Children’s Research Institute | Academic Annual Report 2017-2018
Scientific Advances 2017: A Banner Year for Innovation
In 2017, clinicians and research faculty working at Children’s National Health System published more than 850 research articles about a wide array of topics. A multidisciplinary Children’s Research Institute review group selected the top 10 articles for the calendar year considering, among other factors, work published in high-impact academic journals.
“This year’s honorees showcase how our multidisciplinary institutes serve as vehicles to bring together Children’s specialists in cross-cutting research and clinical collaborations,” says Mark L. Batshaw, M.D., Physician-in-Chief and Chief Academic Officer at Children’s National. “We’re honored that the National Institutes of Health and other funders have provided millions in awards that help to ensure that these important research projects continue.”
The published papers explain research that includes using imaging to describe the topography of the developing brains of infants with congenital heart disease, how high levels of iron may contribute to neural tube defects and using an incisionless surgery method to successfully treat osteoid osteoma. The top 10 Children’s papers:
Reactive oxygen species kickoff muscle repair
Study suggests that indiscriminate antioxidant use could thwart healing process
The response of actin protein following injury to a pair of muscle fibers in an intact biceps muscle.
Taking antioxidants has been thought to stem the muscle soreness from exercise since reactive oxygen species are produced in excess during hard physical activity. However, a study led by researchers from Children’s National Health System finds that taking antioxidants could thwart the processes that repair muscle fibers. According to the study published Sept. 5, 2017, in Science Signaling and featured on the journal’s cover, oxidative species are crucial signals that start the process of repairing muscle fibers.
Mitochondria help injured muscle cells (myofibers) repair by soaking up calcium that enters from the site of injury and using it to trigger increased production of reactive oxygen species. The study’s findings suggest that loading up mitochondria with excess antioxidants inhibits this signaling process, blocking muscle repair, exacerbating myofiber damage and diminishing muscle strength.
“Our results suggest a physiological role for mitochondria in plasma membrane repair in injured muscle cells, a role that highlights a beneficial effect of reactive oxygen species,” says Jyoti K. Jaiswal, M.S.C., Ph.D., principal investigator in the Center for Genetic Medicine Research at Children’s National, associate professor of genomics and precision medicine at The George Washington University School of Medicine and Health Sciences and senior study author. “Our work highlights the need to take a nuanced view of the role of reactive oxygen species, as they are necessary when they are present at the right place and right time. Indiscriminate use of antioxidants actually could harm an adult with healthy muscles as well as a child with diseased muscle.”
The research team is currently examining oxidation in healthy and diseased muscle—for example, muscle damaged by muscular dystrophy—to understand how the oxidant-antioxidant balance is disrupted and how it could be restored efficiently by using existing supplements, such as vitamin E.
How congenital heart disease harms the brain
Study shows importance of brain region that supplies neural stem/progenitor cells
Abnormal neurogenesis and cortical growth in congenital heart disease.
Infants with congenital heart defects (CHDs) can experience myriad neurological deficits. A study led by Children’s National researchers, published online on Jan. 25, 2017, in Science Translational Medicine, offers clues to explain this phenomenon. Their findings suggest that depriving the brain of oxygen, which occurs during development in children who have CHD, could disrupt cellular processes that help the brain’s cortex grow.
The researchers, co-led by Richard A. Jonas, M.D., chief of the Division of Cardiac Surgery; Vittorio Gallo, Ph.D., chief research officer; and Nobuyuki Ishibashi, M.D., director of the Cardiac Surgery Research Laboratory; used a fluorescent dye and superparamagnetic iron oxide nanoparticles to follow the fate of cells derived from the subventricular zone (SVZ), home to the largest stockpile of neural stem/progenitor cells in typically developing brains, in a preclinical model. In postnatal brains, the SVZ supplied the developing cortex with newly generated neurons. These SVZ-derived cells made their way to the prefrontal cortex and the somatosensory cortex of the brain.
However, this process was severely disrupted in preclinical models exposed to chronic hypoxia. As a result, brains were smaller, weighed significantly less and had a significant reduction in cortical gray matter volume. In the prefrontal cortex, there was a significant reduction in white matter neuroblasts both in preclinical models and in post-mortem CHD human tissue.
