Neurosurgery

Laboratories

Alumni

Xiao-Han Chen, MD

Senior Research Specialist in Smith Lab (1995–2009)

Xiao-Han, originally a neuropathologist in China, has dedicated her time mainly toward the research of pathological consequences of brain trauma in the patients and animal models of traumatic brain injury. A major role of her research is to investigate the mechanism of neuronal and axonal degeneration response of the adult brain over a prolonged period of time following a traumatic brain injury, and the relationship between brain injuries and neurodegenerative disease in vivo. In the head rotational acceleration pig model, she has found axonal injury and amyloid beta (Aß) accumulation, which is a hallmark pathological feature of Alzheimer's disease (AD) that is mediated by ß-secretase and presenilin (American Journal of Pathology 2004 165 (2): 357–371). In brain trauma patients, she has recently demonstrated that 1) axonal degeneration and accumulation of interaxonal Aß, as well as its mediators in the brain tissue for up to 10 years post-injury, but no plaque formation; 2) increase of amyloid degrading enzyme neprilsyin is a primary candidate in Aß clearance after brain trauma (Brain Pathology 2008 May (19): 1–10). Additionally, she has focused on evaluating the immediate and evolving effects related to changes in the voltage-gated sodium channels in the white matter following TBI in the pig. She is also assisting some projects of drug study including Novo7 (Exp Neurol 2008 (2): 645-655) and tPA in the treatment of TBI and stroke (Nature Neuroscience 2006 9 (9): 1150–1155).

D. Kacy Cullen, PhD

Post-Doctoral Researcher in Smith Lab (2007–2009)
Currently: Assistant Research Professor of Neurosurgery at the University of Pennsylvania

Dr. Cullen is a post-doctoral researcher whose research interests include traumatic neural injury, neural tissue engineering, and the development of enabling technologies for long-term neurobiological-electromechanical interfaces. His focus is in the application of living tension-grown tissue engineered nerve constructs towards two interrelated thrusts. First, the development of strategies for repairing peripheral nerve damage following trauma, done in collaboration with Kevin Browne, where elongated axonal constructs are surgically implanted to repair large peripheral nerve defects by integrating with host nerve or serving as a growth conduit for regeneration. Second, the engineering of sustained, bi-directional neural prosthetic interfaces, in collaboration with Niranjan Kameswaran, where elongated axonal constructs functionally interact with both host cells and arrays of extracellular electrodes.

Dr. Cullen is a member of the American Society of Mechanical Engineers and the National Neurotrauma Society.

Andrew Eng

Lab Technician (2007–2010)
Currently: Grad student at Northwestern University

Andrew is a recent graduate of Boston University with a developing interest in neuroscience. He collaborates with Min to examine the mechanisms of stretch growth in vitro and the effect of drug treatment in the cortical culture stretch injury model, is a member of the team conducting studies using the pig model, and assists Kevin with the spinal cord project.

Kristin Hamann, PhD, DVM

Post-doctoral Researcher in Smith lab (2010–2011)

Dr. Hamann was a postdoctoral researcher interested in mechanisms of repair and degeneration following head trauma. She received her DVM and PhD from Purdue University. She graduated Magna Cum Laude from Texas A&M University with a BS in Zoology and a Spanish minor.

Amy Kim, BS
Amy Kim, BS

Research Specialist C
amyakim@mail.med.upenn.edu

Amy is a research specialist focusing on the Department of Defense-funded Spinal Cord Injury project. After graduating from Haverford College with a BS in Biology, Amy has spent a number of years focusing on neuroscience research, specifically studying spinal cord injury. Amy uses stretch-grown dorsal root ganglion nerve constructs to bridge extensive SCI lesions in a complete transection model. Her aim is graft integration and functional restoration below the lesion. Amy is also interested in investigating myelination of stretch-grown axon constructs.

Timur Litvinov, MD, PhD
Timur Litvinov, MD

Visiting Scholar
timurlit@mail.med.upenn.edu

Timur is a visiting scholar from Kazan, Russia, with 10 years of clinical experience as a neurosurgeon in traumatic brain injury (TBI). He received a PhD in 2009 after studying late neurological and psychological consequences of TBI, such as the post-concussion syndrome. He has found that the so called mild TBI may have long-term serious sequels, seemingly disproportionate to the severity of the head trauma. He has recently joined the Smith Lab to investigate new mechanisms of brain damage and neuronal regeneration and has been involved in a number of current and prospective experimental projects.

