Cerebral and Peripheral Immune Cell Changes following Rodent Juvenile Traumatic Brain Injury

Area of Science:

• Neuroscience
• Immunology
• Pediatric Traumatology

Background:

• Traumatic brain injury (TBI) is a major cause of death and disability.
• Neuroinflammation is a known consequence of TBI, but its temporal dynamics and impact on immune cells are not fully understood.
• Previous research has not investigated immune cell population changes after TBI using the CHIMERA model.

Purpose of the Study:

• To investigate the temporal changes in inflammatory marker mRNA expression in the acute phase following TBI in juvenile rats.
• To determine acute alterations in brain and circulating immune cell populations after TBI.
• To examine changes in the thymus following TBI.

Main Methods:

• Juvenile male Long Evans rats (post-natal day 30) underwent TBI or sham procedures.
• Animals were euthanized at various time points (0–96 h post-injury) for tissue and blood collection.
• Inflammatory marker mRNA expression was analyzed using qPCR, and immune cell populations were quantified via flow cytometry.

Main Results:

• Pro-inflammatory cytokine TNF-α mRNA expression was significantly elevated at 6 hours post-TBI in both prefrontal cortex and hippocampus.
• Peripheral blood showed increased T cells (total, helper) and B cells at 48 hours post-TBI.
• Brain samples revealed a reduction in monocytes/macrophages, while the thymus exhibited thymic medulla expansion at 48 hours post-TBI.

Conclusions:

• Acute TBI in juvenile rats induces significant changes in inflammatory signaling and immune cell distribution.
• Alterations in cerebral and peripheral immune cells, along with thymic changes, highlight a potential immune vulnerability window during subacute recovery.
• These findings are crucial for understanding pediatric TBI and developing targeted immunomodulatory therapies.