Courtney, J. A. | Search bioRxiv

bioRxiv2020

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.

developmental biology↗

bioRxiv2020

Placental and fetal characteristics of the Ohia mouse line recapitulate outcomes in human hypoplastic left heart syndrome

Congenital heart defects (CHDs) are the most common birth defect worldwide. The morbidity and mortality associated with these defects is compounded by increased frequency of fetal growth abnormalities. In the Ohia mouse model of hypoplastic left heart syndrome (HLHS), the double homozygous genotype is embryonically lethal at mid-pregnancy; a time in which optimal establishment of the placenta is crucial to fetal survival. We aimed to characterize placental and fetal growth and development in the double heterozygous genotype (Sap130m/+Pcdha9m/+) to determine whether the genetic mutations associated with HLHS in the Ohia mouse also affect the placenta. The frequency of fetuses with reduced weight near term was shifted in the Sap130m/+Pcdha9m/+ fetuses compared to wildtype. This shift in fetal weight distribution in the Sap130m/+Pcdha9m/+ fetuses was associated with reduced labyrinth region area (P<0.001) and reduced fetal capillary density (P<0.001) in the placentas. Positive correlations were observed between fetal weight and placenta mRNA expression of several nutrient transporters in the Sap130m/+Pcdha9m/+ fetuses but not observed in the wildtype. Increased protein expression of Slc7a5 (P<0.05) and Slc7a8 (P<0.05) was also found in the placenta of Sap130m/+Pcdha9m/+ fetuses. This data shows, despite a potential compensatory mechanism to increase nutrient transport, abhorrent placental vascularization leads to inadequate fetal growth in the Ohia mouse model. Such differences are similar to findings in studies of human placentas and highlights the importance of this mouse model in continuing to understand the developmental links and disruptions to the heart-placenta axis.

physiology↗