Min Tang-Schomer, PhD

Post-doctoral Researcher in Smith Lab (2006–2010)

Min Tang-Schomer obtained her PhD in Biomedical Engineering from Boston University, specializing in tissue engineering of the microvasculature and cellular behavior in 3D environments. During her postdoctoral training under Dr. Douglas Smith, Min developed research interests in the biomechanical behaviors of the axon. Min set out on two parallel journeys towards pursuing the mechanisms of axon mechanical injury and extreme stretch growth. Her efforts in examining the primary biomechanical mechanisms during TBI led to the finding of microtubule breaking at times of injury to the axon (the FASEB Journal 2010; 24: 1401-1410). This finding provides mechanistic understanding of the characteristic pathological presentations of diffuse axonal injury (DAI) in the brain, and has potential therapeutic implications. In studying the novel approach of axon stretch growth, which produces extremely long axon tracts at surprisingly fast rates, Min uncovered a unique "extrusion" type of growth whereas the axon grows new length from its proximal region, unlike the well-established growth-cone directed axon elongation from its distal end. This work may provide understanding of the under-studied yet fundamental developmental stage of axon growth after they form synaptic contacts, as well as a novel approach for growing long axons. Additionally, Min used innovative engineering approaches to improve existing model systems. For example, she adapted microfluidics techniques to the in vitro axon injury model, in order to generate axon tracts that mimic brain circuits. She also created transplantable nerve conduit as replacement for axon pathways in the brain. The two aspects of axonal biology, growth and injury, complemented with Min's engineering expertise will guide Min in her future pursuit for therapeutic alternatives for nervous system repair.

Xiangsheng Xu, MD

Research Specialist in Smith/Stein Lab until 2009

Xiangsheng's work focuses on the relationship between traumatic brain injury (TBI) and coagulopathy. Trained as a molecular biologist, she is interested in examining the interaction between tissue plasminogen activator (tPA) and certain receptors and their roles in tPA–mediated signal transduction. In conjunction with Dr. Sherman Stein, she is currently researching novel ways of delivering tPA to the site of injury, and is interested in improving the pharmacological efficacy of thromolytic and coagulopathic drugs.

Former Students

Alexander Dickson

Applied Science in Biomedical Science
Class of 2012

Alexander's class project centered around searching for a characteristic vibration frequency that neurons might use to communicate and direct axon outgrowth. The project required the creation of a device to produce vibrations at a specific location in a cortical neural cell culture, and the characterization of this device for accuracy. The device was tested in culture at a variety of frequencies and the effects of the vibrations on cell behavior were recorded. The characteristic frequency has not yet been determined, but we are confident with future study it can be verified, and that it may be used therapeutically to heal trauma to the brain, spine and peripheral nervous system.

Niranjan Kameswaran, Ph.D.

Former Graduate Student (2004–2009)

Niranjan was a doctoral candidate designing a neuro-electrical interface with the aim of restoring peripheral function. His research involved methods of integrating nervous tissue constructs with the damaged host nerve and recording the evoked electrophysiological responses using specially fabricated electrodes. In addition to this, he also assisted Kevin Browne and Dr. Kacy Cullen in the Spinal Cord and PNS repair studies.

Sonia Kartha, BA

Chemistry
Class of 2012

Sonia graduated from the University of Pennsylvania with a BA in Chemistry in 2012. She has been a part of the Smith Lab for the entirety of her undergraduate degree, working on various projects including the development of white matter constructs through the in vitro myelination of stretch-growth constructs and more recently studying the neurochemical changes of amyloid-beta in cortical axons following injury. Her time in the Smith Lab has sparked her interests in neuroscience and she plans to continue studying neurodegeneration within the context of trauma in the future.

Ankur Patel

Former BSE Candidate in Bioengineering

Ankur's work in the lab involved studying cortical axonal injury using an in vitro model. He was specifically characterizing calcium influx and sodium channel expression following repetitive uni-axial injury at various strain levels with Dr. Min Tang-Schomer. He was also working on culturing neurons on electrically conducting polymer fibers.