Plastic Surgery Research Council
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PSRC 60th Annual Meeting

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Non-invasive Objective Evaluation Of Peripheral Neuroregeneration Using Magnetic Resonance Diffusion Tensor Imaging
Nataliya Kostereva, Ph.D1, Vincent Lee, candidate for PhD1, Kimimasa Tobita, PhD1, Jignesh Unadkat, MD1, Jonas Schnider, MD2, Chiaki Komatsu, MD1, Mario Solari, MD1, Vijay Gorantla, MD, PhD1.
1University of Pittsburgh, Pittsburgh, PA, USA, 2University Hospital Berne, Berne, Switzerland.

Purpose
Objective, non-invasive, sequential monitoring of regeneration after peripheral nerve repair is critical for evaluation of the efficacy of re-innervation and treatment strategies that may have important implications in recovery and outcome. We investigated whether diffusion magnetic resonance imaging (MRI) can accurately assess neuroregeneration.
Methods
We used sciatic nerve (SN) transection & repair model in Lewis rats. A wide range of treatment modalities (FK506, Schwann cells (SC), chondroitinase ABC (CH) and IGF-1, alone or in combination) was applied at the time of surgery. At the end points (2 and 5 weeks), SNs were excised and embedded in 1% agarose. Spin echo DTI was performed with following parameters: TE= 27msec, TR= 5000msec, 6 directions, 128 x 128 matrix with 300um resolution. MRI parameters such as fractional anisotropy (FA) was computed and compared with histomorphometry, expression of GAP43 (marker of regeneration), neurofilament M and myelin (nerve functionality).
Results
The analysis of DTI images showed that injured nerves have lower FA values as compared to the naïve nerves. It suggests that in area distally to coaptation site of injured nerves water diffuses in various directions indicating low structural integrity whereas most of the water inside of the naïve nerve diffuses in the same direction. FA has increased or did not change in the proximal and transection segment of injured nerve across groups from 2 to 5 weeks post-surgery. In the distal segment, FA value has increased by a noticeable margin in IGF-1 group and to a lesser degree, in FK506 treated group. This correlated strongly with changes in GAP43 expression, neurofilament M and myelin expressions in the distal nerve fragment.
Conclusions
The results suggest that MRI analysis can be successfully employed as one of the methods for the assessment of neuroregeneration. Comparison of DTI data to validated measures like histomorphometry, immunohistochemistry, electrophysiology (EMG, NCV) and others can enable us to develop an accurate non-invasive evaluation of overall functional outcomes after nerve repair, reconstruction or transplantation.


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