Anthony L. Petraglia

Activated protein C inhibits tissue plasminogen activator–induced brain hemorrhage

Brain hemorrhage is a serious complication of tissue plasminogen activator (tPA) therapy for ischemic stroke. Here we report that activated protein C (APC), a plasma serine protease with systemic anticoagulant, anti-inflammatory and antiapoptotic activities, and direct vasculoprotective and neuroprotective activities, blocks tPA-mediated brain hemorrhage after transient brain ischemia and embolic stroke in rodents. We show that APC inhibits a pro-hemorrhagic tPA-induced, NF-κB–dependent matrix metalloproteinase-9 pathway in ischemic brain endothelium in vivo and in vitro by acting through protease-activated receptor 1. The present findings suggest that APC may improve thrombolytic therapy for stroke, in part, by reducing tPA-mediated hemorrhage.

The Spectrum of Neurobehavioral Sequelae after Repetitive Mild Traumatic Brain Injury: A Novel Mouse Model of Chronic Traumatic Encephalopathy

There has been an increased focus on the neurological sequelae of repetitive mild traumatic brain injury (TBI), particularly neurodegenerative syndromes, such as chronic traumatic encephalopathy (CTE); however, no animal model exists that captures the behavioral spectrum of this phenomenon. We sought to develop an animal model of CTE. Our novel model is a modification and fusion of two of the most popular models of TBI and allows for controlled closed-head impacts to unanesthetized mice. Two-hundred and eighty 12-week-old mice were divided into control, single mild TBI (mTBI), and repetitive mTBI groups. Repetitive mTBI mice received six concussive impacts daily for 7 days. Behavior was assessed at various time points. Neurological Severity Score (NSS) was computed and vestibulomotor function tested with the wire grip test (WGT). Cognitive function was assessed with the Morris water maze (MWM), anxiety/risk-taking behavior with the elevated plus maze, and depression-like behavior with the forced swim/tail suspension tests. Sleep electroencephalogram/electromyography studies were performed at 1 month. NSS was elevated, compared to controls, in both TBI groups and improved over time. Repetitive mTBI mice demonstrated transient vestibulomotor deficits on WGT. Repetitive mTBI mice also demonstrated deficits in MWM testing. Both mTBI groups demonstrated increased anxiety at 2 weeks, but repetitive mTBI mice developed increased risk-taking behaviors at 1 month that persist at 6 months. Repetitive mTBI mice exhibit depression-like behavior at 1 month. Both groups demonstrate sleep disturbances. We describe the neurological sequelae of repetitive mTBI in a novel mouse model, which resemble several of the neuropsychiatric behaviors observed clinically in patients sustaining repetitive mild head injury.

An overview of the basic science of concussion and subconcussion: where we are and where we are going

There has been a growing interest in the diagnosis and management of mild traumatic brain injury (TBI), or concussion. Repetitive concussion and subconcussion have been linked to a spectrum of neurological sequelae, including postconcussion syndrome, chronic traumatic encephalopathy, mild cognitive impairment, and dementia pugilistica. A more common risk than chronic traumatic encephalopathy is the season-ending or career-ending effects of concussion or its mismanagement. To effectively prevent and treat the sequelae of concussion, it will be important to understand the basic processes involved. Reviewed in this paper are the forces behind the primary phase of injury in mild TBI, as well as the immediate and delayed cellular events responsible for the secondary phase of injury leading to neuronal dysfunction and possible cell death. Advanced neuroimaging sequences have recently been developed that have the potential to increase the sensitivity of standard MRI to detect both structural and functional abnormalities associated with concussion, and have provided further insight into the potential underlying pathophysiology. Also discussed are the potential long-term effects of repetitive mild TBI, particularly chronic traumatic encephalopathy. Much of the data regarding this syndrome is limited to postmortem analyses, and at present there is no animal model of chronic traumatic encephalopathy described in the literature. As this arena of TBI research continues to evolve, it will be imperative to appropriately model concussive and even subconcussive injuries in an attempt to understand, prevent, and treat the associated chronic neurodegenerative sequelae.

The pathophysiology underlying repetitive mild traumatic brain injury in a novel mouse model of chronic traumatic encephalopathy.

Background: An animal model of chronic traumatic encephalopathy (CTE) is essential for further understanding the pathophysiological link between repetitive head injury and the development of chronic neurodegenerative disease. We previously described a model of repetitive mild traumatic brain injury (mTBI) in mice that encapsulates the neurobehavioral spectrum characteristic of patients with CTE. We aimed to study the pathophysiological mechanisms underlying this animal model. Methods: Our previously described model allows for controlled, closed head impacts to unanesthetized mice. Briefly, 12-week-old mice were divided into three groups: Control, single, and repetitive mTBI. Repetitive mTBI mice received six concussive impacts daily, for 7 days. Mice were then subsequently sacrificed for macro- and micro-histopathologic analysis at 7 days, 1 month, and 6 months after the last TBI received. Brain sections were immunostained for glial fibrillary acidic protein (GFAP) for astrocytes, CD68 for activated microglia, and AT8 for phosphorylated tau protein. Results: Brains from single and repetitive mTBI mice lacked macroscopic tissue damage at all time-points. Single mTBI resulted in an acute rea ctive astrocytosis at 7 days and increased phospho-tau immunoreactivity that was present acutely and at 1 month, but was not persistent at 6 months. Repetitive mTBI resulted in a more marked neuroinflammatory response, with persistent and widespread astrogliosis and microglial activation, as well as significantly elevated phospho-tau immunoreactivity to 6-months. Conclusions: The neuropathological findings in this new model of repetitive mTBI resemble some of the histopathological hallmarks of CTE, including increased astrogliosis, microglial activation, and hyperphosphorylated tau protein accumulation.

