Placental uptake and metabolism of 25(OH)vitamin D determine its activity within the fetoplacental unit

Pregnancy 25-hydroxyvitamin D [25(OH)D] concentrations are associated with maternal and fetal health outcomes. Using physiological human placental perfusion and villous explants, we investigate the role of the placenta in regulating the relationships between maternal 25(OH)D and fetal physiology. We demonstrate active placental uptake of 25(OH)D-3 by endocytosis, placental metabolism of 25(OH)D-3 into 24,25-dihydroxyvitamin D-3 and active 1,25-dihydroxyvitamin D [1,25(OH)(2)D-3], with subsequent release of these metabolites into both the maternal and fetal circulations. Active placental transport of 25(OH)D-3 and synthesis of 1,25(OH)(2)D-3 demonstrate that fetal supply is dependent on placental function rather than simply the availability of maternal 25(OH)D-3. We demonstrate that 25(OH)D-3 exposure induces rapid effects on the placental transcriptome and proteome. These map to multiple pathways central to placental function and thereby fetal development, independent of vitamin D transfer. Our data suggest that the underlying epigenetic landscape helps dictate the transcriptional response to vitamin D treatment. This is the first quantitative study demonstrating vitamin D transfer and metabolism by the human placenta, with widespread effects on the placenta itself. These data demonstrate a complex interplay between vitamin D and the placenta and will inform future interventions using vitamin D to support fetal development and maternal adaptations to pregnancy.

Automated summary

This study investigates the role of the placenta in regulating the relationship between maternal 25-hydroxyvitamin D concentrations and fetal physiology. The researchers demonstrate that the placenta actively uptakes and metabolizes vitamin D, releasing the metabolites into both the maternal and fetal circulations. They also find that vitamin D exposure induces rapid effects on the placental transcriptome and proteome. These findings highlight the complex interplay between vitamin D and the placenta in supporting fetal development and maternal adaptations to pregnancy.