PsychoGenics is at the forefront of preclinical spinal cord injury (SCI) research, and we are dedicated to fostering the development of innovative therapies that address the complexities of SCI. Our expertise in utilizing the thoracic contusion model of SCI allows us to closely study both primary and secondary lesions. Primary lesions, where bone fragments or other tissues impact the spinal cord, result in immediate tissue loss, axon breakage, and hemorrhages. Secondary lesions evolve from hours to months after the initial injury, characterized by progressive cell death, cyst formation, glial scar, demyelination, and abortive repair processes.

Preclinical SCI Studies Utilizing the Thoracic Contusion Model of SCI

At PsychoGenics, we specialize in preclinical spinal cord injury (SCI) studies using the thoracic contusion model, a clinically relevant approach to assess the efficacy of novel therapies. Our primary lesion induction involves the surgical removal of the T8 vertebral process and lamina, followed by precisely controlled injury delivered by the Infinite Horizon (IH) device. This model faithfully replicates the immediate tissue damage seen in SCI, including axon breakage and hemorrhage. In the secondary phase, our model accounts for the subsequent white and gray matter loss, cyst formation, demyelination, and the development of a glial scar.

Standardized Injury Induction with IH Impactor

Using the IH Impactor, we provide computer-controlled, standard-force injuries ranging from 150 to 250 kilodynes in rats. A higher impact force typically results in a lower Basso-Beattie-Bresnahan (BBB) score, indicating more severe impairment. Our advanced technology allows for the detection and exclusion of lesions that fall out of the desired range or present with technical issues, based on precise impact data. This ensures the high quality and reliability of our SCI research, paving the way for the development of groundbreaking therapies.

Comprehensive Assessment of Your SCI Treatment

We conduct a comprehensive range of preclinical neurobehavioral tests and pathological assessments to assess the impact of your novel SCI therapy on neurorecovery. By evaluating multiple endpoints, we gain an understanding of the therapeutic potential of your intervention, enabling you to advance urgently needed treatments.  

The Basso Beattie Bresnahan (BBB) Locomotor Score is a critical tool in spinal cord injury research, providing a detailed evaluation of recovery progression. This scoring system is divided into three distinct phases, reflecting the gradual recovery of hind-limb function in animal models post-SCI.

  • Phase I, scoring from 0 to 7, identifies the absence of motor function progressing to isolated joint movements.
  • Phase II, with scores from 8 to 13, captures the return of paw placement and stepping.
  • Finally, Phase III, scoring from 14 to 21, indicates advanced motor functions, such as proper toe clearance and tail elevation.

The BBB Locomotor Score is integral to our understanding of SCI recovery, allowing for the assessment of therapeutic efficacy and the mapping of recovery milestones.

BBB Score: Within 24 hours post spinal cord injury (SCI), most animals exhibit complete hind-limb paralysis, reflected by a BBB score of 0. Locomotor function tends to recover and plateau approximately 4-6 weeks after the injury. It is important to note that animals do not regain pre-injury baseline locomotion levels. By adjusting the Infinite Horizon (IH) impact forces, varying lesion severities can be obtained.

BBB Sub-Score: The BBB Sub-Score evaluates unusual recovery patterns post-injury. This sub-score quantifies the recovery of finer motor functions such as toe clearance, paw position, trunk stability, and tail use, independent of forelimb-hindlimb coordination. Initially, after SCI, the majority of animals will have a BBB sub-score of 0, indicating no observable recovery in these specific functions. Animals subjected to a lesion force of 230 kilodynes generally do not regain BBB sub-score points, while some animals with milder lesions (170-200 kilodynes) will show a degree of recovery in these sub-scores.

Gait analysis is crucial in SCI research as it provides valuable insights into the functional impact of spinal cord injuries and the effectiveness of therapeutic interventions aimed at improving motor function and recovery.

Sham rats display a coordinated gait with appropriate hind-paw placement beneath the haunches, proper coordination between front and hind limbs, and balanced left-right hind limb movements. The number of paw prints from both the front and hind limbs is consistent, illustrating an even gait.

In contrast, SCI rats exhibit several gait abnormalities: hind-paws are shifted caudally, front-paws are shifted rostrally, leading to an increased base width. SCI rats lack front-hind limb coordination and diminished left-right limb coordination, and additionally show an increased dependence on front limbs, with a reduced utilization of hind limbs.

