Epigenetic processes associated with neonatal spinal transection.

In early development, the spinal cord in healthy or disease states displays remarkable activity-dependent changes in plasticity, which may be in part due to the increased activity of brain derived neurotrophic factor (BDNF). Indeed, BDNF delivery has been efficacious in partially ameliorating many of the neurobiological and behavioral consequences of spinal cord injury (SCI), making elucidating the role of BDNF in the normative developing and injured spinal cord a critical research focus. Recent work in our laboratory provided evidence for aberrant global and locus-specific epigenetic changes in methylation of the Bdnf gene as a consequence of SCI. In the present study, animals underwent thoracic lesions on P1, with cervical and lumbar tissue being later collected on P7, P14, and P21. Levels of Bdnf expression and methylation (exon IX and exon IV), in addition to global methylation levels were quantified at each timepoint. Results indicated locus-specific reductions of Bdnf expression that was accompanied by a parallel increase in methylation caudal to the injury site, with animals displaying increased Bdnf expression at the P14 timepoint. Together, these findings suggest that epigenetic activity of the Bdnf gene may act as biomarker in the etiology and intervention effort efficacy following SCI.

Early Life Stress Affects Bdnf Regulation: A Role for Exercise Interventions.

Early life stress (ELS) encompasses exposure to aversive experiences during early development, such as neglect or maltreatment. Animal and human studies indicate that ELS has maladaptive effects on brain development, leaving individuals more vulnerable to developing behavioral and neuropsychiatric disorders later in life. This result occurs in part to disruptions in Brain derived neurotrophic factor (Bdnf) gene regulation, which plays a vital role in early neural programming and brain health in adulthood. A potential treatment mechanism to reverse the effects of ELS on Bdnf expression is aerobic exercise due to its neuroprotective properties and positive impact on Bdnf expression. Aerobic exercise opens the door to exciting and novel potential treatment strategies because it is a behavioral intervention readily and freely available to the public. In this review, we discuss the current literature investigating the use of exercise interventions in animal models of ELS to reverse or mitigate ELS-induced changes in Bdnf expression. We also encourage future studies to investigate sensitive periods of exercise exposure, as well as sufficient duration of exposure, on epigenetic and behavioral outcomes to help lead to standardized practices in the exercise intervention field.

Unlocking the epigenome: Stress and exercise induced Bdnf regulation in the prefrontal cortex.

Aversive caregiving in early life is a risk factor for aberrant brain and behavioral development. This outcome is related to epigenetic dysregulation of the brain-derived neurotrophic factor (Bdnf) gene. The Bdnf gene encodes for BDNF, a neurotrophin involved in early brain development, neural plasticity, learning, and memory. Recent work suggests that exercise may be neuroprotective in part by supporting BDNF protein and gene expression, making it an exciting target for therapeutic interventions. To our knowledge, exercise has never been studied as a therapeutic intervention in preclinical rodent models of caregiver maltreatment. To that end, the current study investigated the effect of an adult voluntary wheel running intervention on Bdnf methylation and expression in the prefrontal cortex of rats who experienced aversive caregiving in infancy. We employed a rodent model (Long Evans rats) wherein rat pups experienced intermittent caregiver-induced stress from postnatal days 1-7 and were given voluntary access to a running wheel (except in the control condition) from postnatal days 70-90 as a young adulthood treatment intervention. Our results indicate that maltreatment and exercise affect Bdnf gene methylation in an exon, CG site, and sex-specific manner. Here we add to a growing body of evidence of the ability for our experiences, including exercise, to permeate the brain. Keywords: Early life stress, Bdnf, exercise, prefrontal cortex.

Glia-Driven Brain Circuit Refinement Is Altered by Early-Life Adversity: Behavioral Outcomes.

Early-life adversity (ELA), often clinically referred to as "adverse childhood experiences (ACE)," is the exposure to stress-inducing events in childhood that can result in poor health outcomes. ELA negatively affects neurodevelopment in children and adolescents resulting in several behavioral deficits and increasing the risk of developing a myriad of neuropsychiatric disorders later in life. The neurobiological mechanisms by which ELA alters neurodevelopment in childhood have been the focus of numerous reviews. However, a comprehensive review of the mechanisms affecting adolescent neurodevelopment (i.e., synaptic pruning and myelination) is lacking. Synaptic pruning and myelination are glia-driven processes that are imperative for brain circuit refinement during the transition from adolescence to adulthood. Failure to optimize brain circuitry between key brain structures involved in learning and memory, such as the hippocampus and prefrontal cortex, leads to the emergence of maladaptive behaviors including increased anxiety or reduced executive function. As such, we review preclinical and clinical literature to explore the immediate and lasting effects of ELA on brain circuit development and refinement. Finally, we describe a number of therapeutic interventions best-suited to support adolescent neurodevelopment in children with a history of ELA.