Facial Nerve Axotomy in Mice: A Model to Study Motoneuron Response to Injury

Abstract

The goal of this surgical protocol is to expose the facial nerve, which innervates the facial musculature, at its exit from the stylomastoid foramen and either cut or crush it to induce peripheral nerve injury. Advantages of this surgery are its simplicity, high reproducibility, and the lack of effect on vital functions or mobility from the subsequent facial paralysis, thus resulting in a relatively mild surgical outcome compared to other nerve injury models. A major advantage of using a cranial nerve injury model is that the motoneurons reside in a relatively homogenous population in the facial motor nucleus in the pons, simplifying the study of the motoneuron cell bodies. Because of the symmetrical nature of facial nerve innervation and the lack of crosstalk between the facial motor nuclei, the operation can be performed unilaterally with the unaxotomized side serving as a paired internal control. A variety of analyses can be performed postoperatively to assess the physiologic response, details of which are beyond the scope of this article. For example, recovery of muscle function can serve as a behavioral marker for reinnervation, or the motoneurons can be quantified to measure cell survival. Additionally, the motoneurons can be accurately captured using laser microdissection for molecular analysis. Because the facial nerve axotomy is minimally invasive and well tolerated, it can be utilized on a wide variety of genetically modified mice. Also, this surgery model can be used to analyze the effectiveness of peripheral nerve injury treatments. Facial nerve injury provides a means for investigating not only motoneurons, but also the responses of the central and peripheral glial microenvironment, immune system, and target musculature. The facial nerve injury model is a widely accepted peripheral nerve injury model that serves as a powerful tool for studying nerve injury and regeneration. Video LinkThe video component of this article can be found at

Neurotrophic effects of dental pulp stem cells on trigeminal neuronal cells

“…This enzyme is important for neuron-glial cell interactions; therefore, from day 2 onwards, the cells can no longer be considered genuine glial cells, eliminating out their trophic effects on the cultured neurons 37 . TGNC isolated in this study and grown in the absence of serum showed a great reduction in the number post isolation, as an axotomy of the three main branches of TG was required during the isolation process; thus, there was neuronal loss and profound phenotypic changes as a result of injury 38,39 . This effect was reversed when DPSC-CM was added as a linear trend of neuronal survival/rescuing and neurite outgrowth could be observed over time.…”

CD4+ T cell expression of the IL-10 receptor is necessary for facial motoneuron survival after axotomy

“…Surgical procedure: FNA was performed when mice were 8 weeks old. The detailed surgical procedure has been published previously [27]. Briefly, animals were anesthetized with 2.5% isoflurane, and a small (~4 mm) incision was made posterior to the right ear protuberance using aseptic techniques.…”

The Mouse Levator Auris Longus Muscle: An Amenable Model System to Study the Role of Postsynaptic Proteins to the Maintenance and Regeneration of the Neuromuscular Synapse

“…One main condition to test the role of muscle-derived proteins is the process of NMJ regeneration. Therefore, as a first hint to explore the potential use of the LAL muscle as a model of NMJ regeneration, we refined a previously described procedure to accomplish facial nerve axotomy (Olmstead et al, 2015 ) and analyzed NMJ degeneration and regeneration. With this aim, we performed two procedures of nerve damage; to analyze NMJ degeneration, a 4 mm segment of the posterior auricular branch of the facial nerve was transected, whereas NMJ regeneration was evaluated after a 30 s crush injury of the same facial nerve branch ( Figure 6A ).…”

“…Facial nerve injuries were performed as described (Olmstead et al, 2015 ) with some modifications. Briefly, adult animals were anesthetized by isofluorane inhalation, as described above, and after shaving the right ear posterior region, a surgical 5 mm skin incision was performed to expose the facial nerve branches.…”