Serial block-face scanning electron microscopy reveals neuronal-epithelial cell fusion in the mouse cornea.
AuthorsCourson, Justin A
Landry, Paul T
Behzad, Ali Reza
Hanlon, Sam D
Rumbaut, Rolando E
Smith, C Wayne
Burns, Alan R
KAUST DepartmentElectron Microscopy
Permanent link to this recordhttp://hdl.handle.net/10754/660377
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AbstractThe cornea is the most highly innervated tissue in the body. It is generally accepted that corneal stromal nerves penetrate the epithelial basal lamina giving rise to intra-epithelial nerves. During the course of a study wherein we imaged corneal nerves in mice, we observed a novel neuronal-epithelial cell interaction whereby nerves approaching the epithelium in the cornea fused with basal epithelial cells, such that their plasma membranes were continuous and the neuronal axoplasm freely abutted the epithelial cytoplasm. In this study we sought to determine the frequency, distribution, and morphological profile of neuronal-epithelial cell fusion events within the cornea. Serial electron microscopy images were obtained from the anterior stroma in the paralimbus and central cornea of 8-10 week old C57BL/6J mice. We found evidence of a novel alternative behavior involving a neuronal-epithelial interaction whereby 42.8% of central corneal nerve bundles approaching the epithelium contain axons that fuse with basal epithelial cells. The average surface-to-volume ratio of a penetrating nerve was 3.32, while the average fusing nerve was smaller at 1.39 (p ≤ 0.0001). Despite this, both neuronal-epithelial cell interactions involve similarly sized discontinuities in the basal lamina. In order to verify the plasma membrane continuity between fused neurons and epithelial cells we used the lipophilic membrane tracer DiI. The majority of corneal nerves were labeled with DiI after application to the trigeminal ganglion and, consistent with our ultrastructural observations, fusion sites recognized as DiI-labeled basal epithelial cells were located at points of stromal nerve termination. These studies provide evidence that neuronal-epithelial cell fusion is a cell-cell interaction that occurs primarily in the central cornea, and fusing nerve bundles are morphologically distinct from penetrating nerve bundles. This is, to our knowledge, the first description of neuronal-epithelial cell fusion in the literature adding a new level of complexity to the current understanding of corneal innervation.
CitationCourson, J. A., Smith, I., Do, T., Landry, P. T., Hargrave, A., Behzad, A. R., … Burns, A. R. (2019). Serial block-face scanning electron microscopy reveals neuronal-epithelial cell fusion in the mouse cornea. PLOS ONE, 14(11), e0224434. doi:10.1371/journal.pone.0224434
SponsorsFunded by R01 EY018239. Agency: National Institutes of Health (NIH). Institute: National Eye Institute (NEI). Type: Research Project (R01). Funding number: EY018239. P30 EY07551. Agency: National Institutes of Health (NIH). Institute: National Eye Institute (NEI). Type: Center Core Grant. Funding Number: EY07551. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. We would like to thank Evelyn Brown and Margaret Gondo for their excellent technical assistance.
PublisherPublic Library of Science (PLoS)