title: Dicer-microRNA pathway is critical for peripheral nerve regeneration and functional recovery in vivo and regenerative axonogenesis in vitro.
abstract: Both central and peripheral axons contain pivotal microRNA (miRNA) proteins. While recent observations demonstrated that miRNA biosynthetic machinery responds to peripheral nerve lesion in an injury-regulated pattern, the physiological significance of this phenomenon remains to be elucidated. In the current paper we hypothesized that deletion of Dicer would disrupt production of Dicer-dependent miRNAs and would negatively impact regenerative axon growth. Taking advantage of tamoxifen-inducible CAG-CreERt:Dicer(fl/fl) knockout (Dicer KO), we investigated the results of Dicer deletion on sciatic nerve regeneration in vivo and regenerative axon growth in vitro. Here we show that the sciatic functional index, an indicator of functional recovery, was significantly lower in Dicer KO mice in comparison to wild-type animals. Restoration of mechanical sensitivity recorded in the von Frey test was also markedly impaired in Dicer mutants. Further, Dicer deletion impeded the recovery of nerve conduction velocity and amplitude of evoked compound action potentials in vitro. Histologically, both total number of regenerating nerve fibers and mean axonal area were notably smaller in the Dicer KO mice. In addition, Dicer-deficient neurons failed to regenerate axons in dissociated dorsal root ganglia (DRG) cultures. Taken together, our results demonstrate that knockout of Dicer clearly impedes regenerative axon growth as well as anatomical, physiological and functional recovery. Our data suggest that the intact Dicer-dependent miRNA pathway is critical for the successful peripheral nerve regeneration after injury.
authors.affiliation: Department of Physiology, East Carolina University, Greenville, NC 27834, USA.
authors.forename: Di
authors.initials: D
authors.lastname: Wu
authors.forename: Abdalla
authors.initials: A
authors.lastname: Raafat
authors.forename: Elena
authors.initials: E
authors.lastname: Pak
authors.forename: Stefan
authors.initials: S
authors.lastname: Clemens
authors.forename: Alexander K
authors.initials: AK
authors.lastname: Murashov
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001369:Axons / Q000473:pathology / Q000502:physiology / Q000648:ultrastructure; D002478:Cells, Cultured; D053487:DEAD-box RNA Helicases / Q000172:deficiency / Q000378:metabolism*; D004195:Disease Models, Animal; D004558:Electric Stimulation; D004965:Estrogen Antagonists / Q000494:pharmacology; D047629:Estrogen Receptor beta / Q000235:genetics; D019054:Evoked Potentials, Motor / Q000187:drug effects / Q000235:genetics; D007839:Functional Laterality; D005727:Ganglia, Spinal / Q000166:cytology; D006930:Hyperalgesia / Q000209:etiology; D066298:In Vitro Techniques; D051379:Mice; D008822:Mice, Transgenic; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D009416:Nerve Regeneration / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D009431:Neural Conduction / Q000187:drug effects / Q000235:genetics; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000648:ultrastructure; D020127:Recovery of Function / Q000235:genetics / Q000502:physiology*; D043244:Ribonuclease III / Q000172:deficiency / Q000378:metabolism*; D020426:Sciatic Neuropathy / Q000378:metabolism* / Q000503:physiopathology*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D013629:Tamoxifen / Q000031:analogs & derivatives / Q000494:pharmacology; D013997:Time Factors; D019680:Trinucleotide Repeat Expansion / Q000235:genetics
chemical_list: D004965:Estrogen Antagonists; D047629:Estrogen Receptor beta; D035683:MicroRNAs; D013629:Tamoxifen; C016601:afimoxifene; C509781:Dicer1 protein, mouse; D043244:Ribonuclease III; D053487:DEAD-box RNA Helicases