HERSHEY, Pa. — For nine months, the placenta is the primary support system of the fetus, providing both nourishment and protection. Within hours of birth, it is usually discarded as medical waste. But this organ carries clues for the child’s future health and additional pregnancies for the mother, according to Indira Mysorekar , new vice dean for research, basic science and graduate studies for Penn State College of Medicine.
“It’s the ‘fate map’ of the human, and we throw it away,” said Mysorekar, who is also the Dorothy Foehr Huck and J. Lloyd Huck Chair in Women’s Health and professor of medicine and of cell and biological systems. Mysorekar and two new Penn State researchers in the Department of Medicine — Rafael Tomoya Michita , assistant professor, and Eliza McColl , postdoctoral scholar — recently authored two papers that independently demonstrated how viruses target and impact the placenta, one by tunneling through its barrier and the other by interfering with the organ’s work nourishing the fetus, to varying degrees of success.
In this Q&A, the researchers discussed what drew them to study the commonly discarded placenta, how infections and treatments can affect it differently than other tissues in the body and why it all matters for a child’s development and for women’s health.
Q. What is the placenta, and what does it do?
Mysorekar: The placenta is the organ that connects a mother and her baby. It’s the only organ we generate from the beginning for a single purpose and then discard once that purpose is complete. Throughout pregnancy, it nourishes the fetus and acts as a filter, protecting it from many of the pathogens and environmental hazards the the pregnant woman encounters. And because a great deal of what happens to us later in life can be traced back to early development, the placenta is where our story is recorded.
When a virus — for example, the COVID-19-causing virus, SARS-CoV-2 — reaches the placenta, the signs may not be obvious: the pregnancy may seem normal, and any immune response could appear minimal, but something could have quietly changed. And those changes can resemble or lead to a condition called preeclampsia, where high blood pressure may lead to serious complications, so studying how pathogens affect the placenta could help us understand why some pregnancies suffer complications.
Q. If the placenta is usually discarded, what made you take a closer look at it?
McColl: A lot of people see the placenta as medical waste, but we see it as a wealth of information. It can tell you not only what happened during the pregnancy but also what’s going to happen over the offspring’s childhood and development. Since so few people study it, there are many questions to be answered. If we understand how it works, and how it responds to things like infection, we may be able to anticipate problems for the baby and, eventually, take what we learn back to the woman before her next pregnancy.
Tomoya Michita: I was curious about the genetics of pregnancy, which has been compared by many to be like an organ transplant. If that is the case, why doesn’t the mother’s body reject her own baby? The placental interface is where that tolerance happens. Her immune system holds back to tolerate the fetus, and a virus can take advantage of that. To a virus, it’s a very good place to start growing, and because the mother’s immune system is constantly adapting to keep the developing fetus, it can go unnoticed.
Q. How does the placenta help protect the fetus, and how do pathogens find ways around it?
Mysorekar: The placenta has to protect the fetus and nourish it at the same time. Like Dr. Tomoya Michita mentioned, the baby is a foreign entity for the woman, and there’s an inherent immunological conflict. If a woman is exposed to an infectious organism during pregnancy, her body tries to fight it, which is appropriate. But if it fights too hard, that conflicts with protecting the fetus. Her immune system and the placenta have to balance a fine line.
Tomoya Michita: The placenta is a very strong barrier. When a mother gets an infection, only a few pathogens cross it. This makes the ones that do — like Zika virus, a mosquito-borne virus that drew attention during a major global outbreak when there was an increase in the number of babies born with smaller heads and impaired brain development — so interesting and important to study.
Dr. Mysorekar had previously shown that Zika crossed the placental barrier and could affect the fetus, but the question was how. In our study published in ASM mBio , we demonstrated in mouse models how the virus can induce unusual structures called tunneling nanotubes, which are basically tunnels that connect cells. It suggests that Zika co-opts these tunnels for transmission to the fetus. This study built on our discovery published last year alongside fellow Penn State collaborator Joyce Jose , associate professor of biochemistry and molecular biology.
Among related mosquito-borne viruses, Zika seems to be unique in doing this. That could help explain why pregnant women don’t pass dengue or West Nile virus through the placenta, even though they are in the same family as Zika virus. This is a completely new path viruses could be taking.
Q. What did you find when you looked at placentas from patients who had COVID-19?
McColl: Early in the pandemic, pregnant people with COVID-19 had a higher chance of adverse outcomes, including preeclampsia, and no one understood why. Since my background is in placental nutrient transport, I wanted to know what was happening to the resources a fetus needs.
In a recent study in Cell Reports , we saw that placentas exposed to COVID-19 were storing too much iron, which can trigger a form of cell death called ferroptosis. In other tissues, ferroptosis seems to help the SARS-CoV-2 virus to replicate. In the placenta, we found the opposite: When ferroptosis is activated in placental cells with COVID-19, viral levels go down.
Instead of delivering iron to the baby, the placenta keeps it. It’s a defense mechanism, but it has a cost. Iron is important for brain development and fetal growth, and anemia is more common in babies exposed to the virus during pregnancy.
It’s another reason why it’s so important to study the placenta. Processes we know in other tissues, even within the same infection, can look different here. Several people proposed blocking ferroptosis as a COVID-19 treatment, but in the placenta that could make things easier for the virus. It’s not a one-treatment-fits-all scenario.
Mysorekar: People may often miss these subtle changes or dismiss them as unimportant. But to us, that’s where the real discoveries lie. It’s often the smallest details that reveal the biggest secrets.
Q. Given what you’ve learned from your research, what do you hope women and their families understand about pregnancy and reproductive health?
Mysorekar: Pregnant women should feel empowered to ask questions, understand their health and seek out the resources and support they need. I also encourage women to learn about their mother’s and grandmother’s health and reproductive histories. What happened in previous generations can offer important clues about their own health. And we now understand that a mother’s health during pregnancy can have lifelong implications for her children, both sons and daughters.
But the bigger message is that we need to invest in women’s health. I grew up in capital cities around the world, while Dr. Tomoya Michita and Dr. McColl grew up in rural communities. We’ve seen different sides of the same problem. Women in urban and rural settings face different challenges, but the common thread is that their health needs are too often overlooked and underfunded.
Healthy women are the foundation of healthy pregnancies, healthy placentas, and healthy families. When we invest in women, we’re not just improving their health—we’re investing in the health of their children, their families, and future generations.
A full list of collaborators can be found at ASM mBio and Cell Reports .
These studies were supported in part by the National Institutes of Health (NIH)'s National Institute of Allergy and Infectious Diseases under awards R01AI176505 and K99AI194972-01 , National Institute of Child Health and Human Development under awards R01HD091218 and R01HD119277 and National Institute of General Medical Sciences under awards 5T32GM136554 and R35GM153439 ; the NIH Director’s New Innovator Award; the Shipley Foundation Program for Innovation in Stem Cell Science; the Edward Mallinekrodt, Jr. Foundation; and the Howard Hughes Medical Institute. This content is solely the responsibility of the authors and does not necessarily represent the official views of the funders.
Cell Reports
Experimental study
Lab-produced tissue samples
Placental trophoblasts exhibit iron dysregulation and ferroptosis signaling associated with SARS-CoV-2 restriction
27-Oct-2026