From the field of play to the field of combat: a review of the pharmacological management of concussion.

Traditionally, the medical management of concussion has involved close observation and physical and cognitive rest. Most postconcussive symptoms resolve spontaneously and require only conservative treatment. However, some patients have prolonged recoveries and may benefit from treatment with medications. Some naturally occurring compounds demonstrate multimechanistic neuroprotective properties and may be potential treatment considerations. For the most part, however, current treatments are symptom based for those with persistent postconcussive symptoms. The evidence supporting the various pharmacologic treatments in concussion is equivocal. The choice of which medication to use for a patient depends on the symptom characteristics, and each decision should be made on an individual-case basis. There is a need for well-designed trials investigating the efficacy of various medical therapies.

Activated protein C is neuroprotective and mediates new blood vessel formation and neurogenesis after controlled cortical impact.

OBJECTIVEActivated protein C (APC) is neuroprotective in stroke models and promotes postischemic neovascularization and neurogenesis. We used a controlled cortical impact (CCI) in mice to determine the effects of APC on neuroprotection and angiogenesis and neurogenesis after traumatic brain injury (TBI). METHODSMice were given (1) single-dose APC (0.8 mg/kg intraperitoneally) 15 minutes after injury, (2) multidose APC (0.8 mg/kg intraperitoneally) 15 minutes and 6 to 48 hours after injury, or (3) vehicle. We then assessed the effects of APC on posttraumatic motor function with the rotarod and wire grip and beam balance tasks, and we determined the lesion volumes and studied the formation of new blood vessels and markers of neurogenesis. RESULTSMice treated with single-dose or multidose APC, compared with vehicle, showed significantly improved motor function on all tests. In the single-dose and multidose APC treatment groups, at 7 days after treatment, lesion volume was significantly decreased by 30% and 50%, respectively. Multidose APC, but not single-dose APC, increased new blood vessel formation as shown by CD105+/Ki-67+ double immunostaining by nearly 2-fold at 7 days. Multidose APC also promoted posttraumatic proliferation of neuroblasts in the subventricular zone (SVZ) and their migration from the SVZ to the perilesional area. CONCLUSIONActivated protein C improves functional outcome and is neuroprotective after TBI. It also promotes angiogenesis and survival and migration of neuroblasts from the SVZ to the perilesional area, but the exact role of these brain repair mechanisms remains to be determined. The present findings suggest that APC therapy may hold a significant therapeutic potential for TBI.

Repetitive traumatic brain injury and development of chronic traumatic encephalopathy: a potential role for biomarkers in diagnosis, prognosis, and treatment?

The diagnosis of chronic traumatic encephalopathy (CTE) upon autopsy in a growing number of athletes and soldiers alike has resulted in increased awareness, by both the scientific/medical and lay communities, of the potential for lasting effects of repetitive traumatic brain injury. While the scientific community has come to better understand the clinical presentation and underlying pathophysiology of CTE, the diagnosis of CTE remains autopsy-based, which prevents adequate monitoring and tracking of the disease. The lack of established biomarkers or imaging modalities for diagnostic and prognostic purposes also prevents the development and implementation of therapeutic protocols. In this work the clinical history and pathologic findings associated with CTE are reviewed, as well as imaging modalities that have demonstrated some promise for future use in the diagnosis and/or tracking of CTE or repetitive brain injury. Biomarkers under investigation are also discussed with particular attention to the timing of release and potential utility in situations of repetitive traumatic brain injury. Further investigation into imaging modalities and biomarker elucidation for the diagnosis of CTE is clearly both needed and warranted.

