Blastulation rates of sibling oocytes in two IVF culture media: an evidence-based workflow to implement newly commercialized products

Abstract

Research question

An evidence-based novel commercially available continuous IVF culture medium in compliance with an efficient quality-management system is proposed.

Design

Non-interventional study on sibling oocytes. Intracytoplasmic sperm injection cycles among women aged 42 years or younger that used ejaculated spermatozoa and retrieved four to eight oocytes were included. Sibling oocytes were randomized for culture in the novel Geri-medium or continuous single culture medium (CSCM). Primary outcome measure was blastulation rate per cohort of inseminated oocytes; 1182 oocytes were required to outline down to a 7% difference (power = 80%).

Results

A total of 181 cohorts of sibling oocytes were included. Geri-medium (n = 631 oocytes) and CSCM (n = 643 oocytes) resulted in similar blastulation rates (mean ± SD: 42.8% ± 30.1% versus 43.1% ± 29.0%; Wilcoxon signed rank test = 0.77). Blastocysts cultured in the former (n = 275 versus n = 277) showed longer timings during preimplantation development (P < 0.01) and were poorer quality (26% versus 18%; P = 0.03). Euploidy rate was no different in cycles that underwent preimplantation genetic testing for aneuploidy (n = 113) (117/237 [49%] versus 117/249 blastocysts [47%]; P = 0.6). Ongoing implantation rate was comparable in the study arms after euploid (29/47 [63%] versus 14/ 34 [41%]; P = 0.1) or untested (12/31 [39%] versus 7/18 [39%]; P = 0.3) transfers.

Conclusion

Blastulation rate among cohorts of sibling oocytes cultured in the same incubator is a fast, reliable and comprehensive performance indicator to validate novel commercially available culture medium. The media tested were considered similarly efficient. The differences in blastocyst morphology and developmental timings warrant further investigation, although euploidy and ongoing implantation rates were similar.

Introduction

A quality management system (QMS) is mandatory for any IVF unit according to the regulatory guidelines of most countries; however, many clinics often implement a new culture medium without verifying its effectiveness in their specific setting using proper experimental design. Specifically, even if any novel commercialized culture medium has already undergone the mandatory inspections proving its safety and efficacy as requested by each specific national regulation, e.g. the Conformitè Europèenne (CE) mark in Europe, the goal of a QMS is to guarantee these prerequisites in each specific clinical setting (Sunde et al., 2016). Indeed, a medium is just one of the different elements that constitute a culture system, and its performance is based on the synergy between them. For instance, the type of incubator, whether humified or not, the amount of CO₂ and its effect on the pH of the media, the oxygen tension, and many other chemical and physical factors might all contribute to the variability of the outcomes achieved among different IVF clinics (Swain et al., 2016; Wale and Gardner, 2016). Therefore, the implementation of a culture medium should be considered as part of each clinic's QMS, and it should be conducted in a controlled manner, following a number of key steps (Chronopoulou and Harper, 2015). In fact, no tool or procedure should be introduced without a systematic approach.

Two distinct culture approaches aimed at supporting embryo development to the blastocyst stage have been proposed to date: the ‘back to nature’ sequential approach and the ‘let the embryo choose’ single step approach (Summers and Biggers, 2003; Machtinger and Racowsky, 2012; Quinn, 2012). With the sequential approach, embryos are grown to day 3 in a first medium and then moved to a second medium to reflect the observed changes in concentrations of metabolites and amino acids in the Fallopian tube compared with the uterus (Gardner et al., 1996). Conversely, single culture media allow the embryos to choose the nutrients they require, while minimizing the stress putatively originating from the exposure to an abrupt change in their culture environment on day 3. Single media can be used with a changeover on day 3 or in the absence of refresh (Biggers and Summers, 2008; Costa-Borges et al., 2016). Several comparisons of continuous and sequential media have been conducted, with similar performance reported (Sfontouris et al., 2016). On the contrary, few data have been published on the performance of different single step media in the same conditions (Durand et al., 2016; Sfontouris et al., 2017; Morbeck et al., 2017).

A new commercially available validated medium has recently become available (Geri medium (GEMS) (Genea Biomedx, Sydney, Australia), which contains some additional components usually absent from IVF culture media, i.e. taurine, D-glucose, glycine, L-carnitine, vitamins B5, B12, B9 and C. Among them, taurine, L-carnitine and vitamins B5 and C are antioxidant compounds, critical to limit the damage that might derive from reactive oxygen species during embryo culture in vitro. With the aim of implementing Geri medium clinically, a comparison was undertaken of Geri medium with our internal well-established conditions (previously defined through a quasi-randomized controlled trial published in 2018 (Cimadomo et al., 2018d): culture with the continuous single culture medium (CSCM) (Irvine Scientific, Santa Ana, CA, USA) in an undisturbed environment associated with a time-lapse microscope. The composition of the two media compared in this study and the differences between them, i.e. pH and osmolarity, are presented in Supplementary Table 1.