Histopathological examination of the placenta after delivery in pregnant women with COVID-19

Abstract

Introduction: COVID-19 is a viral disease generated by a new coronavirus named SARS-CoV-2. The consequences of this virus on the human placenta and the newborn are still unclear. IL-6 can disturb the placenta's immunological homeostasis and be employed as an inflammatory marker for the poor prognosis of COVID-19 infection. Bax has some features like being a key protein regulating apoptotic mechanisms and plays an important role in both maintaining dynamic balance and integrity in the placenta as in many tissues. This study aims to indicate the impact of COVID-19 on inflammation and apoptotic pathways in the placenta by using IL-6 and Bax antibodies. 
 Material and Method: COVID-19 positive (n:10) and COVID-19 negative (n:10) normotensive placentas were included. Haematoxylin-eosin staining and immunohistochemical staining (IL-6 and Bax antibodies) were applied. Statistical data of immunohistochemical (IL-6 and Bax expression) staining results were assessed by analyzing the H-score. Biochemical parameters were recorded. Group means were analyzed with a nonparametric Kruskal Wallis Test. 
 Results: In the COVID-19 group, increased syncytial knots, fibrin deposition, inflammation, fibrinoid necrosis, neutrophil accumulation were observed. The COVID-19 group had considerably higher levels of IL-6 and Bax expression than the control group. Furthermore, COVID-19 patients had statistically lower WBC and higher CRP values than normotensive patients. 
 Conclusion: COVID-19 has been linked to placental inflammation and trophoblast cell damage, both of which can result in major maternal and fetal problems during pregnancy. We found intense IL-6 expression in the placentas of pregnant women with COVID-19 infection. A rise in IL-6 levels triggers CRP production, and this increase is linked to the severity of COVID-19 as a risk factor. Also, we suggested that COVID-19 infection triggers the apoptotic process in placental tissue by increasing the expression of the proapoptotic Bax protein. It is clinically very significant to follow up COVID-19 positive pregnancies for maternal and fetal health. During this follow-up, IL-6 and Bax expression levels in the placenta, together with histopathological findings and serum CRP levels, can guide the evaluation of the prognosis, severity and response to treatment of the disease.