Amy Murtha Seeks to Understand Preterm Birth

Research to help physicians reduce the dangers of preterm births

Murtha/Sayres

Using hardware-store parts, medical student Lauren Sayres (right) has engineered a better way to study fetal membranes with her lab director Dr. Amy Murtha.

Third-year medical student Lauren Sayres has an engineering problem. She is working to help Dr. Amy Murtha figure out how certain bacteria contribute to preterm birth. To do that, Sayres wants to conduct experiments with placental membranes. But they’re thin, fragile, and slippery. She tried using a method detailed in one of the few previous studies that have looked at this question. But it involves securing the membrane to a tiny thimble-like device with a rubber band. Sayres is concerned that by handling the membrane so much, she is distressing the cells—causing a cascade of cell signaling that could lead to cell death.

Sayre’s dilemma indicates how little preterm birth has been studied. Only a handful of researchers in the United States focus on exactly what happens to the fetal membranes during pregnancy. There are more trying to understand preterm birth in general.

“The funding for understanding why moms deliver preterm is really limited,” says Murtha, professor and vice chair for research in the Duke Department of OB/GYN and Pediatrics. “But if we can reduce the number of preterm births, then we can reduce the number of babies that end up with the consequences of prematurity, which can be lifelong.”

When Murtha was a medical resident, she took care of pregnant moms who had been ordered to stay on bed rest because their water bags had broken early, which usually means premature labor will follow.

“It was heart-wrenching to watch these moms sit in a hospital room for weeks,” Murtha says. “They didn’t feel sick. They felt fine. But they needed to be there, because if something was going to happen, we needed to be able to intervene quickly. They were putting their whole worlds on hold for their pregnancies.”

Murtha tried to help these moms pass the time while they waited.

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“They would allow me to come stick them for blood every day of their hospital stay. Nobody does that,” Murtha says. “But I heard them say time and time again, ‘I need to figure out why this happened. Not just for me, but for other moms.’”“I would bring them seek-a-word puzzle books and decks of cards, and I’d teach them how to play solitaire if they didn’t know how,” she says. And she asked them to help her with her research, in which she was trying to develop a blood test to identify which of these women were most at risk for infection.

That experience helped motivate Murtha to try to understand and prevent preterm birth. “We don’t really know why moms deliver preterm,” she says. “There are a few things we can do to take better care of moms at risk, but we are not all that skilled at preventing preterm birth.”

Prematurity is the most common cause of infant death. Premature babies are at high risk for respiratory problems, intellectual disabilities, cerebral palsy, visual problems, hearing loss, and feeding and digestive problems. Knowing all that, it doesn’t make sense to wait to intervene until a baby is already born, Murtha says. But it’s difficult to take action when there are no clues that a problem exists.

Right now, the main thing that she can do to prevent preterm births is give pregnant moms progesterone. But deciding whom to give it to, and when, is little better than a shot in the dark.

Obstetrician-gynecologists will likely prescribe progesterone if a pregnant mom had a preterm birth in a prior pregnancy or if her cervix is getting short during pregnancy. But to Murtha, that’s not good enough.

“If it’s your first pregnancy, we really have no good way of knowing if you will need progesterone or not unless the cervix is getting short, which is not very common.” Murtha says. “And once the cervix starts to shorten, something bad is already happening. So it’s kind of late in the game to be initiating a therapy.”

 

IMMUNE SUPPRESSION

Murtha aims to understand why some women deliver early and find a biomarker that can signal when a baby is at risk of being born too early, before outward signs appear. To start, she wants to understand how the hormone progesterone works during normal pregnancies to keep the uterus quiet and suppress inflammatory immune responses in the placental membranes. Some scientists believe that immune suppression plays a role in helping the body maintain a pregnancy.

“When you have a fetus in your body, you have basically an organ system that’s different from mom, and so mom has to be immune suppressed to a degree so that her body doesn’t reject the fetus,” Murtha says.

One of the body’s receptors for progesterone has intrigued Murtha—PGRMC1. Her team has found that this receptor is present in the mom’s white blood cells, particularly in monocytes, and that its levels correlate with levels of a different protein that is a marker of cell death.

“We think that progesterone causes white blood cells to die,” Murtha says. “This makes sense if progesterone’s role is to be anti-inflammatory.”

In fetal membrane cells in culture, if she eliminates PGRMC1, progesterone no longer does its job of reducing inflammation. Maybe, PGRMC1 is the biomarker that Murtha has been looking for. In a small study, her team measured PGRMC1 levels in the white blood cells of five pregnant moms. In the first trimester, one woman’s PGRMC1 levels were almost twice as high as the other women’s. As it turns out, that mom went on to deliver pre-term.

“That suggests to me that maybe there was something going on in this patient early in pregnancy that is different,” Murtha says. “It’s only one patient, so we can’t say.” But she wants to study this further, in a larger number of patients. “This might be a way to identify patients that we should worry about,” she says.

 

THE ROLE OF BACTERIA

In addition, Murtha’s team is exploring the microbiome of the fetal membranes—the whole population of bacteria that reside in the membranes that nurture the fetus during pregnancy. Working with Dr. Patrick Seed, associate professor of pediatrics, Murtha has found that the microbiome is less diverse in the gestational tissues of women who go on to have their water break early (preterm premature onset of rupture of membranes, or PPROM).

“In patients who carry their babies to term, we see that it’s very diverse; it’s a whole mix of bacteria. But in women who have preterm labor or PPROM, there are some dominant organisms that we see—ureaplasma and mycoplasma,” Murtha says.

That work leads us to Sayres’ engineering problem. After trying unsuccessfully to modify the existing device used to study placental membranes, she began scouring hardware stores for a better solution.

“What I found are these low-flow faucet aerators, in the plumbing section. When I saw it, I knew it would be perfect,” she says. Then Sayres found that every store seemed to carry a different brand. “I’ve been to every hardware store in Durham at this point,” she says. “I spent some time researching the different types of materials to make sure they wouldn’t influence the experiments.”

To make the final device, she discarded the filter that aerates the water, leaving behind a round metal ring with two washers in the middle. She can cut a piece of the placental membrane that she wants to study and sandwich it between the two washers, then place that inside the metal ring. “It creates two different chambers, a maternal chamber and a fetal chamber, one on top and one on bottom,” Sayres explains.

The amnion (the part of the membrane that faces the fetus) is in one chamber, and the chorion (the part that faces the maternal surface of the placenta) is in another. She can apply a bacterium to each chamber and be confident it won’t leak from one to the other. So, she can study the effects on each area of the membrane separately and also observe whether the bacterium or its products pass through the membrane easily. Her first experiment is now under way, applying Ureaplasma to each chamber to find out whether it affects the produc­tion of a particular enzyme that may contribute to early rupture of membranes.

“Fetal membranes are the largest surface area between mom and baby. So understanding what’s happening between the mom’s side of the membranes and the baby’s side, and what happens that might compromise that barrier, is really important to understanding preterm birth,” Murtha says.

“There’s a lot of experiments we can do just because of Lauren’s development of this system, that can help us better understand any one of these organisms that we might find to be pathogenic.”

Sayres says she was surprised that a better way to work with these membranes hadn’t been devised before. But an advantage of the field being so little studied is that there is room to make advances. Murtha hopes to speed up the progress. Because all those pregnant moms are out there waiting.

This article originally appeared in Duke Medical Alumni News.