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Unformatted text preview: HAND/PERIPHERAL NERVE Embryonic Stem Cell–Derived Motor Neurons Preserve Muscle after Peripheral Nerve Injury Melody N. Craff, M.D., Ph.D. Jose L. Zeballos, M.D. Timothy S. Johnson, M.D. Milan P. Ranka, B.A. Robert Howard, B.S. Pejman Motarjem, M.D. Mark A. Randolph, M.A.S. Jonathan M. Winograd, M.D. Boston, Mass. Background: The potential of motor neuron progenitor cell transplants to preserve muscle tissue after denervation was studied in in vivo and in vitro adult mammalian model of peripheral nerve injury. Methods: Embryonic stem cells were differentiated to induce cholinergic motor neuron progenitors. Flourescent-labeled progenitor cells were injected into the gastrocnemius muscle of Sprague-Dawley rats ( n 5 10) after denervation by ipilateral sciatic nerve transection. Control rats received injections of either a phosphate-buffered saline solution only ( n 5 12), murine embryonic fibroblast (STO) cells ( n 5 6), or undifferentiated embryonic stem cells ( n 5 6). Muscles were weighed and analyzed at 7 and 21 days using histology, histomorphometry, and immunostaining. Results: Seven days after progenitor cell transplant, both muscle mass and myocyte cross-sectional area were preserved, compared with control muscles, which demonstrated muscle mass reduction to 70 percent and reduction of cross-sectional area to 72 percent of normal. Fluorescent microscopy of trans- planted muscles confirmed the presence of motor neuron progenitors. Presyn- aptic neuronal staining of the transplants overlapped with a-bungarotoxin- labeled muscle fibers, revealing the presence of new neuromuscular junctions. By 21 days, muscle atrophy in the experimental muscles was equal to that of controls and no transplanted cells were observed. Co-culture of the motor neuron progenitor cells and myocytes also demonstrated new neuromuscular junctions by immunofluorescence. Conclusions: Transplanted motor neuron progenitors prevent muscle atrophy after denervation for a brief time. These progenitor cell transplants appear to form new neuromuscular junctions with denervated muscle fibers in vivo and with myocytes in vitro. ( Plast. Reconstr. Surg. 119: 235, 2007.) O ne of the major obstacles to neural recov- ery following peripheral nerve injury and reconstruction is the time-dependent loss of the ability of muscle fibers and sensory end- organs to successfully receive reinnervation and recover function. 1 Once denervated, muscle fi- bers rapidly atrophy and eventually fibrose after 12 to 18 months of denervation to form scar tissue. With a regeneration rate of 1 to 2 mm/ day, a long period of denervation is typically the case in proximal nerve injuries, where the distance between the proximal nerve stump and the distal target organs is great. Chronic muscle atrophy and fibrosis limit the recovery of muscle function following peripheral nerve injury and repair. Prevention of muscle atro- phy using embryonic stem cells following de- nervation may be of significant therapeutic...
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- Fall '10
- Neurobiology, Embryonic stem cells, embryonic stem cell–