Hypoxia and cAMP stimulate vascular endothelial growth factor (VEGF) in human endometrial stromal cells: Potential relevance to menstruation and endometrial regeneration

The human female reproductive tract shows unique cycle-specific changes in vascularization. Vascular endothelial growth factor (VEGF) is a specific va scular endothelial mitogen which is produced by human endometrium and is kn own to be regulated by steroid hormones. Vasoconstriction during menstruati on leads to endometrial hypoxia, a possible stimulus for angiogenesis. In t he current study we tested the hypothesis that hypoxia and cAMP, a known st imulus for endometrial decidualization, can induce VEGF in human endometria l stromal cells. Decidualized as well as non decidualized stromal cells fro m 6 patients were exposed to normoxia (20% oxygen) and hypoxia (2% oxygen) for up to 72h. VEGF levels were assessed by Northern analysis using a 605 b p BamHI fragment of the human VEGF cDNA, and hybridization signals were nor malized to levels of 18S RNA. VEGF protein was determined by ELISA. Hypoxia stimulated VEGF mRNA in decidualized stromal cells by 10.2 fold at 48h com pared to normoxic controls. VEGF protein increased 10 fold by 48h and incre ased further to 13 fold at 72h. In the presence of 2% oxygen VEGF mRNA in n ondecidualized endometrial stromal cells was increased 1.2 - 8 fold between 2 and 72h of treatment. VEGF protein also increased 1.2 - 9 fold in this t ime period, cAMP regulated both VEGF mRNA and protein in non decidualized s tromal cells. VEGF mRNA increased 2-4 fold in 2-72h and protein production showed a 2-6 fold increase. VEGF was seen to be regulated by both cAMP and hypoxia in an additive manner. These results demonstrate that both non-deci dualized and decidualized endometrial stromal cells respond to hypoxia with increasing levels of VEGF. 8Br-cAMP, which is shown to increase VEGF level s in endometrial cells per se, has an additive effect on VEGF production un der hypoxic conditions. This effect may have physiologic and pathophysiolog ic relevance during the process of menstruation and in post menstrual endom etrial repair and angiogenesis.