title: Repair of motor nerve gaps with sensory nerve inhibits regeneration in rats.
abstract: OBJECTIVE
  Sensory nerve grafts are often used to reconstruct injured motor nerves, but the consequences of such motor/sensory mismatches are not well studied. Sensory nerves have more diverse fiber distributions than motor nerves and may possess phenotypically distinct Schwann cells. Putative differences in Schwann cell characteristics and pathway architecture may negatively affect the regeneration of motor neurons down sensory pathways. We hypothesized that sensory grafts impair motor target reinnervation, thereby contributing to suboptimal outcomes. This study investigated the effect of motor versus sensory grafts on nerve regeneration and functional recovery.
  
  
  METHODS
  The authors conducted a prospective, randomized, controlled animal study.
  
  
  METHODS
  Fifty-six Lewis rats were randomized to seven groups of eight animals each. Five-millimeter tibial nerve defects were reconstructed with motor or sensory nerve grafts comprised of single, double, triple, or quadruple cables. Tibial nerve autografts served as positive controls. Three weeks after reconstruction, nerves were harvested for histologic examination and quantitative histomorphometric analysis. Wet muscle masses provided an index of functional recovery.
  
  
  RESULTS
  Nerve regeneration was significantly greater across motor versus sensory nerve grafts independent of graft cross-sectional area or cable number. Motor grafts demonstrated increased nerve density, percent nerve, and total fiber number (P < .05). Normalized wet muscle masses trended toward improved recovery in motor versus sensory groups.
  
  
  CONCLUSIONS
  Reconstruction of tibial nerve defects with nerve grafts of motor versus sensory origin enhanced nerve regeneration independent of cable number in a rodent model. Preferential nerve regeneration through motor nerve grafts may also promote functional recovery with potential implications for clinical nerve reconstruction.
authors.affiliation: Department of Otolaryngology-Head & Neck Surgery, Washington University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Brenner
authors.forename: Jason R
authors.initials: JR
authors.lastname: Hess
authors.forename: Terence M
authors.initials: TM
authors.lastname: Myckatyn
authors.forename: Ayato
authors.initials: A
authors.lastname: Hayashi
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Hunter
authors.forename: Susan E
authors.initials: SE
authors.lastname: Mackinnon
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D008297:Male; D009046:Motor Neurons / Q000637:transplantation / Q000648:ultrastructure; D009416:Nerve Regeneration / Q000502:physiology*; D016067:Nerve Transfer / Q000379:methods*; D009475:Neurons, Afferent / Q000637:transplantation / Q000648:ultrastructure; D011446:Prospective Studies; D011897:Random Allocation; D051381:Rats; D011917:Rats, Inbred Lew; D013979:Tibial Nerve / Q000293:injuries / Q000473:pathology / Q000601:surgery*