Background 
Developing valid imaging biomarkers of stroke recovery are critical for translational stroke research. Diffusion Tensor Imaging (DTI) assesses white matter microstructure in the brain using fractional anisotropy (FA). Diffusion Tensor tractography (DTT) for visual mapping of CST. Our data suggests a possible correlation between neurological recovery and the improvement in FA-DTT. 

Objective 
The purpose of this study was to compare DTI biomarkers of neurological recovery in a canine stroke model over one month after ipsilateral intra-arterial (IA) Mesenchymal Stem Cell (MSC) infusion vs control. 

Methods 
Mongrel-Hounds (n=9), aged 12-36-months. MCA-stroke was induced via endovascular using a detachable-coil over 35-80min. MSC (1-40 million/240cc) or saline/240 cc were infused IA, 48hrs post-stroke. Brain-MRIs were performed prior to IA infusion, and 15 & 30 days post-stroke. FA values of the ipsilesional CST were determined. DTT of the CST was generated. Weekly neurological score-evaluations were performed. Comparison of FA-DTT at 30 days post-stroke between treated vs control. 

Results 
We observed improvement in FA-values 30 days post-stroke in the MSC-group (0.085 ± 0.025, n=5 vs 0.068 ± 0.058, n=4: p=0.82) and a qualitative increase in CST-caliber, not seen in controls. FA-increases in treated animals correlating with faster motor-recovery. FA did not change in the control group. 

Conclusion 
DTI-DTT imaging post IA-MSC therapy showed an increased FA and caliber of CST (DTT) correlating with motor recovery. These findings could support further development of DTI-DTT biomarkers to measure neurological-recovery in experimental models as well in clinical trials of novel stroke-therapies.

DTI FINDINGS OF CORTICOSPINAL TRACT RECOVERY AFTER AN INTRA-ARTERIAL MESENCHYMAL STEM CELL INFUSION IN A CANINE STROKE MODEL