These findings suggest that impaired neurogenesis within the SVZ represents a cellular mechanism underlying hypoxia-induced, region-specific reduction in immature neurons in the cortex.
“We know that CHD reduces cerebral oxygen at a time when the developing fetal brain most needs oxygen. Now, we are beginning to understand the mechanisms of CHD-induced brain injuries at a cellular level, and we have identified a robust supply of cells that have the ability to travel directly to the site of injury and potentially provide help by replacing lost or damaged neurons,” Dr. Ishibashi says.
Brain maturation in preterm babies
Altered blood flow in premature infants could be an early warning for neurodevelopmental problems
Cerebral blood flow (CBF) of key regions of newborns’ brains is altered in very premature infants and may provide an early warning sign of disturbed brain maturation well before such injury is visible on conventional imaging, according to a prospective, observational study published Dec. 4, 2017, in The Journal of Pediatrics led by Catherine Limperopoulos, Ph.D., director of the Developing Brain Research Laboratory at Children’s National.
Blood flows where it is needed most; areas of the brain that are used more heavily receive more. Thus, during brain development, CBF is a good indicator of functional brain maturation since brain areas that are the most metabolically active need more blood.
The team studied 98 preterm infants in the study who were born June 2012 to December 2015, were younger than 32 gestational weeks at birth and who weighed less than 1,500 grams. They matched those preemies by gestational age with 104 infants who had been carried to term.
To study blood flow in the brains of fragile newborns, the researchers relied on arterial spin labeling magnetic resonance imaging, a noninvasive technique that labels the water portion of blood to map how blood flows through infants’ brains in order to describe which regions do or do not receive adequate blood supply.
Very preterm infants had greater absolute cortical cerebral blood flow compared with full-term infants. Within regions, however, the insula, anterior cingulate cortex and auditory cortex for preterm infants received a significantly decreased volume of blood, compared with full-term infants.
Of note, compromised regional brain structures in adults are implicated in multiple neurodevelopmental disorders. “Altered development of the insula and anterior cingulate cortex in newborns may represent early warning signs of preterm infants at greater risk for long-term neurodevelopmental impairments,” says Limperopoulos.
The dangers of overprotection
Protective transcription factor Heat Shock Factor 1 can harm brain development when too much is produced
The developing brain releases a transcription factor called Heat Shock Factor 1 (Hsf1) to shield the vital organ from the ravages of environmental stress. Recent research led by Children’s scientists suggests that this protein actually can contribute to impairing the embryonic brain when too much is produced.
When fetuses are chronically exposed to harmful agents, such as alcohol, ethanol or methyl mercury, the experience can negatively affect brain development in unpredictable ways, with some showing little or no damage and others suffering severe damage.
“From a public health perspective, there is ongoing debate about whether there is any level of drinking by pregnant women that is ‘safe,’” says Kazue Hashimoto-Torii, Ph.D., principal investigator in the Center for Neuroscience Research at Children’s National and senior author of the paper published May 2, 2017, in Nature Communications.
To investigate, the research sleuths used a method that allows a single molecule to fluoresce during stress exposure. They tapped specific environmental stressors, such as ethanol, hydrogen peroxide and methyl mercury – each of which are known to produce oxidative stress at defined concentrations. And, using an experimental model, they examined the Hsf1 activation pattern in the developing cerebral cortex by creating a marker, an encoding gene tagged with a type of fluorescent protein that makes it glow bright red.
“Our results suggest that heterogeneous events of abnormal brain development may occur probabilistically – which explains patterns of cortical malformations that vary with each individual, even when these individuals are exposed to similar levels of environmental stressors,” Dr. Hashimoto-Torii explains.
“It remains unclear which precise threshold of stress exposure represents the tipping point, transforming what should be a neuroprotective response into a damaging response. Even at lower levels of alcohol exposure, however, the risk for fetal neural cells is not zero,” Dr. Hashimoto-Torii adds.
Iron’s role in neural tube defects
Study suggests that iron deficits could cause some cases of neural tube defects, but heavy supplementation has downsides
In a study led by Irene Zohn, Ph.D., a principal investigator in the Center for Neuroscience Research at Children’s National, and published January 31, 2017, in Birth Defects Research, she and colleagues show that iron deficits might cause some cases of neural tube defects (NTD).
