Quantification of Placental Dysfunction in Pregnancy Complications

Background The pathogenetic mechanisms behind placental dysfunction-related complications like preeclampsia and intrauterine growth restriction have remained perplexing till now, in part because of lack of well-defined structural and functional molecular characterisation. There is growing evidence that links trophoblast debris and the existence of syncytial nuclear aggregates (SNA) to the pathogenesis of gestational diseases. Characterisation and quantification of structural and functional parameters of placental dysfunction may give researchers a clearer picture of the mechanisms underlying the development of high risk pregnancy.
Methods Placental samples were obtained from normal term pregnancies, preterm controls, as well as from pregnancies complicated by preeclampsia (PET), intrauterine growth restriction (IUGR) and PET-IUGR. Formalin-fixed, paraffin-embedded sections were visualised with H&E, stained using immunohistochemistry (IHC) and digitally scanned. Using stereological methodology, volumes of placental SNAs, trophoblasts, villi and capillaries were measured. Three dimensional (3D) volume reconstructions of terminal placental villi with SNAs and fibrinoid degenerations were created. IHC-labelled slides were analysed by image analysis algorithms. Differential expression of placental genes and miRNAs, hypothesised to regulate cell death in placental dysfunction, were quantified using RT-qPCR. BeWo cell lines were carried out for in vitro validation of the effects miRNAs regulating programmed cell death (PCD) using flow cytometry and western blotting.
Results Specific morphometric patterns of villous, trophoblasts, SNA and capillary volumes were demonstrated with characteristic higher SNAs and lower capillary volumes in PET placentae with reciprocal patterns in IUGR placentae showing a negative correlation pattern between nuclear aggregates and capillary volumes. Image analysis of immune-labelled slides showed a higher autophagy marker expression in PET and a positive correlation to SNAs as well as a balanced reciprocal expression patterns with apoptosis. Moreover, miR-204 transfected BeWo cells showed a similar balanced reciprocal regulation of autophagy and apoptosis expressions.
Conclusion We have demonstrated that applying stereology-based and image analysis on digitised placental sections can be useful in quantifying and dissecting structural and functional patterns in normal and abnormal placental function. 3D reconstruction model are a novel approach towards placental characterisation in normal and complicated pregnancies. The study also showed that miR-204 plays a vital role in the regulation of placental autophagy and apoptosis, critical in the pathophysiology of placental dysfunction.