A preliminary report of successful cleavage after calcium ionophore activation at ICSI in cases with previous arrest at the pronuclear stage

A case report of a family with developmental arrest of human prokaryotic stage zygote

To study the genetic variation leading to the arrest phenotype of pronuclear (PN) zygotes. We recruited a family characterized by recurrent PN arrest during in vitro fertilization (IVF) and intracytoplasmic sperm injection cycles (ICSI) and performed whole-exome sequencing for 2 individuals. The transcriptome profiles of PN-arrest zygotes were assessed by single-cell RNA sequencing analysis. The variants were then validated by PCR amplification and Sanger sequencing in the affected individuals and other family members. A family characterized by recurrent PN arrest during IVF and ICSI cycles were enrolled after giving written informed consent. Peripheral blood samples were taken for DNA extraction. Three PN-arrest zygotes from patient III-3 were used for single-cell RNA-seq as described. This phenotype was reproduced after multiple cycles of egg retrieval and after trying different fertilization methods and multiple ovulation regimens. The mutant genes of whole exon sequencing were screened and verified. The missense variant c. C1630T (p.R544W) in RGS12 was responsible for a phenotype characterized by paternal transmission. RGS12 controls Ca2+ oscillation, which is required for oocyte activation after fertilization. Single-cell transcriptome profiling of PN-arrest zygotes revealed defective established translation, RNA processing and cell cycle, which explained the failure of complete oocyte activation. Furthermore, we identified proximal genes involved in Ca2+ oscillation-cytostatic factor-anaphase-promoting complex (Ca2+ oscillation-CSF-APC) signaling, including upregulated CaMKII, ORAI1, CDC20, and CDH1 and downregulated EMI1 and BUB3. The findings indicate abnormal spontaneous Ca2+ oscillations leading to oocytes with prolonged low CSF level and high APC level, which resulted in defective nuclear envelope breakdown and DNA replication. We have identified an RGS12 variant as the potential cause of female infertility characterized by arrest at the PN stage during multiple IVF and ICSI.

Calcium ionophore improves embryonic development and pregnancy outcomes in patients with previous developmental problems in ICSI cycles

BACKGROUND

Calcium (Ca²⁺) ionophores are now mainly considered as efficient treatments for fertilization failure. Recently, its application for rescuing poor embryo development was proposed but still non-routine. This study aimed to explore whether Ca²⁺ ionophore improves embryo development and pregnancy outcomes in patients with poor embryo development in previous intracytoplasmic sperm injection (ICSI) cycles.

METHODS

This study included 97 patients undergoing assisted oocyte activation (AOA) with Ca²⁺ ionophore (calcimycin, A23187) treatment. Preimplantation embryonic development and clinical outcomes were compared between ICSI-AOA cycles (AOA group) and previous ICSI cycles of the same patients in which poor embryo developmental potential was present (non-AOA group). Subgroups stratified by maternal age (< 35, 35-40, ≥ 40 years, respectively) were analyzed separately.

RESULTS

A total of 642 MII oocytes were collected in AOA group, and 689 in non-AOA group. Significantly higher day 3 good quality embryo rate (P = 0.034), good quality blastocyst formation rate (P <  0.001), and utilization rate (P <  0.001) were seen in AOA group. Similar results were seen in each subgroup. For pregnancy outcomes, there were significant differences in clinical pregnancy rate (P = 0.039) and live birth rate (P = 0.045) in total group. In subgroup aged < 35 years, biochemical (P = 0.038), clinical (P = 0.041), and ongoing pregnancy rate (P = 0.037) in AOA group were significantly higher than that in non-AOA group. No significant improvement for clinical outcomes for subgroups aged 35-40 and aged ≥40.

CONCLUSION

The study suggests that calcimycin could improve preimplantation development and pregnancy outcomes in patients aged < 35 years with embryo developmental problems in previous ICSI cycles.

Effect of A23187 ionophore treatment on human blastocyst development-a sibling oocyte study

PURPOSE

To investigate whether treatment with commercially available ready-to-use A23187 ionophore (GM508-CultActive) improves embryo development outcome in patients with a history of embryo developmental problems.

METHODS

This is a uni-center prospective study in which sibling oocytes of patients with embryos of poor quality on day 5 in the previous cycle were treated or not with CultActive.

