Colitis induces enteric neurogenesis through a 5-HT4-dependent mechanism.
BACKGROUND
The intestine is known to contain enteric neuronal progenitors, but their precise identity and the mechanisms that activate them remain unknown. Based on the evidence for the neurogenic role of serotonin (5-HT) in the postnatal gut and the observation of enteric neuronal hyperplasia in inflammatory bowel disease, we hypothesized that colitis induces a neurogenic response through 5-HT4 receptor signaling.


METHODS
We examined the effects of 5-HT4 agonism on colonic neurogenesis and gliogenesis in vitro and in vivo in adult mice using dextran sodium sulfate to experimentally induce colitis.


RESULTS
In vitro, 5-HT4 agonism led to increased neuronal proliferation and density. Induction of experimental colitis in vivo similarly resulted in increased numbers of myenteric neurons, and this was inhibited by 5-HT4 antagonism. Interestingly, both in vitro and in vivo, 5-HT4 signaling increased glial cell proliferation but did not increase glial cell numbers, leading us to hypothesize that glia may give rise to neurons. After induction of colitis in normal, Nestin-GFP and Sox2-GFP transgenic mice, it was revealed that multiple glial markers (Sox2, Nestin, and CD49b) became strongly expressed by enteric neurons. Immunoselected enteric glia were found to give rise to neurons in culture, and this was inhibited in the presence of 5-HT4 blockade. Finally, isolated glia gave rise to a neuronal network upon transplantation into aganglionic embryonic avian hindgut.


CONCLUSIONS
These results show that colitis promotes enteric neurogenesis in the adult colon through a serotonin-dependent mechanism that drives glial cells to transdifferentiate into neurons.
*Department of Pediatrics, Mucosal Immunology and Biology Research Center, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts; †Pediatric Neurogastroenterology Program, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts; ‡Department of Pediatric Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts; §Department of Human Morphology and Developmental Biology, Faculty of Medicine, Semmelweis University, Budapest, Hungary; and Department of ‖Medicine, ¶Pathology, **Neurology, and ††Pediatrics, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts.
Jaime
J
Belkind-Gerson
Ryo
R
Hotta
Nandor
N
Nagy
Alyssa R
AR
Thomas
Hannah
H
Graham
Lily
L
Cheng
Juan
J
Solorzano
Deanna
D
Nguyen
Michal
M
Kamionek
Jorg
J
Dietrich
Bobby J
BJ
Cherayil
Allan M
AM
Goldstein
D000818:Animals; D049109:Cell Proliferation; D054338:Cell Transdifferentiation; D002642:Chick Embryo; D003092:Colitis / Q000139:chemically induced / Q000378:metabolism / Q000503:physiopathology*; D003106:Colon / Q000503:physiopathology; D003857:Deoxyuridine / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D016264:Dextran Sulfate; D017615:Enteric Nervous System / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D039421:Integrin alpha2 / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D064231:Nestin / Q000378:metabolism; D055495:Neurogenesis / Q000187:drug effects / Q000502:physiology*; D009457:Neuroglia / Q000166:cytology / Q000187:drug effects; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D055748:SOXB1 Transcription Factors / Q000378:metabolism; D058828:Serotonin 5-HT4 Receptor Agonists / Q000494:pharmacology*; D013449:Sulfonamides / Q000494:pharmacology
D039421:Integrin alpha2; C577485:Nes protein, mouse; D064231:Nestin; D055748:SOXB1 Transcription Factors; D058828:Serotonin 5-HT4 Receptor Agonists; C527783:Sox2 protein, mouse; D013449:Sulfonamides; C107556:RS 67506; D016264:Dextran Sulfate; C031086:5-ethynyl-2'-deoxyuridine; D003857:Deoxyuridine