Share thisRecent developments in technology and technique can mean a reduction in the number of animals used and eliminating many model-induced variables.
Colonoscopy is a powerful diagnostic technique used in human medicine to examine and biopsy the gastrointestinal tract to detect inflammatory and neoplastic changes in patients. Rodent models of intestinal diseases are commonly utilized as biomedical research tools to investigate the processes of inflammation and neoplastic transformation of cells in rodents, and to test novel treatments. Traditionally, rodents are culled in order to analyze their gastrointestinal tract for evidence of colitis and tumor development. However, with recent developments of relatively inexpensive miniaturized videoendoscopic equipment and a newly developed rodent colonoscopy technique, repeat colonic examination in the same rodent is now possible, thus allowing the researcher to accurately track disease model development. This method is useful for monitoring and grading tumors and inflammation over time, as well as for allowing the collection of serial biopsies in the same animal. Performing serial colonoscopies in the same animal results in significantly greater data reliability because the same experimental subject serves both as test and control.
Equipment and Instrumentation
The proper selection of rodent-appropriate colonoscopy equipment is similar to the rodent laparoscopy equipment previously described.1 The instrumentation includes a colonoscope, which is a tubular, lighted instrument using fiber optic fibers to provide visualization of the colon. The colonoscope consists of either a viewing colonoscope (Figure 1) or a colonoscope with a working channel (Figure 2). The working channel allows for introduction of a biopsy forceps for tissue sample collection.
Colorectal tumor models have until now been mostly been induced through laparotomies by the introduction of cells into the lumen of the colon, or by utilizing extracolonic sites such as the injection of tumor cells into the peritoneum or under the renal capsule. Many of these models may not accurately reflect the pathophysiology of human colorectal cancers, making it challenging to translate such data into clinical trials. Rodent colonoscopy provides a method to more accurately characterize these tumors by allowing the development of colorectal tumor models by precise, visualized injections of tumor cells into the walls of specific sites within the gastrointestinal tract. This also allows for the development of solid tumors versus the tendency to create disseminated disease if the tumor cells are injected into the lumen of the gastrointestinal tract. Colonoscopy also allows for the repeat monitoring of subtle changes without more invasive procedures such as laparotomy or laparoscopy. This technique was introduced in rats in 2006 by Haughn et al, where submucosal injections were performed by colonoscopy.2