Hum. Reprod. Advance Access published online on September 8, 2009
Human Reproduction, doi:10.1093/humrep/dep307
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Stress response genes are suppressed in mouse preimplantation embryos by granulocyte-macrophage colony-stimulating factor (GM-CSF)
Research Centre for Reproductive Health, Discipline of Obstetrics and Gynaecology, University of Adelaide, Adelaide, SA 5005, Australia
1Corresponding author. Tel: +61-8-8303-4094; Fax: +61-8-8303-4099; E-mail: sarah.robertson{at}adelaide.edu.au
BACKGROUND: Granulocyte-macrophage colony-stimulating factor (GM-CSF) is known to promote the development and survival of human and mouse preimplantation embryos; however, the mechanism of action of GM-CSF in embryos is not defined.
METHODS: Mouse blastocysts were cultured from zygote stage in vitro with and without recombinant mouse GM-CSF (rmGM-CSF), and in vivo developed blastocysts were flushed from Csf2 null mutant and wild-type mice. The effect of GM-CSF on blastocyst expression of stress response and apoptosis genes was evaluated by microarray, qPCR and immunochemistry.
RESULTS: Microarray analysis of the gene transcription profile showed suppression of stress response and apoptosis gene pathways in blastocysts exposed to rmGM-CSF in vitro. qPCR analysis confirmed that rmGM-CSF inhibited expression of heat shock protein (HSP) and apoptosis pathway genes Cbl, Hspa5, Hsp90aa1, Hsp90ab1 and Gas5 in in vitro blastocysts. Immunocytochemical analysis of HSP 1 (HSPA1A/1B; HSP70), BAX, BCL2 and TRP53 (p53) in in vitro blastocysts showed that HSPA1A/1B and BCL2 proteins were less abundant when embryos were cultured with rmGM-CSF. BAX and TRP53 were unchanged at the protein level, but Bax mRNA expression was reduced after GM-CSF treatment. In in vivo developed blastocysts, Csf2 null mutation caused elevated expression of Hsph1 but not other stress response genes.
CONCLUSIONS: We conclude that GM-CSF inhibits the cellular stress response and apoptosis pathways to facilitate embryo growth and survival, and the protective effects of GM-CSF are particularly evident in in vitro culture media, whereas in vivo other cytokines can partly compensate for absence of GM-CSF.
Key words: blastocyst/GM-CSF/heat shock proteins/stress response/apoptosis
Submitted on June 19, 2009; resubmitted on July 30, 2009; accepted on August 7, 2009.