Paw Analysis: In sham rats, gait analysis typically shows hind paws placed neatly beneath the haunches, aligned with the body’s center, indicative of a healthy, coordinated movement. Conversely, in SCI rats, there is a noticeable shift in paw position: hind paws are displaced backward (caudally) and front paws forward (rostrally), suggesting an adaptive change to maintain balance and movement post-injury.

When examining paw prints, sham rats leave an equal number of front and hind paw impressions, reflecting their symmetrical gait. SCI rats, however, present a different pattern with fewer hind paw prints and a slightly increased number of front paw prints. The extent of this variation in paw print frequency correlates with the severity of the spinal lesion, offering a clear visual cue to the altered gait dynamics caused by spinal cord injury.

Regularity Index in Gait Assessment: The regularity index is a crucial metric in gait analysis, representing the consistency of paw placement in each gait cycle and serving as a measure of limb coordination. In healthy sham animals, this index approximates 1 for both hind limbs and forelimbs, denoting highly coordinated, regular gait patterns. Following spinal cord injury (SCI), there is a marked decrease in the regularity index for hind limbs, reflecting disrupted coordination and gait irregularity. In contrast, the index for forelimbs often increases, possibly as a compensatory mechanism to maintain stability and locomotion despite hind limb dysfunction.

In the Horizontal Ladder Test, animals are observed walking on a ladder with irregularly spaced rungs. Sham rats typically exhibit few errors with both front and hindlimbs, demonstrating their ability to navigate the irregular spacing effectively. In contrast, SCI (Spinal Cord Injury) rats display a significant increase in hindlimb errors post-injury, highlighting the impact of the injury on their motor function. Interestingly, front limb errors remain minimal in both sham and SCI rats, indicating a retained or less affected front limb coordination despite the injury.

Neurofilament light chain and neurofilament heavy chain are critical biomarkers in spinal cord injury (SCI) research, reflecting the extent of neuronal damage and axonal degradation. These cytoskeletal proteins, measurable in cerebrospinal fluid and blood plasma, provide objective indicators of injury severity and neurodegenerative progression in SCI. Their quantification aids in the diagnosis and monitoring of SCI, offering potential targets for therapeutic intervention and evaluation of treatment efficacy.

Neurofilament Light Chain (NF-L): Neurofilament Light Chain (NF-L) stands out as a sensitive biomarker for spinal cord injury (SCI), indicating axonal damage and neuronal disruption through elevated plasma levels shortly after injury. Although both NF-L and Neurofilament Heavy Chain (NF-H) are pivotal in assessing SCI, NF-L’s rapid response rate offers a distinct advantage for early detection, setting it apart from NF-H, which typically signifies more pronounced or long-term neuronal injury.

Within twenty-four hours post-SCI, both NF-L and Glial Fibrillary Acidic Protein (GFAP) are significantly increased in SCI rats compared to sham rats, pinpointing acute neuronal and astrocytic damage.

Neurofilament Heavy Chain (NF-H): Neurofilament Heavy Chain (NF-H) is an additional key biomarker that provides critical information on the severity and progression of neuronal injury. As a larger cytoskeletal component compared to its light chain counterpart, NF-H is released into the plasma following neuroaxonal damage and is associated with more severe and chronic aspects of SCI. Elevated levels of NF-H in plasma, discernible from sham-operated animals, serve as a robust indicator of such damage. Notably, one week after SCI, NF-H levels can differentiate between degrees of injury severity, offering a time-dependent profile of neurodegenerative changes. This ability to detect variances in injury severity underscores the importance of NF-H as a biomarker in the evaluation of spinal cord injuries and the potential to guide therapeutic interventions.

Immunohistochemistry in SCI offers investigations into a wide range of relevant markers, such as the determination of lesion volumes, for instance, in concert with neuron numbers, neuroinflammation, and macrophages, as shown in Figure 1. Lesion size (Figure 2) and neuroinflammatory markers (e.g., Figure 3) increase with the severity of lesion impact.

Figure 1: The intensity of CD68 (aqua) and Iba1 (red) labeling increases with the severity of the lesion, indicating stronger immune response markers. NeuN labeling, visible in green, highlights the loss of neurons due to the lesions. It’s important to note that CD68 labeling may also include auto-fluorescent debris and blood cells, which are not directly related to the immune response.

Figure 2: Lesion size (here as average size per 4 sections) has shown to significantly increase linearly with severity of lesions. (∑ = significant versus all groups, ANOVA followed by Fisher’s LSD test). 

Figure 3: Spinal cord injury results in increased microglial activation (labeled using Iba1 antibody) depending on the severity of the lesion. Sham samples show normal microglia. 

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