3 transfers. Based on 'intent to treat' (cycle start), clinical pregnancy rates were 4/190 (2.1%), 5/234 (2.1%) and 7/304 (2.3%) and live birth rates were 2/190 (1.1%), 1/234 (0.43%) and 4/304 (1.3%) in 2014, 2015 and 2016, respectively. With reference to embryo transfer, clinical pregnancy rates were 4/140 (2.9%), 5/159 (3.1%) and 7/167 (4.2%) and live birth rates were 2/140 (1.4%), 1/159 (0.63%) and 4/167 (2.4%) for the same years. The results for 2016 also included what are probably the two oldest autologous IVF pregnancies ever reported in the literature. These results were obtained with patient ages, percentage of cycle cancellations and other adverse outcome parameters steadily increasing year by year. CONCLUSIONS: Female age above 42 is widely viewed as the ultimate barrier to conception with IVF. Data reported here, although small and preliminary, demonstrate that potential outcomes are better than widely perceived, while pregnancy and live birth rates remain significantly inferior to donor egg recipient cycles. However, for selected women at very advanced ages, especially with higher egg/embryo numbers, autologous oocyte IVF offers a better option than widely acknowledged, if they are given individualized age-specific care.