Neuroprotective role of calreticulin after spinal cord injury in mice.

Accumulating evidence suggests that endoplasmic reticulum (ER) stress and unfolded protein response (UPR) are involved in the pathology of spinal cord injury (SCI). To determine the role of the UPR-target molecule in the pathophysiology of SCI, we analyzed the expression and the possible function of calreticulin (CRT), a molecular chaperone in the ER with high Ca binding capacity, in a mouse SCI model. Spinal cord contusion was induced in T9 by using the Infinite Horizon impactor. Quantitative real-time polymerase chain reaction confirmed increase of Calr mRNA after SCI. Immunohistochemistry revealed that CRT expression was observed mainly in neurons in the control (sham operated) condition, while it was strongly observed in microglia/macrophages after SCI. Comparative analysis between wild-type (WT) and Calr mice revealed that the recovery of hindlimb locomotion was reduced in Calr mice, based on the evaluation using the Basso Mouse Scale and inclined-plane test. Immunohistochemistry also revealed more accumulation of immune cells in Calr mice than in WT mice, at the epicenter 3 days and at the caudal region 7 days after SCI. Consistently, the number of damaged neuron was higher in Calr mice at the caudal region 7 days after SCI. These results suggest a regulatory role of CRT in the neuroinflammation and neurodegeneration after SCI.