Biomechanical changes in oxazolone-induced colitis in BALB/C mice.

Ulcerative colitis (UC) is associated with intestinal and extra intestinal clinical manifestations. The profound organic changes in UC indicate that the colonic mechanical and mechanosensory functions are affected. The aim was to study acute morphological and biomechanical properties of the distal colon in oxazolone-induced UC in BALB/C mice. Six normal male BALB/C mice and 10 oxazolone-induced UC mice were studied. UC was induced by epicutaneous and intrarectal administration of oxazolone. The mechanical test was done as a distension experiment where the colon was distended up to 20 cmH2O. The pressure, outer diameter and length were recorded simultaneously. Circumferential and longitudinal stresses and strains were computed. The intestinal specimens were processed for histology. The mucosa was infiltrated with acute and chronic inflammatory cells. Mucosal bleeding, irregular ulcers crypt abscess, and destruction of the epithelial border were observed. Although, the mucosa in ulcers was much thinner than in the normal controls, the mucosa and submucosa around the ulcer were thicker than in the normal controls (P<0.05). Oxazolone-induced colitis increased the circumferences and wall cross-sectional area (P<0.01), the opening angle and residual strain at the serosa increased (P<0.01). Furthermore, the circumferential and longitudinal stiffness increased in the UC wall and was most pronounced in longitudinal direction. The opening angle and residual strain was linearly correlated to the wall thickness, area and inflammation degree. In conclusion, morphological and biomechanical changes of the colon occurred during the development of UC. The increased stiffness may contribute to the abnormal function in patients with UC.