Placental mRNA and Protein Expression of VDR, CYP27B1 and CYP2R1 Genes Related to Vitamin D Metabolism in Preeclamptic Women

(1) Background: Considerable evidence indicates that the occurrence of preeclampsia (PE) is associated with a reduced vitamin D (VD) level. Several studies have found that VD deficiency is correlated with disturbed trophoblast invasion, reduced angiogenesis and increased vasoconstriction. Because the vitamin D receptor (VDR) and CYP27B1 and CYP2R1 hydrolases are strongly involved in VD metabolism, the goal of the present study was to evaluate their genes and proteins expression in the placentas from preeclamptic women. (2) Methods: Samples and clinical data were obtained from 100 Polish women (41 women with preeclampsia and 59 healthy pregnant controls). The whole PE group was divided into subgroups according to gestation week of pregnancy ending before and after 34 gestational weeks (early/late-onset preeclampsia (EOPE/LOPE)). However, finally, to reduce confounding by differences in gestational age, the EOPE group was excluded from the analysis of mRNA and protein placental expression, and we focus on the comparison between LOPE and control groups. The placental VDR, CYP27B1 and CYP2R1 mRNA expression was analyzed using RT-PCR, and placental protein levels were determined by ELISA assay. (3) Results. (3.1) Placental gene expression: Expression levels of both genes, CYP27B1 (1.17 vs. 1.05 in controls, p = 0.006) and CYP2R1 (2.01 vs. 1.89 in controls, p = 0.039), were significantly higher in preeclamptic placentas than in the control group. Interestingly, VDR expression was significantly lower in placentas from the PE group (1.15 vs. 1.20 in controls, p = 0.030). After dividing all preeclamptic women into subgroups only for the CYP27B1 gene, a significantly higher placental expression in the LOPE subgroup than the healthy controls was observed (padj = 0.038). (3.2) Placental protein expression: The results revealed that protein expression levels of CYP27B1 in the preeclamptic group were similar (5.32 vs. 5.23 in controls, p = 0.530). There was a significant difference in median VDR and CYP2R1 protein levels between studied groups (VDR: 2.56 vs. 3.32 in controls, p < 0.001; CYP2R1: 1.32 vs. 1.43 in controls, p = 0.019). After stratification of preeclamptic women into subgroups, a significant difference was observed only in the VDR protein level. The medians in the LOPE subgroups were significantly lower compared to the healthy control group. In the whole study group, the placental VDR protein level was inversely correlated with systolic and diastolic blood pressure (all p < 0.001), and positively correlated with gestational age (p < 0.001) and infant birth weight (p = 0.014). (4) Conclusions: Lower mRNA and protein expression of VDR in preeclamptic placentas, and also VDR protein expression, could play a pivotal role in preeclampsia development. Additionally, the higher mRNA expression of both CYP27B1 and CYP2R1 hydrolase genes in placentas from preeclamptic women could indicate the compensatory role of these enzymes in preeclampsia etiology. Our results also indicate that placental VDR protein level could be one of the factors modulating blood pressure in pregnant women, as well as influencing gestational age and infant birth weight. Considering the importance of these findings, future studies are warranted.