Search Results (6)

Age-related decline in oocyte quality is closely associated with mitochondrial dysfunction and oxidative imbalance, which disrupt redox-sensitive meiotic signaling and compromise embryo developmental competence. Rescue in vitro maturation (r-IVM) enables the utilization of immature oocytes retrieved during conventional in vitro fertilization (IVF) cycles. However, the developmental potential of r-IVM oocytes remains limited, particularly in women of advanced maternal age. This study evaluated whether transient caffeine supplementation during r-IVM improves the developmental competence of immature human oocytes in clinical assisted reproduction technology cycles. Immature oocytes obtained during conventional IVF were cultured with or without short-term caffeine exposure during r-IVM prior to standard culture conditions. After maturation, metaphase II oocytes underwent intracytoplasmic sperm injection, and embryonic development was assessed by fertilization rate, day 3 good-quality embryo formation, and blastocyst development. Although caffeine supplementation did not significantly affect nuclear maturation rates, it significantly increased fertilization efficiency and the proportion of good-quality embryos compared with controls. These effects were most pronounced in women aged ≥37 years. Time-lapse morphokinetic analysis further revealed more synchronized developmental kinetics in embryos derived from caffeine-treated oocytes, resembling those derived from in vivo-matured oocytes. Collectively, these findings suggest that transient caffeine exposure during r-IVM enhances post-fertilization developmental competence. The underlying mechanisms remain to be elucidated, and future studies are required to determine whether redox-sensitive meiotic pathways and mitochondrial function are involved. Full article

The sperm-specific phospholipase C zeta (PLCζ) protein is widely considered as the predominant physiological stimulus for initiating the Ca²⁺ release responsible for oocyte activation during mammalian fertilization. The increasing number of genetic and clinical reports that directly link PLCζ defects and/or deficiencies with oocyte activation failure (OAF) necessitates the use of a powerful therapeutic intervention to overcome such cases of male factor infertility. Currently, in vitro fertilization (IVF) clinics treat OAF cases after intracytoplasmic sperm injection (ICSI) with Ca²⁺ ionophores. Despite their successful use, such chemical agents are unable to trigger the physiological pattern of Ca²⁺ oscillations. Moreover, the safety of these ionophores is not yet fully established. We have previously demonstrated that recombinant PLCζ protein can be successfully used to rescue failed oocyte activation, resulting in efficient blastocyst formation. Herein, we produced a maltose binding protein (MBP)-tagged recombinant human PLCζ protein capable of inducing Ca²⁺ oscillations in mouse oocytes similar to those observed at fertilization. Circular dichroism (CD) experiments revealed a stable, well-folded protein with a high helical content. Moreover, the recombinant protein could retain its enzymatic properties for at least up to 90 days after storage at −80 °C. Finally, a chick embryo model was employed and revealed that exposure of fertilized chicken eggs to MBP-PLCζ did not alter the embryonic viability when compared to the control, giving a first indication of its safety. Our data support the potential use of the MBP-PLCζ recombinant protein as an effective therapeutic tool but further studies are required prior to its use in a clinical setting. Full article

Phospholipase C Zeta 1 (PLCZ1) is considered a major sperm-borne oocyte activation factor. After gamete fusion, PLCZ1 triggers calcium oscillations in the oocyte, resulting in oocyte activation. In assisted fertilization, oocyte activation failure is a major cause of low fertility. Most cases of oocyte activation failures in humans related to male infertility are associated with gene mutations and/or altered PLCZ1. Consequently, PLCZ1 evaluation could be an effective diagnostic marker and predictor of sperm fertilizing potential for in vivo and in vitro embryo production. The characterization of PLCZ1 has been principally investigated in men and mice, with less known about the PLCZ1 impact on assisted reproduction in other species, such as cattle and horses. In horses, sperm PLCZ1 varies among stallions, and sperm populations with high PLCZ1 are associated with cleavage after intracytoplasmic sperm injection (ICSI). In contrast, bull sperm is less able to initiate calcium oscillations and undergo nuclear remodeling, resulting in poor cleavage after ICSI. Advantageously, injections of PLCZ1 are able to rescue oocyte failure in mouse oocytes after ICSI, promoting full development and birth. However, further research is needed to optimize PLCZ1 diagnostic tests for consistent association with fertility and to determine whether PLCZ1 as an oocyte-activating treatment is a physiological, efficient, and safe method for improving assisted fertilization in cattle and horses. Full article

