Meng Lingbin, Huang Tao, Sun Chengsan, Hill David L, Krimm Robin
Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY 40292, USA.
Department of Psychology, University of Virginia, Charlottesville, VA 22904, USA.
Exp Neurol. 2017 Jul;293:27-42. doi: 10.1016/j.expneurol.2017.03.016. Epub 2017 Mar 25.
Taste nerves readily regenerate to reinnervate denervated taste buds; however, factors required for regeneration have not yet been identified. When the chorda tympani nerve is sectioned, expression of brain-derived neurotrophic factor (BDNF) remains high in the geniculate ganglion and lingual epithelium, despite the loss of taste buds. These observations suggest that BDNF is present in the taste system after nerve section and may support taste nerve regeneration. To test this hypothesis, we inducibly deleted Bdnf during adulthood in mice. Shortly after Bdnf gene recombination, the chorda tympani nerve was unilaterally sectioned causing a loss of both taste buds and neurons, irrespective of BDNF levels. Eight weeks after nerve section, however, regeneration was differentially affected by Bdnf deletion. In control mice, there was regeneration of the chorda tympani nerve and taste buds reappeared with innervation. In contrast, few taste buds were reinnervated in mice lacking normal Bdnf expression such that taste bud number remained low. In all genotypes, taste buds that were reinnervated were normal-sized, but non-innervated taste buds remained small and atrophic. On the side of the tongue contralateral to the nerve section, taste buds for some genotypes became larger and all taste buds remained innervated. Our findings suggest that BDNF is required for nerve regeneration following gustatory nerve section.
味觉神经能够轻易再生，以重新支配失神经支配的味蕾；然而，再生所需的因素尚未确定。当鼓索神经被切断时，尽管味蕾丧失，但脑源性神经营养因子（BDNF）在膝状神经节和舌上皮中的表达仍然很高。这些观察结果表明，神经切断后BDNF存在于味觉系统中，可能支持味觉神经再生。为了验证这一假设，我们在成年小鼠中诱导性敲除了Bdnf基因。在Bdnf基因重组后不久，单侧切断鼓索神经，导致味蕾和神经元均丧失，与BDNF水平无关。然而，神经切断八周后，再生受到Bdnf基因敲除的不同影响。在对照小鼠中，鼓索神经再生，味蕾重新出现并获得神经支配。相比之下，缺乏正常Bdnf表达的小鼠中，很少有味蕾获得神经支配，因此味蕾数量仍然很低。在所有基因型中，获得神经支配的味蕾大小正常，但未获得神经支配的味蕾仍然很小且萎缩。在与神经切断侧相对的舌侧，某些基因型的味蕾变大，所有味蕾均保持神经支配。我们的研究结果表明，BDNF是味觉神经切断后神经再生所必需的。
