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TFC Team 2023

Stress relief: can continuous culture in a low lactate culture media reduce numerical chromosomal abnormalities and therefore improve euploidy rates?


OBJECTIVE:

To compare PGT-A results from embryos cultured in a new formulation of culture media against those embryos cultured in a sequential or single-step culture system.

DESIGN:

Retrospective analysis in private reproductive technology programs.

MATERIALS AND METHODS:

From 2016 – 2018, embryos in two separate IVF laboratories (Lab A & B) were either cultured to the blastocyst stage in a sequential culture system (G-Series™, Vitrolife), Continuous Single Culture® (CSCM) or Continuous Single Culture®- NX (CSCM-NX) (Irvine Scientific®). CSCM-NX contains a lower concentration of lactate compared to traditional culture media. All embryos were cultured in 6% CO2 in reduced oxygen. A sequential media change was performed with embryos cultured in G-Series™ on Day 3 (from G1™ to G2™) whereas embryos cultured in both CSCM and CSCM-NX were cultured undisturbed for 7 days. Trophectoderm biopsy was performed on either Day 5, 6, or 7 of blastocyst development and embryo ploidy status was determined by PGT-A through NextGen Sequencing (Ovation Genetics). Embryos reported as normal had no detectable copy number aberration, at a threshold of ≤30%.

RESULTS:

A total of 6,655 embryos cultured in either sequential, CSCM and CSCM-NX culture media were biopsied for PGT-A. 53.9% of embryos cultured in CSCM-NX were identified as euploid compared to 44.3% of embryos cultured in the sequential system. This difference was highly significant (P<0.001). Embryos cultured in CSCM or CSCM-NX low lactate medium and subsequently biopsied, 46.6% were euploid compared to 57.1% respectively. This difference was also highly significant (P<0.001).

CONCLUSION:

An excess of lactate present in culture medium may be a contributing factor to unwarranted stress on an embryo. This strain on metabolic efficiency can subsequently alter embryo development and cellular integrity which may increase the occurrence of mitotic aneuploidy by affecting spindle assembly and chromosome segregation in dividing cells. For the first time, we report a highly significant difference in euploidy rates from embryos cultured in a low lactate, single-step culture media. Our results show that by simply changing our selection of culture media we experienced a 10% increase in euploid embryos. Stimulation protocols, the PGT-A testing platform and overall embryo culture protocols remained consistent. Further assessment of subsequent pregnancy outcomes is currently ongoing.

% PGT-A Euploid Blastocysts

LAB A Normal % Normal Abnormal Total
Sequential 697 44.3% 876 1573
CSCM-NX 558 53.9% 478 1036
LAB B
CSCM 1594 46.6% 1823 3417
CSCM-NX 359 57.1% 270 629

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