Panel A, Overview of the chβA-EGFP transgenic model for assessing the trophoblast cell lineage. EGFP expression was monitored at the placentation site in wild-type female rats mated to homozygous chβA-EGFP transgenic male rats. Panel B, Validation of EGFP and cytokeratin expression profiles at the gestation day 18.5 placentation sites of wild-type female rats mated to homozygous chβA-EGFP transgenic male rats. Image b1, EGFP fluorescence; Image b2, immunostaining with anti-GFP; Image b3, immunostaining with anti-cytokeratin. Please note the robust EGFP fluorescence throughout the uterine mesometrial compartment, which has a similar distribution to EGFP immunoreactivity, and cytokeratin immunoreactivity. Panel C, Gestational profile of EGFP expression in the placentation sites of wild-type female rats mated to homozygous chβA-EGFP transgenic male rats. Panel D, Effects of maternal hypoxia on of EGFP fluorescence at the placentation site. Wild-type female rats were mated to homozygous chβA-EGFP transgenic male rats. Maternal hypoxia exposure (equivalent to 11% oxygen) was initiated on gestation day 6.5 and continued to day 13.5 when animals were sacrificed (image d2). Gestationally matched pair-fed rats exposed to ambient conditions were used as controls (image d1). Please note that maternal hypoxia stimulated the invasion of extraembryonic-derived EGFP positive cells into the maternal uterine vasculature. Scale bar = 0.5 mm.