Abstract
OBJECTIVE: Paraplegia from spinal cord ischemia (SCI) is a life-altering complication of aortic surgery. Although various strategies have been employed to enhance spinal cord perfusion, no pharmaceutical agents have been used clinically to mitigate the risk of SCI. Inhibition of calcium/calmodulin-dependent protein kinase II (CaMKII) pathway has shown neuroprotective effects in rodent cerebral ischemia; however, its role in spinal cord ischemia-reperfusion injury has yet to be investigated. This study aims to evaluate the potential of CaMKII inhibition with tatCN19o in preventing SCI in a mouse model. METHODS: Male C57BL/6 mice (aged 7-9 weeks) were used. Both treatment and control groups underwent aortic cross-clamping to induce SCI. The aorta (distal to left carotid artery) and the left subclavian were clamped for 4 minutes. Sham mice had aortic exposure without clamping. tatCN19o (0.1 mg/kg) or placebo was administered intraperitoneally 10 minutes before and 24 hours after SCI. Sham mice received placebo at the same time points. Postoperative motor function was assessed during the first hour and every 12 hours for 48 hours using the Basso Motor Scale (0-9, from no to full function). Mice not surviving until 48 hours were excluded. Spinal cord histological analysis was performed. A blinded motor neuron cell count of lumbar anterior horn was conducted using 20× imaging by 2 reviewers. RESULTS: Based on behavioral scores, sham mice (n = 3) regained full motor function within 30 minutes after surgery. All tatCN19o mice (n = 12) recovered faster with full motor scores by 12 hours postoperatively (9 ± 0 vs 7 ± 0.7; P = .02), compared with controls (n = 11). Motor function declined in both groups after 24 hours. At 48 hours, tatCN19o mice had significantly improved motor function (8.2 ± 0.8 vs 3.1 ± 1.3; P = .004) that did not differ significantly from sham (P = .288). In contrast to sham and tatCN19o-treated mice, the lumbar anterior horn of untreated SCI mice showed minimal surviving motor neurons, with vacuolization and pyknosis, suggesting both necrosis and apoptosis. Motor neuron counts were higher in tatCN19o mice than controls (13.2 ± 1.1 vs 7.2 ± 1.6 cells/1200px diameter area; P = .01). CONCLUSIONS: Inhibiting CaMKII with tatCN19o significantly preserved lower extremity motor function in a mouse SCI model. As in brain tissues, the CaMKII pathway is critical in spinal cord ischemia-reperfusion injury. Further studies are needed to explore CaMKII signaling in SCI and optimize tatCN19o dosing and timing.