During mammalian fertilization, repetitive rises of intracellular calcium called calcium oscillations are required for full activation of oocytes. Therefore, oocytes such as round spermatid injected or somatic cell nuclear transferred require additional artificial activation which mimics the calcium oscillations. It is well recognized that sperm specific phospholipase C (PLCζ) is a strong candidate as the sperm factor which can induce calcium oscillations and, at least in mammals, the genetic mutation of PLCζ in human causes male infertility due to the lack of calcium oscillations in the oocytes. Recent studies showed that the sperm lacking PLCζ (Plcz1^−/−) still could induce rise(s) of intracellular calcium in the oocytes after IVF but not intracytoplasmic sperm injection (ICSI). In the ICSI oocytes, no pronuclear formation or development to the two-cell stage was observed. However, it is still unclear whether additional activation treatment can rescue the low developmental ability of Plcz1^−/−-sperm-derived oocytes after ICSI. In this study, we examined whether oocytes injected with a Plcz1^−/− sperm can develop to term by additional artificial activation. In oocytes injected a Plcz1^−/− sperm and Plcz1^−/− and eCS (another candidate of the sperm factor) double knockout sperm (Plcz1^−/−eCS^−/−), the rates of pronuclear formation were very low (2.0 ± 2.3% and 6.1 ± 3.7%, respectively) compared to control (92.1 ± 2.6%). However, these rates were dramatically improved by additional procedures of PLCζ-mRNA injection or SrCl₂ treatment (Plcz1^−/− sperm + PLCζ mRNA, Plcz1^−/− sperm + SrCl₂ and Plcz1^−/−eCS^−/− sperm + PLCζ mRNA; 64.2 ± 10.8%, 89.2 ± 2.4% and 72.6 ± 5.4%, respectively). Most of the oocytes were developed to the two-cell stage. After embryo transfer, healthy pups were obtained in all these groups (Plcz1^−/− sperm + PLCζ mRNA:10.0 ± 2.8%, Plcz1^−/− sperm + SrCl₂:4.0 ± 4.3% and Plcz1^−/−eCS^−/− sperm + PLCζ mRNA: 10.0 ± 5.7%). The rate in Plcz1^−/− sperm + SrCl₂ group was significantly lower than that in control (26.0 ± 2.4%). Taken together, our present results show that additional activation treatment such as SrCl₂ and PLCζ mRNA can fully support to develop to term even in oocyte injected Plcz1^−/− sperm. In addition, PLCζ-induced oocyte activation is more suitable for successful development to term compared to that such as phenomenon induced by SrCl₂. These findings will contribute to improvement for male-dependent human infertility and reproductive technologies in other mammalian species. Full article

This study aims to analyze the cycle characteristics, pregnancy, and neonatal outcomes in early rescue intracytoplasmic sperm injection (r-ICSI) cycles in normal and hyper-ovarian response women in their first IVF/ICSI attempts. Data from short-term in vitro fertilization (IVF, N = 7148), early r-ICSI (N = 618), and ICSI (N = 1744) cycles were retrospectively analyzed from normal and hyper-ovarian women who underwent their first IVF/ICSI cycles at our center from October 2015 to October 2021. The r-ICSI group was subdivided into partial r-ICSI (N = 451) and total r-ICSI (N = 167) based on the number of fertilized oocytes in the IVF part. Cyclic characteristics, pregnancy, delivery and neonatal outcomes in the fresh cycle were compared among the four groups; pregnancy, delivery and neonatal outcomes in frozen-thawed cycles were compared regarding cleavage and blastocyst transfers derived from r-ICSI cycles. Partial r-ICSI cycles showed different cyclic characteristics compared to total r-ICSI cycles, presenting as elevated AMH and estradiol levels on trigger day and an increased number of oocytes retrieved. Early r-ICSI delayed blastocyst development as seen by the increase in the number of day 6 blastocysts. There was no significant difference among the groups in clinical pregnancy, pregnancy loss, and live birth in fresh cleavage-stage embryo transfer cycles. However, early r-ICSI groups showed a reduction in clinical pregnancy and live birth rates in fresh blastocyst transfer cycles but not in the frozen-thawed cycles. For pregnant women, early r-ICSI did not show a negative effect on the risk of preterm birth, Cesarean section, neonatal birth weight, and sex ratio. In conclusion, early r-ICSI had comparable pregnancy, delivery, and neonatal outcomes when compared with short-term IVF and ICSI groups in fresh cleavage-stage embryo transfer cycles, but early r-ICSI did result in reduced pregnancy outcomes in fresh blastocyst embryo cycles, possibly due to delayed blastocyst development and asynchronization with the endometrium. Full article

The rescue in vitro maturation (rIVM) of germinal vesicle oocytes (GVs) has been proposed to improve the total number of mature oocytes in women undergoing fertility preservation. Currently, there is no consensus about the clinical utility of this practice, and heterogeneity in the protocols used may influence the final outcomes. This study investigated the developmental potential of mature metaphase II (MII) human oocytes obtained from GVs after rIVM and the impact of applying vitrification at different timepoints either before or after rIVM. After randomization, oocytes were assigned to undergo rIVM and thereafter vitrification or intracytoplasmic sperm injection (ICSI), or to undergo direct vitrification-warming and thereafter rIVM and ICSI. The likelihood of obtaining MII oocytes was just slightly higher in the fresh rIVM group compared to the vitrification-warming-rIVM group. When comparing fresh rIVM that underwent subsequently ICSI, the fertilization and developmental rates up to the blastocyst stage were seen to be reduced in both groups that underwent vitrification either before or after rIVM. Although some blastocysts were obtained in the fresh rIVM-ICSI group, the efficacy of these methods was low overall, suggesting that the further development of protocols for IVM conducted early after denudation is needed to improve the final results of rIVM aiming at fertility preservation. Full article