Leukaemia inhibitory factor significantly enhances the blastocyst formation rates of human embryos cultured in serum-free medium

The aim of this study was to investigate the effect of leukaemia inhibitory factor (LIF) on human blastocyst formation rates in vitro. To do this, it was first necessary to devise a complex serum-free medium (CSFM) in which to test its activity. Blastocyst formation rates in CSFM microdrops (18.4%) showed no difference to those obtained previously for embryos cultured in 1 ml T6 medium containing 10% serum (25%). The majority of blastocysts were of optimal blastocyst grade (BG1/BG2) as compared to the poor grade (BG3). The percentage of BG1/BG2 blastocysts was decreased in CSFM microdrops (10.2%) compared to that observed in T6 medium (24.8%). Addition of 1000 IU/ml LIF to CSFM microdrops increased the blastocyst formation rate from 18.4 to 43.6% (P = 0.025) and increased the percentage of BG1/BG2 blastocysts (33%; P = 0.025) to levels comparable with those observed in T6 medium. Thus LIF significantly increased the quality and number of human blastocysts formed in CSFM medium, increasing the potential for blastocyst transfer in human in-vitro fertilization (IVF).