Models of mild traumatic brain injury: translation of physiological and anatomic injury

: Mild traumatic brain injury (TBI) has become a rising epidemic, affecting millions of people each year. Even though it is the most common type of brain injury, our understanding of the science underlying mild TBI is just in its infancy. There has been an explosion of basic science research interest in mild TBI, as emerging clinical evidence is suggestive that concussion and subconcussion may result in detrimental long-term neurological sequelae, particularly when occurring repetitively. Many animal models have been developed to study the different pathological mechanisms implicated in TBI, and more recently there has been a heightened focus on modeling mild TBI in the laboratory as well. The most widely used models of TBI have been adapted for experimental mild TBI research, although more work still remains. The ability to create improved diagnostic measures and treatment approaches for concussion depend on the development and characterization of clinically relevant models of mild TBI. This review aims to provide a broad general overview of the current efforts to model mild TBI in animals and the challenges and limitations that exist in translating this behavioral, physiological, and anatomic knowledge from the bench to the clinical arena. ABBREVIATIONS:: CBF, cerebral blood flowCCI, controlled cortical impactCTE, chronic traumatic encephalopathyFPI, fluid percussion injuryLOC, loss of consciousnessMWM, Morris water mazeNSS, neurological severity scorePCI, projectile concussive impactTBI, traumatic brain injury. Language: enMild traumatic brain injury (TBI) has become a rising epidemic, affecting millions of people each year. Even though it is the most common type of brain injury, our understanding of the science underlying mild TBI is just in its infancy. There has been an explosion of basic science research interest in mild TBI, as emerging clinical evidence is suggestive that concussion and subconcussion may result in detrimental long-term neurological sequelae, particularly when occurring repetitively. Many animal models have been developed to study the different pathological mechanisms implicated in TBI, and more recently there has been a heightened focus on modeling mild TBI in the laboratory as well. The most widely used models of TBI have been adapted for experimental mild TBI research, although more work still remains. The ability to create improved diagnostic measures and treatment approaches for concussion depend on the development and characterization of clinically relevant models of mild TBI. This review aims to provide a broad general overview of the current efforts to model mild TBI in animals and the challenges and limitations that exist in translating this behavioral, physiological, and anatomic knowledge from the bench to the clinical arena.

Activated protein C analog with reduced anticoagulant activity improves functional recovery and reduces bleeding risk following controlled cortical impact

The anticoagulant activated protein C (APC) protects neurons and vascular cells from injury through its direct cytoprotective effects that are independent of its anticoagulant action. Wild-type recombinant murine APC (wt-APC) exerts significant neuroprotection in mice if administered early after traumatic brain injury (TBI). Here, we compared efficacy and safety of a late therapy for TBI with wt-APC and 3K3A-APC, an APC analog with approximately 80% reduced anticoagulant activity but normal cytoprotective activity, using a controlled cortical impact model of TBI. Mice received 0.8 mg/kg intraperitoneally of recombinant murine 3K3A-APC, wt-APC or saline at 6, 12, 24 and 48 h after injury. 3K3A-APC (n=15) relative to wt-APC (n=15) improved motor and sensorimotor recovery within the first three days post-trauma as demonstrated by rotarod (p<0.05) and beam balance test (p<0.05), respectively. Both, wt-APC and 3K3A-APC reduced the lesion volume seven days after injury by 36% (n=8; p<0.01) and 56% (n=8; p<0.01), respectively, compared to saline (n=8). Three days post-TBI, the hemoglobin levels in the injured brain were increased by approximately 3-fold after wt-APC treatment compared to saline indicating an increased risk for intracerebral bleeding. In contrast, comparable levels of brain hemoglobin in 3K3A-APC-treated and saline-treated mice suggested that 3K3A-APC treatment did not increase risk for bleeding after TBI. Thus, compared to wt-APC, 3K3A-APC is more efficacious and safer therapy for TBI with no risk for intracerebral hemorrhage.

Outcomes after anterior cervical discectomy and fusion in professional athletes

BACKGROUND Significant controversy exists regarding when an athlete may return to contact sports after anterior cervical discectomy and fusion (ACDF). Return-to-play (RTP) recommendations are complicated due to a mix of medical factors, social pressures, and limited outcome data. OBJECTIVE The aim of this study was to characterize our diagnostic and surgical criteria, intervention, postoperative imaging results, and rehabilitation and report RTP decisions and outcomes for professional athletes with cervical spine injuries. METHODS Fifteen professional athletes who had undergone a 1-level ACDF by a single neurosurgeon were identified after a retrospective chart and radiographic review from 2003 to 2012. Patient records and imaging studies were recorded. RESULTS Seven of the 15 athletes presented with neurapraxia, 8 with cervical radiculopathy, and 2 with hyperintensity of the spinal cord. Cervical stenosis with effacement of the cerebrospinal fluid signal was noted in 14 subjects. The operative level included C3-4 (4 patients), C4-5 (1 patient), C5-6 (8 patients), and C6-7 (2 patients). All athletes were cleared for RTP after a neurological examination with normal findings, and radiographic criteria for early fusion were confirmed. Thirteen of the 15 players returned to their sport between 2 and 12 months postoperatively (mean, 6 months), with 8 still participating. The RTP duration of the 5 who retired after full participation ranged from 1 to 3 years. All athletes remain asymptomatic for radicular or myelopathic symptoms or signs. CONCLUSION After a single-level ACDF, an athlete may return to contact sports if there are normal findings on a neurological examination, full range of neck movement, and solid arthrodesis. There may be an increased risk of the development of adjacent segment disease above or below the level of fusion. Cord hyperintensity may not necessarily preclude RTP.