Biotinylated dextran amine tracing of nerve tracts determines regeneration of corticospinal tracts after neural stem cell transplantation

We investigated regeneration of the corticospinal tract and rearrangement of corticospinal nerves after spinal cord injury by biotinylated dextran amine （BDA） nerve tract tracing after neural stem cell transplantation. Neural stem cell transplantation increased motor function scores of rats at 3 weeks after spinal cord transection injury at the thoracic 10 segment. A proportion of BDA-labeled corticospinal tract regenerated through the spinal cord injury site at 12 weeks after transplantation. Electron microscopy revealed that the regenerated BDA-labeled nerve terminals formed new synaptic connections with neurons at the distal end of the injured site. These findings indicate that BDA nerve tract tracing effectively provides anatomic and morphological evidence of recovery after spinal cord injury.

Brain injury in combination with tacrolimus promotes the regeneration of injured peripheral nerves

Both brain injury and tacrolimus have been reported to promote the regeneration of injured peripheral nerves. In this study, before transection of rat sciatic nerve, moderate brain contusion was（or was not） induced. After sciatic nerve injury, tacrolimus, an immunosuppressant, was（or was not） intraperitoneally administered. At 4, 8 and 12 weeks after surgery, Masson＇s trichrome, hematoxylin-eosin, and toluidine blue staining results revealed that brain injury or tacrolimus alone or their combination alleviated gastrocnemius muscle atrophy and sciatic nerve fiber impairment on the experimental side, simultaneously improved sciatic nerve function, and increased gastrocnemius muscle wet weight on the experimental side. At 8 and 12 weeks after surgery, brain injury induction and/or tacrolimus treatment increased action potential amplitude in the sciatic nerve trunk. Horseradish peroxidase retrograde tracing revealed that the number of horseradish peroxidase-positive neurons in the anterior horn of the spinal cord was greatly increased. Brain injury in combination with tacrolimus exhibited better effects on repair of injured peripheral nerves than brain injury or tacrolimus alone. This result suggests that brain injury in combination with tacrolimus promotes repair of peripheral nerve injury.

End-to-side neurorrhaphy repairs peripheral nerve injury：sensory nerve induces motor nerve regeneration

End-to-side neurorrhaphy is an option in the treatment of the long segment defects of a nerve.It involves suturing the distal stump of the disconnected nerve（recipient nerve） to the side of the intimate adjacent nerve（donor nerve）.However,the motor-sensory specificity after end-to-side neurorrhaphy remains unclear.This study sought to evaluate whether cutaneous sensory nerve regeneration induces motor nerves after end-to-side neurorrhaphy.Thirty rats were randomized into three groups：（1） end-to-side neurorrhaphy using the ulnar nerve（mixed sensory and motor） as the donor nerve and the cutaneous antebrachii medialis nerve as the recipient nerve;（2） the sham group：ulnar nerve and cutaneous antebrachii medialis nerve were just exposed;and（3） the transected nerve group：cutaneous antebrachii medialis nerve was transected and the stumps were turned over and tied.At 5 months,acetylcholinesterase staining results showed that 34% ± 16% of the myelinated axons were stained in the end-to-side group,and none of the myelinated axons were stained in either the sham or transected nerve groups.Retrograde fluorescent tracing of spinal motor neurons and dorsal root ganglion showed the proportion of motor neurons from the cutaneous antebrachii medialis nerve of the end-to-side group was 21% ± 5%.In contrast,no motor neurons from the cutaneous antebrachii medialis nerve of the sham group and transected nerve group were found in the spinal cord segment.These results confirmed that motor neuron regeneration occurred after cutaneous nerve end-to-side neurorrhaphy.

Comparison of commonly used retrograde tracers in rat spinal motor neurons

The purpose of this study was to investigate the effect of four fluorescent dyes, True Blue（TB）, Fluoro-Gold（FG）, Fluoro-Ruby（FR）, and 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate（Di I）, in retrograde tracing of rat spinal motor neurons. We transected the muscle branch of the rat femoral nerve and applied each tracer to the proximal stump in single labeling experiments, or combinations of tracers（FG-Di I and TB-Di I） in double labeling experiments. In the single labeling experiments, significantly fewer labeled motor neurons were observed after FR labeling than after TB, FG, or Di I, 3 days after tracer application. By 1 week, there were no significant differences in the number of labeled neurons between the four groups. In the double-labeling experiment, the number of double-labeled neurons in the FG-Di I group was not significantly different from that in the TB-Di I group 1 week after tracer application. Our findings indicate that TB, FG, and Di I have similar labeling efficacies in the retrograde labeling of spinal motor neurons in the rat femoral nerve when used alone. Furthermore, combinations of Di I and TB or FG are similarly effective. Therefore, of the dyes studied, TB, FG and Di I, and combinations of Di I with TB or FG, are the most suitable for retrograde labeling studies of motor neurons in the rat femoral nerve.