Article

Reinnervation of the tibialis anterior following sciatic nerve crush injury: A confocal microscopic study in transgenic mice

Washington University in St. Louis, San Luis, Missouri, United States
Experimental Neurology (Impact Factor: 4.7). 10/2007; 207(1):64-74. DOI: 10.1016/j.expneurol.2007.05.028
Source: PubMed

ABSTRACT

Transgenic mice whose axons and Schwann cells express fluorescent chromophores enable new imaging techniques and augment concepts in developmental neurobiology. The utility of these tools in the study of traumatic nerve injury depends on employing nerve models that are amenable to microsurgical manipulation and gauging functional recovery. Motor recovery from sciatic nerve crush injury is studied here by evaluating motor endplates of the tibialis anterior muscle, which is innervated by the deep peroneal branch of the sciatic nerve. Following sciatic nerve crush, the deep surface of the tibialis anterior muscle is examined using whole mount confocal microscopy, and reinnervation is characterized by imaging fluorescent axons or Schwann cells (SCs). One week following sciatic crush injury, 100% of motor endplates are denervated with partial reinnervation at 2 weeks, hyperinnervation at 3 and 4 weeks, and restoration of a 1:1 axon to motor endplate relationship 6 weeks after injury. Walking track analysis reveals progressive recovery of sciatic nerve function by 6 weeks. SCs reveal reduced S100 expression within 2 weeks of denervation, correlating with regression to a more immature phenotype. Reinnervation of SCs restores S100 expression and a fully differentiated phenotype. Following denervation, there is altered morphology of circumscribed terminal Schwann cells demonstrating extensive process formation between adjacent motor endplates. The thin, uniformly innervated tibialis anterior muscle is well suited for studying motor reinnervation following sciatic nerve injury. Confocal microscopy may be performed coincident with other techniques of assessing nerve regeneration and functional recovery.

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Available from: Daniel A Hunter, Jun 10, 2014
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    • "As the longest nerve in the body, the sciatic nerve comprises both motor and sensory fibers, and is widely used for studying peripheral nerve-related physiopathology[9]. The sciatic nerve crush model is one of the most common models of peripheral nerve injury[9,10]. Similar to other models of sciatic nerve injury (for example, sciatic nerve transection), nerve crush also causes disruption of neuronal axons, but leaves the basal laminae of Schwann cells intact, thus benefiting the regeneration of injured nerves[11]. "
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    Full-text · Article · Dec 2015 · PLoS ONE
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    • "Schwann cells from young and old mice have been shown to differ both morphologically and in their ability to cover the motor endplate (Chai et al., 2011). The number of cells at the neuromuscular junction increases after skeletal muscle denervation, and based on Schwann cell markers, not all are Schwann cells (Magill et al., 2007). Future studies should determine the identity of the other cells and how they contribute to reinnervation. "
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    • "Hence, axons detected after this point are regenerating fibers. Indeed, 2 weeks after the crush, WT axons exhibit robust retargeting to the NMJs, as described previously (Magill et al., 2007). We assessed the retargeting by counting the number of postsynaptic endplates colocalized with axonal YFP fluorescence and found that 80% of the YFP-positive WT Figure 1. "
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    ABSTRACT: Here we demonstrate that the dual leucine zipper kinase (DLK) promotes robust regeneration of peripheral axons after nerve injury in mice. Peripheral axon regeneration is accelerated by prior injury; however, DLK KO neurons do not respond to a preconditioning lesion with enhanced regeneration in vivo or in vitro. Assays for activation of transcription factors in injury-induced proregenerative pathways reveal that loss of DLK abolishes upregulation of p-STAT3 and p-cJun in the cell body after axonal injury. DLK is not required for the phosphorylation of STAT3 at the site of nerve injury but is necessary for retrograde transport of p-STAT3 to the cell body. These data demonstrate that DLK enhances regeneration by promoting a retrograde injury signal that is required for the activation of the neuronal proregenerative program.
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