Abstract: ObjectiveTo investigate the development of apoptosis during ischemia/reperfusion (IR) injury and acute rejection, and to explore the significance of apoptosis in the Graft Mesenteric Lymph Node (GALT) in a rat heterotopic small bowel transplant (SBT) model.MethodsSBT was performed in F344/N rats with either freshly harvested or preserved (4 h, in ringer lactate solution at 4 ℃) syngeneic and allogeneic (Wistar/A-F344/N) grafts. Bowel and GALT samples were collected 2 h after reperfusion and on small bowel transplant postoperative days (POD) 1, 4, and 7. Histopathology assessment of the graft and GALT were prepared for hematoxylin-eosin (H&E) staining. Apoptosis was detected by the TUNEL and the electron microscope. ResultsThe number of apoptotic cells 2 h after reperfusion increased profoundly in association with preservation. After a significant decrease on POD 1, the apoptotic cells rose again between POD 3 and 7 only in allogeneic grafts. On the other hand, the apoptotic cells in allogeneic GLAT markedly increased from POD 1 to day 3; at that time point, neither histological findings of rejection nor increase in apoptotic crypt cells were present in the graft jejunum. ConclusionIR injury and acute rejection may both induce extensive apoptosis. The graft jejunum distinct second increase in apoptosis may be an early and specific sign of acute rejection. Apoptosis of GLAT cells was well correlated with and ahead of progression of acute rejection.

Key words: small bowel transplant (SBT), apoptosis, Graft Mesenteric Lymph Node (GALT), rejection, ischemia/reperfusion (IR)