New research in the Journal of Leukocyte Biology reveals that perinatal chronic hypoxia triggers neuroinflammation and myelin loss in the developing brain, producing lasting behavioral deficits.
Researchers report that sustained low oxygen exposure shortly after birth disrupts white matter development in mice, causing persistent hypomyelination and motor learning problems. If similar processes occur in humans, these findings could help explain why infants who experience neonatal hypoxia—from cyanotic congenital heart disease, extreme prematurity, or severe lung disease—often show learning and developmental impairments later in childhood. Greater understanding of this mechanism may guide the development of targeted therapies to protect the developing brain.
In the study, investigators exposed mouse pups to chronic low oxygen from postnatal day 3 through day 28, while control animals were maintained in normal room air (approximately 21% oxygen). They evaluated white matter maturation by measuring myelin proteins, counting oligodendrocytes (the myelin-producing glial cells), assessing overall brain inflammation, and detecting activation of immune cells that can target the nervous system. The team also examined recovery by allowing a four-week period after hypoxic exposure to determine whether damage resolved or persisted.
Key findings included an early reduction in mature myelin and a long-term deficit in white matter even weeks after returning to normal oxygen conditions. Although progenitor oligodendrocyte numbers initially increased, BrdU labeling demonstrated a reduction in dividing progenitor cells, indicating impaired replacement of mature myelinating cells and defective myelin formation. These cellular deficits correlated with sustained motor learning impairments in the mice.
Importantly, the study identified a pronounced neuroinflammatory response accompanying hypomyelination. Perinatal chronic hypoxia promoted infiltration of CD4 T cells into the developing cortex and an increase in peripheral myelin-specific CD4 T cells, suggesting an autoimmune component directed against oligodendrocytes and myelin. This neuroimmune interaction—combining a shortage of mature myelin-producing glia with active, autoreactive immune cells—may contribute substantially to early hypomyelination and subsequent functional deficits.
“We found that chronic hypoxia is a state of neuroinflammation in the developing brain,” said Lakshmi Raman, MD, one of the researchers involved in the work from the Department of Pediatrics at the University of Texas Southwestern Medical Center. She noted that therapies aimed at reducing damaging inflammation during or after hypoxic exposure could potentially limit brain injury and reduce the risk of developmental delay in affected infants.
John Wherry, Ph.D., Deputy Editor of the Journal of Leukocyte Biology, commented that the study’s implications could be clinically actionable. He suggested that interventions such as optimized oxygen supplementation and anti-inflammatory strategies might be explored to protect the neonatal brain. The broader connection between hypoxia and inflammation is now recognized in diverse clinical contexts, and targeting inflammatory pathways may offer new treatment avenues for hypoxic injury to the nervous system.
Source: Cody Mooneyhan – Federation of American Societies for Experimental Biology
Image Source: The image is in the public domain
Original Research: Abstract for “Perinatal chronic hypoxia induces cortical inflammation, hypomyelination, and peripheral myelin-specific T cell autoreactivity” by Sterling B. Ortega, Xiagmei Kong, Ramgopal Venkataraman, Allen Michael Savedra, Steven G. Kernie, Ann M. Stowe, and Lakshmi Raman in Journal of Leukocyte Biology. Published online January 2016. doi:10.1189/jlb.5HI0914-447R
Abstract
Perinatal chronic hypoxia induces cortical inflammation, hypomyelination, and peripheral myelin-specific T cell autoreactivity
Perinatal chronic hypoxia (pCH) is a significant risk factor for brain injury and long-term morbidity during key stages of brain development, including neurogenesis, neuronal migration, and myelination. Using a rodent model, the investigators observed an early decrease in mature myelin following pCH. Although the number of oligodendrocyte progenitor cells rose, BrdU labeling exposed a reduction in dividing progenitors, indicating defective replacement of mature oligodendrocytes and impaired myelinogenesis. Mice subjected to pCH continued to show hypomyelination and persistent motor deficits weeks after the hypoxic exposure ended. The study also revealed a novel neuroimmunologic interaction: pCH provoked infiltration of CD4 T cells into the developing cortex and increased peripheral myelin-specific CD4 T cells, suggesting oligodendrocyte-directed autoimmunity. Both the loss of mature myelin-producing glia and the active recruitment of autoreactive, myelin-specific CD4 T cells likely contribute to early hypomyelination of the developing central nervous system. Elucidating mechanisms of hypoxia-driven autoimmunity will improve understanding of the neuroimmune axis in perinatal CNS disease and may highlight targets to prevent long-term functional disability.
“Perinatal chronic hypoxia induces cortical inflammation, hypomyelination, and peripheral myelin-specific T cell autoreactivity” by Sterling B. Ortega et al. in Journal of Leukocyte Biology. Published online January 2016. doi:10.1189/jlb.5HI0914-447R