| Objective: Morphological changes of the mouse jejunum, ileum and colon,changes in the distribution and number of BrdU or Ki67immune response-positiveproliferative cells in the intestinal epithelium and that in β-catenin expression levelsin the intestinal villi and intestinal glands were observed after different doses of γ-rayirradiation, to understand the degree of intestinal injury and the proliferative status ofintestinal epithelial cell lines after γ-ray irradiation, so as to explore the effect of γ-rayirradiation on the intestinal epithelial cell proliferation and the role of intestinalepithelial proliferative cells in intestinal mucosal injury and repair as well as thepotential mechanisms involved in it, therefore to provide experimental basis for thefurther study of radioactive intestinal injury.Methods: Seventy-two male C57BL/6mice were randomly divided into fourgroups, the normal control group and the4Gy,8Gy, and15Gy irradiation groups. Theanimal models were established by whole body irradiation once-only with60Co γ-ray.The mice in each group were weighed and sacrificed at Day1,3, and5, respectively.Intraperitoneal injection of BrdU (120mg/kg body weight) was performed2hoursbefore the mice were sacrificed. The jejunum, ileum and colon were taken, fixed in4%formaldehyde solution, paraffin-embedded, and sliced. Following HE staining,intestinal histopathological changes were observed and the height of intestinal villiand the depth of intestinal glands of the jejunum and ileum were measured; the BrdU-or Ki67-positive cells and the β-catenin expression level in the intestine weremeasured by immunohistochemical assay, and then relevant stereological analyseswere made after photographing with the image analysis system, to measure andcalculate the number density of BrdU-or Ki67-positive cells in the mucousepithelium and the average optical density of β-catenin protein in the intestinal villiand intestinal glands of each intestine segments. The differences of the parametersbetween each group were compared with statistical software SPSS17.0.Results:1. Medium (8Gy) and high (15Gy) doses of γ-ray irradiation inducedlassitude, reduction of food intake and weight loss of the mice; all the irradiated mice died within four days after15Gy irradiation.2. Varying degrees of injury occurred in the mouse intestinal mucosa afterirradiation of different doses. The degree of injury was aggravated with increasingdoses. In the15Gy irradiation group, the injury was most serious on Day3, while inthe4Gy and8Gy groups, the injury was significant and had some recovery to Day5.The injury in the ileum was more serious than that in the other segments of theintestine. The morphometry showed shorter villi and shallower intestinal glandsfollowing γ-ray irradiation.3. Under normal conditions, the number density of BrdU-positive cells in theileum> in the jejunum> in the colon. After γ-ray irradiation, the number density ofBrdU-positive cells in each segment of the intestine reduced with increasingirradiation doses. Significant reduction could be seen on the first day after irradiationat low-dose irradiation, and the reduction was significantly lower in various parts ineach dose group (except for the colon in the4Gy group) compared with the normalcontrol group (P <0.01for all). The number density of BrdU-positive cells of eachsegment in the4Gy and8Gy groups gradually re-increased over time after irradiation,which returned close to the normal level in the4Gy group, whereas it wassignificantly reduced over time in the15Gy group.4. Under normal conditions, the number density of Ki67-positive cells in thevilli> in the intestinal glands, with that in the villi of ilium> of jejunum, and that inthe intestinal glands of jejunum> of colon> of ileum. After γ-ray irradiation, thenumber density of Ki67-positive cells in the intestinal villi and/or intestinal glandsreduced with increasing irradiation doses, with the effect on the intestinal glandsgreater than on the villi. By comparing the data on the first day after irradiation, thenumber density of Ki67-positive cells with low-dose irradiation was significantlyreduced, and that in various parts in each dose group (except for the intestinal glandsof ileum) was significantly lower compared with the normal control group (P <0.01for all). The number density of Ki67-positive cells of each segment in the4Gy and8Gy groups was gradually re-increased over time after irradiation, which returnedclose to the normal level on Day5in the4Gy group, whereas it was significantlyreduced over time in the15Gy group. The number density of Ki67-positive cells in the intestinal villi and intestinal glands was positively correlated with the height ofvilli and the depth of intestinal glands.5. In control animals, β-catenin in crypt cells was detected in the plasmamembrane,cytoplasm and nucleus. In irradiation groups, β-catenin was largelyrestricted to the plasma membrane and cytoplasm but was not evidentin the nucleus.Under normal conditions,the average optical density of β-catenin in mouse intestinalglands> in villi, with that in the villi of jejunum> of ileum, and that in the intestinalglands of jejunum> of ileum> of colon. The average optical density of β-catenin inthe intestine villi and/or intestinal glands reduced with increasing irradiation doses,with the effect on intestinal glands greater than that on villi, which was mostsignificant on the first day after irradiation (P <0.01). The average optical density ofβ-catenin of various parts in the4Gy and8Gy groups was gradually re-increased overtime after irradiation, which was returned close to the normal level on Day5in the4Gy group, whereas it was significantly reduced over time in the15Gy group.Conclusions:1. Different doses of γ-ray irradiation can cause varying degrees ofinjury of the mouse intestinal mucosa, that is, the larger the dose is, more serious theinjury is.2. After different doses of γ-ray radiation, the BrdU of the intestinal glands, thenumber of Ki67-positive cells of the intestinal glands and villi, and β-cateninexpression level were significantly decreased, indicating that irradiation can affect theintestinal cell proliferation. The number of intestinal proliferative cells was positivelycorrelated to the height of intestinal villi and the depth of intestinal glands.3. After low and medium doses of γ-ray irradiation, the intestinal injury, thenumber of intestinal epithelial proliferative cells and the expression level of β-cateninprotein can gradually restore. |
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