Bone Marrow Mesenchymal Stem Cell Transplantation For The Treatment Of Experimental Megacolon Experimental Study

OBJECTIVE: To establish a rat model of experimental aganglionosis for MSCs transplantation, and investigate the alteration of ion transport across the colonic epithelium in the rat model. METHODS: Ninety Sprague Dawley rats , 8-9 weeks old, were randomly divided into two groups: treatment group(n=45) and control group(n=45). All animals were operated upon under Ketamine anesthesia. In treatment group, 0.1% benzalkonium chloride (BAC) was applied onto the serosa for 40 minutes, and then the colon was washed well with 0.9% normal saline. For the control group, 0.9% saline was applied using the same method in treatment group. Macroscopic and microscopic observations, contrast roentgenogrphy of colon, colon manotery, pharmacologic examinations for contraction of colonic smooth muscle, and detection of ion transport of colonic epithelium by the short-circuit current were performed at an interval of 1w, 2w, 3w, 4w and 8w after operation.RESULTS: 1 week after BAC treatment, the rats had abdominal distention. Roentagenographic examination and autopsy revealed a narrowed segment accompanied by distended proximal colon filled with massive feces, and the longer the duration after treatment, the more serious distention. Manotery showed the abolition of reflex contraction in colonic smooth muscle, and pharmacologic examinations indicated supersensitivity to acetylcholine. Histologic examinations revealed transparent reduction and vacuolation of ganglion cells 1 week after BAC treatment with complete disappearence of 3 weeks after BAC treatment. As for the short-circuit current(Isc) of colonic epithelium, as compared to control group, the PD and basal Isc decreased significantly, and the ratio of amiloride-sensitive Isc /basal Isc was increased in treatment group. In addition, the forskolin-induced Isc was increased significantly, but the DPC inhibition of the forskolin-induced Isc was decreased, and transepithelium electrical resistance(TER) showed no difference between treatment and control group.CONCLUSIONS: 1. The animal model for experimental aganglionosis was successfully established by applying 0.1%BAC onto the serosa of descending colon, providing an experimental basis for the future MSCs transplantation and differentiation into neuronal cells in rat colon. 2. The epithelial barrier function was normal in aganglionosis rat colonic epithelium, while the ion transport was disordered. From this result, we can infer that the problem of constipation in rat with aganglionsis is not only due to abnormal smooth muscle and sphincter function but also to a disorder of ion transport in the colon.