Chronic maternal hypertension affects placental gene expression and differentiation in rabbits

Abstract

Background: Previously, we have shown that adult offspring from hypertensive rabbits develop hypertension.

Method: We aimed to determine the effects of mild (+15 mmHg) and moderate (+25 mmHg) increases in maternal blood pressure and plasma renin activity on placental differentiation and expression of components of the renin-angiotensin system and 11[beta]-hydroxysteroid dehydrogenase type 2 mRNA in rabbits. Placentas were collected from normotensive (sham), mild (2-kidney-1-cellophane wrapped; 2K-1W) and moderate (2-kidney-2-cellophane wrapped; 2K-2W) hypertensive groups at gestational age of 14, 21 and 28 days. Placental gene expression was quantified by reverse transcriptase-PCR, and morphometry was assessed by videoimage analyses of placental sections.

Results: Fetal weight was similar between groups across gestation. In the 2K-1W group at gestational age day 14, fetal-to-placental weight ratio was increased (approximately 34%) as were volumes of fetal capillaries ([up arrow]56%) and maternal blood space at gestational age day 21 ([up arrow]55%) compared with sham (all P < 0.05). In the 2K-2W group, fetal-to-placental weight ratio was increased at gestational age day 21 (approximately 25%; P < 0.01) with an accompanying reduction in placental weight, and at gestational age day 28, volume density of fetal capillaries was increased (approximately 22%; P < 0.05). Placental renin mRNA was lower in both the 2K-1W (approximately 88%) and 2K-2W (approximately 98%) groups at gestational age day 28 (all P < 0.01). Placental 11[beta]-hydroxysteroid dehydrogenase type 2 mRNA was lower in the 2K-1W (approximately 36%) and 2K-2W (approximately 31%) groups at gestational age day 14 and greater (approximately 36%) in the 2K-2W group at gestational age day 21 (all P < 0.01). Associations between placental AT1R and AT2R mRNA and placental differentiation were disturbed by hypertension.

Conclusion: Mild and moderate maternal hypertension differentially alters placental structure and gene expression that may affect placental functional capacity and contribute to programming of hypertension in offspring.