A new experimental model to allow use of clinical-scale endoscopes in small-animal tumor models

The evaluation of novel endoscopes may require testing in experimental tumor models, particularly when employing new biomarkers. Tumor models, however, exist almost exclusively in small animals. Therefore, we aimed to develop an experimental setting that allows the use of clinical-scale endoscopes in small animals.

In our approach, the proximal large bowel with intact blood supply is exposed on a movable and height-adjustable table. The endoscope's tip may be inserted into the bowel; the dark environment of the bowel lumen in vivo is simulated by mounting a light-tight curtain around the endoscope. Proof-of-principle experiments were done in Wag/Rij rats following cecal injection of the cell line R1H.

Using high-definition television white-light endoscopy, narrow-band and autofluorescence imaging, and miniprobe-based confocal laser microscopy (CLM) marked differences were observed between normal mucosa and tumors. Depending on the techniques, mean examination times ranged from 3 to 10 minutes. Even after 90 minutes the colon displayed an intact blood supply, imaged by Evans blue injection and by CLM.

These experiments demonstrate that our model allows in vivo examination of small-animals by clinical-scale endoscopes. Therefore, it may be useful for evaluation, at various stages of GI carcinogenesis, of both new biomarkers and endoscopic technologies.