Oestrogen and progesterone receptors in the marmoset endometrium: changes during the ovulatory cycle, early pregnancy and after inhibition of vascular endothelial growth factor, GnRH or ovariectomy

Marmosets are widely used, but detailed studies on localisation of endometrial oestrogen receptors α and β (ERα and ERβ ), and the progesterone receptor (PR) are lacking. These receptors were localised and semi-quantitatively analysed throughout the ovulatory cycle, weeks 2, 3 and 4 of pregnancy and after treatment with GnRH antagonist, vascular endothelial growth factor (VEGF) Trap or ovariectomy. The PR in epithelial cells increased markedly between the mid- and late proliferative phases before declining in the mid-secretory phase and pregnancy. PR in stromal cells was present throughout the cycle and levels were maintained in pregnancy. ERα was present at the mid-proliferative phase and increased in glands at the late proliferative and early secretory phases, before declining at the late secretory phase and week 4 of pregnancy. Stromal ERα showed a similar trend, but decreased earlier, by the mid-secretory phase. ERβ was highly expressed in epithelial cells throughout the cycle and in pregnancy. In stroma, increases in ERβ expression were observed at the late proliferative phase with the staining index decreasing by half as the secretory phase progressed and in pregnancy. GnRH antagonist, VEGF Trap or ovariectomy caused significant reductions in PR and ERβ expression, but not in ERα when compared with the late proliferative phase of the normal cycle. Endothelial cells expressed ERβ , but not ERα or PR. It is concluded that the steroid receptor profile in the marmoset endometrium is generally similar to the human and should provide a useful model for studies on hormonal manipulation of the endometrium.