The researchers worked with an experimental model with a mutation in a gene that transports iron across cell membranes, including the cells that supply embryos with iron. To determine if NTDs develop in this model because of reduced iron transport, the researchers gave groups of female experimental models a diet high in folic acid, a diet high in iron, a diet high in both nutrients or standard chow. All of these experimental models then became pregnant with embryos that harbored the same mutation.
While about 80 percent of offspring from the females fed a standard diet during pregnancy had NTDs, feeding a diet high in iron prevented NTDs in half of the offspring. This lower rate was similar in the offspring of mothers fed a diet high in both folic acid and iron, but not for those whose mothers ate just a diet high in folic acid, which had NTD rates as high as those who ate the standard chow.
Together, Dr. Zohn says, these experiments show that iron plays an important role in the development of the neural tube and that deficits in iron might cause some cases of NTDs. However, she notes, reducing NTDs isn’t nearly as simple as supplementing pregnant women’s diets with iron. In the same study, the researchers found that when they gave normal experimental models that didn’t have the flatiron mutation concentrated iron supplements, folate stores dropped.
“Even though our results demonstrate that iron is important for proper neural tube development,” Dr. Zohn says, “giving extra iron definitely has its downsides.”
Watching hematopoietic stem cells engraft after bone marrow transplant
Novel imaging agent could signal engraftment weeks before traditional techniques
Patients who undergo hematopoietic stem cell (HSC) transplants receive daily blood tests to gauge successful engraftment. Thus far, there has been no way beyond these daily blood tests to assess whether the newly infused cells have survived and have begun to grow in the bone marrow. However, research published online Dec. 13, 2017, by The Lancet Haematology and co-led by Kirsten M. Williams, M.D., a blood and bone marrow transplant specialist at Children’s National, suggests that a new imaging agent can safely show engraftment as early as days after transplant.
The study evaluated an investigational imaging test called 18F-fluorothymidine (18F-FLT) that’s incorporated into HSCs and can be seen on various types of common clinical imaging exams. To determine whether this compound can readily and safely visualize transplanted HSCs, Williams and colleagues tested it on 23 patients with various forms of high-risk leukemia. One day before they were infused with these donor HSCs, and then at five or nine days, 28 days, and one year after transplantation, the patients underwent imaging with this agent.
Each of these patients had successful engraftment, reflected in blood tests two to four weeks after their HSC transplants. However, the results of the imaging exams revealed a far more complicated and robust story.
The 18F-FLT showed that the donor cells took a complex journey as they engrafted, migrating to the patients’ livers and spleens, thoracic spines, the axial spines, the sternum, the arms and legs, and finally the bones that make up the trunk of the body. The radiation in 18F-FLT did not adversely affect engraftment. Additionally, images could identify success of their engraftments potentially weeks faster than they would have through traditional blood tests.
“What happens with HSCs always has been a mystery,” Dr. Williams says. “Now we can start to open that black box.”
Experimental model raises safety question about plastics in life-saving devices
Study in preclinical model suggests that phthalate could adversely affect cardiovascular health
An experimental model exposed to di-2-ethylhexyl-phthalate (DEHP), a chemical that can leach from plastic-based medical devices, experienced altered autonomic regulation, heart rate variability and cardiovascular reactivity, according to a study led by Children’s National researchers. The study, published online Nov. 6, 2017, in the American Journal of Physiology, is the first to show such an association between phthalate chemicals used in everyday medical devices like IV tubing and cardiovascular health.
“Plastics have revolutionized medical devices, transformed how we treat blood-based diseases and helped to make innovative cardiology procedures possible,” says Nikki Gillum Posnack, Ph.D., study senior author and assistant professor at the Sheikh Zayed Institute for Pediatric Surgical Innovation. “Because phthalate chemicals are known to migrate out of plastic products, our study highlights the importance of adopting safer materials, chemical additives and/or surface coatings for use in medical devices to reduce the risk of inadvertent exposure.”
Patients undergoing extensive interventions to save their lives may be exposed to multiple plastic-based devices, she adds.
In order to assess the safety of phthalate chemicals used in such medical devices, the Children’s-led research team implanted adult experimental models with radiofrequency transmitters that monitored their heart rate variability, blood pressure and autonomic regulation. Then, they exposed the experimental models to DEHP, a softener used in making the plastic polymer, polyvinyl chloride.