RESULTS

Two hundred forty-seven metaphase II (MII) oocytes from 19 cycles performed between 2016 and 2019 were included in the study. After ICSI, the sibling oocytes were assigned to the treatment group or to the control group, following an electronically generated randomization list. A number of 122 MII were treated with CultActive and 125 MII had no treatment and were assigned to the control group. No difference in fertilization rate (p = 0.255) or in the capacity of embryos to reach good quality on day 5 (p = 0.197) was observed between the two groups. The utilization rates defined as the number of embryos transferred or cryopreserved per mature oocyte (p = 0.438) or per fertilized oocytes (p = 0.299) were not significantly different between the treated group and the control group.

CONCLUSION

The results of the current study do not support the use of CultActive in cases with embryo developmental problems.

Calcium chloride dihydrate supplementation at ICSI improves fertilization and pregnancy rates in patients with previous low fertilization: a retrospective paired treatment cycle study

PURPOSE

To determine if 5mM calcium chloride dihydrate supplementation of the Polyvinylpyrrolidone (PVP) media at the time of ICSI (ICSI-Ca) improves fertilization, utilization, and clinical pregnancy rates compared to ICSI alone, particularly in patients with a history of low fertilization (< 50%).

METHODS

Retrospective study between 2016 and 2021 at Monash IVF Victoria on a paired cohort of patients (n = 178 patients) where an ICSI cycle was analyzed coupled with the subsequent ICSI-Ca cycle. The paired cohort was further subdivided into a low-fertilization cohort (< 50% fertilization on previous cycles: n = 66 patients) compared to the remaining patients with fertilization ≥ 50% (n = 122). Exclusion criteria included donor cycles, PGT patients, surgical sperm retrieval, women ≥ 45 years old, patients with > 6 cycles, and patients with ≤ 5 inseminated oocytes.

RESULTS

Calcium supplementation significantly increased both fertilization (28.8% ICSI vs 49.7% ICSI-Ca, P < 0.0001) and clinical pregnancy rate (4.9% ICSI vs 25.0% ICSI-Ca: P < 0.05) in the low-fertilization cohort but not in the normal-fertilization cohort. Interestingly, utilization rate significantly increased in the normal-fertilization cohort (32.6% ICSI vs ICSI-Ca: 44.9%, P < 0.01) but not in the low-fertilization cohort, although the number of embryos utilized per patient after ICSI-Ca increased in both groups.

CONCLUSION

Calcium supplementation does not appear to be a detrimental addition to ICSI and may improve IVF outcomes, particularly for patients with a history of low fertilization. Further investigations including prospective case-matched studies or a RCT are required to confirm these findings.

OUP accepted manuscript

BACKGROUND

Oocyte activation deficiency (OAD) is attributed to the majority of cases underlying failure of ICSI cycles, the standard treatment for male factor infertility. Oocyte activation encompasses a series of concerted events, triggered by sperm-specific phospholipase C zeta (PLCζ), which elicits increases in free cytoplasmic calcium (Ca²⁺) in spatially and temporally specific oscillations. Defects in this specific pattern of Ca²⁺ release are directly attributable to most cases of OAD. Ca²⁺ release can be clinically mediated via assisted oocyte activation (AOA), a combination of mechanical, electrical and/or chemical stimuli which artificially promote an increase in the levels of intra-cytoplasmic Ca²⁺. However, concerns regarding safety and efficacy underlie potential risks that must be addressed before such methods can be safely widely used.

OBJECTIVE AND RATIONALE

Recent advances in current AOA techniques warrant a review of the safety and efficacy of these practices, to determine the extent to which AOA may be implemented in the clinic. Importantly, the primary challenges to obtaining data on the safety and efficacy of AOA must be determined. Such questions require urgent attention before widespread clinical utilization of such protocols can be advocated.

SEARCH METHODS

A literature review was performed using databases including PubMed, Web of Science, Medline, etc. using AOA, OAD, calcium ionophores, ICSI, PLCζ, oocyte activation, failed fertilization and fertilization failure as keywords. Relevant articles published until June 2019 were analysed and included in the review, with an emphasis on studies assessing large-scale efficacy and safety.

OUTCOMES

Contradictory studies on the safety and efficacy of AOA do not yet allow for the establishment of AOA as standard practice in the clinic. Heterogeneity in study methodology, inconsistent sample inclusion criteria, non-standardized outcome assessments, restricted sample size and animal model limitations render AOA strictly experimental. The main scientific concern impeding AOA utilization in the clinic is the non-physiological method of Ca²⁺ release mediated by most AOA agents, coupled with a lack of holistic understanding regarding the physiological mechanism(s) underlying Ca²⁺ release at oocyte activation.

