Mapping the molecular basis for growth related phenotypes in industrial producer CHO cell lines using differential proteomic analysis

Background The ability to achieve high peak viable cell density earlier in CHO cell culture and maintain an extended cell viability throughout the production process is highly desirable to increase recombinant protein yields, reduce host cell impurities for downstream processing and reduce the cost of goods. In this study we implemented label-free LC-MS/MS proteomic profiling of IgG4 producing CHO cell lines throughout the duration of the cell culture to identify differentially expressed (DE) proteins and intracellular pathways associated with the high peak viable cell density (VCD) and extended culture VCD phenotypes. Results We identified key pathways in DNA replication, mitotic cell cycle and evasion of p53 mediated apoptosis in high peak VCD clonally derived cell lines (CDCLs). ER to Golgi vesicle mediated transport was found to be highly expressed in extended culture VCD CDCLs while networks involving endocytosis and oxidative stress response were significantly downregulated. Conclusion This investigation highlights key pathways for targeted engineering to generate desirable CHO cell phenotypes for biotherapeutic production.

P–382 Association of extended culture to blastocyst and gestational trophoblastic disease risk following IVF/ICSI assisted reproduction cycles: An analysis of large UK National database

Study question Is there any association between stage of embryo at transfer based on extended in vitro culture and gestational trophoblastic disease risk during assisted reproduction? Summary answer No significant association between stages of embryo transfer from zygote stage to blastocyst stage was found after analysing 540376 cycles of IVF and ICSI. What is known already Gestational trophoblastic disease (GTD), commonly referred to as molar pregnancy, results from abnormal proliferation of the trophoblast with a reported incidence of ∼1 in 700 in the UK. Despite technological advances such as ICSI, PGT and selection of normally fertilised (2PN) embryos, there are reported cases of GTD following assisted reproduction. Blastocyst transfer is associated with higher pregnancy and live birth rates but evidence is lacking whether extended embryo culture to blastocyst stage influences implantation of an abnormal embryo or abnormal trophoblastic proliferation leading to GTD. Study design, size, duration A retrospective study was carried out using Human Fertilisation and Embryology Authority (HFEA) anonymised register data from 1999 to 2016. HFEA holds the longest running register for fertility treatment data in the world and is the national database for fertility treatment data in UK. A total of 540376 fresh IVF or ICSI assisted reproduction cycles were analysed. Participants/materials, setting, methods There were 1033588 treatment cycles during the study period but only 540376 cycles met the inclusion criteria of fresh IVF or ICSI. Cycles with incomplete data, frozen embryo transfers, donor treatment or surrogacy were excluded. A subgroup analysis of those with primary subfertility was performed after excluding subjects with secondary infertility in order to exclude an effect of a previous molar pregnancy. Multivariate regression analysis was used to adjust for possible confounders. Main results and the role of chance 78 molar pregnancies were reported in the original sample giving a prevalence of 4/10000 live births (78/228461), much lower than the prevalence given with natural pregnancies. Prevalence of molar pregnancy amongst the study population after meeting exclusion criteria was 4 /10000 livebirths (53/156683). Incidence of molar pregnancy was not statistically different between treatment type (0.0001 vs 0.00009). Significantly higher incidence of GTD was seen in the 40 to 42 age category compared to 18–34 category(OR 1.86(95% CI 8.7–3.75)),in par with known higher GTD risk in women above 40 in the general population. Of interesting note, although the incidence of molar pregnancy was significantly lower in women undergoing assisted reproduction increased risk with advancing age is not totally eliminated with treatment. There was no significant association between the occurrence of molar pregnancy with the type and cause for infertility and number of embryos transferred. Crude (1.06 (95% CI 0.852–1.31)) and adjusted odds ratios (1.07 (95% CI (0.857–1.32)) did not show any association between day of embryo transfer and molar pregnancy even after adjusting for age and excluding secondary infertility. Selection of blastocyst stage embryo after extended culture did not alter the likelihood of having a GTD compared to cleavage stage embryo. Limitations, reasons for caution The retrospective analysis of anonymised HFEA data limited adjustments for confounders such as smoking, previous history of GTD, ethnicity etc that predispose to GTD. Caution needs to be exercised for under-reporting of GTD to HFEA and lack of information on type of GTD identified. Wider implications of the findings: Though GTD cannot be prevented by IVF/ICSI, the incidence is significantly low and extended culture is not associated with higher risk of abnormal trophoblastic proliferation or GTD occurrence with IVF/ ICSI treatment. These findings would aid informed implications counselling and reassurance of patients during assisted reproduction treatments. Trial registration number Not applicable

