Analgesic effects of intra-articular botulinum toxin Type B in a murine model of chronic degenerative knee arthritis pain

Figures & data

Table 1 Gait impairment criteria

0	Mouse refuses to walk on treadmill
1	Mouse walks up to 30% of the allotted time without touching dividers, jumping, splaying its legs, or dragging hindquarters; displays severe inconsistencies in gait
2	Mouse walks up to 60% of the allotted time without touching dividers, jumping, splaying its legs, or dragging hindquarters; displays moderate inconsistencies in gait
3	Mouse walks up to 90% of the allotted time without touching dividers, jumping, splaying its legs, or dragging hindquarters; displays minor inconsistencies in gait
4	Mouse walks the entire time without touching dividers, jumping, splaying its legs, or dragging hindquarters; displays no inconsistencies in gait.

Table 2 Grasp impairment criteria

0	Mouse gives no resistance to being pulled across screen; unable to grasp the screen
1	Minimal force needed to pull the mouse across the screen; significant difficulty grasping the screen
2	Moderate force needed to pull the mouse across the screen; moderate difficulty grasping the screen
3	Significant force needed to pull the mouse across the screen; minimal difficulty grasping the screen
4	Full force needed to pull the mouse across the screen; no difficulty grasping the screen.

Table 3 Cling impairment criteria

0	Mouse cannot hold on when the screen is tilted vertically
1	Mouse has shown that it can grip the screen when vertical but falls during every inversion
2	The mouse falls off the screen during two inversions or falls off the screen during one inversion and displays instability during the other two inversions
3	The mouse falls off the screen once or shows instability during two inversions
4	The mouse does not display instability with any inversion.

Figures 1 A) Evoked pain response: Measurement of joint tenderness (left knee) and B) Spontaneous pain behavior: Measurement of gait changes.

Notes: Seventeen mice with collagenase-induced arthritis of the left knee were treated at four weeks with intra-articular botulinum neurotoxin Type B (Myobloc^®) 0.02 IU in 5 μL of normal saline in the arthritic left knee. Animals were examined three days following intra-articular botulinum neurotoxin Type B to allow time for botulinum effects. Significant improvements in evoked pain response and spontaneous pain behavior (visual gait analysis) were noted following intra-articular botulinum neurotoxin Type B (P = 0.0134 and P = 0.0419, respectively). Gait improved by 43%, and evoked pain response was decreased by 49.5% following intra-articular botulinum neurotoxin Type B treatment. Treatment control groups included seven arthritic mice receiving either 5 or 10 μL intra-articular normal saline in the arthritic left knee at four weeks following intra-articular collagenase. Animals were examined three days following normal saline injections and compared with untreated arthritic animals (n = 40). No significant change in evoked pain response or spontaneous pain behavior (visual gait analysis) was noted following intra-articular normal saline (P = 0.9043 and P = 0.2250, respectively).
Abbreviations: naïve, 40 animals prior to induction of arthritis in the left knee; Arthritic, 40 animals four weeks post intra-articular collagenase into the arthritic left knee; Arth/BoNT/B, 17 animals four weeks post intra-articular collagenase into the left knee (arthritic), three days post intra-articular botulinum neurotoxin Type B into the arthritic left knee; Arth/saline, seven animals four weeks post intra-articular collagenase into the left knee (arthritic), three days post intra-articular saline into the arthritic left knee.

Figure 2 Safety assessment: Limb strength.

Notes: The 17 animals receiving intra-articular botulinum neurotoxin Type B were assessed for changes in strength three days following intra-articular botulinum neurotoxin Type B. No significant change in grasp or cling scores were noted following intra-articular botulinum neurotoxin Type B compared with untreated arthritic animals (P = 0.0704 and P = 0.2752, respectively). The seven animals receiving intra-articular normal saline injections had no significant change in grasp or cling scores (P = 0.3964, P = 0.7457, respectively).
Abbreviations: arthritic, 40 animals four weeks post intra-articular collagenase into the arthritic left knee; Arth/BoNT B, 17 animals four weeks post intra-articular collagenase into the left knee (arthritic), three days post intra-articular botulinum neurotoxin Type B into the arthritic left knee; Arth/saline, seven animals four weeks post intra-articular collagenase into the left knee (arthritic), three days post intra-articular saline into the arthritic left knee.

Figure 3 Hematoxylin and eosin stained normal right knee.

Note: Normal-appearing articular cartilage (arrowhead), meniscus (arrow), and synovium (asterisk).

Figure 4 Arthritic left knee stained with hematoxylin and eosin.

Note: Irregularities and thinning of articular cartilage (arrowheads) and early osteophyte formation (arrow) consistent with degenerative arthritis.