Oral Presentation ESA-SRB-APEG-NZSE 2022

Mouse preimplantation embryo development in vitro requires endogenous sphingosine-1-phosphate (S1P)/S1PR signalling (#118)

Monique Rayhanna 1 , Margot Day 1 , Michael Morris 1
  1. The University of Sydney, Sydney, NSW, Australia

The addition of specific growth factors to in vitro embryo culture medium improves the viability of cultured preimplantation embryos. For example, sphingosine-1-phosphate (S1P) improves oocyte maturation (Cheng et al., 2015; Jee et al., 2011), rate of blastocyst formation (Jee et al., 2011), and decreases rates of apoptosis throughout development (Guzel et al., 2018; Roth and Hansen, 2004). The mechanism by which S1P improves development is poorly understood. The current study aims to determine the expression of the 5 isoforms of S1P receptor (S1PR) in mouse preimplantation embryos and the role of endogenous S1PR1-3 signalling in preimplantation embryo development in vitro. Immunofluorescence staining demonstrated that S1PRs 1, 3, and 5 are expressed throughout all stages of preimplantation development but that localisation differs for each: in the blastocyst, S1PR1 was predominantly nuclear and expressed in the trophectoderm and hypoblast cells, S1PR2 and S1PR3 were expressed in the nucleus and cytoplasm respectively of all cells of the blastocyst, and S1PR5 was localised to the cytoplasm of trophectoderm cells. Treatment of embryos with competitive inhibitors of S1PR1, S1PR2, and S1PR3 decreased the percentage of embryos that developed to the blastocyst stage, with mortality occurring at compaction, cavitation, and cleavage stages, respectively. Together, the differing expression and localisation of S1PR1-5 and differences in the timing of mortality from antagonising S1PR1-3 suggests that, while endogenous S1P/S1PR signalling is required for mouse preimplantation embryo development in vitro, individual S1PRs may be part of different axes of S1P/S1PR signalling at different times across mouse preimplantation development. Understanding S1P/S1PR signalling and its role within preimplantation embryo development would facilitate a greater understanding of the molecular mechanisms underpinning embryo development, and potentially allowing us to improve in vitro embryo culture for clinical, research, and agricultural purposes.

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