Impaired labyrinth formation prevents the establishment of the maternal-fetal interface in conditional Hand1-deficient mice

IntroductionCongenital heart defects (CHD) affect approximately 1% of all live births, and often require complex surgeries at birth. Placental development and function is vital to ensure normal fetal development. We have previously demonstrated abnormal placental development and vascularization in human CHD placentas, and placental expression changes in genes important for heart development. Hand1 has roles in both heart and placental development and is implicated in CHDs including double right outlet, hypoplastic left heart syndrome, and septal defects; however, Hand1 involvement in placental vascularization and development is under-investigated. We utilized the Hand1A126fs/+ murine model to investigate Hand1 in placentation and vascularization. MethodsHand1A126fs/+ female mice were time-mated with Nkx2.5cre (placenta- and heart-specific) males to produce either Nkx2.5cre;Hand1+/+ or Nkx2.5cre;Hand1A126fs/+ fetuses. Feto-placental units were harvested at timepoints from E8.5 to E14.5 for histological analysis; vascular assessment by immunohistochemistry for Hand1, CD-31, and CK-7; and angiogenesis by qPCR. ResultsEmbryonic lethality occurs in Nkx2.5cre/Hand1A126fs/+ by E14.5 due to a failure of placental labyrinth formation and vascularization. Chorionic trophoblasts did not form, although trophoblast giant cell subtypes were present. Fetal vessels failed to develop properly and were significantly lower in the labyrinth by day E12.5. Placental growth factor levels were significantly increased, and Angiopoietin2 expression trended higher in Nkx2.5cre/Hand1 A126fs/+ placental labyrinths compared to control littermates. ConclusionWe demonstrate that Hand1 expression in placental chorion and trophoblast is necessary for proper patterning of the labyrinth and vascularization within the labyrinth. Multiple angiogenic factors known to be expressed in trophoblast were disrupted in Nkx2.5cre/Hand1 A126fs/+ placental labyrinths compared to control littermates. Alterations in Hand1 expression represent a potential mechanism for abnormal placentation and early miscarriage in cases of CHD.