Figure 6.

Mild epithelial damage, mucin retention, mucin type changes, and goblet cell hyperplasia in P10 Gfra1^hypo/hypomice. (A1–2) H&E and AB-PAS (A3) staining of coronal colon sections from P10 WT mice. In WT mice, the mucosa is thin and compact with an evenly palisading, regular surface epithelium. The crypts of Lieberkühn (A1 and A3, white arrow) in the colon are shallow and straight. Goblet cells (A1–3, white arrowhead) are abundant in surface epithelium and within the proximal third of the crypts, but less abundant at the crypt bases (A3). The goblet cells in the surface epithelium and in the proximal parts of the crypts contain PAS-positive neutral mucins, staining deep purple (A3, white arrowhead). The goblet cells in the basal parts of the crypts primarily contain AB-positive acidic droplets, staining light blue (A3, black open arrowhead). (B and C) In Gfra1^hypo/hypo mice, the colon crypts (B1, B3, and C1, white arrow) are mildly to moderately dilated, with variable levels of mucin retention (B2, black bold arrow). The surface of the mucosa in the colon of Gfra1^hypo/hypo mice is bumpy in appearance (compare A1 with B1), and epithelial cells grow in disorganized, undulating rows with partly overlapping nuclei (B1, black arrow). The height variation of the epithelial cells (B2, blue bold arrow), the round to oval bland nuclei (B2, black arrowhead), increased eosinophilia in the apical cytoplasm (B2, red arrowheads), and the indistinct cell borders (B2, white open arrowhead) are indicative of degeneration and mild epithelial damage. Unlike in WT mice (A3), the goblet cells in Gfra1^hypo/hypo mice often are abundant in the basal parts of the crypts (C2, white arrowheads) and show a shift toward the production of PAS-positive (ie, neutral) mucins (compare C2 with A3). (D) Quantification of goblet cells in WT, Gfra1^WT/hypo, and Gfra1^hypo/hypo mice, for which the number of goblet cells is increased both in proximal (P < .001 and P < .01) and distal colons (P < .001) compared with both heterozygous and WT animals; N = 6–8 animals per genotype. (E) Gfra1^hypo/hypo mice and Gfra1^WT/hypo have fewer AB-positive cells per crypt compared with WT colon (P < .001 and P < .05, N = 4–5). (F) AB-PAS staining from WT and hypomorphic duodenum at P10. (G) Quantification of goblet cells (F, white arrows) in WT, Gfra1^WT/hypo, and Gfra1^hypo/hypo mice in P10 duodenum (N = 4 per genotype). (H) Quantification of PAS-positive goblet cells, AB-positive goblet cells were absent in duodenum (N = 4 mice per genotype). *P < .05, **P < .01, and ***P < .001. col, colon. Analysis of variance and the Tukey multiple comparisons test, data are presented as means ± SEM. All summary data are presented as means ± SEM.