Human organ chip research shows that a common antimalarial combination could reverse the negative effects of malnutrition in the female digestive tract that lead to low birth weight infants
By Lindsay Brownell
(BOSTON) — Wars, drought, displacement, and instability are causing a dramatic increase in the number of pregnant and breastfeeding women around the world who suffer from malnutrition. Without access to sufficient nutrients in the womb, babies born to these women are more likely to die due to complications like pre-term birth, low birth weight, and susceptibility to diseases like malaria. To try to reduce the risk of malarial infection, the World Health Organization recommends that pregnant women in low-income countries be treated with a combination of the antimalarial drugs sulfadoxine and pyrimethamine (SP). Curiously, a recent study found that this treatment also seemed to increase the birth weight of treated mothers’ babies, regardless of whether they contracted malaria.
Intrigued by this finding, which was brought to their attention by members of the Bill and Melinda Gates Foundation, a team of scientists at the Wyss Institute decided to investigate the phenomenon using its human Intestine Chip. With support from the Foundation, the team found that chips exposed to malnutrition conditions displayed classic features of intestinal dysfunction, and that these issues were almost fully resolved by the addition of SP. The research is published in eBioMedicine.
“Our primary goal in conducting this study was to find ways to promote maternal health and improve birth outcomes,” said first author Seongmin Kim, Ph.D., a Postdoctoral Fellow at the Wyss Institute. “I’m driven to pursue meaningful research that benefits women, including my beloved mother, wife, and daughter who is still in utero. I hope that this work galvanizes future clinical studies to significantly improve human health worldwide.”
Modeling malnutrition
When Kim read the study suggesting that SP improved infant birth weight by counteracting malnutrition, he searched for more clinical data about the drug’s effects on the human intestine. But he found nothing. “Very few clinical trials include pregnant women for ethical reasons, and there was no existing human in vitro model to use for studying this drug. But I knew we could use our Intestine Chip to create the missing model and generate some useful data,” says Kim.
The Wyss Institute’s Organ Chip technology faithfully replicates many functions of human organs inside a device about the size and shape of a USB memory stick. The chip has two parallel channels separated by a porous membrane. One channel is coated with human blood vessel cells to mimic the vascular system, while the other channel is coated with living human organ cells. In the case of the Intestine Chip, rhythmic stretching is applied to the device to replicate the conditions that human intestines experience due to muscular waves of peristalsis during digestion.
In previous work, the team built a version of the Intestine Chip that replicated pediatric environmental enteric dysfunction (EED), a devastating childhood disease caused by long-term malnutrition. Kim sought to extend the team’s demonstrated approach in modeling pediatric EED to newly model the intestine of mothers, investigating how malnutrition affected them. He and his coauthors obtained tissue biopsy samples from healthy young women and cultured the cells inside the Intestine Chip, creating miniature versions of their small intestines in the lab.
To mimic healthy intestine, they flowed a nutrient-rich medium through the blood vessel channel to mimic the delivery of nutrients through the bloodstream, and confirmed that the cells in the intestinal channel were healthy and functional, as the team had previously demonstrated in the pediatric EED chips. They spontaneously developed villi-like structures that replicate the tiny projections found on human intestinal cells, produced mucus, and maintained an intact intestinal barrier between the cells.
Then, the team switched out the medium for a nutrient-deficient version that lacked niacinamide (a vitamin) and tryptophan (an essential amino acid). The result was similar to that observed in the pediatric EED chips: the villi were noticeably shorter, there was less mucus production, and the connections between the cells had begun to break down, creating a “leaky gut.” These changes were detectable on the genetic level as well, with lower activity of genes associated with villi formation and mucus production. The researchers had created a functional Organ Chip model of the intestinal effects of malnutrition in adults for the first time.
SP to the rescue
The team could now use this new model to investigate how SP might affect these negative hallmarks of malnutrition. First, they added the drug combination to the Intestine Chip along with the nutrient-rich medium for three days and observed no significant changes. Then, they added SP to chips that had only received the nutrient-deficient medium and looked malnourished. The results were clear: the villi grew taller, mucus production went up, and the intestinal barrier function improved.
But just because the SP-treated Intestine Chips looked more normal didn’t necessarily mean that they were getting better nutrition. Thus, the team went further to look specifically at how SP affected nutrient absorption from the chips. They analyzed the RNA molecules that were present in healthy, malnourished, and SP-treated malnourished chips. They found that genetic pathways that are critical for digestion; the metabolism of triglycerides, fatty acids, and vitamins; and intestinal absorption of vital nutrients were suppressed in their nutrient-deficient chips.
When those chips were treated with SP, the same analysis showed a reactivation of many metabolic and absorption pathways. Another experiment using a fluorescently labeled fatty acid found that malnourished chips absorbed 3.5 times less of the fatty acid compared to healthy chips, but this effect was reversed when the malnourished chips were treated with SP.
“Our research shows that SP treatment does indeed have multiple direct effects on the human adult female intestine, which could help explain why pregnant mothers who are prophylactically treated with SP as an antimalarial therapy had babies with healthier birth weights,” said co-author Girija Goyal, Ph.D., a Senior Scientist at the Wyss Institute. “The increased surface area of the villi in Intestine Chips treated with SP increases the surface area available to absorb nutrients from the blood, the thicker mucus layer protects the intestinal cells from pathogens, and the increased expression of genes that are crucial for nutrient and fatty acid absorption helps maintain health.”
Another known effect of malnutrition is increased inflammation in the intestine, which can cause a host of problems. Consistent with these previous results, the team detected higher levels of multiple pro-inflammatory cytokines in malnourished Intestine Chips compared to healthy chips. When the chips were given SP, their cytokine levels went down, and the level of a specific protein called LCN2 increased. LCN2 is known to maintain a healthy intestinal microbiome and protect against inflammation.
Finally, because immune cells can also mediate inflammation, the researchers introduced human peripheral blood mononuclear cells (PBMCs) into the blood vessel channel of the Intestine Chip. They found that in malnourished chips, these immune cells stuck to the surface of the intestinal channel, indicating a potential immune response. This behavior was also significantly reduced by SP treatment.
Hope for mothers and babies in the future
While they are excited about their results, the researchers caution that their human Intestine Chip model does not replicate pregnancy, so it does not provide direct evidence of how the treatment of maternal malnutrition with SP impacts their babies’ health. Pregnancy introduces many new factors into a mother’s biology including hormonal changes and immune responses, so further in-depth clinical trials of SP are required to establish its safety and efficacy for pregnant women.
“This work makes a clear argument that SP should be further explored as a potential treatment for the serious global health problem of malnutrition, which will only get worse as climate change and related conflicts affect the poorest and most vulnerable populations around the world,” said senior author and Wyss Founding Director Don Ingber, M.D., Ph.D. “We also hope our Intestine Chip can help answer other important questions related to intestinal health and disease on the global scale.” Ingber is also the Judah Folkman Professor of Vascular Biology at Harvard Medical School and Boston Children’s Hospital, and the Hansjörg Wyss Professor of Bioinspired Engineering at the Harvard John A. Paulson School of Engineering and Applied Sciences.
Additional co-authors include Abidemi Junaid from the Wyss Institute; former Wyss Institute members Arash Naziripour, Pranav Prabhala, and Viktor Horváth; and David Breault from Harvard Medical School, BCH, and the Harvard Stem Cell Institute.
This research was supported by the Bill and Melinda Gates Foundation, the Wyss Institute at Harvard University, and the National Institutes of Health through grant P30 DK034854. The findings and conclusions contained within are those of the authors and do not necessarily reflect positions or policies of the Bill & Melinda Gates Foundation.