Differential expression of vascular endothelial growth factor-A isoforms in the mouse uterus during early pregnancy.

While vascular endothelial growth factor (VEGF)-A mediates endometrial vascular remodelling during early pregnancy in mice, individual VEGF-A isoforms have not been investigated, despite their different biological properties. Using mice as a model, the expression of VEGF-A isoforms and receptors in the mouse uterus during early pregnancy was quantified. It was postulated that selected isoform expression would increase concurrent with increased endometrial endothelial cell proliferation at this time. Uteri were collected on days 1-5 of pregnancy and mRNA expression was quantified by quantitative reverse-transcription polymerase chain reaction, VEGF-A protein by Western blot and VEGF receptor (VEGFR)-2 by immunohistochemistry. The lowest expression of isomers Vegf(120) and Vegf(164) was observed on day 2 of pregnancy, increasing thereafter. Vegfr-2 mRNA expression was significantly higher on days 3-5 of pregnancy relative to days 1-2 (P<0.05). No significant changes were noted in Vegf(188), Nrp1 or Nrp2 mRNA. VEGF(188) protein expression was consistently higher than other isoforms. These data demonstrate differential regulation of VEGF-A isoforms in mouse uterus during early pregnancy.