miR-210 regulates placental adaptation to maternal hypoxic stress during pregnancy†.

MicroRNA (miR)-210 is a well-known hypoxia-inducible small RNA. Increasing in vitro evidence demonstrate its involvement in regulating multiple behaviors of placental trophoblasts. However, direct in vivo evidence remains lacking. In the present study, we generated a miR-210-deficient mouse strain using CRISPR/Cas9 technology, in which miR-210 expression was markedly deficient in various tissues. Little influence on fertility rate and litter size was observed after the deletion of miR-210 in mice. Continuous exposure of pregnant mice to hypoxia (10.5% O2) from E6.5 to E10.5 or to E18.5 led to reduction in fetal weight, and such fetal weight loss was markedly worsened in miR-210-knockout dams. Analysis of the placental structure demonstrated the reduced expansion of placental spongiotrophoblast layer and hampered development of labyrinth fetal blood vessels in knockout mice compared to the wildtype controls upon hypoxia stimulation. The findings indicate that miR-210 participates in regulating placental adaptation to hypoxic stress during pregnancy.