RESUMEN
【Objective】 To establish the optimal treatment model of Bletilla striata polysaccharide （BSP） on dextran sodium sulfate （DSS）-induced ulcerative colitis （UC） in mice. 【Methods】 We randomly divided 48 male C57BL/6 mice into normal control group， DSS model group （25 g/L DSS）， BSP low-， medium- and high-dose groups （25 g/L DSS + 95， 190， 380 mg/kg BSP）， and salazosulfapyridine （SASP） （25 g/L DSS + 320 mg/kg SASP， positive control） group. Mice in the normal control group drank distilled water freely， while the other groups were given 25 g/L DSS solution to drink freely for 7 days. From the second day， the low-， medium- and high-dose BSP groups and SASP （positive control）group were administered by gavage according to body mass. The normal control group and DSS model group were given the same amount of normal saline once a day for 7 consecutive days. The mice’s blood pressure was recorded every day. Mental state， body mass， stool characteristics and bloody stool were used to calculate the mice’s disease activity index （DAI）. The mice were killed on the 9th day， and their colonic tissues were taken for hematoxylin eosin （HE） staining and histopathological scoring. The expression of tight junction protein Claudin-1 in colonic tissues was detected by Western blotting. 【Results】 Compared with the normal control group， the DSS model group had obvious clinical manifestations， histopathological changes and reduced body weight， increased histopathological score and DAI score （P<0.05）， and decreased expression of tight junction protein Claudin-1 in colon tissue （P<0.05）. Compared with those in DSS model group， the clinical manifestations of UC and colonic mucosal injury in low-， medium- and high-dose BSP groups were improved in varying degrees. The high-dose （380 mg/kg） BSP group had the best effect. The degree of body weight reduction， histopathological score and DAI score in this group were significantly lower than those in DSS model group （P<0.05）， whereas the expression of Claudin-1 increased significantly （P<0.05）. 【Conclusion】 When BSP was administered by gavage at 380 mg/kg， the therapeutic effect on UC mice induced by 25 g/L DSS was the best. This model can be used as an effective one for further studies on Striata Bletilla polysaccharide in UC mice.