Poster abstracts

Poster number 83 submitted by Randall Carpenter

Humanized mice as a novel model for the study of inflammation after spinal cord injury

Randall S. Carpenter (Neuroscience Graduate Studies Program, The Ohio State University, Columbus, Ohio), Kristina A. Kigerl (Center for Brain and Spinal Cord Repair, The Ohio State University, Columbus, Ohio), Stefan Niewiesk (Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio), Phillip G. Popovich (Center for Brain and Spinal Cord Repair, The Ohio State University, Columbus, Ohio)

Abstract:
Developing pre-clinical spinal cord injury (SCI) models that better reflect the human condition will aid in the translation of potential therapeutics from bench to bedside. Immunocompromised mice, such as NOD-SCID-IL2rg/null (NSG), support engraftment of human blood stem cells and the development of a fully functional human immune system. Thus, humanized NSG (hNSG) mice could be utilized to more accurately reflect the inflammatory response during spinal cord injury and repair.

Newborn NSG mice were engrafted with human CD34+ hematopoietic stem cells, underwent a moderate SCI 12-14 weeks later, and allowed to recovery for 28 days. SCI resulted in an immediate loss of coordinated hind limb function with gradual recovery that plateaus at a BMS score of 4 (occasional plantar stepping). Mean lesion volume was 0.67 mm3 and lesion length 2076 µm. Spinal cord lesions were devoid of neurons and myelinated axons, with a rim of spared tissue containing a GFAP labeled glial scar. The lesion core consisted of Iba-1 immunolabeled phagocytic cells characteristic of macrophages that infiltrate the lesion after injury.

Flow cytometry of blood samples confirmed that 50% of total circulating cells were of human origin (hCD45+), and three distinct monocyte subtypes were identified by levels of cell surface markers CD14 and CD16. Labeling of spinal cord tissue with hCD45 identified the presence of human immune cells in the lesion core, many with a phagocytic phenotype typical of macrophages.

We have demonstrated that hNSG mice engraft human blood stem cells, resulting in the development of circulating human immune cells with specific populations of monocytes resembling those observe in humans. hNSG mice have recovery profiles and spinal cord lesions similar to what has been observed in other mouse strains. Finally, human immune cells were present in the lesion core and displayed a phenotype similar to phagocytic macrophages. In all, humanized mice represent a novel model for the study of inflammation after spinal cord injury.

Keywords: Spinal Cord Injury, Inflammation, Immunology