P-257 Transcriptomic signature of live birth revealed in cumulus cells of women undergoing an ICSI cycle for infertility treatment
Authors: Sachs M , Makieva S , Xie M , Velasco Gil A , Ille F , Schmidhauser M , Saenz de Juano Ribes M , Ulbrich S , Leeners B 
Published: June 2023

Abstract

Study question
Is the transcriptome of cumulus cells surrounding an oocyte that was fertilised and transferred predictive of live birth?

Summary answer
Live birth is associated with a distinct transcriptomic signature in cumulus cells isolated from an oocyte that was fertilised and transferred.

What is known already
The selection of the best embryo for transfer is currently based on standard morphological assessment, which is intrinsically subjective, and time-lapse monitoring, which fails to show benefit in predicting pregnancy. Alternative non-invasive selection methods are in development including analysis of cumulus cells (CCs) isolated from oocytes that resulted in an eligible embryo for transfer. However the majority of the existing studies were conducted using outdated methodologies such as transcriptomic analysis with PCR and microarrays. Moreover, the studies associating CCs’ transcriptome with clinical and embryological outcomes lack consensus due to non-homogenous cohorts while the outcome of live birth is inadequately explored.

Study design, size, duration
CC samples (n = 17), collected between 2018 and 2021 and biobanked, were retrospectively selected for RNA sequencing on the basis of their embryo transfer outcome. Thus, we analysed CCs associated with an oocyte that resulted in pregnancy (n = 6), no pregnancy (n = 7), live birth (n = 5) and pregnancy without live birth (n = 5). Differential gene expression analysis identified the differentially expressed genes (DEGs) between the groups in relation to pregnancy and live birth.

Participants/materials, setting, methods
The samples were retrieved from subfertile couples undergoing controlled ovarian stimulation and intracytoplasmic sperm injection with subsequent unbiopsied fresh or frozen embryo transfer at the IVF centre of University Hospital Zurich. Maternal age was below 43 years. Libraries from CCs were prepared using the Smart-seq2 pipeline and the RNA sequencing was performed on the NovaSeq 6000 system. The DESeq2 workflow was conducted and the threshold for the adjusted p-values (FDR) was set to 0.05.

Main results and the role of chance
No DEGs emerged when comparing the transcriptomic profiles of cumulus cells between the “no pregnancy” and “pregnancy” groups. However, 139 DEGs were identified in the comparison between the “pregnancy without live birth” and “live birth” groups. 28 DEGs were familiar and relevant to competent cumulus-oocyte-complexes: CTGF (fold change: 4.38, FDR: 0.005), SERPINE2 (fc: 3.08, FDR: 0.0002), PCK1 (fc:3.04, FDR: 0.0001), HHIP (fc:2.69, FDR: 0.006), HS3ST (fc:2.45, FDR: 0.009) and BIRC5 (fc: -2.69, FDR 0.0001) among others. Functional enrichment analysis of DEGs revealed that the incidence of live birth is associated with promotion of pathways such as runt-related transcription factor 1 (RUNX1/2) signalling, glycosaminoglycan biosynthesis and sonic hedgehog signalling (SHH), and reduction in pathways such as glycosphingolipid biosynthesis and pyrimidine metabolism in cumulus cells.

Limitations, reasons for caution
We reveal the transcriptome associated with live birth in CCs analysed with RNAseq on a limited number of samples. Consolidation of these findings via utilisation of a validation prospective cohort is pending.

Wider implications of the findings
CCs’ transcriptome could inform the development of non-invasive biomarkers to predict the chance of live birth across a group of embryos eligible for transfer. The transcriptomic findings inspire further explorations in the field of cumulus-oocyte bidirectional communication and establishment of oocyte competence.

Trial registration number
N/A