Lrig3 is Required in Recovery from Acute Inflammatory Assault

46 pagesBackground and Aim. The mouse colon contains a suite of genes that provide a framework from which the structure and function of the colon is tightly regulated. The colon contains crypts: small, U-shaped invaginations in the epithelial layer that absorb water and secrete mucus. A gene from this suite of regulatory genes is called Leucine-rich repeats and immunoglobulin-like domains 3 (Lrig3), may regulate the size and structure of a specialized region of the colonic crypts. In homeostasis, Lrig3-/- mice have longer colons, taller crypts, more cells per crypt, and more stem and progenitor cells than wildtype (WT) mice. This indicates that Lrig3 is required for restricting the size of the stem cell niche. It is unknown if these abnormalities perturb the regenerative capabilities of the colon. The aim of my study was to test the hypothesis that loss of Lrig3 impairs colonic regeneration after acute inflammatory assault. Method. To address our study aims, we administered WT (B6, n=4) and Lrig3-/- mice (n=4) 3% Dextran Sodium Sulfate (DSS) in drinking water for seven days to cause crypt destruction and local inflammation. We initially sought to examine crypt regeneration over the subsequent seven days, but the Lrig3-/- mice lost >20% of their body weight and the study had to be halted 24 hours after resumption of normal drinking water, due to this extreme and unexpected weight loss. We then sacrificed all mice in both cohorts at this time, extracted the colons and performed anatomical, morphometric, protein expression, and analysis for genes associated with crypt structure and regeneration. Results. Lrig3-/- mice displayed a higher susceptibility to DSS treatment than WT as supported by greater weight loss and increased colon shortening. Compared to WT mice, Lrig3-/- mice expressed lower levels of Ki-67+ cells/epithelial area (p=0.045). Lrig3-/- mice also had decreased Lrig1-positive cells per crypt (p<0.01). Cell death analysis revealed a greater number of TUNEL-positive cells in the base of the crypt of Lrig3-/- mice (p