Knowledge Base

Introduction

Injury to the spinal cord often results in impaired body functions, including sensory and autonomic functions (bladder control, gut control, etc.), but also locomotor functions. In animal research, many experimental treatments are tested for their efficacy to stimulate a recovery of the impaired body functions, and these studies mostly focus on locomotor functions. Hence, it is of utmost importance to have disposal of a behavioral test that meets the following criteria:

• Objectivity
• Ease of use for large animal groups
• Sensitivity in the detection of locomotor parameters

One of the most frequently used behavioral tests in rat spinal cord injury research is the BBB locomotor rating scale (1). However, a rather low objectivity and sensitivity in the detection of locomotor parameters is associated with the BBB locomotor rating scale, and the highly objective and sensitive CatWalk gait analysis may have major benefits in this respect (2). In the current rat spinal cord injury experiment, both BBB and CatWalk gait analysis were used to test the behavioral implications of a cell transplantation treatment.

Material and Methods

A dorsal hemisection injury was performed on the low-thoracic spinal cord of adult male rats (Lewis strain). Ten animals were thereafter subjected to a cell transplantation treatment, including the use of olfactory ensheathing cell transplants and biologically degradable matrix implants; eight animals were left untreated. Before injury and at multiple time points after injury (3, 6, and 9 weeks) the animals were behaviorally tested using both the BBB locomotor rating scale and the CatWalk gait analysis.

Experiment

A vast majority (>95%) of the animals were able to make consecutive runs without hesitation across the glass plate of CatWalk after only 1-2 weeks of a non-intensive training period (animals were required to make 2 runs per day under a food restriction paradigm of 12g/day). Three, six, and nine weeks after the operation, the animals needed to re-perform on CatWalk. This required no additional training, but only a 24-hour food deprivation period.

The practical part of the behavioral testing consists of:

1. Arming the software on the computer that receives information from a video camera positioned underneath the CatWalk runway and which will detect light reflected from the runway surface that is evoked by pressure on the runway surface (by e.g. a paw placement).
2. Putting the rat on one side of the CatWalk runway.
3. Starting up the system electronically by a simple button-click.
4. Letting the animal walk to the other side of the runway.
5. Storing the available software file on the computer hard disk.

With the same CatWalk software, the run can be easily analysed. For this, the software program only needs identification of the correct paws (right fore, right hind, left fore, and left hind). A large amount of locomotor parameters is subsequently obtained and can be quickly analysed by processing in Microsoft Office software (Open Office and Excel). The recording and subsequent analysis will take about 5 minutes per run.

Results and Discussion

The dorsal hemisection injury caused directly a significant drop in BBB locomotor score (BBB score approximately 4) in all animals. As a result of spontaneous recovery, all animals slowly recovered in the first week (BBB score approximately 11). None of the animals showed a recovery to coordination between fore and hindpaws. CatWalk analysis, however, showed that the animals had a high degree of coordination during locomotion. Implementation of these findings into the BBB score strongly enhanced this score (BBB score approximately 15) (3,4).

Next to this, other behavioral parameters, including the stride length of the hindlimbs, were found to be affected by the injury and partly recovered in the cell transplanted animals, but not in control animals. In conclusion, the use of the CatWalk enabled detection of coordinated locomotion in the animal groups and enabled objective measurement of functional treatment effects.

References

1. Basso, D., Beattie, M., Bresnahan, J., (1995). A sensitive and reliable locomotor rating scale for open field testing in rats. Journal of Neurotrauma, 12, 1-21.
2. Hamers, F., Lankhorst, A., van Laar, T., Veldhuis, B., Gispen, W., (2001). Automated quantitative gait analysis during overground locomotion in the rat: Its application to spinal cord contusion and transection injuries. Journal of Neurotrauma, 18, 187-201.
3. Koopmans, G., Deumens, R., Honig, W., Hamers, F., Steinbusch, H., Joosten, E., (2005). The assessment of locomotor function in spinal cord injured rats: The importance of objective analysis of coordination. Journal of Neurotrauma, 22, 214-225.
4. Deumens, R., Koopmans, G., Honig, W., Maquet, V., Jerome, R., Steinbusch, H., Joosten, E., (2006). Chronically injured corticospinal axons do not cross large spinal lesion gaps after a multifactorial transplantation strategy using olfactory ensheathing cell/olfactory nerve fibroblast biomatrix bridges. Journal of Neuroscience Research, 83, 811-820.

Contact Information

Ronald Deumens, Department Anesthesiology, Institute Brain and Behavior, Maastricht University, Maastricht, The Netherlands (Email: [email protected]).

Download the original PDF: CatWalk XT Case Study: Spinal Cord Injury (PDF)