P-382 Pre-selected for an award: Association of extended culture to blastocyst and gestational trophoblastic disease risk following IVF/ICSI assisted reproduction cycles: An analysis of large UK National database

Study question Is there any association between stage of embryo at transfer based on extended in vitro culture and gestational trophoblastic disease risk during assisted reproduction? Summary answer No significant association between stages of embryo transfer from zygote stage to blastocyst stage was found after analysing 540376 cycles of IVF and ICSI. What is known already Gestational trophoblastic disease (GTD), commonly referred to as molar pregnancy, results from abnormal proliferation of the trophoblast with a reported incidence of ∼1 in 700 in the UK. Despite technological advances such as ICSI, PGT and selection of normally fertilised (2PN) embryos, there are reported cases of GTD following assisted reproduction. Blastocyst transfer is associated with higher pregnancy and live birth rates but evidence is lacking whether extended embryo culture to blastocyst stage influences implantation of an abnormal embryo or abnormal trophoblastic proliferation leading to GTD. Study design, size, duration A retrospective study was carried out using Human Fertilisation and Embryology Authority (HFEA) anonymised register data from 1999 to 2016. HFEA holds the longest running register for fertility treatment data in the world and is the national database for fertility treatment data in UK. A total of 540376 fresh IVF or ICSI assisted reproduction cycles were analysed. Participants/materials, setting, methods There were 1033588 treatment cycles during the study period but only 540376 cycles met the inclusion criteria of fresh IVF or ICSI. Cycles with incomplete data, frozen embryo transfers, donor treatment or surrogacy were excluded. A subgroup analysis of those with primary subfertility was performed after excluding subjects with secondary infertility in order to exclude an effect of a previous molar pregnancy. Multivariate regression analysis was used to adjust for possible confounders. Main results and the role of chance 78 molar pregnancies were reported in the original sample giving a prevalence of 4/10000 live births (78/228461), much lower than the prevalence given with natural pregnancies. Prevalence of molar pregnancy amongst the study population after meeting exclusion criteria was 4 /10000 livebirths (53/156683). Incidence of molar pregnancy was not statistically different between treatment type (0.0001 vs 0.00009). Significantly higher incidence of GTD was seen in the 40 to 42 age category compared to 18-34 category(OR 1.86(95% CI 8.7-3.75)),in par with known higher GTD risk in women above 40 in the general population. Of interesting note, although the incidence of molar pregnancy was significantly lower in women undergoing assisted reproduction increased risk with advancing age is not totally eliminated with treatment. There was no significant association between the occurrence of molar pregnancy with the type and cause for infertility and number of embryos transferred. Crude (1.06 (95% CI 0.852-1.31)) and adjusted odds ratios (1.07 (95% CI (0.857-1.32)) did not show any association between day of embryo transfer and molar pregnancy even after adjusting for age and excluding secondary infertility. Selection of blastocyst stage embryo after extended culture did not alter the likelihood of having a GTD compared to cleavage stage embryo. Limitations, reasons for caution The retrospective analysis of anonymised HFEA data limited adjustments for confounders such as smoking, previous history of GTD, ethnicity etc that predispose to GTD. Caution needs to be exercised for under-reporting of GTD to HFEA and lack of information on type of GTD identified. Wider implications of the findings Though GTD cannot be prevented by IVF/ICSI, the incidence is significantly low and extended culture is not associated with higher risk of abnormal trophoblastic proliferation or GTD occurrence with IVF/ ICSI treatment. These findings would aid informed implications counselling and reassurance of patients during assisted reproduction treatments. Trial registration number not applicable