LIMITATIONS, REASONS FOR CAUTION

The number of studies with clinical relevance using AOA remains significantly low. A much wider range of studies examining outcomes using multiple AOA agents are required.

WIDER IMPLICATIONS

In addition to addressing the five main challenges of studies assessing AOA safety and efficacy, more standardized, large-scale, multi-centre studies of AOA, as well as long-term follow-up studies of children born from AOA, would provide evidence for establishing AOA as a treatment for infertility. The delivery of an activating agent that can more accurately recapitulate physiological fertilization, such as recombinant PLCζ, is a promising prospect for the future of AOA. Further to PLCζ, many other avenues of physiological oocyte activation also require urgent investigation to assess other potential physiological avenues of AOA.

STUDY FUNDING/COMPETING INTERESTS

D.G. was supported by Stanford University’s Bing Overseas Study Program. J.K. was supported by a Healthcare Research Fellowship Award (HF-14-16) made by Health and Care Research Wales (HCRW), alongside a National Science, Technology, and Innovation plan (NSTIP) project grant (15-MED4186-20) awarded by the King Abdulaziz City for Science and Technology (KACST). The authors have no competing interests to declare.

Ionophore application for artificial oocyte activation and its potential effect on morphokinetics: a sibling oocyte study

PURPOSE

To evaluate whether ionophore application at the oocyte stage changes the morphokinetics of the associated embryos in cases of artificial oocyte activation.

METHODS

In a prospective sibling oocyte approach, 78 ICSI patients with suspected fertilization problems had half of their MII-oocytes treated with a ready-to-use ionophore (calcimycin) immediately following ICSI (study group). Untreated ICSI eggs served as the control group. Primary analyses focused on morphokinetic behavior and the presence of irregular cleavages. The rates of fertilization, utilization, pregnancy, and live birth rate were also evaluated.

RESULTS

Ionophore-treated oocytes showed a significantly earlier formation of pronuclei (t2PNa) and a better synchronized third cell cycle (s3) (P < .05). The rate of irregular cleavage was unaffected (P > .05). Ionophore treatment significantly improved the overall rates of fertilization (P < .01) and blastocyst utilization (P < .05).

CONCLUSION

Ionophore application does not negatively affect cleavage timing nor is it associated with irregular cleavage.

Molecular Drivers of Developmental Arrest in the Human Preimplantation Embryo: A Systematic Review and Critical Analysis Leading to Mapping Future Research

Developmental arrest of the preimplantation embryo is a multifactorial condition, characterized by lack of cellular division for at least 24 hours, hindering the in vitro fertilization cycle outcome. This systematic review aims to present the molecular drivers of developmental arrest, focusing on embryonic and parental factors. A systematic search in PubMed/Medline, Embase and Cochrane-Central-Database was performed in January 2021. A total of 76 studies were included. The identified embryonic factors associated with arrest included gene variations, mitochondrial DNA copy number, methylation patterns, chromosomal abnormalities, metabolic profile and morphological features. Parental factors included, gene variation, protein expression levels and infertility etiology. A valuable conclusion emerging through critical analysis indicated that genetic origins of developmental arrest analyzed from the perspective of parental infertility etiology and the embryo itself, share common ground. This is a unique and long-overdue contribution to literature that for the first time presents an all-inclusive methodological report on the molecular drivers leading to preimplantation embryos’ arrested development. The variety and heterogeneity of developmental arrest drivers, along with their inevitable intertwining relationships does not allow for prioritization on the factors playing a more definitive role in arrested development. This systematic review provides the basis for further research in the field.

Use of phospholipase C zeta analysis to identify candidates for artificial oocyte activation: a case series of clinical pregnancies and a proposed algorithm for patient management

OBJECTIVE

To investigate the applicability of phospholipase C zeta (PLCζ) analysis in assisting the clinical decision-making process when considering artificial oocyte activation (AOA) for infertile males in assisted reproductive technology.

DESIGN

Fifty-six males (43 infertile/13 fertile) were screened using our PLCζ assay.

SETTING

Fertility unit/university laboratory.

PATIENT(S)

Infertile males with abnormal sperm morphology or total fertilization failure, low fertilization rate (<50%), or repeated fertilization failure in assisted reproductive technology.

INTERVENTION(S)

We analyzed PLCζ levels in sperm from fertile and infertile males. Eligible patients subsequently underwent intracytoplasmic sperm injection (ICSI)/artificial oocyte activation (AOA) with calcimycin (GM508).

