Euploid but failing to implant? Insights from trophectoderm transcriptomics of euploid blastocysts using an in vitro model.

OBJECTIVE

To investigate transcriptomic differences in mural trophectoderm (TE) cells of euploid human blastocysts on the basis of their ability to remain attached in extended in vitro culture and to identify gene expression profiles associated with competence for implantation.

DESIGN

Prospective in vitro experimental cohort study involving ribonucleic acid sequencing of mural TE biopsies from euploid blastocysts and extended culture up to day 11.

SUBJECTS: Fifteen euploid blastocysts donated by 16 couples undergoing intracytoplasmic sperm injection and preimplantation genetic testing for aneuploidy. Transcriptomic comparison focused on 10 euploid blastocysts, classified as attached (n = 5) or unattached (n = 5) after extended in vitro culture, and the rest were excluded for various reasons.

EXPOSURE: Development outcome of euploid blastocysts during extended in vitro culture (adhesion vs. non-adhesion to the culture surface on day 11), used as the basis for differential gene expression analysis.

MAIN OUTCOME MEASURES: Identification of differentially expressed genes and deregulated molecular pathways between attached and unattached euploid embryos, including functional enrichment analysis to explore their potential roles in embryo viability and implantation.

RESULTS

Transcriptomic analysis revealed 85 differentially expressed genes between unattached and attached euploid blastocysts, including genes involved in cellular adhesion (e.g., SPON2 and VTN), immune modulation (HLA-G and IL12A), metabolism (NNMT and CYP3A7), and mitochondrial function. Unattached embryos displayed down-regulation of ribosome biogenesis, mitochondrial proteins, and chromosomal segregation pathways and up-regulation of genes related to immune response and cytoskeletal organization.

CONCLUSION

The study demonstrates that mural TE gene expression differs significantly between euploid blastocysts that attach and those that do not, highlighting molecular pathways potentially linked to implantation success. Despite human implantation typically occurring through the polar TE, mural TE transcriptomic profiles may provide predictive value for embryo selection and deepen our understanding of early implantation biology. Further validation through proteomic studies and larger cohorts is needed to confirm these candidate biomarkers.