Use of a Conformational Switching Aptamer for Rapid and Specific Ex Vivo Identification of Central Nervous System Lymphoma in a Xenograft Model

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Description

Improved tools for providing specific intraoperative diagnoses could improve patient care. In neurosurgery, intraoperatively differentiating non-operative lesions such as CNS B-cell lymphoma from operative lesions can be challenging, often necessitating immunohistochemical (IHC) procedures which require up to 24-48 hours. Here,

Improved tools for providing specific intraoperative diagnoses could improve patient care. In neurosurgery, intraoperatively differentiating non-operative lesions such as CNS B-cell lymphoma from operative lesions can be challenging, often necessitating immunohistochemical (IHC) procedures which require up to 24-48 hours. Here, we evaluate the feasibility of generating rapid ex vivo specific labeling using a novel lymphoma-specific fluorescent switchable aptamer. Our B-cell lymphoma-specific switchable aptamer produced only low-level fluorescence in its unbound conformation and generated an 8-fold increase in fluorescence once bound to its target on CD20-positive lymphoma cells. The aptamer demonstrated strong binding to B-cell lymphoma cells within 15 minutes of incubation as observed by flow cytometry. We applied the switchable aptamer to ex vivo xenograft tissue harboring B-cell lymphoma and astrocytoma, and within one hour specific visual identification of lymphoma was routinely possible. In this proof-of-concept study in human cell culture and orthotopic xenografts, we conclude that a fluorescent switchable aptamer can provide rapid and specific labeling of B-cell lymphoma, and that developing aptamer-based labeling approaches could simplify tissue staining and drastically reduce time to histopathological diagnoses compared with IHC-based methods. We propose that switchable aptamers could enhance expeditious, accurate intraoperative decision-making.

Date Created
2015-04-15
Agent

Severe traumatic brain injury induces cortical remodeling in the pediatric inhibitory network

Description
Pediatric traumatic brain injury (TBI) is a leading cause of death and disability in children. When TBI occurs in children it often results in severe cognitive and behavioral deficits. Post-injury, the pediatric brain may be sensitive to the

Pediatric traumatic brain injury (TBI) is a leading cause of death and disability in children. When TBI occurs in children it often results in severe cognitive and behavioral deficits. Post-injury, the pediatric brain may be sensitive to the effects of TBI while undergoing a number of age-dependent physiological and neurobiological changes. Due to the nature of the developing cortex, it is important to understand how a pediatric brain recovers from a severe TBI (sTBI) compared to an adult. Investigating major cortical and cellular changes after sTBI in a pediatric model can elucidate why pediatrics go on to suffer more neurological damage than an adult after head trauma. To model pediatric sTBI, I use controlled cortical impact (CCI) in juvenile mice (P22). First, I show that by 14 days after injury, animals begin to show recurrent, non-injury induced, electrographic seizures. Also, using whole-cell patch clamp, layer V pyramidal neurons in the peri-injury area show no changes except single-cell excitatory and inhibitory synaptic bursts. These results demonstrate that CCI induces epileptiform activity and distinct synaptic bursting within 14 days of injury without altering the intrinsic properties of layer V pyramidal neurons. Second, I characterized changes to the cortical inhibitory network and how fast-spiking (FS) interneurons in the peri-injury region function after CCI. I found that there is no loss of interneurons in the injury zone, but a 70% loss of parvalbumin immunoreactivity (PV-IR). FS neurons received less inhibitory input and greater excitatory input. Finally, I show that the cortical interneuron network is also affected in the contralateral motor cortex. The contralateral motor cortex shows a loss of interneurons and loss of PV-IR. Contralateral FS neurons in the motor cortex synaptically showed greater excitatory input and less inhibitory input 14 days after injury. In summary, this work demonstrates that by 14 days after injury, the pediatric cortex develops epileptiform activity likely due to cortical inhibitory network dysfunction. These findings provide novel insight into how pediatric cortical networks function in the injured brain and suggest potential circuit level mechanisms that may contribute to neurological disorders as a result of TBI.
Date Created
2015
Agent

Traumatic brain injury induces rapid enhancement of cortical excitability in juvenile rats

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Description
Following a traumatic brain injury (TBI) 5-50% of patients will develop post traumatic epilepsy (PTE). Pediatric patients are most susceptible with the highest incidence of PTE. Currently, we cannot prevent the development of PTE and knowledge of basic

Following a traumatic brain injury (TBI) 5-50% of patients will develop post traumatic epilepsy (PTE). Pediatric patients are most susceptible with the highest incidence of PTE. Currently, we cannot prevent the development of PTE and knowledge of basic mechanisms are unknown. This has led to several shortcomings to the treatment of PTE, one of which is the use of anticonvulsant medication to the population of TBI patients that are not likely to develop PTE. The complication of identifying the two populations has been hindered by the ability to find a marker to the pathogenesis of PTE. The central hypothesis of this dissertation is that following TBI, the cortex undergoes distinct cellular and synaptic reorganization that facilitates cortical excitability and promotes seizure development. Chapter 2 of this dissertation details excitatory and inhibitory changes in the rat cortex after severe TBI. This dissertation aims to identify cortical changes to a single cell level after severe TBI using whole cell patch clamp and electroencephalogram electrophysiology. The work of this dissertation concluded that excitatory and inhibitory synaptic activity in cortical controlled impact (CCI) animals showed the development of distinct burst discharges that were not present in control animals. The results suggest that CCI induces early "silent" seizures that are detectable on EEG and correlate with changes to the synaptic excitability in the cortex. The synaptic changes and development of burst discharges may play an important role in synchronizing the network and promoting the development of PTE.
Date Created
2014
Agent