Semester

Summer

Date of Graduation

2013

Document Type

Dissertation

Degree Type

PhD

College

School of Medicine

Department

Physiology, Pharmacology & Neuroscience

Committee Chair

Charles L. Rosen.

Abstract

The translation of therapeutic agents for ischemic stroke and traumatic brain injury from the preclinical laboratory to clinical trials has been fraught with failure as evident by the 1,000+ preclinical studies that have failed to translate to a proven therapeutic clinically. Numerous potential reasons for these shortcomings have been identified and include the use of animal models that fail to capture clinically relevant risk factors or injury parameters, targeting of pathological events occurring rapidly after injury but before the likely time of patient presentation for treatment, emphasis on acute rather than chronic outcome measures, and mismatch in outcome measures used between preclinical and clinical studies. To address these shortcomings, we describe the use of aged animals in a clinically relevant model of ischemic stroke produced through thrombus insertion and reperfusion mediated via administration of tissue plasminogen activator (tPA), the only FDA-approved pharmacologic agent for treatment of ischemic stroke. Using this ischemic stroke model with tPA administered at 2 hours post-stroke, we demonstrate the neuroprotective properties of bryostatin-1, a protein kinase c (PKC) modulator. Specifically, bryostatin-1 treated animals displayed an improved survival rate, reduced infarct volume, and diminished functional impairment following ischemic stroke. As tPA administration is limited clinically by the time of presentation, extending the therapeutic window will be therapeutically advantageous. We show, in our aged model of ischemic stroke, that administration of a recombinant human apyrase (APT 102), a novel form of the naturally occurring human apyrase/ADPase, improves the safety and efficacy of tPA administration at 6 hours post-stroke based on functional and histological endpoints. Furthermore, we characterized behavioral and functional deficits following ischemia at numerous time points in order to more closely replicate clinical studies that emphasize behavioral outcomes rather than the use of infarct volume or other histological measures as an experimental endpoint. These studies demonstrate a significant correlation between infarct volume and functional ability, particularly with regards to striatal infarcts. Similar paradigms were applied to a diffuse axonal injury model and revealed no substantive deficits between injured and non-injured animals within one week of trauma. This indicates the challenge of identifying injury severity in preclinical trauma models as the lack of deficits is more representative of subconcussive injury rather than concussion or more substantive brain injury. Using this diffuse axonal injury model, we also explore preventative measures drawing on biologically inspired discovery. We show for the first time, the ability to reduce intracranial injury through manipulation of the vasculature through an externally applied device. Data from these studies demonstrate potential advances addressing the shortcomings associated with neural injury research, namely the development and use of clinically relevant animal models, selection of appropriate experimental endpoints, and varied approaches to both improving neural injury prevention and treatment.

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