MAIN OUTCOME MEASURE(S)

PLCζ localization and level and the proportion of sperm expressing PLCζ. Thresholds of PLCζ deficiency, fertilization rates, pregnancy rates, and live birth rates of AOA and non-AOA cycles.

RESULT(S)

Compared with 13 fertile controls, 34 of the 43 infertile males had significantly lower levels of PLCζ and/or a significantly lower proportion of sperm exhibiting PLCζ. Of these 34 patients, 15 showed a significant PLCζ reduction in both parameters, which we termed "PLCζ deficiency." Five PLCζ-deficient patients opted for AOA; all five achieved fertilization, and four achieved clinical pregnancies and live births. The fertilization rate improved significantly from 18.6% (ICSI) to 56.8% (ICSI/AOA). The clinical pregnancy rate and live birth rate with AOA were both 40% per initiated cycle. Youden index analysis revealed that the cutoffs below which infertile males were likely to benefit from AOA were 71% for the proportion of sperm expressing PLCζ and 15.57 arbitrary units for mean PLCζ level.

CONCLUSION(S)

PLCζ analysis is a useful diagnostic tool to determine patient eligibility for subsequent AOA treatment.

Calcium Ionophore (A23187) Rescues the Activation of Unfertilized Oocytes After Intracytoplasmic Sperm Injection and Chromosome Analysis of Blastocyst After Activation

Calcium is a crucial factor in regulating the biological behavior of cells. The imbalance of calcium homeostasis in cytoplasm will cause abnormal behavior of cells and the occurrence of diseases. In intracytoplasmic sperm injection (ICSI) cycle, the dysfunction of oocyte activation caused by insufficient release of Ca²⁺ from endoplasmic reticulum is one of the main reasons for repeated fertilization failure. Calcium ionophore (A23187) is a highly selective calcium ionophore, which can form stable complex with Ca²⁺ and pass through the cell membrane at will, effectively increasing intracellular Ca²⁺ levels. It has been reported that calcium ionophore (A23187) can activate oocytes and obtain normal embryos. However, there are few studies on unfertilized oocytes after calcium ionophore (A23187) rescue activation in ICSI cycle. The purpose of this study was to analyze the effects of calcium ionophore (A23187) rescue activation on the activation of unfertilized oocytes, embryonic development potential, embryonic development timing and chromosomal aneuploidy, and to compare and analyze the clinical data of patients with calcium ionophore (A23187) activation in clinical application. The results showed that a certain proportion of high-quality blastocysts with normal karyotype could be obtained after calcium ionophore (A23187) rescue activation of unfertilized oocytes, and it did not have a significant effect on the timing of embryo development. In clinical practice, direct activation with calcium ionophore (A23187) after ICSI was better than rescue activation the next day. In conclusions, the studies on the effectiveness and safety of calcium ionophore (A23187) rescue activation for oocytes with ICSI fertilization failure can enable some patients to obtain usable, high-quality embryos during the first ICSI cycle.

Novel mutations in the PLCZ1 gene associated with human low or failed fertilization

Background

Fertilization failure (FF) is a complex reproductive disorder characterized by the failure of pronuclei formation during fertilization. In addition to some cases caused by iatrogenic problems and known genetic factors, there are still many unexplained aspects of FF. Here, we aimed to assess the clinical and genetic characteristics of two families experiencing primary infertility with FF.

Methods

We have characterized two families from China. All of the infertile couples presented with similar clinical phenotypes, that is, partial or total fertilization failure in repeated cycles. We performed Sanger sequencing of their WEE2, TLE6, and PLCZ1 genes, and further bioinformatics and functional analyses were performed to identify the pathogenic elements of the variants.

Results

We identified novel compound heterozygous mutations c.1259C>T (p.P420L) and c.1733T>C (p.M578T) in the PLCZ1 gene in a male patient of family 1 with total fertilization failure, and another novel homozygous mutation c.1727T>C (p.L576P) in the same gene in a male patient of family 2 with partial fertilization failure. These three novel mutations were absent in the control cohort and in the databases. The amino acids were conserved at their positions among six different species. All mutant amino acids were located in key domains and were predicted to impair hydrolytic activity and lead to PLCZ1 dysfunction. Further functional detection revealed that the three mutations could significantly impair the catalytic activity of PLCZ1.

