A Novel Rat Forelimb Transplantation Model that Allows for Optimized Measurement of Functional Recovery following VCA
Joshua D. Budihardjo, BSc, Barbara Kern, MD, Caroline Cadmi, -, Sara Mermulla, MD, Amy Quan, MPH, Joseph Lopez, MD, Sinan Xiang, -, Mohammed Khusheim, MD, Jae Sung Park, PhD, Ahmet Hoke, MD, PhD, W.P. Andrew Lee, MD, Sami Tuffaha, MD, Gerald Brandacher, MD.
Johns Hopkins Medical Institutes, Baltimore, MD, USA.
Studies to investigate strategies to improve functional outcomes in VCA are limited by the lack of appropriate animal models. The rat hindlimb transplant model is used for histologic and electrophysiological measures of nerve regeneration but does not allow for reliable assessment of behavioral functional recovery. We developed a novel forelimb transplant model to address this specific problem.
Rat orthotopic forelimb transplantation was performed at the mid-humerus level with anastomosis of brachial vessels. Median and radial nerves were approximated in the experimental group, but left in discontinuity in the control group (N=6/group) to determine the degree of functional return due to nerve regeneration. Functional recovery was tested by measuring grip strength using a force transducer and evaluating performance of repetitive feeding movements. Median nerve histomorphometry and flexor digitorum myofiber cross-sectional area analysis were performed at 12 weeks.
Long-term allograft survival (>120 days) was successfully achieved with cyclosporine A (10mg/kg/day). Animals in the control group did not regain grip strength after transplantation, while the experimental group demonstrated 57%+/-5.5% return of baseline grip strength (p<0.05). Forelimb function scores (0-9) were significantly greater in the experimental group than the controls. (3.7+/-0.49 vs. 1.2+/-0.37; p<0.05). Muscle histology and nerve histomorphometry are pending.
Rat forelimb transplantation represents the first VCA model that allows for reliable and reproducible measurement of functional recovery in addition to histologic measures of reinnervation.
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