Chronic Spinal Compression Model in Minipigs: A Systematic Behavioral, Qualitative, and Quantitative Neuropathological Study

Abstract

The goal of the present study was to develop a porcine spinal cord injury (SCI) model, and to describe the neurological outcome and characterize the corresponding quantitative and qualitative histological changes at 4-9 months after injury. Adult Gottingen-Minnesota minipigs were anesthetized and placed in a spine immobilization frame. The exposed T12 spinal segment was compressed in a dorso-ventral direction using a 5-mmdiameter circular bar with a progressively increasing peak force (1.5, 2.0, or 2.5 kg) at a velocity of 3 cm/sec. During recovery, motor and sensory function were periodically monitored. After survival, the animals were perfusion fixed and the extent of local SCI was analyzed by (1) post-mortem MRI analysis of dissected spinal cords, (2) qualitative and quantitative analysis of axonal survival at the epicenter of injury, and (3) defining the presence of local inflammatory changes, astrocytosis, and schwannosis. Following 2.5-kg spinal cord compression the animals demonstrated a near complete loss of motor and sensory function with no recovery over the next 4-9 months. Those that underwent spinal cord compression with 2 kg force developed an incomplete injury with progressive partial neurological recovery characterized by a restricted ability to stand and walk. Animals injured with a spinal compression force of 1.5 kg showed near normal ambulation 10 days after injury. In fully paralyzed animals (2.5 kg), MRI analysis demonstrated a loss of spinal white matter integrity and extensive septal cavitations. A significant correlation between the magnitude of loss of small and medium-sized myelinated axons in the ventral funiculus and neurological deficits was identified. These data, demonstrating stable neurological deficits in severely injured animals, similarities of spinal pathology to humans, and relatively good post-injury tolerance of this strain of minipigs to spinal trauma, suggest that this model can successfully be used to study therapeutic interventions targeting both acute and chronic stages of SCI.

Assessment of motor recovery and MRI correlates in a porcine spinal cord injury model

“…Their general health was evaluated daily by one member of our team. Detailed assessment of the motor function was carried out by two independent investigators on the 7 th and 12 th post-SCI day using the 14-point porcine neurological motor scoring system (PNM score) -based on the BBB evaluation system elaborated for rats (Basso et al 1995) and modified for pigs (Navarro et al 2012).…”

Development of a Locomotor Rating Scale for Testing Motor Function in Sheep

“…A preliminary checklist of motor patterns was developed from adaptations of the rodent BBB Locomotor Rating Scale [3], the porcine neurologic motor scoring system [4], and observations of locomotion in normal lambs. Motor function behaviors were added, modified, or removed after observation of all animals.…”

“…To perform this test, animals were observed walking over a 4"x4" wooden bar in an open field as described by Navarro et al [4]. Ability to walk over the bar qualifies as a pass.…”

“…In order to evaluate therapies that augment in utero repair to improve distal motor function, a uniform scale for locomotion assessment is essential. The Basso, Beattie, Bresnahan (BBB) Locomotor Rating Scale is a well-validated and widely used scale for locomotor testing in rodent spinal cord injury models [3]; it has been successfully adapted for use in a porcine model [4]. In this study, this locomotion rating system was adapted for use in sheep as a comprehensive and reliable measure of distal motor function.…”

Potential variables affecting the quality of animal studies regarding pathophysiology of traumatic spinal cord injuries

“…26 It is worth noting that, in some studies, weight of animals at the beginning of study is used as a reflection of age. [27][28][29] Housing The housing conditions are specified in the ethical approval. The exact values for temperature, humidity, lighting, noise and amount of food and water should be within a certain range.…”