Understanding the Impact of COVID-19 on the Human Placenta

Introduction

Since the beginning of the COVID-19 pandemic, many studies have been conducted to understand the ability of SARS-CoV-2 to replicate in the human placenta.

The Significance of Understanding Placental Response

To date, scientific evidence is inconclusive, so answering this question, along with understanding the placental response to other viral infections during pregnancy, is critical to developing effective prevention and treatment strategies for both mother and child.

Novel Approach: Mapping the Placental Immune Microenvironments

To shed light on the interaction between viruses and the human placenta, scientists at Baylor College of Medicine and Texas Children’s Hospital took a novel approach and developed a high-resolution map that depicts a range of different immune microenvironments in healthy placentas from uninfected pregnancies and pregnancies affected by Covid-19 infection.

Findings of the Study

Using this card, they found that in several confirmed cases of maternal COVID-19, the virus was found in the placenta at various levels.

In other confirmed cases, no signs of virus replication were found in the placenta. They also found multiple simultaneous immune responses in placental niches, including both anti-inflammatory niches, where viral replication was apparently well controlled, and sites of inflammation with associated virus persistence, including several cases of damage to the placenta.

“The main goal of our study was to study how these immune cells regulate themselves in small areas of the placenta, which is an important first step in understanding the interactions that occur between the virus and placental cells,” said first author Dr. Enrico Barroso, Research Fellow in Obstetrics and Gynecology at the Kjersti Aagaard Laboratory.

Breakthrough Techniques: Spatial Transcription

The use of groundbreaking techniques such as “spatial transcription” is allowing the scientists behind this study and other pregnancy researchers to begin to understand how sometimes (but not always) placental immune cells successfully control virus growth and, in rare cases, gain strength.

The scientists began by creating a detailed catalog of placental cell types (called a spatial transcriptome map), which shows the sites of active gene expression in niches in the placenta’s delicate architecture.

A Detailed Placental Map

A team led by Agard, Professor of Molecular and Human Genetics, Molecular Biology, Molecular Physiology, and Biophysics at Baylor, created a high-resolution map of the placenta using single-cell mononuclear transcriptome and spatial transcriptome in carefully selected analyzes that revealed a dynamic immune environment in healthy individuals’ placenta.

Possible Outcomes of COVID-19 Infection

The team then analyzed the placentas of mothers with Covid-19 and found evidence supporting three possible outcomes of the infection.

First, they identified cases where the Covid-19 virus was not found in the placenta, indicating that the virus had been destroyed before entering it. Second, in other cases, low levels of the virus were present in the placenta and were associated with minimal viral replication, anti-inflammatory response, and limited inflammatory outcomes. And third, in rare cases, the virus spread widely in niches that also showed signs of a pro-inflammatory immune response and tissue damage.

“Based on this exciting work led by Barroso, we suggest that in most cases, the placenta likely responds to COVID-19 and other viruses by reducing replication in these small niches of the immune microenvironment and reducing immune responses,” said Agard, “at such a small local level.

Conclusion

Understanding the impact of COVID-19 on the human placenta is crucial for developing effective prevention and treatment strategies. The innovative mapping approach used in this study has provided valuable insights into the interaction between viruses and the placenta’s immune microenvironments. Further research in this field will contribute to the overall knowledge of viral infections during pregnancy and their impact on both maternal and fetal health.

Source

Source: Medical Express