A Direct Comparison of Three Clinically Relevant Treatments in a Rat Model of Cervical Spinal Cord Injury

Abstract

Recent preclinical studies have identified three treatments that are especially promising for reducing acute lesion expansion following traumatic spinal cord injury (SCI): riluzole, systemic hypothermia, and glibenclamide. Each has demonstrated efficacy in multiple studies with independent replication, but there is no way to compare them in terms of efficacy or safety, since different models were used, different laboratories were involved, and different outcomes were evaluated. Here, using a model of lower cervical hemicord contusion, we compared safety and efficacy for the three treatments, administered beginning 4 h after trauma. Treatment-associated mortality was 30% (3/10), 30% (3/10), 12.5% (1/8), and 0% (0/7) in the control, riluzole, hypothermia, and glibenclamide groups, respectively. For survivors, all three treatments showed overall favorable efficacy, compared with controls. On open-field locomotor scores (modified Basso, Beattie, and Bresnahan scores), hypothermia- and glibenclamide-treated animals were largely indistinguishable throughout the study, whereas riluzole-treated rats underperformed for the first two weeks; during the last four weeks, scores for the three treatments were similar, and significantly different from controls. On beam balance, hypothermia and glibenclamide treatments showed significant advantages over riluzole. After trauma, rats in the glibenclamide group rapidly regained a normal pattern of weight gain that differed markedly and significantly from that in all other groups. Lesion volumes at six weeks were: 4.8±0.7, 3.5±0.4, 3.1±0.3 and 2.5±0.3 mm(3) in the control, riluzole, hypothermia, and glibenclamide groups, respectively; measurements of spared spinal cord tissue confirmed these results. Overall, in terms of safety and efficacy, systemic hypothermia and glibenclamide were superior to riluzole.

Keywords: glibenclamide; hypothermia; rat; riluzole; spinal cord injury; sulfonylurea receptor 1 (Sur1).

FIG. 1.

Survival curves for the four groups. All deaths occurred during the first week after trauma. CTR, untreated controls; SCI, spinal cord injury. The apparent trend was not statistically significant.

FIG. 2.

Autonomic function. Rectal temperature (A), heart rate (B), and ipsilateral ptosis (C) were measured on Days 1, 3 and 7 in the four groups, as indicated. bpm, beats per minute; CTR, untreated controls; GLIB, glibenclamide. For all measures, values in the four groups converged by Day 7.

FIG. 3.

Arousal scores and motor scores. Arousal scores (A) and motor scores (B) were measured on Days 1, 3, and 7 in the four groups, as indicated. CTR, untreated controls; GLIB, glibenclamide. For arousal scores at Day 7, values in the four groups converged; for motor scores at day 7, CTR vs. hypothermia and CTR vs. glibenclamide, both p<0.05; CTR vs. riluzole, p>0.05 by Kruskall-Wallis test with Dunn's post hoc comparisons.

FIG. 4.

Serum glucose. Serum glucose levels were measured on Days 1, 3, and 7 in the four groups, as indicated. For the data at day 7, p=0.15 by one-way analysis of variance.

FIG. 5.

Modified Basso, Beattie, and Bresnahan (mBBB) scores and angled plane. Modified BBB scores for the ipsilateral and contralateral hindlimb (A), and performance on the up-angled and down-angled inclined plane (B) were measured on Days 1, 3, and 7 and at weekly intervals thereafter in the four groups, as indicated. For the ipsilateral and contralateral mBBB scores at six weeks: untreated controls (CTR) vs. riluzole, CTR vs. hypothermia, and CTR vs. glibenclamide, all p<0.05 by Kruskall-Wallis test with Dunn's post hoc comparisons. For the inclined plane data at six weeks: CTR vs. riluzole, CTR vs. hypothermia, and CTR vs. glibenclamide, all p>0.05, by one-way analysis with Fisher's post hoc comparisons. Color image is available online at www.liebertpub.com/neu

FIG. 6.

Beam balance scores and accelerating rotarod. (A) Performance on beam balance was measured on Days 1, 3, and 7 and at weekly intervals thereafter in the four groups, as indicated. For the data at six weeks: untreated controls (CTR) vs. hypothermia and CTR vs. glibenclamide, both p<0.05; CTR vs. riluzole, p>0.05, by Kruskall-Wallis test with Dunn's post hoc comparisons. (B) Performance on the accelerating rotarod was measured during the fifth week in the four groups, as indicated; CTR vs. riluzole, CTR vs. hypothermia, and CTR vs. glibenclamide, all p<0.05 by one-way analysis of variance with Fisher's post hoc comparisons.

FIG. 7.

Body weight. Body weights were measured at baseline, on Days 1, 3, and 7 and at weekly intervals thereafter in the four groups, as indicated. For the data at six weeks: glibenclamide vs. untreated controls (CTR) and glibenclamide vs. hypothermia, p<0.05; glibenclamide vs. riluzole p>0.05 by one-way analysis of variance with Fisher's post hoc comparisons.

FIG. 8.

Lesion sizes and size of spared spinal cord tissue. (A) Hematoxylin and eosin-stained coronal sections obtained at the epicenter of injury from representative spinal cords six weeks after trauma in each of the four groups, as indicated. (B) Lesion areas as a function of distance from the epicenter (left) and box plots of lesion volumes (right) for each of the four groups, as indicated; negative numbers, rostral; small square, mean; percentiles as indicated; untreated controls (CTR) vs. riluzole, p>0.05; CTR vs. hypothermia, p<0.05 (*); CTR vs. glibenclamide, p<0.01 (**); by one-way analysis of variance (ANOVA) with Fisher's post hoc comparisons. (C) Area of spared spinal cord tissue as a function of distance from the epicenter (left) and box plots of spared spinal cord tissue volumes (right) for each of the four groups, as indicated; CTR vs. riluzole, p>0.05; CTR vs. hypothermia and CTR vs. glibenclamide, both p<0.01 (**); by one-way ANOVA with Fisher's post hoc comparisons. Color image is available online at www.liebertpub.com/neu