Murine microvideo endoscopy of the colonic microcirculation

Abstract

Natural orifice endoscopy in small animal models has been limited in the past by instrument size and optical performance. In this report, we investigate the feasibility of using a recently developed microvideo endoscopy system to evaluate the colon microcirculation. Using a murine model of acute colitis, microvideo endoscopy was useful in mapping the topography of inflammation as well as identifying relevant structures in the microcirculation. We conclude that natural orifice endoscopy is a useful method for the minimally invasive longitudinal assessment of the colonic mucosal microcirculation.

Figure 1

The clinical course of mice after the instillation of TNBS. A) The diminished activity level (increased severity score), ruffled fur and occasional rectal prolapse is characteristic of this model. B) The weight loss declines over 4 days after which the mice generally recover their body weight over the next week.

Figure 2

Gross appearance of the hapten-induced colitis. A-C) The dilated appearance of the colon 96 hours after the intralumenal instillation of TNBS. The bowel was variably dilated in the ascending, transverse and descending colons. D) The degree of colonic distension was apparent immediately after laparotomy: a typical dilated transverse colon is shown.

Figure 3

Intralumenal video colonoscopic view of the control colon (N=4). The colonoscopy was notable for the pink mucosa and virtual transparency of the colonic wall. In areas (C, ellipse), the peritoneal contents could be appreciated beyond the colon wall.

Figure 4

Intralumenal video colonoscopic view of the TNBS-stimulated colon 96 hours after instillation (N=4). The colonoscopy was notable for the thick and edematous wall, superficial mucosal ulceration and inspisated stool.

Figure 5

Scanning electron microscopy of the mouse colon. A) The mucosal plexus is characterized by polygonal capillaries surrounding colonic crypts. The variable topography is apparent at this level of resolution (bar=500um). B) The draining veins (red overlay), continuous with the mucosal plexus, are prominent in the setting of acute colitis.

Figure 6

Dilated mucosal vessels in acute colitis enhanced with a FITC-dextran plasma tracer and examined by fluorescence video colonoscopy (N=4). The dilated mucosal vessels are apparent in almost all areas of Matts 2-3 grade colitis. Of interest, local trauma of the mucosa occasionally produced extravasation of the fluorescent tracer into the lumen (C, ellipse), but more frequently produced focal hemorrhage from the friable mucosa (D, ellipse).