Repair of the Enteric Nervous System through Vagal-Mediated Expansion of Neural Stem Cells
Author(s):
Simone Langness, UC San Diego; Brian Eliceiri, UC San Diego; Raul Coimbra, UC San Diego; Todd Costantini, UC San Diego
Background: The enteric nervous system (ENS) is composed of enteric glia cells and enteric neurons and is a key regulator of epithelial function within the gut as well as an important mediator of the gut response to injury. In order to restore gut barrier function after injury, epithelial cells and cells of the ENS must be repaired or replaced. We have previously shown that the vagus nerve alters the ENS response to injury via direct innervation of the gut. Recently, a population of multipotent progenitor cells called “enteric neural stem cells” (ENSC) have been identified in the intestine that are capable of differentiating into enteric neurons and enteric glia cells. The ability of these ENSCs to respond to intestinal injury and the role of the vagus nerve in mediating their expansion is unknown.
Hypothesis: We hypothesized that intestinal ischemia/reperfusion (I/R) injury would result in an expansion of the gut ENSC population and that the ENSC response to injury would be mediated by the vagus nerve.
Methods: Mice were subjected to intestinal I/R injury by superior mesenteric artery occlusion (SMAO) for 30 minutes. In a separate cohort of animals, abdominal vagotomy was performed prior to SMAO. The terminal ileum was harvested at several timepoints after injury. Gut barrier function was evaluated by measuring in vivo permeability to FITC-Dextran. Quantification of gut ENSCs was accomplished using flow cytometry by measuring the CD49b+ Lineage- population.
Results: Intestinal I/R injury caused histologic gut injury at 4 and 24 hours post-injury. Intestinal I/R injury was associated with a significant increase in the ENSC population compared to sham at 2, 4 and 8 hours after injury. Maximum ENSC increase occurred at 4 hours post-injury (2.1% versus 4.6%, p<0.001) and returned to baseline by 24 hours. Vagotomy prevented the injury-induced increase in the ENSC population seen at 4 hours after I/R with ENSC percentage similar to sham (see Figure). Vagotomy was associated with delayed restoration of gut barrier function, with increased intestinal permeability seen in vagotomized animals at 48 hours post-injury compared to I/R alone.
Conclusions: The ENSC population within the gut undergoes expansion following acute injury through a vagal-dependent pathway. Given that an intact ENS is required to maintain intestinal barrier function, augmenting repair of the ENS by stimulating or recruiting ENSC may result in improved kinetics of injury resolution.