Localisation of epidermal growth factor (EGF), its specific receptor (EGF-R) and aromatase at the materno-fetal interface during placentation in the pregnant mare.

The research investigates the role of Epidermal Growth Factor (EGF), its specific receptor (EGF-R) and aromatase enzyme in placenta development during horse pregnancy. The results suggest these elements work together, promoting fast growth and enhanced vascularisation of the placenta.

Methodology and Findings

• The research was conducted using placental interface tissues harvested from 11 horse uteri between 20 and 68 days of gestation.
• The tissues were immunocytochemically stained to identify the presence and intensity of Epidermal Growth Factor (EGF), its specific receptor (EGF-R), and the enzyme, aromatase.
• EGF was found in endometrial glands and epithelia from day 20, with an increase in staining intensity for the protein between days 30 and 40, corresponding with the secretion of equine Chorionic Gonadotrophin (eCG) and the commencement of attachment and complex interaction between the allantochorion and endometrium.
• EGF-R appeared strongly on both non-invasive and invasive trophoblast surfaces, also showing an increase in staining intensity between days 30 and 40.
• Aromatase, an enzyme crucial for converting androgens to estrogens, was strongly and consistently present from day 12 in the non-invasive trophoblast of the allantochorion, but not the invasive trophoblast of the chorionic girdle.

Significance of Findings

• The findings back the hypothesis that, during horse pregnancy, the maternal growth factor EGF, along with maternally and fetally secreted estrogens, facilitate the rapid growth and extensive vascularisation of the non-invasive, epitheliochorial, microcotyledonary placenta.
• This synergy likely leads to the birth of the precocious foal after only 11 months gestation.
• Understanding these biological mechanisms could be significant in managing equine reproductive health and breeding practices.