Dataset Information

COVID-19 and vertical transmission: assessing the expression of ACE2/TMPRSS2 in the human fetus and placenta to assess the risk of SARS-CoV-2 infection.

ABSTRACT:

Background

Pregnant women have been identified as a potentially at-risk group concerning COVID-19 infection, but little is known regarding the susceptibility of the fetus to infection. Co-expression of ACE2 and TMPRSS2 has been identified as a prerequisite for infection, and expression across different tissues is known to vary between children and adults. However, the expression of these proteins in the fetus is unknown.

Methods

We performed a retrospective analysis of a single cell data repository. The data were then validated at both gene and protein level by performing RT-qPCR and two-colour immunohistochemistry on a library of second-trimester human fetal tissues.

Findings

TMPRSS2 is present at both gene and protein level in the predominantly epithelial fetal tissues analysed. ACE2 is present at significant levels only in the fetal intestine and kidney, and is not expressed in the fetal lung. The placenta also does not co-express the two proteins across the second trimester or at term.

Interpretation

This dataset indicates that the lungs are unlikely to be a viable route of SARS-CoV2 fetal infection. The fetal kidney, despite presenting both the proteins required for the infection, is anatomically protected from the exposure to the virus. However, the gastrointestinal tract is likely to be susceptible to infection due to its high co-expression of both proteins, as well as its exposure to potentially infected amniotic fluid.

Tweetable abstract

This work provides detailed mechanistic insight into the relative protection & vulnerabilities of the fetus & placenta to SARS-CoV-2 infection by scRNAseq & protein expression analysis for ACE2 & TMPRSS2. The findings help to explain the low rate of vertical transmission.

SUBMITTER: Beesley MA

PROVIDER: S-EPMC8652560 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:It has been shown that vertical transmission of the SARS-CoV-2 strain is relatively rare, and there is still limited information on the specific impact of maternal SARS-CoV-2 infection on vertical transmission. The current study focuses on a transcriptomics analysis aimed at examining differences in gene expression between placentas from mother-newborn pairs affected by COVID-19 and those from unaffected controls. Additionally, it investigates the in situ expression of molecules involved in placental inflammation. The Papa Giovanni XXIII Hospital in Bergamo, Italy, has recorded three instances of intrauterine transmission of SARS-CoV-2. The first two cases occurred early in the pandemic and involved pregnant women in their third trimester who were diagnosed with SARS-CoV-2. The third case involved an asymptomatic woman in her second trimester with a twin pregnancy, who unfortunately delivered two stillborn fetuses due to the premature rupture of membranes. Transcriptomic analysis revealed significant differences in gene expression between the placentae of COVID-19-affected mother/newborn pairs and two matched controls. The infected and control placentae were matched for gestational age. According to the Benjamani-Hochberg method, 305 genes met the criterion of an adjusted p-value of less than 0.05, and 219 genes met the criterion of less than 0.01. Up-regulated genes involved in cell signaling (e.g., CCL20, C3, MARCO) and immune response (e.g., LILRA3, CXCL10, CD48, CD86, IL1RN, IL-18R1) suggest their potential role in the inflammatory response to SARS-CoV-2. RNAscope® technology, coupled with image analysis, was utilized to quantify the surface area covered by SARS-CoV-2, ACE2, IL-1β, IL-6, IL-8, IL-10, and TNF-α on both the maternal and fetal sides of the placenta. A non-statistically significant gradient for SARS-CoV-2 was observed, with a higher surface coverage on the fetal side (2.42 ± 3.71%) compared to the maternal side (0.74 ± 1.19%) of the placenta. Although not statistically significant, the surface area covered by ACE2 mRNA was higher on the maternal side (0.02 ± 0.04%) compared to the fetal side (0.01 ± 0.01%) of the placenta. IL-6 and IL-8 were more prevalent on the fetal side (0.03 ± 0.04% and 0.06 ± 0.08%, respectively) compared to the maternal side (0.02 ± 0.01% and 0.02 ± 0.02%, respectively). The mean surface areas of IL-1β and IL-10 were found to be equal on both the fetal (0.04 ± 0.04% and 0.01 ± 0.01%, respectively) and maternal sides of the placenta (0.04 ± 0.05% and 0.01 ± 0.01%, respectively). The mean surface area of TNF-α was found to be equal on both the fetal and maternal sides of the placenta (0.02 ± 0.02% and 0.02 ± 0.02%, respectively). On the maternal side, ACE-2 and all examined interleukins, but not TNF-α, exhibited an inverse mRNA amount compared to SARS-CoV-2. On the fetal side, ACE-2, IL-6 and IL-8 were inversely correlated with SARS-CoV-2 (r = -0.3, r = -0.1 and r = -0.4, respectively), while IL-1β and IL-10 showed positive correlations (r = 0.9, p = 0.005 and r = 0.5, respectively). TNF-α exhibited a positive correlation with SARS-CoV-2 on both maternal (r = 0.4) and fetal sides (r = 0.9) of the placenta. Further research is needed to evaluate the correlation between cell signaling and immune response genes in the placenta and the vertical transmission of SARS-CoV-2. Nonetheless, the current study extends our comprehension of the molecular and immunological factors involved in SARS-CoV-2 placental infection underlying maternal-fetal transmission.