title: An enteroendocrine cell-enteric glia connection revealed by 3D electron microscopy.
abstract: The enteroendocrine cell is the cornerstone of gastrointestinal chemosensation. In the intestine and colon, this cell is stimulated by nutrients, tastants that elicit the perception of flavor, and bacterial by-products; and in response, the cell secretes hormones like cholecystokinin and peptide YY--both potent regulators of appetite. The development of transgenic mice with enteroendocrine cells expressing green fluorescent protein has allowed for the elucidation of the apical nutrient sensing mechanisms of the cell. However, the basal secretory aspects of the enteroendocrine cell remain largely unexplored, particularly because a complete account of the enteroendocrine cell ultrastructure does not exist. Today, the fine ultrastructure of a specific cell can be revealed in the third dimension thanks to the invention of serial block face scanning electron microscopy (SBEM). Here, we bridged confocal microscopy with SBEM to identify the enteroendocrine cell of the mouse and study its ultrastructure in the third dimension. The results demonstrated that 73.5% of the peptide-secreting vesicles in the enteroendocrine cell are contained within an axon-like basal process. We called this process a neuropod. This neuropod contains neurofilaments, which are typical structural proteins of axons. Surprisingly, the SBEM data also demonstrated that the enteroendocrine cell neuropod is escorted by enteric glia--the cells that nurture enteric neurons. We extended these structural findings into an in vitro intestinal organoid system, in which the addition of glial derived neurotrophic factors enhanced the development of neuropods in enteroendocrine cells. These findings open a new avenue of exploration in gastrointestinal chemosensation by unveiling an unforeseen physical relationship between enteric glia and enteroendocrine cells.
authors.affiliation: Departments of Medicine, Duke University Medical Center, Durham, North Carolina, United States of America.
authors.forename: Diego V
authors.initials: DV
authors.lastname: Bohórquez
authors.affiliation: Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.
authors.forename: Leigh A
authors.initials: LA
authors.lastname: Samsa
authors.affiliation: Renovo Neural Incorporation, Cleveland, Ohio, United States of America.
authors.forename: Andrew
authors.initials: A
authors.lastname: Roholt
authors.affiliation: Renovo Neural Incorporation, Cleveland, Ohio, United States of America.
authors.forename: Satish
authors.initials: S
authors.lastname: Medicetty
authors.affiliation: Departments of Medicine, Duke University Medical Center, Durham, North Carolina, United States of America.
authors.forename: Rashmi
authors.initials: R
authors.lastname: Chandra
authors.affiliation: Departments of Medicine, Duke University Medical Center, Durham, North Carolina, United States of America ; Veterans Affairs Medical Center, Durham, North Carolina, United States of America.
authors.forename: Rodger A
authors.initials: RA
authors.lastname: Liddle
mesh_terms: D000818:Animals; D022081:Cell Surface Extensions / Q000648:ultrastructure*; D019858:Enteroendocrine Cells / Q000378:metabolism / Q000648:ultrastructure*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007382:Intermediate Filaments / Q000648:ultrastructure; D051379:Mice; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning / Q000379:methods*; D022142:Secretory Vesicles / Q000648:ultrastructure*