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Optical Imaging and Microendoscopy of Traumatic Brain Injury

(Developmental Collaborator-Driven Research Project)

UC Davis: G Gurkoff, P Schwartzkroin, R Berman, B Lyeth, FYS Chuang; 

Stanford: T Ko, MJ Schnitzer

According to the Centers for Disease Control, there is an average of 1.5 million reported cases of Traumatic Brain Injury (TBI) per year resulting in over 1 million emergency department visits, 235,000 hospitalizations and 50,000 deaths annually. One of the limitations of TBI research is the inability to conduct longitudinal studies either in vitro or in vivo making it difficult to study either the mechanisms or the treatment of TBI over the progression of the disease. We hope to combine existing and well characterized TBI models with several biophotonic techniques (such as spinning disk confocal, surface enhanced Raman spectroscopy, super-resolution microscopy, and microendoscopy) to enhance the spatial and temporal resolution of our experiments.  With greater understanding of the mechanisms and progression of TBI-induced injury, we stand a better chance in developing successful therapeutic interventions 

We are studying a number of TBI models including 1) Ellis Model of Mechanical Cell Injury: cortical neurons and astrocytes are cultured atop a silastic membrane. A mechanical strain is applied to those cells (akin to human TBI) creating a mild, moderate or severe injury. There is an injury dependent physiological response of cultured cells to injury including sodium and calcium influx which leads to cellular pathology and subsequent cell death. 2) Cortical Contusion Injury (CCI): CCI is a model of focal TBI.  A small craniotomy is made and an impactor is driven into the cortex. Both depth and rate of impact are controlled to create a range of severities. Outcome measures including cell death and cognitive performance correlate with injury severity. 3) Fluid Percussion Injury (FPI): FPI is a model of diffuse TBI.  A small craniotomy is made and fluid pulse is driven into the cortex.  Adjusting the force of the injected fluid allows for a range of injury severities.  Outcome measures including cell death and cognitive performance which correlates with injury severity.

Our goal is to apply a range of advanced imaging modalities to the investigation of the in vivo TBI models. These modalities include in vivo imaging using microendoscopy. In the same way as with the tumor study, we plan to investigate TBI by using these same mouse models to compare an injury to one hemisphere to the control hemisphere. Animals will be imaged long-term by taking advantage of fluorescent probes.  Using both an arc-lamp source and 2-photon microscopy we will follow the TBI-induced pathophysiology in both the cortex (cortical window) and hippocampus (microendoscope). Our primary interests include changes in the vasculature, cell death and stem cells.

Fluorescent labeled neurons and astrocytes have been obtained and initial data fluorescent imaging data is being obtained for intact and injured cells in culture. Super-resolution images using our new OMX microscope are now being generated.