title: Macroscopic in vivo imaging of facial nerve regeneration in Thy1-GFP rats.
abstract: OBJECTIVE
  Facial nerve injury leads to severe functional and aesthetic deficits. The transgenic Thy1-GFP rat is a new model for facial nerve injury and reconstruction research that will help improve clinical outcomes through translational facial nerve injury research.
  
  
  OBJECTIVE
  To determine whether serial in vivo imaging of nerve regeneration in the transgenic rat model is possible, facial nerve regeneration was imaged under the main paradigms of facial nerve injury and reconstruction.
  
  
  METHODS
  Fifteen male Thy1-GFP rats, which express green fluorescent protein (GFP) in their neural structures, were divided into 3 groups in the laboratory: crush-injury, direct repair, and cross-face nerve grafting (30-mm graft length). The distal nerve stump or nerve graft was predegenerated for 2 weeks. The facial nerve of the transgenic rats was serially imaged at the time of operation and after 2, 4, and 8 weeks of regeneration. The imaging was performed under a GFP-MDS-96/BN excitation stand (BLS Ltd).
  Facial nerve injury.
  
  
  METHODS
  Optical fluorescence of regenerating facial nerve axons.
  
  
  RESULTS
  Serial in vivo imaging of the regeneration of GFP-positive axons in the Thy1-GFP rat model is possible. All animals survived the short imaging procedures well, and nerve regeneration was followed over clinically relevant distances. The predegeneration of the distal nerve stump or the cross-face nerve graft was, however, necessary to image the regeneration front at early time points. Crush injury was not suitable to sufficiently predegenerate the nerve (and to allow for degradation of the GFP through Wallerian degeneration). After direct repair, axons regenerated over the coaptation site in between 2 and 4 weeks. The GFP-positive nerve fibers reached the distal end of the 30-mm-long cross-face nervegrafts after 4 to 8 weeks of regeneration.
  
  
  CONCLUSIONS
  The time course of facial nerve regeneration was studied by serial in vivo imaging in the transgenic rat model. Nerve regeneration was followed over clinically relevant distances in a small number of experimental animals, as they were subsequently imaged at multiple time points. The Thy1-GFP rat model will help improve clinical outcomes of facial reanimation surgery through improving the knowledge of facial nerve regeneration after surgical procedures.
  
  
  METHODS
  NA.
authors.affiliation: Division of Plastic and Reconstructive Surgery, Medical University of Vienna, Vienna, Austria.
authors.forename: Eva
authors.initials: E
authors.lastname: Placheta
authors.affiliation: Division of Plastic and Reconstructive Surgery, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Wood
authors.affiliation: Division of Plastic and Reconstructive Surgery, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Christine
authors.initials: C
authors.lastname: Lafontaine
authors.affiliation: Division of Plastic and Reconstructive Surgery, Medical University of Vienna, Vienna, Austria.
authors.forename: Manfred
authors.initials: M
authors.lastname: Frey
authors.affiliation: Division of Plastic and Reconstructive Surgery, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Tessa
authors.initials: T
authors.lastname: Gordon
authors.affiliation: Division of Plastic and Reconstructive Surgery, The Hospital for Sick Children, Toronto, Ontario, Canada3Department of Surgery, University of Toronto, Toronto, Ontario, Canada4Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada5I.
authors.forename: Gregory H
authors.initials: GH
authors.lastname: Borschel
mesh_terms: D000818:Animals; D001369:Axons / Q000502:physiology; D001707:Biopsy, Needle; D003952:Diagnostic Imaging / Q000379:methods; D004195:Disease Models, Animal; D020220:Facial Nerve Injuries / Q000175:diagnosis / Q000601:surgery*; D049452:Green Fluorescent Proteins; D007150:Immunohistochemistry; D008297:Male; D009416:Nerve Regeneration / Q000502:physiology*; D010525:Peripheral Nerves / Q000637:transplantation*; D011897:Random Allocation; D051381:Rats; D011914:Rats, Inbred BN; D055647:Rats, Transgenic; D020127:Recovery of Function; D012680:Sensitivity and Specificity; D016378:Tissue Transplantation / Q000379:methods
chemical_list: D049452:Green Fluorescent Proteins