Hypoxic-ischemic brain injury remains a significant problem in the US and globally, affecting 3-5/1000 liveborn infants in the US, and contributing to 23% of neonatal deaths globally. Therapeutic hypothermia decreases the outcomes of death and neurodevelopmental disability, but only by approximately 15%, so outcomes remain poor for 50% of affected, treated infants. Biomarkers that accurately reflect the degree of brain injury the timing and evolution of injury, and response to therapy are critically needed for clinical management of these patients and for research. Ideal biomarkers would differentiate infants who do not require treatment from those at risk of permanent sequelae; infants that might benefit from intervention from those for whom treatment is futile; and would identify infants who are within a therapeutic window for a specific treatment. Such biomarkers would also be important for research because they would allow for the accurate identification of at-risk infants, decreasing variability among enrolled subjects, thereby decreasing the numbers of patients required for adequately powered studies. We have developed a nonhuman primate model of perinatal asphyxia in which brain injury is induced by occlusion of the umbilical cord prior to birth. Our nonhuman primate model provides an unmatched opportunity to assess circulating and excreted metabolites and proteins after a timed injury, and to study structural biomarkers as brain injury evolves. The response to therapeutic hypothermia will be determined, and potential biomarkers will be correlated with neurodevelopmental outcomes. Finally, at necropsy, this clinical information can be correlated to pathologic outcomes. We hypothesize that by combining sequential metabolomic, proteomic, and structural assessments, we will develop an assessment panel for hypoxic ischemic encephalopathy (HIE) that will, with high sensitivity and specificity, diagnose early severity of illness, prognosis, and likely response to therapeutic hypothermia with long term neurodevelopmental status as a final outcome. Using a macaque nemestrina model of HIE we will develop: 1) Sensitive and specific diagnostic early biomarkers of severity of acute brain injury. To ensure accuracy of categorization, we will use neurobehavioral and structural (MRI and necropsy) outcomes at 6 months of age as a gold standard; 2) Early prognostic biomarkers of long term outcomes of HIE, using sequential evaluations of the proteome, metabolome, MRI and MRS to correlate individual acute response to injury with long-term structural and functional outcomes; and 3) We will develop biomarkers which predict an individual's response to therapeutic hypothermia. Results of this study will be directly applicable to both clinical practice, and will also advance the field by defining biomarkes that can be used for research purposes.
Implementation of therapeutic hypothermia has improved outcomes of infants born after perinatal asphyxia, showing proof-of-concept that interventions can improve outcomes. But 50% of affected infants still die or suffer long-term neurodevelopmental consequences including cerebral palsy and mental retardation. Biomarkers are needed to improve care of these infants and to inform research efforts to move the field forward.
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