Apoptosis of interstitial cells of Cajal in deep muscular layer of small intestine in rats with multiple organ dysfunction syndrome

Abstract

To observe the apoptosis of interstitial cells of Cajal in deep muscular layer (ICC-DMP) of small intestine in rats with multiple organ dysfunction syndrome (MODS) as a result of bacterial peritonitis, and the expression of c-kit (an ICC phenotype marker) and Bax/Bcl-2, in order to investigate the mechanism of gastrointestinal motility dysfunction in MODS. According to the random number table, 40 Wistar rats were randomly divided into two groups: control group (n=20) and MODS group (n=20). The MODS model in rats was reproduced by intraperitoneal injection of 8×10(8) cfu/mL Escherichia coli suspension 1 mL, and the control group was given the same amount of normal saline. After 24 hours, the upper small intestine was harvested for examination. Ultrastructure of ICC-DMP was observed using electron microscope. The network structure of ICC-DMP and the expression of c-kit and Bax/Bcl-2 were observed and determined with immunofluorescence and laser scanning confocal microscope. Macroscopic observation revealed that the gastrointestinal motility of rats was normal in the control group. Compared with the control group, gastro intestine was significantly expanded with parulytic ileus in MODS group. It was shown by transmission electron microscopy that intermediate filament structure of ICC-DMP was clear without swelling of mitochondria; chromatin distributed uniformly with small amounts of heterochromatin aggregated in perinuclear. Compared with the control group, intermediate filament structure of ICC-DMP was fuzzy, and mitochondria were swollen obviously in MODS group; chromatin was assembled in nucleus centre. It was shown by laser scanning confocal microscope that the network structure of ICC-DMP was clear, the expression of c-kit and Bcl-2 was strongly and overlapping; the expression of Bax was weak and scatter distributed. Compared with control group, ICC-DMP quantity in MODS group was significantly reduced (cells/HP: 15.80±2.30 vs. 25.70±3.97, t=6.819, P=0.000 ), and ICC network was incomplete. The expression of c-kit and Bcl-2 was significantly decreased as compared with control group [ c-kit (fluorescence intensity): 129.56±36.90 vs. 307.23±40.07, t=10.314, P=0.000; Bcl-2 (fluorescence intensity): 103.23±25.19 vs. 378.92±43.79, t=17.259, P=0.000], whereas, the expression of Bax was significantly increased (fluorescence intensity: 270.94±36.98 vs. 92.57±20.92, t=-13.277, P=0.000 ). The mechanism of gastrointestinal motility dysfunction in MODS maybe closely related to ultrastructural damage of ICC-DMP, changes of c-kit phenotypic and activation of mitochondrial apoptosis pathway.