Assessing mitochondrial quantity and ranking (mitoscore) in euploid single embryo frozen transfers demonstrates a lower mitoscore is significantly better

Abstract

Objective Mitochondria are cellular power houses acting as the principal site for ATP production. Mitochondrial function, mtDNA gene expression, and energy are required to undergo necessary cellular divisions in the formation of a high quality embryo. Unlike other cellular organelles, mitochondria contain their own DNA (mtDNA). It is known that mitochondrial functions are imperative during preimplantation development, however the quantity of mtDNA an embryo requires is unknown. Our current best practices for embryo selection include day of development, morphology grade and preimplantation genetic testing for aneuploidy (PGT-A). In this study we compared clinical pregnancy rates of our current protocols for embryo selection and any relationship to the Mitoscore ranking. Design Retrospective analysis of clinical outcomes as they associate with laboratory characteristics for embryo development, embryo quality and Mitoscore ranking. Materials & Methods During days 5-7 of embryo development, trophectoderm biopsy was performed on blastocysts by an embryologist using a laser to remove 3-5 trophectoderm cells for PGT-A. The biopsied cells are washed through buffer media, loaded into PCR tubes and frozen in a -20°C freezer until analysis. Whole genome amplification and next generation sequencing (NGS) using the Ion ReproSeq PGS Kit for 24 chromosome aneuploidy screening using the Ion Reporter software was performed. The genetic analysis uses complex algorithms to delineate mtDNA scores (Mitoscore). Frozen single euploid embryo transfer decisions were based on embryo developmental day and overall embryo quality grading criteria but did not include Mitoscore ranking. Pregnancy outcomes were analyzed and assessed as they associated with the Mitoscore number and its rank in the cohort. Results From this study we learned that using our current embryo selection criteria, excluding Mitoscores, resulted in only a 64.4% overall pregnancy rate. However, in embryos with Mitoscore values Conclusions Correlation with the Mitoscore data demonstrated that