Study Of The Effect Of Bombesin On Bacterial Translocation Following Small Bowel Transplantation In Rats

Background: Small bowel transplantation (SBTx) has recently become a valid therapeutical option for patients with short bowel syndrome (SBS) with a 5-year graft survival rate close to 70% in some centers. These results were obtained as consequence of the refinement of the operative techniques, ameliorated immunomodulation, and postoperative care. However, infectious complications which had been considered as the effect of bacterial translocation are still the major cause of intestinal graft loss and patient death. Laparotomy , preservation and ischemia reperfusion(I/R) injury, abnormal motility, lymphaticdisruption, aberrant systemic venous drainage, rejection, and antibiotic therapy could all be implicated to damage the mucosa and the mucosal immune of the graft which enhanced the productivity of intestinal bacterial translocation(BT) .Recent research indicated that enhancing the recovery from the small bowel barrier and gut immune injuries could decrease the productivity of the intestinal bacterial translocation.At present ,the regimens which decrease the rate of intestinal bacterial translocation Including the removing intestine bacterial ,the TPN or EN with Glutamine (Gln) or epidermal growth factor(EGF) after small bowel transplantation. However, these regimens of Gln and EGF could enhance the rejection. At the same time ,there were some arguments about the removing the intestinal bacterial that it could injure the intestinal mucosa . Bombesin (BBS), a tetradecapeptide originally isolated from the skin of the European frog Bombina bombina is equivalent to mammalian gastrin-releasing peptide(GRP), was known to have wide spectrum of biological actions on the gastrointestinal tract. It could induce the release of almost all intestinal hormones except secretin. In the previous study, it was shown that BBS could stimulate crypt cell proliferation and prevent mucosal atrophy in the intestinal injury, even recover from the immune of the intestinal mucosa injury. In this case,BBS was employed in this study to address it's decreasing BT effect in rats receiving SBT.Objective: In order to find out whether BBS can decrease BT in case of immunosuppression in rats receiving SBT , a refined model of segmental small bowel transplantation in rats was established and the effects of BBS on the recovery from villus injury and the first immune of graft after SBT, BT rate ,the serum endotoxin level and the mortality were investigated.Method: Part I ninety six SD rats were used as both donor and recipient animals. Surgical procedures were performed The 20-cm proximal jejunum and ileum was harvested along with the aortic cuff and portal vein as a long vascular pedicle using Taguchi's modification. The vascular pedicle was gently flushed with iced saline ,Graft was revascularized by performing end-to-side anastomoses of the aorta and portal vein to the recipient's abdominal aorta and inferior vena cava. The recipient were divided into two groups according difference which the ends were exteriorized through the abdominal wall. Both ends exteriorized group : both ends were exteriorized through the abdominal wall (n=2x23), One end exteriorized group: one end were exteriorized through the abdominal wall(n=2x23).The mortality was calculated and the configuration of the graft mucosa was observed by SM 7 post operation days.Part II One hundred and thirty SD rats were employed in which 10 undergoing virtual operations were set to be control and they received subcutaneous injection of saline (1.5 ml). Small bowel transplantation was performed in 120 SD rats and the animals were randomly divided into two groups: BBS group (n=2x30)receiving BBS (15ug/kg/day) and FK506(0.5mg/kg/day) injection subcutaneously , transplantation control group(n=2x30) receiving saline(1.5ml) and FK506(0.5mg/kg/day) injection subcutaneously after the operation. Conform was injected in the loop 12.5 post operation day After 14 PODs .The content of the CD3+,CD4+,CD8+,CD45RA+ lymphocytic subpopulation in the lamina propria layer and the Peyer's patches were determined . The configuration of the graft mucosa was observed by SM and SEM. Mesenteric lymph node (MLN) and liver were resected and used as target tissue of bacterial culture .The BT rates and contents were calculated as well, The serum endotoxin level was measured by USP bacterial endotoxintest, the mortality was calculated.Result: Part I There was no difference in levels of villus height ,crypt depths , mucosa volume and the mortality in two groups, P>0.05.Part II1. The contents of CD3+,CD4+,CD8+,CD45RA+ of lymphocytic subpopulation in the lamina propria layer and the Peyer's patches in the transplantation control group decreased significantly (50% to 60% in the control group) .The mucosal immune function hampered largely . But in the BBS group, the injury was ameliorated significantly .The difference of the contents of CD3+,CD8+,CD45RA+ between the transplantation control group and the BBS group was statistically significant, P<0.05 .However, There was no difference CD4+ content between the transplantation control group and BBS group, P>0.05. The results suggest that BBS could improve the recovery from the injury of the first stage immune of the transplanted bowel. 2. The operation and the regimen of FK5O6 damaged the mucosa of the graft largely. However, in the tansplantation control group, on 14 POD's, villi were flattened and thinning, and villus blunting was marked compared with those in the BBS group . On the other hand, the villi of the grafts in the BBS group were well maintained, and the volume of lamina mucosa was adequate compared with that of the transplantation control. This implied that BBS administration can stimulate the graft mucosa to maintain epithelial cells and the mucosa volume after intestinal transplantation. 3 The bacterial translocation rate in the liver and MLN in the transplantation control group: BBS group , control group was 82.8% and 22.2% and 10% respectively . The contents of bacterial translocoation in transplantation control group , BBS group , control group was (7.80±3.23)xl03CFU/g , (2.67±1.35)xl03CFU/g , 0.9xl03CFU/g respectively , which differed from each other significantly, P<0.05. This suggested that BBS administration could decrease the bacterial translocation rate and contents. 4.The concentration of serum endotoxin in the transplantation control group , BBS group and control group was (0.5564 ±0.086)EU/L, (0.1013±0.042)EU/L, (0.0282+0.0124) EU/L respectively, PO.05 . This suggested that BBS administration could decrease serum endotoxin level after SBT. 5.The mortality in the transplantation control group, BBS group was 46.7% and 13.3% The difference are statistically significant, P<0.05.It suggest that BBS administration candecrease the mortality of rats after SBT.Conclusion: (D The method which one end of the graft exteriorized may be more useful and convenient in future BT studies after SBT .? In rats, SBT could injure the mucosal barrier and the mucosal immune. (3) BBS administration could decrease the bacterial translocation rate and content ,the serum endotoxin level ,the mortality after SBT. by maintaining the mucosal barrier and the mucosal immune.? BBS administration may be a new useful therapy means to decrease infection rate and increase survival rate after SBT.