1141584386 Cell type specific regulation of human placenta growth factor

Abstract

Background: Maternal serum levels of PlGF are significantly lower in preeclamptic patients than in normal pregnant women. PlGF mRNA expression is cell type specific with high levels in trophoblast but comparatively low levels in most nontrophoblast. Despite two consensus hypoxia response elements (HREs), PlGF expression is down regulated by hypoxia in trophoblast, but increased in other cell types. These observations suggest unique regulatory mechanisms control PlGF expression. We sought to characterize PlGF promoter regions which function to regulate transcription rates in different cell types and under hypoxia.Methods: Regions of human PlGF gene (−1521/+34), (−828/+34), (−698/+34) were cloned into a reporter vector and (−844/−677) was cloned into a minimal TK promoter containing expression vectors. Trophoblast (JEG3 and JAR), and nontrophoblast (HeLa and hEK‐293) were transiently transfected to determine functional responsiveness of the regions. A PlGF gene region containing two HREs was cloned upstream of a TK containing vector to determine hypoxia (1% O2) responsiveness.Results: PlGF (−1521/+34), (−828/+34) regions showed high promoter activity in trophoblast cells, but little activity in nontrophoblast cells. PlGF (−844/−677) cloned downstream of the TK reporter, augmented promoter activity in trophoblast but not nontrophoblast cells. When cloned upstream to the TK promoter, this region significantly decreased activity in nontrophoblast cells. Surprisingly, the PlGF region containing HREs produced little increase in minimal promoter activity during hypoxia in any of the cells.Conclusions: PlGF transcription is cell type specific and a region of PlGF (−828/−698) may act as an enhancer in trophoblast yet mediates repressor activity in nontrophoblast. The putative HREs in PlGF 5’UTR do not seem to increase PlGF transcription under hypoxia suggesting that they are not essential for governing PlGF expression. Further understanding of transcriptional regulation of PlGF in trophoblast may facilitate approaches to increase expression during preeclampsia.