Sacral neural crest‐derived cells enter the aganglionic colon of Ednrb^−/− mice along extrinsic nerve fibers

Abstract

Both vagal and sacral neural crest cells contribute to the enteric nervous system in the hindgut. Because it is difficult to visualize sacral crest cells independently of vagal crest, the nature and extent of the sacral crest contribution to the enteric nervous system are not well established in rodents. To overcome this problem we generated mice in which only the fluorescent protein-labeled sacral crest are present in the terminal colon. We found that sacral crest cells were associated with extrinsic nerve fibers. We investigated the source, time of appearance, and characteristics of the extrinsic nerve fibers found in the aganglionic colon. We observed that the pelvic ganglion neurons contributed a number of extrinsic fibers that travel within the hindgut between circular and longitudinal muscles and within the submucosa and serosa. Sacral crest-derived cells along these fibers diminished in number from fetal to post-natal stages. A small number of sacral crest-derived cells were found between the muscle layers and expressed the neuronal marker Hu. We conclude that sacral crest cells enter the hindgut by advancing on extrinsic fibers and, in aganglionic preparations, they form a small number of neurons at sites normally occupied by myenteric ganglia. We also examined the colons of ganglionated preparations and found sacral crest-derived cells associated with both extrinsic nerve fibers and nascent ganglia. Extrinsic nerve fibers serve as a route of entry for both rodent and avian sacral crest into the hindgut.

Neural Crest Cells Contribute an Astrocyte-like Glial Population to the Spleen

“…We observed the failure of NCC migration into the distal hindgut in EdnrB NCC −/− animals (Fig. 1A), consistent with our prior reports with other fluorophores in this model22. Examination of post-natal (P) day 21 bowel revealed normal, pelleted stools in the distal colon of EdnrB NCC +/− animals, while the EdnrB NCC −/− animals demonstrated distal bowel obstruction, with proximal colonic dilation and a large stool burden in the colon, consistent with a HSCR phenotype (Fig.…”

Enteric nervous system development: migration, differentiation, and disease

“…While vagal and sacral ENCDCs express the same ENCDC-specific markers (3, 49), a RNA microarray comparing vagal and sacral chick neural tube explants (49) indicated that sacral-derived crest expressed less RET mRNA than vagal crest, and their behavior was partially transformed to that of vagal crest by RET overexpression. A study in mice where the vagal wave front was significantly delayed (NC-specific Ednrb deletion) confirmed the finding that RET expression was reduced in sacral ENCDCs (61). Notably, in the Ret −/− and Gfra1 −/− mouse models of total intestinal aganglionosis (57, 30) and a conditional Ednrb ablation model of colonic aganglionosis (61), rare intrinsic neurons can be found within the most-distal bowel.…”

“…A study in mice where the vagal wave front was significantly delayed (NC-specific Ednrb deletion) confirmed the finding that RET expression was reduced in sacral ENCDCs (61). Notably, in the Ret −/− and Gfra1 −/− mouse models of total intestinal aganglionosis (57, 30) and a conditional Ednrb ablation model of colonic aganglionosis (61), rare intrinsic neurons can be found within the most-distal bowel. These almost certainly represent the remnants of the sacral ENCDC population.…”

Altered neuronal density and neurotransmitter expression in the ganglionated region of Ednrb null mice: implications for Hirschsprung's disease

“…However, they are absent from the distal third of the Ednrb null colon and are decreased in number and size in the proximal (PMC) and distal mid‐colon (DMC) (Figs B and B, D, F). The aganglionic region of Ednrb null animals contains a number of rostrally directed fibers (Figs B and F) . The myenteric ganglia in the entire Ednrb het colon and in the PMC of Ednrb nulls are generally arranged in rows perpendicular to the longitudinal axis of the gut.…”