PLASTICITY OF THE CENTRAL NERVOUS SYSTEM AND FUNCTIONAL RECOVERY FOLLOWING SPINAL CORD INJURY By ADELE ELIZABETH BLUM A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2010 1 © 2010 Adele Elizabeth Blum 2 To my fiancé, my parents, and my sister, thank you for everything 3 ACKNOWLEDGMENTS First and foremost, I would like to thank everyone who has been there along the way to help me through this seemingly endless endeavor. There are so many people who have touched me one way or another and I greatly appreciate everything everyone has done for me. First, I would like to thank my biggest support system, my family. My parents and sister, Cheryl, Fred, and Robyn Blum, have always been supportive in every task I have undertaken. They have been there for me during the ups and downs and have given all of the advice I needed to succeed. I would not be the person I am today without the love and support that they have given me throughout my life. In addition, I am extremely lucky to have such a close extended family who has all given me the confidence and strength throughout this time. Next, I would like to express my complete gratitude to my fiancé, Nick. He has been there for me every step of the way. I can’t wait to spend the rest of my life with him. Next, I need to thank two very dear friends, Meredith Wang and Lauren Simmons, for their amazing support! I am not sure what I would have done without our weekly girls’ night. The one night of the week that I looked forward to relaxing and catching up. The Howland lab has been a home away from home for the past six years. I need to thank first and foremost Dr. Dena Howland, my mentor, who skillfully guided me through this process. Wilbur O’Steen, the best lab manager, thank you for all of your help and advice. Past lab mates including Dr. Nicole Tester and Dr. Stephanie Jefferson who taught me a lot of techniques that I have used throughout this research process. Current lab member, Sarah Mondello, thanks for all of the company. Lab is never boring when you are around. Last, but not least, I must thank my dissertation committee members, Dr. Paul Reier, Dr. Floyd Thompson, Dr. Steven Kautz, and Dr. Andrea Behrman. Thank you for all of your advice 4 and guidance. This process was made a lot better because I was able to discuss science with some of the best minds in the field. 5 TABLE OF CONTENTS page ACKNOWLEDGMENTS.................................................................................................................... 4 LIST OF FIGURES .............................................................................................................................. 9 ABSTRACT ........................................................................................................................................ 10 CHAPTER 1 BACKGROUND ......................................................................................................................... 12 Inhibitory Environment of the Central Nervous System after Spinal Cord Injury ................. 12 Myelin-Associated Molecules ............................................................................................ 13 Fibrotic Glial Scar Formation in Response to Central Nervous System Injury............... 15 Extracellular Matrix Molecule: Chondroitin Sulfate Proteoglycans ................................ 17 Developmental role ...................................................................................................... 18 Role in neural regeneration.......................................................................................... 18 Overcoming inhibition after central nervous system injury ...................................... 20 Inhibitory Molecules Distant From a Spinal Cord Lesion ................................................ 21 Plasticity of the Central Nervous System .................................................................................. 22 A Motor System Effected by Spinal Cord Injury: Locomotion ............................................... 25 Feline Model of Locomotion .............................................................................................. 25 Intraspinal Circuits............................................................................................................... 26 Supraspinal Control ............................................................................................................. 28 Anatomy of the corticospinal and rubrospinal tracts ................................................. 28 Role of the corticospinal and rubrospinal tracts in locomotion................................. 31 Beneficial Effects of Locomotor Training ......................................................................... 33 2 ALTERED OBSTACLE NEGOTIATION FOLLOWING LOW THORACIC HEMISECTION IN THE CAT .................................................................................................. 35 Introduction ................................................................................................................................. 35 Methods ....................................................................................................................................... 36 Spinal Hemisection Surgery................................................................................................ 37 Training and Assessments ................................................................................................... 38 Response type ............................................................................................................... 38 3-dimensional (3-D) angular kinematics .................................................................... 39 Approach and maximum heights................................................................................. 39 Vertical limb displacement .......................................................................................... 40 Histology .............................................................................................................................. 40 Statistical Analyses .............................................................................................................. 41 Results .......................................................................................................................................... 41 Basic Locomotion and Obstacle Negotiation..................................................................... 41 Qualitative Characterization of Post-Injury Obstacle Negotiation ................................... 42 Quantification of Post-Injury Obstacle Negotiation .......................................................... 43 6 Efficiency of Obstacle Negotiation .................................................................................... 44 Joint Contribution ................................................................................................................ 46 Leading Limb Preference .................................................................................................... 46 Discussion .................................................................................................................................... 47 Translational Impact ............................................................................................................ 48 Pathways Involved in Functional Recovery....................................................................... 49 Adaptive Strategies .............................................................................................................. 51 Locomotor Training Effects ................................................................................................ 52 Conclusions .......................................................................................................................... 53 3 PLASTICITY OF MULTIPLE PATHWAYS CONTRIBUTE TO AXONAL BRIDGING OF THE LESION SITE FOLLOWING INCOMPLETE SPINAL CORD INJURY IN THE ADULT CAT ................................................................................................ 61 Introduction ................................................................................................................................. 61 Methods ....................................................................................................................................... 63 Surgical Procedures ............................................................................................................. 63 Spinal hemisection injury and general care ................................................................ 63 Tract tracing .................................................................................................................. 64 Immunohistochemistry and Neuron Counts ...................................................................... 64 Statistics................................................................................................................................ 65 Results .......................................................................................................................................... 66 Propriospinal and Rubrospinal Tract Projections in the Normal Spinal Cord ................. 66 Quantification of Propriospinal Neurons ........................................................................... 67 Quantification of Rubrospinal