Propylthiouracil Is Teratogenic in Murine Embryos

Background: Hyperthyroidism during pregnancy is treated with the antithyroid drugs (ATD) propylthiouracil (PTU) and methimazole (MMI). PTU currently is recommended as the drug of choice during early pregnancy. Yet, despite widespread ATD use in pregnancy, formal studies of ATD teratogenic effects have not been performed. Methods: We examined the teratogenic effects of PTU and MMI during embryogenesis in mice. To span different periods of embryogenesis, dams were treated with compounds or vehicle daily from embryonic day (E) 7.5 to 9.5 or from E3.5 to E7.5. Embryos were examined for gross malformations at E10.5 or E18.5 followed by histological and micro-CT analysis. Influences of PTU on gene expression levels were examined by RNA microarray analysis. Results: When dams were treated from E7.5 to E9.5 with PTU, neural tube and cardiac abnormalities were observed at E10.5. Cranial neural tube defects were significantly more common among the PTU-exposed embryos than those exposed to MMI or vehicle. Blood in the pericardial sac, which is a feature indicative of abnormal cardiac function and/or abnormal vasculature, was observed more frequently in PTU-treated than MMI-treated or vehicle-treated embryos. Following PTU treatment, a total of 134 differentially expressed genes were identified. Disrupted genetic pathways were those associated with cytoskeleton remodeling and keratin filaments. At E 18.5, no gross malformations were evident in either ATD group, but the number of viable PTU embryos per dam at E18.5 was significantly lower from those at E10.5, indicating loss o

Structural defects in E10.5 murine embryos.

<p>Includes live embryos only.</p><p>Chi-square \ test.</p

Heat map showing the differential gene expression of 139 genes between PTU and vehicle treated groups.

<p>Heat map generated in GenomeStudio compares the average detection signals of genes between PTU and control groups. Total RNA was collected at E10.5 from whole-embryos treated between E7.5–E9.5,. Three PTU and three control RNA samples were tested and genes with a significant p-value (p<0.001) were displayed. Scale bar indicates detection signal.</p

Crown-rump length and viability of E10.5 murine embryos.

1<p>Mixed model with repeated measure analysis (adjusted by Tukey approach for multiple comparisons) between PTU vs. vehicle and MMI vs. vehicle.</p><p>SE, Standard Error.</p

Expression of Genes in the Cytoskeleton remodeling and keratin filament pathways were altered by PTU treatment.

<p>Cytoskeleton structure in most eukaryotic cells consists of three distinct interconnected, filament systems: Actin filaments, Microtubules and intermediate filaments. Cell assembly is integrated by the network of intermediate filaments (IFs) and by their interactions with other cytoskeleton structural elements defining cytoarchitecture and cytodynamics. The IF network is critically involved in cell shape control and imparts intracellular mechanical strength. The experimental data are visualized on the map in red (increased expression or up-regulation) histogram. The height of the histogram corresponds to the relative expression value for a particular gene/protein.</p

Morphometic Analysis of Embryos at E18.5 based on MicroCT images.

1<p>ANOVA.</p

PTU exposure during embryogenesis induces blood in the pericardium.

<p>Representative images of E10.5 embryos treated with (A, C) vehicle and (B, D) PTU (100 mg/kg) showing blood in the pericardial sac of PTU-treated embryo (arrowhead). (C, D) MicroCT scans showing sagittal 3D images of whole embryos. Scale bars = 0.5 mm.</p

PTU exposure during embryogenesis and effects in E18.5 embryos.

<p>Embryos treated <i>in utero</i> from E7.5–E9.5 were analyzed at E18.5. Representative MicroCT scans showing sagittal 3D images of whole embryos indicate no differences between the treatment groups of vehicle, PTU, and MMI. Left panel shows location of morphometic measurements (a. Snout: upper lip to soft palate. b. Fronto-occipital: frontal to occipital lobes. c. Aorta-apex diameter: aortic valve to left ventricular. d. Biventricular diameter: right to left ventricle). Scale bars = 5 mm.</p