Objective:To explore the effect of Tangshen Formula (TSF),a Chinese herbal medicine,on interstitial cells of Cajal (ICC) in the colon of diabetic rats.Methods:Fifty-four male Wistar rats were randomly divided into normal control (NC,n=14) and high-fat diet (HFD) groups (n=40).After 6 weeks,the rats in the HFD group were injected intraperitoneally streptozotocin once (30 mg/kg).Thirty rats with fasting blood glucose higher than 11.7 mmol/L were randomly divided into diabetes (DM) and TSF groups,15 rats in each group.Rats in the NC and DM groups were intragastrically administered with saline,and those in the TSF group were given with TSF (2.4 g/kg) once daily for 20 weeks.Expression levels of Bax,Bcl-2,and caspase-3 in colonic smooth muscle layer were measured by Westem blotting and immunohistochemical staining.The number of ICC was determined by immunohistochemical staining.Immunofluorescence was used for analyzing the ratio of classically activated macrophages (M1) and altematively activated macrophages (M2) to total macrophages.Electron microscopy was used to observe the epithelial ultrastructure and junctions.Results:TSF appeared to partially prevented loss of ICC in DM rats (P＜0.05).Compared with the NC group,expression levels of Bcl-2,Bax,caspase-3,and TNF-α as well as the ratio of M1 to total macrophages increased in DM rats (all P＜0.05),and the ratio of M2 to total macrophages decreased (P＜0.05 or P＜0.01).Compared with the DM group,TSF decreased the expression levels of abovementioned proteins and restore M2 to total macrophages ratio (P＜0.05 or P＜0.01).TSF appeared to attenuate the ultrastructural changes of epithelia and improve the tight and desmosome junctions between epithelia reduced in the DM rats.Conclusions:Reduced number of ICC in DM rats may be associated with damage of the intestinal barrier.The protective effects of TSF on ICC may be through repair of the epithelial junctions,which attenuates inflammation and inflammation-initiated apoptosis in colon of DM rats.