Changes of colonic mucosal microcirculation and histology in two colitis models - An experimental study using intravital microscopy and a new histological scoring system

This study investigated capillary blood flow (CBF) and pathomorphological a lterations in the mucosa of different bowel segments at different times aft er disease onset in rats with colitis induced by either trinitrobenzensulfo nic acid (TNBS) or mitomycin-C. CBF was determined by intravital microscopy using fluorescein-labeled erythrocytes. The histological degree of inflamm ation was assessed by a new scoring system. Severe acute histological chang es were found in the distal colon 24 hr after induction of TNBS colitis (sc ore: 8.9 +/- 1.0). CBF was increased (2.9 +/- 0.05 vs. 2.6 +/- 0.04 nl/min in healthy controls). The histological alterations persisted until day 3 (8 .5 +/- 0.9) when CBF significantly decreased (1.8 +/- 0.05 nl/min). After 1 5 days, moderate acute inflammation was still detectable histologically (5. 4 +/- 1.3), but CBF had returned to normal values. In mitomycin-C colitis, changes developed mainly in the proximal colon: After three days, there was mild inflammation (2.8 +/- 1.2) with normal CBF (2.5 +/- 0.1 nl/min). Afte r seven days, the inflammation had increased (4.8 +/- 1.1), while CBF had d ecreased (1.5 +/- 0.06 nl/min). These changes persisted for six weeks (5.3 +/- 0.7; 1.2 +/- 0.05 nl/min). These data suggest that disturbed colonic mi crocirculation may play an important role in the pathogenesis of inflammato ry bowel disease regardless of the histopathomorphological alterations.