NIH Public Access

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


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.

Download full-text


Available from: Daniel A Hunter, Jun 10, 2014
27 Reads
  • Source
    • "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. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Pericytes are perivascular cells that envelop and make intimate connections with adjacent capillary endothelial cells. Recent studies show that they may have a profound impact in skeletal muscle regeneration, innervation, vessel formation, fibrosis, fat accumulation, and ectopic bone formation throughout life. In this review, we summarize and evaluate recent advances in our understanding of pericytes' influence on adult skeletal muscle pathophysiology. We also discuss how further elucidating their biology may offer new approaches to the treatment of conditions characterized by muscle wasting.
    Frontiers in Aging Neuroscience 09/2014; 6:245. DOI:10.3389/fnagi.2014.00245 · 4.00 Impact Factor
  • Source
    • "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. "
    [Show abstract] [Hide abstract]
    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.
    Neuron 06/2012; 74(6):1015-22. DOI:10.1016/j.neuron.2012.04.028 · 15.05 Impact Factor
  • Source
    • "The use of the thy1 gene promoter, coupled with the GFP gene, permits expression predominantly in neuronal tissue (Feng et al., 2000; Morris, 1985; Vidal et al., 1990). Previously, our laboratory has used these transgenic mice to directly visualize nerve regeneration in vivo, and muscle reinnervation at motor endplates (Hayashi et al., 2007a; Magill et al., 2007). 0165-0270/$ – see front matter © 2011 Elsevier B.V. All rights reserved. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In order to evaluate nerve regeneration in clinically relevant hindlimb surgical paradigms not feasible in fluorescent mice models, we developed a rat that expresses green fluorescent protein (GFP) in neural tissue. Transgenic Sprague-Dawley rat lines were created using pronuclear injection of a transgene expressing GFP under the control of the thy1 gene. Nerves were imaged under fluorescence microscopy and muscles were imaged with confocal microscopy to determine GFP expression following sciatic nerve crush, transection and direct suturing, and transection followed by repair with a nerve isograft from nonexpressing littermates. In each surgical paradigm, fluorescence microscopy demonstrated the loss and reappearance of fluorescence with regeneration of axons following injury. Nerve regeneration was confirmed with imaging of Wallerian degeneration followed by reinnervation of extensor digitorum longus (EDL) muscle motor endplates using confocal microscopy. The generation of a novel transgenic rat model expressing GFP in neural tissue allows in vivo imaging of nerve regeneration and visualization of motor endplate reinnervation. This rat provides a new model for studying peripheral nerve injury and regeneration over surgically relevant distances.
    Journal of Neuroscience Methods 02/2012; 204(1):19-27. DOI:10.1016/j.jneumeth.2011.10.011 · 2.05 Impact Factor
Show more