P–552 Delayed blastocyst development is associated with a higher risk of aneuploidy in patients of advanced maternal age

Study question Is delayed blastocyst development, assessed by the day of trophectoderm (TE) biopsy, associated with higher rates of aneuploidy? Summary answer Our findings show an association between delayed blastocyst development and poorer prognosis, in terms of euploidy rates, in patients of advanced maternal age. What is known already Extended culture of embryos past day 5 of development has become routine practice in all freeze-all cycles, including those applying preimplantation genetic testing for aneuploidies (PGT-A). As healthy live births have been obtained from day 6 and day 7 blastocysts, increasing the pool of embryos available for PGT-A is beneficial, particularly for patients of advanced maternal age who face higher cancellation rates. Nevertheless, the association between delayed blastocyst development and aneuploidy rates remains unclear. As current studies have reported opposing findings, detailed analysis of the chromosomal constitution of slowly developing embryos remains paramount. Study design, size, duration Retrospective, international, multicentre cohort study of 4211 patients undergoing preimplantation genetic testing for aneuploidy (PGT-A) from January 2016 to July 2020. We evaluated the chromosomal status of 14757 blastocysts tested using TE biopsy and next generation sequencing (NGS). Both autologous and donation cycles were included in the analysis. Cycles were excluded if they utilised preimplantation genetic testing for monogenic disorders (PGT-M) or preimplantation genetic testing for structural rearrangements (PGT-SR). Participants/materials, setting, methods We evaluated euploidy, aneuploidy and mosaicism rates reported in day 5 (n = 9560), day 6 (n = 4753) and day 7 (n = 262) blastocysts, stratified by SART-defined maternal age categories (<35, 35–37, 38–40, 41–42, >42). We further assessed the type and frequency of abnormalities reported in all blastocysts classified as clinically unsuitable, according to the day of biopsy. Finally, we examined the specific chromosomes affected in embryos diagnosed with a single uniform (n = 3882) or single mosaic (n = 518) abnormality. Main results and the role of chance The mean maternal age within our patient cohort was 39.9±3.7. Overall, slowly developing blastocysts were significantly more likely to be classified as clinically unsuitable (60.6%) compared to day 5 embryos (55.2%; p < 0.0001). This correlation was also observed when stratified by age, with the exception of the <35 age group (p = 0.25). Markedly, the risk of aneuploidy in slowly developing blastocysts became progressively higher with advancing maternal age (p < 0.0001). We did not observe any significant differences in the types of abnormalities diagnosed in slowly developing embryos compared to day 5 blastocysts. Nevertheless, abnormalities affecting all chromosomes were present at the blastocyst stage. Single trisomies and monosomies were the most frequent across all age groups, and were equally prevalent in day 5, 6 and 7 blastocysts. These most commonly affected chromosomes 16, 22, 21 and 15. We observed no significant differences in the incidence of segmental aneuploidies in relation to the day of biopsy, across all age groups. When considered separately, day 7 blastocysts presented with higher rates of structural aberrations, however low numbers limited statistical power. Finally, delayed blastocyst development was not associated with higher mosaicism rates (p = 0.79). Interestingly, single mosaic trisomies and monosomies were most frequently associated with chromosome 19. Limitations, reasons for caution Due to the retrospective nature of the study, full elucidation of all potential confounders may not be possible in all instances. The low number of day 7 blastocysts limited statistical power. As such, the results from day 6 and day 7 embryos were evaluated together. Wider implications of the findings: Our findings offer an important clinical resource for counselling patients of advanced maternal age. Maternal aging may be associated with a higher incidence of aneuploidy in slowly developing blastocysts. Nevertheless, extended culture increases the pool of biopsiable blastocysts, ultimately improving the chance of having a euploid embryo for transfer. Trial registration number NA