Effect of CLIP3 Upregulation on Astrocyte Proliferation and Subsequent Glial Scar Formation in the Rat Spinal Cord via STAT3 Pathway After Injury

Spinal cord injury (SCI) is a devastating event resulting in neuron degeneration and permanent paralysis through inflammatory cytokine overproduction and glial scar formation. Presently, the endogenous molecular mechanisms coordinating glial scar formation in the injured spinal cord remain elusive. Signal transducer and activator of transcription 3 (STAT3) is a well-known transcription factor particularly involving in cell proliferation and inflammation in the lesion site following SCI. Meanwhile, CAP-Gly domain containing linker protein 3(CLIP3), a vital cytoplasmic protein, has been confirmed to providing an optimal conduit for intracellular signal transduction and interacting with STAT3 with mass spectrometry analysis. In this study, we aimed to identify the expression of CLIP3 in the spinal cord as well as its role in mediating astrocyte activation and glial scar formation after SCI by establishing an acute traumatic SCI model in male adult rats. Western blot analysis revealed that CLIP3 increased gradually after injury, reached a peak at day 3. The immunohistochemistry staining showed the same result in white matter. With double immunofluorescence staining, we found that CLIP3 was expressed in glial cells and significant changes of CLIP3 expression occurred in astrocytes during the pathological process. Statistical analysis demonstrated there was a correlation between the number of positive cells stained by CLIP3 and STAT3 in the spinal cord after SCI. Co-immunoprecipitation further indicated that CLIP3 interacted with STAT3 in the injured spinal cord. Taken together, our study clearly suggested that CLIP3 played an essential role in astrocyte activation, associating with the STAT3 pathway activation induced by SCI.