Introduction: Spinal cord injury (SCI) is a devastating condition affecting roughly 253,000 patients in US. As a result of the injury, several functional impairments in breathing, bladder control and limb movements drastically reduce the patient's quality of life. Current treatments include administering steroids and rehabilitation. The root cause -traumatic loss or degeneration of neural tissue - is not targeted. Our overall goal is to assess the effectiveness of an injectable gelatin-based matrix with specific growth factors in spinal cord tissue repair. It is imperative to include in the precinical animal investigation the non-invasive imaging modality that, in addition to be able to provide longitudinal assessments in the animal model, will also be able to be employed in an ultimate human trial. In this work employing a rat model, we present ex-vivo spinal cord MRIs with a proof of principle that critical characteristics of the injury site can be evaluated by MRI, and correlated with behavioral assessment of spinal cord injury. Materials and Methods: Twelve lewis rats (300 g) underwent survival surgery that induced a 1 mm T8 hemiresection injury to their spinal cord. On Day 0, the control group was injected with 15 m' of geiatin-hydroxyphenyl propionic acid (Gtn-HPA) matrix (Gel only group,n=6) and the experimental group was injected with 15 μl of Gtn-HPA matrix with epidermal growth factor (Gel + EGF group, dose - 6 μg/rat). Behavioral behavioral data were employed from historical untreated controls. Every week until sacrifice, rats underwent open field locomotor test and their hindlimb function was rated as per the Beartie, Basso, Brashnahan (BBB) scale from 0 (complete paralysis) to 21 (normal gait). The rater was blinded to the groups. After 4 weeks, they were sacrificed by transcadial perfusion and relvant spine region was preserved in 4% PFA at 4°C. After sacrifice. T2-weighted coronal MRI images of the spinal cords with injury site were obtained in a 7T Bruker Scanner (resolution = 75 μm, slice thickness = 250 μm). Lesion volume was calculated using ImageJ. Results and Discussion: We were able to obtain high-resolution MRI images showing the lesion site and the surrounding tissue in greater detail giving further insights (Figure 1) Add Figure 1. For Gtn-HPA + EGF group, average lesion volume was calculated to be 12.53 mm3, which was found to be lower than Gel only group, 15.27 mm3 (p = 0.05, Figure 2) Add Figure 2. After 4 weeks, the Gel+EGF group rats showed greater functional improvement from 5.3 to 13.5 average BBB score (A = 8.2), while the Gel only group showed improvement from 5.3 to 11 ((A = 5.7) (p = 0.05, Figure 3) Add Figure 3. Results from MRI correlate with the results from functional assessemnt of the rats using BBB scale. Conclusion: Our work provides a proof of principle that Gtn-HPA gel with EGF reduces the lesion volume contributing to greater protection of the surrounding healthy tissue. Moreover, our preliminary work suggests that MRI can be used as a tool to non-invasively study important critical parameters of the lesion site such as lesion volume. Encouraging results motivate us to further test various doses of EGF and relevant factors to induce tissue regeneration in our animal model. We aim to test a combinatorial approach with Gtn-HPA gel, EGF and a cell types such as bone-marrow derived mesenchymal stem cells.
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