| Abstract No.: | A-C1111 |
| Country: | Canada |
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| Title: | A ROLE FOR LIPOCALIN 2 IN SPINAL CORD INJURY |
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| Authors/Affiliations: | 1 Khizr Rathore*; 1 Adriana Redensek; 1 Ruben Lopez-vales; 2 Manuela Santos; 1 Samuel David;
1 McGill University Health Centre, Centre for Research in Neuroscience, Montreal, QC, Canada; 2 University of Montreal Hospital Centre, Montreal, QC, Canada
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| Content: | Lipocalin 2 (Lcn2) is an acute phase protein involved in the innate immune response and in the apoptosis of cells, and has been implicated in a number of inflammatory disorders. Earlier reports had shown that Lcn2 sequesters iron-loaded siderophores. This iron chelation was shown to be the basis of its bacteriostatic function as well as its ability to induce and promote apoptosis in certain mammalian cells. Our previous work in spinal cord contusion injury has shown that iron-mediated oxidative mechanisms can promote significant secondary damage after SCI. Based on these results we hypothesized that Lcn2 may play a role in spinal cord injury.
Objectives: To assess the role of Lcn2 in spinal cord contusion injury.
Materials and Methods: Using the IH impactor, 60 kdyne spinal cord contusion injuries were performed on Lcn2-/- mice and C57BL/6 controls. Functional recovery was assessed in these mice for a period of 28 days using the Basso Mouse Scale, an open-field locomotor test. Tissue was harvested for mRNA expression studies, western blotting and histological assessment at 1, 3, 7, 14, 21 and 28 days post injury.
Results: We first assessed the expression of Lcn2 after spinal cord injury. Based on semi-quantitative RT-PCR analysis, there is ~ 4-fold induction of Lcn2 mRNA expression in the injured spinal cord at 1 dpi and this induction is maintained through 3, 7, 21 days post injury. Western blot analysis revealed that Lcn2 is robustly induced in the injured spinal cord after SCI, with expression peaking at 1dpi being ~14 fold higher than uninjured animals. Lcn2 protein levels then dropped to ~3 fold higher at 3dpi and remained at those levels through to 28dpi. Immunofluorescent staining in frozen sections revealed a few Mac-1+ microglia around the lesion site positive for Lcn2 at 7 dpi. At 28 dpi Lcn2 labeling was localized to GFAP+ reactive astrocytes surrounding the lesion site. Functional recovery was significantly better in Lcn2-/- mice than in control animals.
Lcn2-/- mice scored a 4.1, which corresponds to occasional stepping, at day 10. In comparison control animals scored a 3.0, corresponding to paw placement but no stepping. At day 28 Lcn2-/- mice scored a 4.9. In contrast, control mice scored a 3.8, and none were frequently stepping (a score of 5). Fine motor skills including paw placement and co-ordination were also significantly better in Lcn2-/- mice.
Conclusions: Our results show that Lcn2 is induced after spinal cord injury and that it plays a detrimental role after SCI. Lcn2-/- mice have significantly better functional recovery compared to wildtype controls. At present, experiments are underway to elucidate the mechanisms through which Lcn2 exerts its detrimental effects after SCI.
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