Sonic hedgehog expression correlates with fundic gland differentiation in the adult gastrointestinal tract

Abstract

Background: Sonic hedgehog (Shh) is an important endodermal morphogenetic signal during the development of the vertebrate gut. It controls gastrointestinal patterning in general, and gastric gland formation in particular. We have previously shown that Shh regulates gastric gland proliferation in the adult but detailed analysis of its expression along the adult gastrointestinal tract has never been undertaken. We therefore studied Shh expression along the normal human and rodent adult gastrointestinal tract as well as in intestinal metaplasia of the stomach, gastric and intestinal metaplasia of the oesophagus, and gastric heterotopia in Meckel's diverticulum.

Methods: The studies were performed with in situ hybridisation and by immunohistochemistry using an antibody that recognises the Shh precursor form.

Results: We found that in the normal gastrointestinal tract, high levels of Shh were expressed in the fundic glands of the stomach. Shh expression was also found in fundic gland metaplasia and heterotopia. However, Shh expression was lost in intestinal metaplasia of the stomach.

Conclusion: We found a strong correlation between Shh expression and fundic gland differentiation. Our current study therefore provides evidence that in addition to its role in gastric epithelial development, Shh plays a unique role in gastric epithelial differentiation in adults.

Figure 1

Sonic hedgehog (Shh) mRNA expression along the human gastrointestinal tract. Shh expression was detected (blue stain) in the fundic glandular region (B) of the adult stomach. Shh was not detected in the oesophagus (A) or the antrum of the stomach (C). A few positive cells were found at the base of the crypts in the small intestine (arrows in D and in blow up of boxed area in E) and some of the crypts of the colon (F, arrow).

Figure 2

Sonic hedgehog (Shh) protein expression along the human and murine gastrointestinal tract. (A–G) Sections of the human gastrointestinal tract; immunohistochemical staining with an antibody against the Shh precursor protein. We found intense staining in the fundic glands (B) whereas no staining was found in the oesophagus (A), antrum (C), Brunner’s glands (D), duodenum (E), ileum (F), or colon (G). Sections of the murine gastrointestinal tract (H–N) gave the same results. Shown are: forestomach (H), fundic glands (I), antral glands (J), duodenum (K), jejunum (L), ileum (M), and colon (N). Control experiments in three adjacent sections are also shown (O–Q). No signal was found in the human fundic gland with isotype control antibody (O) and the signal detected with the anti-Shh antibody (P) was efficiently blocked with a blocking peptide (Q).

Figure 3

Sonic hedgehog (Shh) expression was lost in intestinal metaplasia of the stomach. Immunohistochemical triple stain of Shh (blue), mucin (MUC)5AC (red), and MUC2 (brown). (A–C) Specimens of two different patients with intestinal metaplasia. (A) This specimen shows normal glands with MUC5AC expressing pit cells (arrowhead, red stain), Shh expressing gland cells (arrow, blue stain), and adjacent metaplastic glands with MUC2 expressing goblet cells (asterisk, brown stain). (B) Blow up of boxed area in (A); note MUC5AC expression by goblet cells around the pit gland transition. (C) Another example of metaplastic gland (asterisk) amid normal Shh expressing glands (arrow). (D) Although most cases showed replacement of only the glands or both pits and glands by intestinal cells, in this patient we observed a mix of intestinal MUC2 expressing goblet cells (brown) and gastric MUC5AC expressing pit cells (red) in the pit region. (E–G) Three types of goblet cells were observed in this study: goblet cells that expressed exclusively MUC2 (arrow in E), goblet cells that coexpressed MUC2 and MUC5AC (arrow in F), and goblet cells that expressed only MUC5AC (arrow in G).

Figure 4

Sonic hedgehog (Shh) was expressed in fundic gland ectopies. (A–C) Three different cases of Meckel’s diverticulum. (A) No Shh was detected in a Meckel’s specimen with purely intestinal histology. (B) Shh staining (brown precipitate, arrow) in a gastric fundic gland adjacent to a region of goblet cell containing intestinal histology (asterisk). (C) Double stain of the gastric mucin MUC5AC (blue, arrow) and Shh (brown, asterisks) in a Meckel’s diverticulum with fundic gland histology. (D, E) Oesophageal metaplasias. (D) No Shh was detected in the intestinal metaplasia of Barrett’s mucosa. (E) A case of fundic gland metaplasia of the oesophagus with Shh expressing cells (brown precipitate, asterisk).