Lack of discreet colocalization of epithelial apoptosis to the atretic precursor in the colon of the Fibroblast growth factor receptor 2IIIb mouse and staining consistent with cellular movement suggest a revised model of atresia formation

Abstract

Background: Colonic atresias in the Fibroblast growth factor receptor 2IIIb (Fgfr2IIIb) mouse model have been attributed to increased epithelial apoptosis and decreased epithelial proliferation at embryonic day (E) 10.5. We therefore hypothesized that these processes would colocalize to the distal colon where atresias occur (atretic precursor) and would be excluded or minimized from the proximal colon and small intestine. Results: We observed a global increase in intestinal epithelial apoptosis in Fgfr2IIIb −/− intestines from E9.5 to E10.5 that did not colocalize to the atretic precursor. Additionally, epithelial proliferations rates in Fgfr2IIIb −/− intestines were statistically indistinguishable to that of controls at E10.5 and E11.5. At E11.5 distal colonic epithelial cells in mutants failed to assume the expected pseudostratified columnar architecture and the continuity of the adjacent basal lamina was disrupted. Individual E-cadherin-positive cells were observed in the colonic mesenchyme. Conclusions: Our observations suggest that alterations in proliferation and apoptosis alone are insufficient to account for intestinal atresias and that these defects may arise from both a failure of distal colonic epithelial cells to develop normally and local disruptions in basal lamina architecture.

New developments in the biology of fibroblast growth factors

“…Fgf10 is expressed in GI tract mesenchyme and signals to epithelium. Mice lacking Fgf10 or Fgfr2b have impaired development of the stomach, duodenum, cecum, and colon (Danopoulos et al, 2017; Kowalkowski et al, 2020; Lv et al, 2019). For example, genetic knockout of Fgf10 or Fgfr2b results in duodenal or colonic atresia in mice (M. L. M. Jones, Sarila, et al, 2020; Kowalkowski et al, 2020; Teague et al, 2018).…”

“…Mice lacking Fgf10 or Fgfr2b have impaired development of the stomach, duodenum, cecum, and colon (Danopoulos et al, 2017; Kowalkowski et al, 2020; Lv et al, 2019). For example, genetic knockout of Fgf10 or Fgfr2b results in duodenal or colonic atresia in mice (M. L. M. Jones, Sarila, et al, 2020; Kowalkowski et al, 2020; Teague et al, 2018). Examination of the colonic epithelium in Fgfr2b −/− mice showed increased apoptosis but normal levels of proliferation.…”

“…Examination of the colonic epithelium in Fgfr2b À/À mice showed increased apoptosis but normal levels of proliferation. Epithelial histology showed lack of a pseudostratified columnar architecture and discontinuity of the adjacent basal lamina with individual E-cadherin (Cdh1) expressing cells found in the colonic mesenchyme (Kowalkowski et al, 2020).…”