Vascular endothelial growth factor (VEGF) mRNA splice variants are differentially expressed in human blastocysts

The aim of our study was to detect and characterize mRNA expression of VEGF isoforms VEGF(121), VEGF(145), VEGF(165), VEGF(189), and VEGF(206) in huma n blastocysts. We recently demonstrated VEGF mRNA expression during human p reimplantation embryo development, and further information regarding the al ternatively spliced mRNAs resulting in freely secreted proteins or proteins bound to cell surface heparan-sulphate proteoglycans is needed to better u nderstand the process of angiogenesis during implantation. Human blastocyst s unsuitable for transfer obtained from the IVF programme at Stanford Unive rsity were examined by reverse transcription/hemi-nested polymerase chain r eaction for their expression of VEGF mRNA splice variants. VEGF mRNA was ex pressed in 17 out of 19 (89%) blastocysts. Of the 17 blastocysts, VEGF(121) mRNA was detected in 88%, VEGF(145) mRNA in 100%, VEGF(165) mRNA in 71%, a nd VEGF(189) mRNA in 24% of blastocysts. There was co-expression of mRNA fo r VEGF(121) and VEGF(145) only in 29% blastocysts, of mRNA for VEGF(165) an d VEGF(145) only in 12%, and of mRNA for VEGF(121), VEGF(145) and VEGF(165) in 59% blastocysts, VEGF(206) mRNA could not be detected. In conclusion, w e demonstrated that blastocysts express the mRNAs encoding for the free VEG F proteins, enabling the implanting embryo to immediately induce angiogenes is at the implantation site.