Traumatic brain injury (TBI) affects 2.5 million people annually within the United States alone, with over 300,000 severe injuries resulting in emergency room visits and hospital admissions. Severe TBI can result in long-term disability. Post traumatic epilepsy (PTE) is one of the most debilitating consequences of TBI, with an estimated incidence that ranges from 2% to 50% based on severity of injury. Conducting studies of PTE poses many challenges, because many subjects with TBI never develop epilepsy, and it can be more than 10 years after TBI before seizures begin. One of the unmet needs in the study of PTE is an accurate biomarker of epileptogenesis, or a panel of biomarkers, which could provide early insights into which TBI patients are most susceptible to PTE, providing an opportunity for prophylactic anticonvulsant therapy and enabling more efficient large-scale PTE studies. Several recent reviews have provided a comprehensive overview of this subject (Neurobiol Dis, 123, 2019, 3; Neurotherapeutics, 11, 2014, 231).

In this review, researchers describe acute and chronic imaging methods that detect biomarkers for PTE and potential mechanisms of epileptogenesis. They also describe shortcomings in current acquisition methods, analysis, and interpretation that limit ongoing investigations that may be mitigated with advancements in imaging techniques and analysis.

A blow to the head or powerful shock wave on the battlefield can cause immediate, significant damage to a person’s skull and the tissue beneath it. But the trauma does not stop there. The impact sets off a chemical reaction in the brain that ravages neurons and the networks that supply them with nutrients and oxygen.

It is the secondary effects of traumatic brain injury (TBI), which can lead to long-term cognitive, psychological and motor system damage [as well as post-traumatic epilepsy], that piqued the interest of a team of NJIT biomedical engineers. To counter them, they are developing a therapy, to be injected at the site of the injury, which shows early indications it can protect neurons and stimulate the regrowth of blood vessels in the damaged tissue.

The challenge, researchers say, is that brain cells don’t regenerate as well as other tissues, such as bone, which may be an evolutionary strategy for preserving the synaptic connections that retain memories. To date, there is no effective treatment for restoring damaged neurons. The body’s protective mechanisms also make it difficult to penetrate the blood-brain barrier, which hampers the delivery of medications.

“Nerve cells respond to trauma by producing excessive amounts of glutamate, a neurotransmitter that under normal conditions facilitates learning and memory, but at toxic levels overexcites cells, causing them to break down. Traumatic brain injury can also result in the activation and recruitment of immune cells, which cause inflammation that can lead to short- and long-term neural deficits by damaging the structure around cells and creating a chronic inflammatory environment,” says Biplab Sarkar, a post-doctoral fellow in biomedical engineering and member of the team that presented this work at a recent American Chemical Society conference.

The team’s treatment consists of a lab-created mimic of ependymin, a protein shown to protect neurons after injury, attached to a delivery platform — a strand of short proteins called peptides, contained in a hydrogel — that was developed by Vivek Kumar, director of NJIT’s Biomaterial Drug Development, Discovery and Delivery Laboratory. After injection, the peptides in the hydrogel reassemble at the localized injury site into a nanofibrous scaffold that mimics extracellular matrix, the supporting structure for cells. These soft materials possess mechanical properties similar to brain tissue, which improves their biocompatibility. They promote rapid infiltration by a variety of stem cells which act as precursors for regeneration and may also provide a biomimetic niche to protect them.

Now in preclinical animal trials, rats injected with the hydrogel retained twice as many functioning neurons at the injury site as compared to the control group. They also formed new blood cells in the region.

“The idea is to intervene at the right time and place to minimize or reverse damage. We do this by generating new blood vessels in the area to restore oxygen exchange, which is reduced in patients with a TBI, and by creating an environment in which neurons that have been damaged in the injury are supported and can thrive,” Kumar says. “While the exact mechanism of action for these materials is currently under study, their efficacy is becoming apparent. Our results need to be expanded, however, into a better understanding of these mechanisms at the cellular level, as well as their long-term efficacy and the resulting behavioral improvements.”

Collaborators James Haorah, an associate professor of biomedical engineering, and his graduate student Xiaotang Ma at NJIT’s Center for Injury Biomechanics, Materials and Medicine have shown how a number of TBI-related chemical effects can disrupt and destroy integral brain vasculature in the blood-brain barrier, the brain’s protective border, promoting chronic inflammation that can lead to symptoms such as post-traumatic stress disorder and anxiety, among others. Their current work provides insights into the potential neuroprotective and regenerative response guided by the Kumar lab’s materials, while future studies will attempt to analyze other mediators of inflammation and blood flow in the brain.

Featuring the work of CURE PTE Initiative members Dr. Oleskii Shandra and Dr. Stefanie Robel

Focal traumatic brain injury (TBI) induces astrogliosis, a process essential to protecting uninjured brain areas from secondary damage. However, astrogliosis can cause loss of astrocyte homeostatic functions and possibly contributes to comorbidities such as posttraumatic epilepsy (PTE).

Scar-forming astrocytes seal focal injuries off from healthy brain tissue. It is these glial scars that are associated with epilepsy originating in the cerebral cortex and hippocampus. However, the vast majority of human TBIs also present with diffuse brain injury caused by acceleration-deceleration forces leading to tissue shearing. The resulting diffuse tissue damage may be intrinsically different from focal lesions that would trigger glial scar formation.

This study used mice of both sexes in a model of repetitive mild/concussive closed-head TBI, which only induced diffuse injury, to test the hypothesis that astrocytes respond uniquely to diffuse TBI and that diffuse TBI is sufficient to cause PTE. Astrocytes did not form scars and classic astrogliosis characterized by upregulation of glial fibrillary acidic protein was limited. Surprisingly, an unrelated population of atypical reactive astrocytes was characterized by the lack of glial fibrillary acidic protein expression, rapid and sustained downregulation of homeostatic proteins and impaired astrocyte coupling.

After a latency period, a subset of mice developed spontaneous recurrent seizures reminiscent of PTE in human TBI patients. Seizing mice had larger areas of atypical astrocytes compared with nonseizing mice, suggesting that these atypical astrocytes might contribute to epileptogenesis after diffuse TBI.

In the United States, almost 3 million people sustain a traumatic brain injury (TBI) every year. The vast majority of these injuries are categorized as mild (?90%) and do not require hospitalization. Mild TBI is also frequently categorized as concussion, and it remains controversial as to whether, and to what extent mild TBI is a risk for the development of post-traumatic epilepsy.

It is well established, on the other hand, that severe TBI can lead to the development of a range of negative sequela in humans, including epilepsy. Moreover, the epileptogenic effects of severe TBI have been confirmed in rodents following controlled cortical impact and fluid percussion injury. In both rodent models [of PTE], a craniectomy is performed to expose the dura, and injury is induced either by a rigid impact device or hydraulically induced pressure. Both models can produce severe injuries, including neuronal loss, hemorrhage, extensive inflammatory changes, and mortality. These models have provided a wealth of data about potential epileptogenic mechanisms of severe TBI, but do not provide insight into the effects of mild TBI on epileptogenesis.

To address this gap in knowledge, Shandra and colleagues developed a closed-head model of post-traumatic epilepsy in mice following repetitive, mild TBI.