Amino acids are known to play important roles in preimplantation embryo development, including regulation of cell volume and metabolism. Inclusion of l-glutamine, glycine and betaine in embryo culture medium has been shown to improve development in vitro by acting as organic osmolytes, thereby regulating cell volume. The purpose of the present study was to examine the effect of l-proline on preimplantation mouse embryo development in vitro. One-cell stage embryos were cultured in modified HTF, at low density (1 embryo/100 μL) and high density (1 embryo/μL) in the presence and absence of amino acids. Development of the embryos was scored every 24 h until the blastocyst stage. At low density, l-proline significantly increased the proportion of embryos developing to the blastocyst stage. This effect was abolished by culture at high density, suggesting that l-proline was activating a pathway similar to that involved in autocrine signalling by trophic factors in the preimplantation embryo. The improvement in development observed in the presence of l-proline was not due to its action as an organic osmolyte since the osmolality of the medium was 270 mOsm. Furthermore, glycine and betaine, which are known to act as osmolytes in embryos, had no effect on blastocyst development. In embryonic stem cells L-proline is taken up by an amino acid transporter and is involved in the regulation of growth and differentiation (1). The present data suggest that l-proline may have a similar, important role in preimplantation development.
(1) JM Washington, J Rathjen, F Felquer, A Lonic, MD Bettess, N Hamra, L Semendric, BSN Tan, J-A Lake, RA Keough, MB Morris and PD Rathjen (2010) Am J Physiol Cell Physiol 298: C982–C992.
Preimplantation embryo development in vitro: cooperative interactions among embryos and role of growth factors.
