PNAS Plus: High-resolution contrast-enhanced microCT reveals the truethree-dimensional morphology of the murine placenta

摘要

Genetic engineering of the mouse genome identified many genes that are essential for embryogenesis. Remarkably, the prevalence of concomitant placental defects in embryonic lethal mutants is highly underestimated and indicates the importance of detailed placental analysis when phenotyping new individual gene knockouts. Here we introduce high-resolution contrast-enhanced microfocus computed tomography (CE-CT) as a nondestructive, high-throughput technique to evaluate the 3D placental morphology. Using a contrast agent, zirconium-substituted Keggin polyoxometalate (Zr-POM), the soft tissue of the placenta (i.e., different layers and cell types and its vasculature) was imaged with a resolution of 3.5 µm voxel size. This approach allowed us to visualize and study early and late stages of placental development. Moreover, CE-CT provides a method to precisely quantify placental parameters (i.e., volumes, volume fraction, ratio of different placental layers, and volumes of specific cell populations) that are crucial for statistical comparison studies. The CE-CT assessment of the 3D morphology of the placentas was validated (i) by comparison with standard histological studies; (ii) by evaluating placentas from 2 different mousestrains, 129S6 and C57BL/6J mice; and (iii) by confirming theplacental phenotype of mice lacking phosphoinositol 3-kinase (PI3K)-p110α.Finally, the Zr-POM–based CE-CT allowed for inspection of the vasculaturestructure in the entire placenta, as well as detecting placental defects inpathologies characterized by embryonic resorption and placental fusion. Takentogether, Zr-POM–based CE-CT offers a quantitative 3D methodology toinvestigate placental development or pathologies.