Characterizing the Impact of Compression Duration and Deformation-Related Loss of Closure Force on Clip-Induced Spinal Cord Injury in Rats

Abstract

The clip-induced spinal cord injury (SCI) rat model is pivotal in preclinical SCI research. However, the literature exhibits variability in compression duration and limited attention to clip deformation-related loss of closure force. We aimed to investigate the impact of compression duration on SCI severity and the influence of clip deformation on closure force. Rats received T10-level clip-induced SCI with durations of 1, 5, 10, 20, and 30 s, and a separate group underwent T10 transection. Outcomes included functional, histological, electrophysiological assessments, and inflammatory cytokine analysis. A tactile pressure mapping system quantified clip closure force after open-close cycles. Our results showed a positive correlation between compression duration and the severity of functional, histological, and electrophysiological deficits. Remarkably, even a brief 1-s compression caused significant deficits comparable to moderate-to-severe SCI. SSEP waveforms were abolished with durations over 20 s. Decreased clip closure force appeared after five open-close cycles. This study offers critical insights into regulating SCI severity in rat models, aiding researchers. Understanding compression duration and clip fatigue is essential for experiment design and interpretation using the clip-induced SCI model.

Keywords: clip compression; clip fatigue; closure force; compression duration; spinal cord injury.

Figure 1

Effects of compression duration on the severity of locomotor functional and electrophysiological deficits in a clip compression rat model of SCI. (A) Experimental timeline of this presented study. (B) Quantitative results of the Basso–Beattie–Bresnahan scores. (C) Representative micrographs of traces of somatosensory evoked potential. ^a p < 0.05, vs. normal, ^b p < 0.05, vs. 1 s, ^c p < 0.05, vs. 5 s, ^d p < 0.05, vs. 10 s, ^e p < 0.05, vs. 20 s, ^f p < 0.05, vs. 30 s.

Figure 2

Effects of compression duration on the severity of histological deficits in a clip compression rat model of SCI. (A) Representative photographs of dissected spinal cords after clip compression and transection injuries. (B) Representative micrographs of LFB staining of coronally sectioned spinal cord sections. (C) Quantitative results of LFB staining. ^a p < 0.05, vs. 1 s, ^b p < 0.05, vs. 5 s, ^c p < 0.05, vs. 10 s, ^d p < 0.05, vs. 20 s, ^e p < 0.05, vs. 30 s.

Figure 3

Effects of repetitive clip application on the closure force of the clip. (A) Photographs of the versatile I-Scan tactile pressure mapping system. (1) Photograph of aneurysm clips used in this study. (2) Photograph of the data acquisition electronics of the pressure mapping system. (3) Photograph of the data acquisition electronics connected with the plate sensor. (4) Photograph of the experimental setting for detecting the closure force of the clips. (B) Quantitative results of the closure force of the clips.