Reelin protects from colon pathology by maintaining the intestinal barrier integrity and repressing tumorigenic genes

We previously reported that reelin, an extracellular matrix protein first known for its key role in neuronal migration, reduces the susceptibility to dextran sulphate sodium (DSS)-colitis. The aim of the current study was to determine whether reelin protects from colorectal cancer and how reelin defends from colon pathology. In the colon of wild-type and of mice lacking reelin (reeler mice) we have analysed the: i) epithelium cell renewal processes, ii) morphology, iii) Sox9, Cdx2, Smad5, Cyclin D1, IL-6 and IFNγ mRNA abundance in DSS-treated and untreated mice, and iv) development of azoxymethane/DSS-induced colorectal cancer, using histological and real time-PCR methodologies. The reeler mutation increases colitis-associated tumorigenesis, with increased tumours number and size. It also impairs the intestinal barrier because it reduces cell proliferation, migration, differentiation and apoptosis; decreases the number and maturation of goblet cells, and expands the intercellular space of the desmosomes. The intestinal barrier impairment might explain the increased susceptibility to colon pathology exhibited by the reeler mice and is at least mediated by the down-regulation of Sox9 and Cdx2. In response to DSS-colitis, the reeler colon increases the mRNA abundance of IL-6, Smad5 and Cyclin D1 and decreases that of IFNγ, conditions that might result in the increased colitis-associated tumorigenesis found in the reeler mice. In conclusion, the results highlight a role for reelin in maintaining intestinal epithelial cell homeostasis and providing resistance against colon pathology.