mRNA expression of leukaemia inhibitory factor (LIF) and its receptor subunits glycoprotein 130 and LIF-receptor-beta in bovine embryos derived in vitro or in vivo.

Leukaemia inhibitory factor (LIF) plays an essential role during cell differentiation and implantation in the mouse exerting its effects via the two dimerizing receptor subunits glycoprotein 130 (gp130) and LIF-receptor beta (LR-beta). This study investigated the mRNA expression of bovine LIF (bLIF), gp130 and LR-beta in pooled or individual bovine oocytes and embryos generated in vitro or in vivo after superovulation. Transcripts of gp130 and LR-beta were detectable in as little material as 1/3 oocyte equivalent and bLIF transcripts in two embryo equivalents employing a simple, rapid and robust one-step reverse transcription-polymerase chain reaction (RT-PCR) protocol using random hexamer priming during reverse transcription and 60 amplification cycles in the PCR. All mRNA fragments were also found in cumulus cells and various bovine tissues. While gp130 and LR-beta mRNA were present in pooled material throughout embryo development in vitro from the immature oocyte to the hatched blastocyst, bLIF-transcripts were absent in immature oocytes, inconsistently expressed from the matured oocyte up to the 16-cell stage as well as in blastocysts dependent on embryo batch. It was not found in morulae, but again present in hatched blastocysts. In contrast, in in-vivo derived embryos no bLIF was found, LR-beta was not detected at the morula to blastocyst transition while gp130 transcripts were observed from the morula to the hatched blastocyst. In individual embryos the mRNA expression pattern was similar for both in-vitro and in-vivo derived embryos as found in pooled material. These results indicate perturbation of the mRNA expression pattern of the specific LIF-LIF-receptor system in embryos generated in vitro that could lead to abnormal differentiation of the cell compartments forming the blastocyst. Cumulus cells, frequently used as supportive factor in co-culture in bovine in-vitro embryo production, are a rich source of the LIF-LIF-receptor system acting in a paracrine and/or autocrine manner. The biological function of the LIF-LIF-receptor system during bovine preimplantation development warrants further investigation.