Maturation-dependent response of neurogenesis after traumatic brain injury in children.
OBJECTIVE
Traumatic brain injury (TBI) is the leading cause of acquired disability in children, yet innate repair mechanisms are incompletely understood. Given data from animal studies documenting neurogenesis in response to trauma and other insults, the authors investigated whether similar responses could be found in children of different ages after TBI.


METHODS
Immunohistochemistry was used to label doublecortin (DCX), a protein expressed by immature migrating neuroblasts (newborn neurons), in specimens from patients ranging in age from 3 weeks to 10 years who had died either after TBI or from other causes. Doublecortin-positive (DCX+) cells were examined in the subventricular zone (SVZ) and periventricular white matter (PWM) and were quantified within the granule cell layer (GCL) and subgranular zone (SGZ) of the dentate gyrus to determine if age and/or injury affect the number of DCX+ cells in these regions.


RESULTS
The DCX+ cells decreased in the SVZ as patient age increased and were found in abundance around a focal subacute infarct in a 1-month-old non-TBI patient, but were scarce in all other patients regardless of age or history of trauma. The DCX+ cells in the PWM and dentate gyrus demonstrated a migratory morphology and did not co-localize with markers for astrocytes, microglia, or macrophages. In addition, there were significantly more DCX+ cells in the GCL and SGZ of the dentate gyrus in children younger than 1 year old than in older children. The density of immature migrating neuroblasts in infants (under 1 year of age) was significantly greater than in young children (2-6 years of age, p = 0.006) and older children (7-10 years of age, p = 0.007).


CONCLUSIONS
The main variable influencing the number of migrating neuroblasts observed in the SVZ, PWM, and hippocampus was patient age. Trauma had no discernible effect on the number of migrating neuroblasts in this cohort of patients in whom death typically occurred within hours to days after TBI.
Program in Experimental and Molecular Medicine, Dartmouth College, Hanover, New Hampshire;
Sabrina R
SR
Taylor
Colin
C
Smith
Brent T
BT
Harris
Beth A
BA
Costine
Ann-Christine
AC
Duhaime
D000367:Age Factors; D001921:Brain / Q000378:metabolism*; D001930:Brain Injuries / Q000378:metabolism / Q000503:physiopathology*; D002455:Cell Division; D002465:Cell Movement; D002552:Cerebral Ventricles / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D018891:Dentate Gyrus / Q000378:metabolism; D000089622:Doublecortin Domain Proteins; D000089662:Doublecortin Protein; D005260:Female; D005455:Fluorescent Antibody Technique; D006624:Hippocampus / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D055495:Neurogenesis; D009474:Neurons; D009479:Neuropeptides / Q000378:metabolism*
C000714328:DCX protein, human; D000089622:Doublecortin Domain Proteins; D000089662:Doublecortin Protein; D008869:Microtubule-Associated Proteins; D009479:Neuropeptides