STAT-1 Decoy-Oligodeoxynukleotid verbessert die mukosale Perfusion im Modell der akuten Abstoßung am Dünndarmtransplantat der Ratte

Abstract

Purpose of the Study: Microcirculatory blood flow in acutely rejecting small bowel transplants is severely compromised mainly due to the interaction of leukocytes with the vascular endothelium. Recruitment and activation of these leukocytes at the surface of the endothelium involves several adhesion and co-stimulatory molecules such as, e. g. CD40. Binding of activated T helper cells expressing the corresponding ligand (CD154) to endothelial cells leads to a reciprocal stimulation of the two cell types that may play an important role in acute allograft rejection. Down-regulation of the exaggerated expression of CD40 in endothelial cells under pro-inflammatory conditions may therefore provide an effective means by which T helper cell-endothelial cell interaction and hence transplant rejection could be attenuated. To this end, a decoy oligodeoxynucleotide (dODN) strategy targeting STAT-1, the main transcription factor involved in CD40 expression under pro-inflammatory conditions, was developed. Methods: Heterotopic small bowel transplantation (SBTx) was performed in the fully allogeneic BN (RTln) to LEW (RT11) rat strain combination without immunosuppressive therapy. After excision, University of Wisconsin (UW) solution containing either no additives (control group, n = 6), the STAT-1 consensus dODN (final concentration of 20 μM, n = 6) or the corresponding mutant dODN (dODN control group, n = 6) was infused into the donor organs via the mesenteric artery access and then incubated for 2 h at 4 – 8°C. The UW solution was flushed out of the grafts immediately before implantation was completed. Intravital microscopy analysis of an exteriorized jejunal segment of the donor small bowel was performed on postoperative day 7. The percentages of perfused villi and villus stasis, mucosal and muscular functional capillary densities (FCD), capillary diameters and red blood cell velocities, and finally permanent leukocyte adherence to post-capillary venules in the submucosa were assessed. Results: Mucosal perfusion and perfusion of the muscle layers, as assessed by villi and muscle layer FCD, were markedly reduced both in the control and in the dODN control group to approximately 10% of the level in the syngeneic LEW to LEW rat strain combination. In comparison, mucosal perfusion was 4-fold higher in the consensus dODN group, red blood cell velocity 10-fold, and perfusion index 3-fold. Stasis was reduced by 60% and the number of leukocytes sticking to the endothelium by 25%, although the latter effect did not gain statistical significance. Conclusions: Blockade of STAT-1-mediated gene expression, in particular that of CD40 in endothelial cells under pro-inflammatory conditions, by pre-treating the donor organ with an appropriate dODN helps to maintain microcirculatory blood flow and hence organ function in acutely rejecting small bowel transplants in the rat.