Tiny Biomarkers for Small Patients with Brain Injuries

When a newborn baby begins experiencing respiratory problems, lethargy, or seizures after an acute perinatal event or difficult labor, the clock starts ticking.¹ Physicians must rapidly evaluate the infant for further signs of neonatal encephalopathy (NE), a heterogeneous neurological dysfunction syndrome often caused by brain injury, to determine if they should initiate treatment. However, they still lack biomarkers to predict if the neonate has brain damage, the severity of the injury, and if the patient will respond to therapy.

In a recently published Scientific Reports paper, scientists determined that specific microRNAs (miRNA) detected within blood samples could serve as potential diagnostic and predictive biomarkers of NE.² These noninvasive markers could help physicians make critical decisions about a patient's care and highlight potential avenues for future therapy development.

It is relatively unknown what causes the hypoxia in the majority of patients who develop NE, with clinicians able to attribute only approximately 15-29 percent of cases to known oxygen deprivation events, such as placental abruption or umbilical cord prolapse.^3,4 After the initial brain damage resulting from a hypoxic event, the newborns enter a six hour latency period before they undergo extensive neuronal death.⁵ This damage can lead to long-term complications including cerebral palsy, intellectual disabilities, and epilepsy.

A combined image that shows two men. The man on the left is in front of a tree and a building. The man on the right is in front of a grey backdrop.

Firas Kobeissy (left), Michael Weiss (right), and their team evaluated the microRNA profiles of neonates with and without suspected brain injuries to discover novel biomarkers.

Firas Kobeissy and University of Florida Health.

Although scientists have identified protein-based biomarkers of brain injury, miRNA-based markers have several advantages.⁶ miRNA are small, noncoding RNA molecules that can alter the translation of mRNA. “One miRNA can regulate [many] different markers,” said Firas Kobeissy, a neuroscientist at Morehouse School of Medicine and author of the study. “miRNA are [also] found in different biofluids, are very stable, and their detection by PCR is very easy.”

To establish if miRNA could serve as diagnostic biomarkers, Kobeissy and his team acquired blood samples from infants who experienced hypoxic stress in utero from the Florida Neonatal Neurologic Network registry and biorepository. Clinicians identify these neonates by measuring the pH of the umbilical cord blood, where an acidic pH indicates oxygen deprivation. But not all neonates with acidosis will develop NE. To determine if there are differences in the miRNA expression profiles of newborns with suspected moderate or severe brain injuries and those with acidosis that did not develop NE, the researchers used a microarray to measure the levels of 65 neurology-associated miRNA in blood samples collected zero to six hours after birth. They found elevated levels of miR34c-5p, miR491-5p, and miR346 in the NE group compared to the no NE group, indicating that these three miRNA species could be potential diagnostic biomarkers of the syndrome.

The development of a rapid [NE] biomarker is kind of the holy grail in the field at the moment.
- Eric Peeples, University of Nebraska Medical Center

Physicians attempt to minimize brain damage in neonates with suspected moderate or severe brain injuries by treating them during the latency period with therapeutic hypothermia, where they reduce the temperature of the infants by 2-4°C for 72 hours before slowly warming them up.⁷ However, they only establish the severity of the injuries following this treatment by employing magnetic resonance imaging (MRI). Of the newborns previously assessed in the NE group, clinicians classified half of them with no or mild injuries and the other half with moderate or severe injuries. To identify potential predictive biomarkers, the researchers compared the miRNA levels of infants in these two categories by reanalyzing the blood samples acquired after birth but before cooling. They observed upregulation of several miRNA species in patients with no/mild injury including miR-15b-5p and miR-16-5p, which are known inducers of apoptosis.⁸ Researchers associate apoptosis with neuronal death that occurs after the latency period, whereas the initial injury results primarily from necrosis.⁹ Because therapeutic hypothermia helps to reduce the secondary damage, they hypothesize that patients with higher levels of these molecules, and thus potentially experiencing more apoptosis than necrosis, may respond better to treatment, leading to less severe brain injuries.

“We really struggle to generate both sensitive and specific diagnoses for these babies in a quick time period,” said Eric Peeples, a neonatologist at the University of Nebraska Medical Center, who was not involved in the study. “The development of a rapid [NE] biomarker is kind of the holy grail in the field at the moment.” In the future, Peeples would like to see if the researchers can link these potential miRNA biomarkers to long-term outcomes and use them to identify neonates with NE that clinicians would not currently diagnose with the syndrome using the existing markers. “There is plenty to be done, but this is a great start,” Peeples said.

“I am very hopeful that this article will stimulate interest in microRNAs and interest in biomarkers as rapid bedside tests to help us identify the severity and degree of brain injury,” said Michael Weiss, a neonatologist at the University of Florida and coauthor of the research. “As new adjunct therapies become available, [these markers] could also help identify the kids that may benefit from other therapies.”