Abstract
BackgroundAdrenomedullin (AM) is a potent vasodilator peptide and is also involved in various physiological activities. In humans and rodents, AM is found in the uteroplacental unit and may be responsible for fetal development and maintenance of placental function. This study investigated 1) the mRNA expression patterns of AM and its receptor components (calcitonin receptor-like receptor (CRLR), receptor activity modifying protein (RAMP) 2 and RAMP3) during pregnancy and 2) mRNA and protein localization of AM, CRLR and RAMPs in the bovine placentome.MethodsFor real-time quantitative RT-PCR, bovine uteroplacental tissues were collected from Day 25, 60, 100, 150, 200 and 250 of gestation and separated into uterine caruncle (CAR), intercaruncular endometrium (ICAR), extra-embryonic membranes on Day 25 and cotyledonary villous after Day 60 (EEM-COT) and intercotyledonary chorion (ICOT). In situ hybridization and immunohistochemistry was performed to investigate the cellular localization of mRNA and protein of AM, CRLR, RAMP2 and RAMP3 in the placentome on Day 56, 150 and 230 of gestation and interplacentomal tissues on Day 56 of gestation.ResultsAM mRNA was highly expressed on Day 200 in EEM-COT, CAR and ICAR. CRLR mRNA was highly expressed on Day 60 in all portions. RAMP2 mRNA was also highly expressed on Day 60 in ICOT and ICAR. In EEM-COT, mRNA expression of CRLR and RAMP2 decreased from Day 150 to 250. RAMP3 mRNA was highly expressed on Day 150 in EEM-COT, ICOT and ICAR. A distinct AM mRNA and protein signal were only found in trophoblast binucleate cells (BNCs), whereas those of CRLR, RAMP2 and RAMP3 were detected in cotyledonary villous and caruncular epithelial cells. In interplacentomal tissues, AM was detected in BNCs of fetal membrane and a small part of luminal epithelium, endothelial lineage of blood vessels and glandular epithelium of the endometrium. Distinct signals of CRLR, RAMP2 and RAMP3 were found in trophoblast cells, luminal epithelium, stroma under the epithelium, endothelial lineage of blood vessels and glandular epithelium.ConclusionsOur results indicate that the AM system in the bovine uteroplacental unit may be activated at placentation and transition from the mid to late gestation period. Locally produced AM in the BNCs may play a crucial role in regulation of placental vascular and cellular functions during pregnancy.
Highlights
Adrenomedullin (AM) is a potent vasodilator peptide and is involved in various physiological activities
The mRNA expression level of RAMP2 was higher on Day 150 in embryonic membrane (EEM)-COT and on Day 60 in intercotyledonary chorion (ICOT) than on Day 100 and 250 (Figure 1C)
RAMP3 mRNA expression in EEM-COT and ICOT was higher on Day 150 compared with Days 25, 60, 100 and 250 (Figure 1D)
Summary
Adrenomedullin (AM) is a potent vasodilator peptide and is involved in various physiological activities. Ruminants have an epitheliochorial-cotyledonary placenta, which is formed at the interface between endometrial caruncles (CAR) and fetal cotyledon (COT) and especially characterizes the migration of trophoblast binucleate cells (BNCs) [1]. Both fetal and maternal components of bovine. Trophoblast giant cells abundantly express AM mRNA [18] Both AM and RAMP3 mRNA levels in rat placenta were higher in mid than in late gestation [19]. AM heterozygous knockout mice had reduced fertility caused by restricted fetal growth due to a high incidence of abnormal trophoblast cell invasion followed by morphological placental defects [22]
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