Placental development during early pregnancy: Effects of embryo origin on expression of chemokine ligand twelve (CXCL12)

• CXCL12 localization in sheep during early gestation and after ART is discussed.
• CXCL12 is localized in endometrial stroma, endometrial glands, and trophoblast cells.
• Greater CXCL12 protein in trophoblast on days 22 and 24 compared to 18, 20, and 28.
• Greater CXCL12 protein in naturally bred ewes compared to ART.
• Decreased CXCL12 in trophoblast of ART embryos may compromise placentation.

The aim was to localize chemokine ligand twelve (CXCL12) in sheep placental tissues during early gestation and after assisted reproductive technologies (ART). Uteri were collected from naturally (NAT) mated ewes and ewes receiving embryo transfer (ET), in vitro fertilization (IVF) or in vitro activation (IVA). CXCL12 was immunolocalized to endometrial stroma, glands, and trophoblast. Greater CXCL12 immunoreactivity was present in trophoblast on day 22 and 24 and in NAT ewes compared to IVF and IVA. Increased CXCL12 expression suggests CXCL12 promotes implantation and placentation. Decreased CXCL12 in IVF and IVA embryos, may compromise pregnancy establishment when utilizing ART methods.