Alumni
D. Kacy Cullen, PhD
Post-Doctoral Researcher in Smith Lab from 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.
Min Tang–Schomer, PhD
Post-doctoral Researcher in Smith Lab from 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.
Xiao–Han Chen, MD
Senior Research Specialist in Smith Lab from 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).
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.
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.
Former Students
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.
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.
