Toll-like receptor (Tlr) 4 is a lipopolysaccharide (LPS) receptor that contributes to the regulation of intestinal cell homeostasis, a condition that is altered in the intestines of cystic fibrosis mice. Herein, we assessed whether Tlr4 genotype influences cystic fibrosis intestinal disease by producing and phenotyping 12-wk (adult)- and 4-day (neonate)-old mice derived from BALB cystic fibrosis transmembrane conductance regulator, Cftr+/tm1Uncand C.C3- Tlr4Lps-d/J ( Tlr4−/−), progenitors. Intestinal disease was assayed through mouse survival, crypt-villus axis (CVA) length, cell proliferation, bacterial load, bacterial classification, inflammatory cell infiltrate, and mucus content measures. Of the 77 Cftr−/−(CF) mice produced, only one Cftr/ Tlr4 double-mutant mouse lived to the age of 12 wk while the majority of the remainder succumbed at ∼4 days of age. The survival of CF Tlr4+/−mice exceeded that of both CF Tlr4+/+and Cftr/ Tlr4 double-mutant mice. Adult CF mice presented increased Tlr4 expression, CVA length, crypt cell proliferation, and bacterial load relative to non-CF mice, but no differences were detected in Tlr4+/−compared with Tlr4+/+CF mice. The double-mutant neonates did not differ from Tlr4+/+or Tlr4+/−CF mice by intestinal CVA length or bacterial load, but fewer Tlr4+/−CF neonates presented with luminal mucus obstruction in the distal ileum, and the intestinal mast cell increase of CF mice was not evident in double-mutant neonates. We conclude that Tlr4 deficiency reduces the survival, but does not alter the intestinal phenotypes, of extended CVA or increased bacterial load in BALB CF mice.
Enhanced intestinal epithelial cell proliferation in diabetic rats correlates with β-catenin accumulation