Conclusions

We identified three novel mutations in PLCZ1 associated with partial and total fertilization failure and have provided new evidence about the genetic basis of FF.

A novel mutation in the TUBB8 gene is associated with complete cleavage failure in fertilized eggs

PURPOSE

Cleavage of the zygote during human reproduction is a key event of early embryonic development. The genetic events associated with idiopathic embryonic cleavage failure are not certain. Mutations in the tubulin beta 8 class VIII (TUBB8) gene have been reported to be associated with oocyte maturation, fertilization, and developmental arrest. Here, we aimed to assess the clinical and genetic characteristics of complete cleavage failure in fertilized eggs.

METHODS

We have characterized a patient with a 9-year history of primary infertility in a non-consanguineous family from China. The patient presented complete cleavage failure in all two-pronuclear (2PN) fertilized oocytes after 2 cycles of in vitro fertilization (IVF). We performed Sanger sequencing of the TUBB8 gene in the patient, and further bioinformatics analysis to identify pathogenesis of gene.

RESULTS

A novel homozygous mutation, c.322G > A (p.Glu108Lys), was detected, and this change was absent from 179 control subjects. Glutamic acid is highly conserved at this position, and replacement by lysine was predicted to be repelled by the α-tubulin positive region, disrupting the α-β tubulin interaction.

CONCLUSIONS

Our findings presented a homozygous mutation of TUBB8 associated with complete cleavage failure in fertilized eggs and provided new data for the genotype-phenotype of TUBB8-related diseases.

Single Ca2+ transients vs oscillatory Ca2+ signaling for assisted oocyte activation: limitations and benefits

Oocyte activation is a calcium (Ca²⁺)-dependent process that has been investigated in depth, in particular, regarding its impact on assisted reproduction technology (ART). Following a standard model of signal transduction, Ca²⁺ drives the meiotic progression upon fertilization in all species studied to date. However, Ca²⁺ changes during oocyte activation are species specific, and they can be classified in two modalities based on the pattern defined by the Ca²⁺ signature: a single Ca²⁺ transient (e.g. amphibians) or repetitive Ca²⁺ transients called Ca²⁺ oscillations (e.g. mammals). Interestingly, assisted oocyte activation (AOA) methods have highlighted the ability of mammalian oocytes to respond to single Ca²⁺ transients with normal embryonic development. In this regard, there is evidence supporting that cellular events during the process of oocyte activation are initiated by different number of Ca²⁺ oscillations. Moreover, it was proposed that oocyte activation and subsequent embryonic development are dependent on the total summation of the Ca²⁺ peaks, rather than to a specific frequency pattern of Ca²⁺ oscillations. The present review aims to demonstrate the complexity of mammalian oocyte activation by describing the series of Ca²⁺-linked physiological events involved in mediating the egg-to-embryo transition. Furthermore, mechanisms of AOA and the limitations and benefits associated with the application of different activation agents are discussed.

The combination of calcium ionophore A23187 and GM-CSF can safely salvage aged human unfertilized oocytes after ICSI

PURPOSE

Artificial oocyte activation using calcium ionophores and enhancement of embryonic developmental potential by the granulocyte-macrophage colony-stimulating factor (GM-CSF) have already been reported. In this study, we evaluated the synergistic effect of these two methods on aged human unfertilized oocytes after intracytoplasmic sperm injection (ICSI). Then, we cultured the resulting embryos to the blastocyst stage and screened them for chromosomal abnormalities, to assess the safety of this protocol.

METHODS

Aged human oocytes deemed unfertilized after ICSI were activated, either by briefly applying the calcium ionophore A23187 alone (group A) or by briefly applying the ionophore and then supplementing the culture medium with recombinant human GM-CSF (rhGM-CSF) (group B). Next, the development was monitored in a time-lapse incubator system, and ploidy was analyzed by array comparative genomic hybridization (aCGH), after whole embryo biopsy and whole genome amplification. Differences between oocytes and resulting embryos in both groups were evaluated statistically.

RESULTS

Oocytes unfertilized after ICSI can be activated with the calcium ionophore A23187 to show two pronuclei and two polar bodies. Addition of rhGM-CSF in the culture medium of A23187-activated oocytes enhances their cleaving and blastulation potential and results in more euploid blastocysts compared to the culture medium alone.

CONCLUSIONS

This study shows that activating post-ICSI aged human unfertilized oocytes with a combination of a calcium ionophore and a cytokine can produce good-morphology euploid blastocysts.