Histidine-rich glycoprotein derived peptides affect endometrial angiogenesis <i>in vitro</i> but has no effect on embryo development

<p>Histidine-rich glycoprotein (HRG) is an abundant plasma protein involved in multiple biological processes including immunology, vascularisation, and coagulation. These processes are of importance in regulating embryo development and implantation. A specific polymorphism in the <i>HRG</i> gene, <i>HRG</i> C633T, has an impact on various aspects of fertility, such as oocyte quality, endometrial receptivity, and possibly the capacity of the embryo itself to implant. To further examine the potential role of the <i>HRG</i> C633T polymorphism in regulating endometrial angiogenesis and on embryo development, two HRG peptides were constructed. These HRG peptides correspond to the amino acids 169-203 of the protein which, in turn, reflects the C633T polymorphism in the gene. The HRG proline or serine peptides were added to cultures of primary human endometrial endothelial (HEE) cells and to human embryos <i>in vitro</i>. The HRG peptides inhibited vascular endothelial growth factor (VEGF) induced proliferation and migration and promoted tube formation of HEE cells. The embryos were monitored using a time-lapse system (EmbryoScope®). Except for a prolonged time from first cleavage after thawing to development of the morula, no difference in embryo morphokinetics or embryo quality was noted in human embryos cultured in the presence of the HRG proline peptide. Taken together, these results suggest that treatment with a specific HRG peptide might prime the endometrium for implantation and be beneficial for adequate placentation. However, addition of a specific HRG proline peptide to human embryos has no beneficial effects in terms of embryo development.</p> <p><b>Abbreviations</b>: HRG: histidine-rich glycoprotein; HEE: human endometrial endothelial; VEGF: vascular endothelial growth factor; TSP: thrombospondin; SNP; single nucleotide polymorphism; IVF: <i>in vitro</i> fertilization; CLESH-1: CD36 LIMPII Emp structural homology domain-1; ECM: endothelial cell medium; FBS: fetal bovine serum; cDNA: complementary DNA