Hitting a moving target: Basic mechanisms of recovery from acquired developmental brain injury

The pediatric athlete: younger athletes with sport-related concussion

Although much of the lay media attention surrounding sport-related concussion (SRC) focuses on professional athletes, SRC is a common injury in pediatric sports. The anatomy, biomechanics, and response to injury of the developing pediatric brain differ from those of the adult. Similarly, the neurocognitive abilities of the child are developing more rapidly than in an adult. The effects of concussive brain injury on the life of a child are different from those of an adult. This article focuses on the aspects of SRC that are specific to the younger athletes.

Age-related changes in the oligodendrocyte progenitor pool influence brain remodeling after injury

Brain remodeling occurs after all forms of brain injury, though the mechanisms underlying this phenomenon are mostly unknown. Neural stem and progenitor cells are one source of endogenous cells that may contribute to brain remodeling and subsequent recovery. In addition, certain populations of progenitors are particularly susceptible to injury, and their depletion may lead to the impairment of developmental processes that vary with age. We particularly focus on glial progenitors, which are more abundant postnatally and particularly susceptible to acquired brain injuries such as traumatic brain injury. We have recently characterized a novel transgenic mouse that expresses herpes thymidine kinase under the control of the neural-progenitor-specific nestin promoter and allows for temporally induced ablation of dividing progenitors. By genetically depleting dividing cortical progenitors at various times, we identify postnatal day 7 (P7) to P14 as a critical period for oligodendrogenesis. Targeted ablation of dividing progenitors during this window leads to cell-specific depletion of oligodendrocyte precursors expressing platelet-derived growth factor receptor-α and corresponding myelination and motor deficits. This modeling provides insight into how the age at which white matter injury occurs influences both injury severity and subsequent recovery.

Molecular and physiological responses to juvenile traumatic brain injury: focus on growth and metabolism

Traumatic brain injury (TBI), one of the most frequent causes of neurologic and neurobehavioral morbidity in the pediatric population, can result in lifelong challenges not only for patients, but also for their families. Survivors of a brain injury experienced during childhood - when the brain is undergoing a period of rapid development - frequently experience unique challenges as the consequences of their injuries are overlaid on normal developmental changes. Experimental studies have significantly advanced our understanding of the mechanisms and underlying molecular underpinnings of the injury response and recovery process following a TBI in the developing brain. In this paper, normal and TBI-related alterations in growth, development and metabolism are comprehensively reviewed in the postweanling/juvenile age range in the rat (postnatal days 21-60). As part of this review, TBI-related changes in gene expression are presented, with a focus on the injury-induced alterations related to cerebral growth and metabolism, and discussed in the context of existing literature related to physiological and behavioral responses to experimental TBI. Increasing evidence from the existing literature and from our own gene microarray data indicates that molecular responses related to growth, development and metabolism may play a particularly important role in the injury response and the recovery trajectory following developmental TBI. While gene expression analysis shows many of these changes occur at the level of transcription, a comprehensive review of other studies suggests that the control of metabolic substrates may preferentially be regulated through changes in transporters and enzymatic activity. The interrelation between cellular metabolism and activity-dependent neuroplasticity shows great promise as an area for future study for an optimal translation of experimental data to clinical TBI, with the ultimate goal of guiding therapeutic interventions.

Effects of saccharin intake on hippocampal and cortical plasticity in juvenile and adolescent rats

The sensory system is developed and optimized by experiences given in the early phase of life in association with other regions of the nervous system. To date, many studies have revealed that deprivation of specific sensory experiences can modify the structure and function of the central nervous system; however, the effects of sensory overload remains unclear. Here we studied the effect of overloading the taste sense in the early period of life on the synaptic plasticity of rat hippocampus and somatosensory cortex. We prepared male and female Sprague Dawley rats with ad libitum access to a 0.1% saccharin solution for 2 hrs per day for three weeks after weaning on postnatal day 22. Saccharin consumption was slightly increased in males compared with females; however, saccharin intake did not affect chow intake or weight gain either in male or in female rats. We examined the effect of saccharin-intake on long term potentiation (LTP) formation in hippocampal Schaffer collateral pathway and somatosensory cortex layer IV - II/III pathways in the 6-week old saccharin-fed rats. There was no significant difference in LTP formation in the hippocampus between the control group and saccharin-treated group in both male and female rats. Also in the somatosensory cortex, we did not see a significant difference in LTP among the groups. Therefore, we conclude that saccharin-intake during 3~6 weeks may not affect the development of physiological function of the cortical and hippocampal synapses in rats.