Vascular Endothelial Growth Factor A and VEGFR-1 Change during Preimplantation in Heifers.

Daniel Chiumia,Stefan Bauersachs,Katrin Giller,Susanne E Ulbrich,Horst-Dieter Reichenbach,Anna-Katharina Hankele,Valeri Zakhartchenko,Anna E Groebner,Katy Schulke

doi:10.3390/ijms21020544

Abstract

Vascular endothelial growth factor A (VEGFA) plays a critical angiogenic role in the endometrium of placentalia during preimplantation. The role of VEGFA and its receptors is not fully characterised in bovine reproduction. We analysed the mRNA expression of VEGFA isoforms 121, 165 and 189, and VEGF receptors 1 and 2 in three experimental settings (A, B and C). We compared intercaruncular endometrium of cyclic to pregnant heifers at Days 12, 15 and 18 post insemination (Day 0), and between Day 15 and Day 18 conceptuses (A). We further compared caruncular versus intercaruncular endometrium at Day 15 (B), and endometrium of heifers carrying embryos originating from somatic cell nuclear transfer (SCNT) versus in vitro fertilisation (IVF) at Day 18 (C). Endometrial VEGFA protein was localised and quantified. Pregnant heifers displayed lower intercaruncular endometrial mRNA expression of VEGFA-121 (p = 0.045) and VEGFA-189 (p = 0.009) as well as lower VEGFA protein abundance (p < 0.001) at Day 15. The VEGFA protein was localised in intercaruncular luminal, glandular epithelium and in tunica muscularis of blood vessels. At Day 15, caruncular endometrium displayed higher VEGFA mRNA expression than intercaruncular endometrium (p < 0.05). Intercaruncular endometrial VEGFA protein at Day 18 was higher in abundance in SCNT than in IVF (p = 0.038). Therefore, during preimplantation in cattle, there may be a need for timely physiological reduction in intercaruncular endometrial VEGFA expression in favour of the caruncular area to facilitate a gradient towards the implantation sites. A higher expression of VEGFA in SCNT may predispose for later placentation abnormalities frequently observed following SCNT.

Highlights

Embryonic losses heavily affect bovine reproduction and contribute to low calving rates (50 to 60%) despite high fertilisation rates (~90%) [1]
The activities of vascular endothelial growth factor A (VEGFA) are mediated by the membrane receptors VEGFR-1 and VEGFR-2, which are the universal regulators of endothelial cell functions [9]
Comparing the nonpregnant and pregnant heifers, we did not find any significant differences in E2 concentrations at day of the estrous cycle (Day) 12, 15 and 18 post insemination

Summary

Introduction

Embryonic losses heavily affect bovine reproduction and contribute to low calving rates (50 to 60%) despite high fertilisation rates (~90%) [1]. The isoforms differ first in their heparin and heparan sulfate-binding abilities [4] and second regarding whether the isoform encodes a pro- or antiangiogenic protein [5]. Among these three isoforms, VEGFA-165 is the prototypical VEGFA isoform that induces a robust agonist through the receptor signaling responses and is taken as a reference isoform for investigating other VEGFA isoforms [6]. The activities of VEGFA are mediated by the membrane receptors VEGFR-1 and VEGFR-2, which are the universal regulators of endothelial cell functions [9]. VEGFR-1 regulates proliferation of endothelial cells during angiogenesis and VEGFR-2 is involved in migration and proliferation of endothelial cells during vessel maintenance [10]

Methods

Results

Discussion

Conclusion