Quantif ication of Macrophage Response in Contusion and Laceration Spinal Cord Injuries

F a c u l t y M e n t o r Michelle Tu’s interest in stem cells began when she read about the promise of stem cell research; she was amazed by their unique features, especially their ability to differentiate into any cell type in the body. She was drawn to Professor Keirstead’s study on humanembryonic stem cell-derived oligodendrocyte progenitor cells in spinal cord injury. Michelle describes her research experience as eye-opening and inspiring. Through her experience, she has acquired a genuine passion for stem cell research. Michelle spent the summer of 2007 conducting stem cell research at UC San Francisco and graduated from UCI in spring 2008. She hopes to continue into graduate school and ultimately become a stem cell scientist. S cord injury (SCI) is damage to the spinal cord that leads to physiological impairment. This loss of function can be partly attributed to the chronic progressive demyelination of axons following SCI. We have previously shown that transplantation of human embryonic stem cell-derived oligodendrocyte progenitor cells after contusion injury results in enhanced remyelination and locomotor recovery. We recently demonstrated that contusion and laceration SCI pathologically differ. Examining the inflammatory response following SCI may reveal different responses to contusions and lacerations, which may explain the difference in myelin pathology. Our study examined macrophages, which have been shown to play a role in both demyelination and remyelination. We also looked at macrophages in grey and white matter following SCI. Eight female rats received contusion injuries and eight more received laceration injuries. Animals were sacrificed three and fourteen days post injury. Spinal cords were removed and embedded in optical coherence tomography compound. Through immunohistochemistry, the temporal and spatial response of macrophages was quantified. We found more macrophages in contusion than laceration injuries and more macrophages in grey than white matter, suggesting that the inflammatory and macrophage response correlates with the extent of different pathologies. This knowledge will aid in developing better targeted SCI therapies.