Society for Neuroscience Chicago 2015 Spinal Cord Injury: Therapeutic Strategies Trauma
Support: NIH Grant NS069765
Effects of reduction of suppressors of cytokine signaling-3 (socs3) expression on dendritic outgrowth and demyelination after spinal cord injury
Authors: K. PARK, C.-Y. LIN, K. LI, *Yu-Shang LEE; Neuroscience, Cleveland Clinic., Cleveland, OH
Abstract: Suppressors of cytokine signaling-3 (SOCS3) is associated with limitations of nerve growth capacity after injury to the central nervous system. Although genetic manipulations of SOCS3 can enhance axonal regeneration after optic injury, the role of SOCS3 in dendritic outgrowth after spinal cord injury (SCI) is still unclear. The present study investigated the endogenous expression of SOCS3 and its role in regulating neurite outgrowth in vitro. IL-6 induces SOCS3 expression at the mRNA and protein levels in neuroscreen-1 (NS-1) cells. In parallel to SOCS3 expression, interleukin-6 (IL-6) induced tyrosine phosphorylation of signal transducer and activator of transcription 3 (STAT3) in NS-1 cells. Lenti-viral delivery of short hairpin RNA (shSOCS3) (Lenti-shSOCS3) to decrease SOCS3 expression into NS-1 cells enhanced IL-6-induced tyrosine phosphorylation of STAT3 (P-STAT3 Tyr705) and promoted neurite outgrowth. In addition, we determined if reduction of SOCS3 expression by microinjection of Lenti-shSOCS3 into spinal cord enhance dendrite outgrowth in spinal cord neurons after SCI. Knocking down of SOCS3 in spinal cord neurons with Lenti-shSOCS3 enhanced complete SCI-induced P-STAT3 Tyr705. Immuno-histochemical analysis showed that complete SCI induced a significant reduction of microtubule association protein 2 (MAP-2) positive (MAP-2+) dendrites in the gray and white matter at 1 and 4 weeks after injury. The SCI induced reduction of MAP-2+ dendrites was inhibited by infection with Lenti-shSOCS3 in areas both rostral and caudal to the lesion at 1 and 4 weeks after complete SCI. Furthermore, shSOCS3 treatment enhanced up-regulation of growth associated protein-43 (GAP-43) expression, which co-localized with MAP-2+ dendrites in white matters and MAP-2+ cell bodies in gray matters, indicating Lenti-shSOCS3 may induce dendritic regeneration after SCI. Moreover, we demonstrated that Lenti-shSOCS3 decreased SCI-induced demyelination in white matter of spinal cord both rostral and caudal to the injury site 1 week post-injury, but not rostral to the injury at 4 weeks. Collectively, these results suggest that SOCS3 has negatively regulatory effects on dendritic regeneration, at least in part by inhibition of dendritic loss, through negative regulation of STAT3 signaling after SCI.
Disclosures: K. Park: None. C. Lin: None. K. Li: None. Yu-Shang Lee: None