Vaillancourt, Cathy

Abstract Since the beginning of the COVID-19 pandemic, vulnerable populations such as pregnant persons have been at higher risk of severe symptoms and poor outcomes. Although reports of SARS-CoV-2 vertical transmission remain rare, several studies showed that maternal infection during pregnancy can induce histomorphological and inflammatory alterations in the placenta. However, the permissiveness of human trophoblasts to various variants of the virus remains poorly characterized. In this study, human primary villous cytotrophoblasts isolated from term placentas, along with trophoblastic cell lines BeWo, JEG-3, and HIPEC-65 were infected with the ancestral SARS-CoV-2 strain, which disseminated worldwide in early 2020. Permissiveness was assessed with quantitative RT-PCR, immunostaining of viral protein Nucleocapsid, and plaque assays. To investigate viral entry routes, cells were treated with Camostat mesylate (an inhibitor of the co-entry factor TMPRSS2) or chloroquine phosphate (an endosomal entry inhibitor) and viral fitness was assessed by plaque assays. Primary villous cytotrophoblasts and JEG-3 cells were also tested for infection with three pre-omicron SARS-CoV-2 variants of concern. Our results show that primary villous cytotrophoblasts are permissive to all tested SARS-CoV-2 strains in vitro. Infection with the ancestral SARS-CoV-2 strain relies mainly on a non-canonical endosomal entry pathway. Notably, JEG-3 cells represent an appropriate and convenient model for studying trophoblast infection by SARS-CoV-2, as they exhibit high permissiveness to the ancestral strain, and the SARS-CoV-2 entry pathway is similar to that in villous cytotrophoblasts. Overall, this study reveals that the cytotrophoblastic permissiveness to SARS-CoV-2 depends on the viral genetic nature and provides new insights into its entry route in human trophoblasts.

AbstractMelatonin has been proposed as a possible treatment for the deleterious effects of hypoxia/reoxygenation (H/R), such as autophagy, inflammation, and apoptosis. Pathological pregnancies, such as preeclampsia, are associated with placental H/R, and decreased placental melatonin synthesis as well as lower melatonin levels in the placenta and maternal plasma. However, the effects of exogenous melatonin on inflammation and autophagy induced by pregnancy complications associated with H/R await investigation. This study aimed to determine as to whether melatonin protects human primary villous trophoblasts against H/R‐induced autophagy, inflammation, and apoptosis. Human primary villous cytotrophoblasts were isolated and immunopurified from normal term placentas. These cells were then exposed or not to 1 mmol/L melatonin for 72 hour in normoxia (8% O2), thereby inducing differentiation into syncytiotrophoblast that was then exposed to H/R (0.5% O2, for 4 hour) or normoxia. H/R decreased endogenous melatonin synthesis (by 68%) and interleukin (IL)‐10 levels (by 72%), coupled to increased tumor necrosis factor (TNF) (by 114%), IL‐6 (by 55%), and NFκB (by 399%), compared to normoxia. Melatonin treatment reversed the H/R effect, restoring IL‐10, TNF, and IL‐6 levels to those of the normoxia condition. Melatonin, as well as NFκB inhibition, enhanced autophagy activation, consequently increasing syncytiotrophoblast survival in H/R conditions. This study suggests that H/R, which is present in pregnancy complications, inhibits endogenous melatonin production, thereby contributing to reduced syncytiotrophoblast viability. Results indicate that exogenous melatonin treatment may afford protection against H/R‐induced damage, thereby enhancing placental cell survival, and contributing to improved fetal outcomes.