DEHP-treated pre-clinical models had decreased heart rate variability with lower-than-normal variation in the intervals between heartbeats. The experimental models also showed an exaggerated mean arterial pressure response to ganglionic blockade. And in response to a stressor, the experimental models in the treatment group displayed enhanced cardiovascular reactivity as well as prolonged blood pressure recovery, according to the study team.
“Our findings,” Posnack says, “underscore the importance of additional studies to explore the potential impact of phthalate chemicals on organ function.”
“The National Institutes of Health awarded Posnack $3.4 million to provide insights that could accelerate development of safer biomaterials.”
Incisionless surgery for bone tumors with MR-HIFU
Procedure holds advantages over the standard treatment at most U.S. hospitals
Doctors from the Sheikh Zayed Institute for Pediatric Surgical Innovation at Children’s National Health System, led by Karun Sharma, M.D., Ph.D., director of Interventional Radiology, completed a clinical trial that demonstrates how osteoid osteoma can be safely and successfully treated using an incisionless surgery method called magnetic resonance-guided, high-intensity focused ultrasound (MR-HIFU).
Published in The Journal of Pediatrics on Aug. 17, 2017, the study compares nine patients, ages 6 to 16 years old, who were treated for this common benign but painful bone tumor using MR-HIFU with a nine-patient historical control group, ages 6 to 10 years old, who were treated at Children’s National using radiofrequency ablation (RFA) surgery. RFA is the standard treatment at most U.S. hospitals.
The study results show that treatment using MR-HIFU is feasible and safe for patients, eliminating the incisions or exposure to ionizing radiation that is associated with the RFA procedure. Children’s National is the first U.S. children’s hospital to successfully use MR-HIFU to treat osteoid osteoma.
CT-guided RFA, the most commonly used osteoid osteoma treatment, requires drilling through muscle and soft tissue into bone and also exposes the patient and operator to radiation from the imaging necessary to guide the probe that is inserted to heat and destroy tumor tissue.
“Our objective is to provide a noninvasive treatment option for children with osteoid osteoma and we’re very pleased with the results of this clinical trial,” says Dr. Sharma, principal investigator for the osteoid osteoma trial. “We have now shown that MR-HIFU can be performed safely with clinical improvement that is comparable to RFA, but without any incisions or ionizing radiation exposure for children.”
Understanding health disparities
Racial, ethnic disparities in pediatric readmission rates for chronic disease vary by health condition
Disparities in pediatric readmission rates for chronic conditions such as asthma, depression, diabetes, migraines, and seizures vary, with the lowest one-year readmissions recorded for depression and the highest one-year readmission rates seen for seizure, according to retrospective analyses of hospitalizations at 48 children’s hospitals.
Health disparities for asthma and diabetes readmissions began to emerge by as early as three weeks after hospitalization; the highest one-year readmission rates for these conditions were seen among non-Latino blacks. Meanwhile, disparities for migraine and seizure readmissions became apparent as early as six weeks after hospitalization, with the highest one-year readmission rates seen in non-Latino whites.
“Children of all races should have equal opportunity to experience the best clinical outcomes. The study findings should help to highlight untapped opportunities to personalize care to reduce readmission disparities,” says Kavita Parikh, M.D., M.S.H.S., associate professor of pediatrics in the Division of Hospitalist Medicine at Children’s National Health System and lead author of the study published April 21, 2017, in The Journal of Pediatrics.
The research team analyzed deidentified hospitalization data from 2013 for children aged 0 to 18 at hospitals that account for roughly 20 percent of the nation’s pediatric hospitalizations. Among children within the study, non-Latino white patients accounted for the majority of readmissions for migraines (56.4 percent) and depression (67.9 percent). Non-Latino blacks registered the highest percentage of asthma readmissions (43.2 percent) followed by non-Latino whites (28.2 percent).
The study team called for additional research to help tease out other variables that influence readmission disparities.
“In order to ensure that children across the nation benefit from the very best health care,” Dr. Parikh adds, “we need to identify the full spectrum of factors that contribute to health care inequities and fine-tune how we manage patients before and after hospitalization to narrow gaps in care.”