Maturation-dependent response of the piglet brain to scaled cortical impact

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Abstract
Object. The goal of this study was to investigate the relationship between maturational stage and the brain's response to mechanical trauma in a gyrencephalic model of focal brain injury. Age-dependent differences in injury response might explain certain unique clinical syndromes seen in infants and young children and would determine whether specific therapies might be particularly effective or even counterproductive at different ages.Methods. To deliver proportionally identical injury inputs to animals of different ages, the authors have developed a piglet model of focal contusion injury by using specific volumes of rapid cortical displacement that are precisely scaled to changes in size and dimensions of the growing brain. Using this model, the histological response to a scaled focal cortical impact was compared at 7 days after injury in piglets that were 5 days, 1 month, and 4 months of age at the time of trauma. Despite comparable injury inputs and stable physiological parameters, the percentage of hemisphere injured differed significantly among ages, with the youngest animals sustaining the smallest lesions (0.8%, 8.4%, and 21.5%, for 5-day-, 1-month-, and 4-month-old animals, respectively, p = 0.0018).Conclusions. These results demonstrate that, for this particular focal injury type and severity, vulnerability to mechanical trauma increases progressively during maturation. Because of its developmental and morphological similarity to the human brain, the piglet brain provides distinct advantages in modeling age-specific responses to mechanical trauma. Differences in pathways leading to cell death or repair may be relevant to designing therapies appropriate for patients of different ages.