Histological features of acute pancreatic allograft rejection after pancreaticoduodenal transplantation in the rat.

For characterization of histopathological changes during pancreas graft rejection, pancreaticoduodenal transplants were performed in three groups: (1) Brown Norway into diabetic Lewis rats without immunosuppression, (2) Brown Norway into diabetic Lewis rats with cyclosporin A, and (3) Lewis into Lewis rats. Diffuse inflammatory infiltration of the acini by mononuclear cells indicated the onset of rejection (stage I). Shortly after acinar infiltration, damage to small and large interlobular excretion ducts occurred. This took the form of florid circumferential inflammation and vacuolar degeneration of epithelium similar to the bile duct damage seen in primary biliary cirrhosis, graft-versus-host disease, and liver allograft rejection (stage II). Thereafter, endothelialitis and destruction of islets were evident, consistent with a more advanced and irreversible stage of rejection (stage III). Acinar inflammation and moderate duct lesions were not prevented by immunosuppression but were delayed. Nonetheless, severe vascular changes and loss of islets were avoided. We conclude that duct lesions are a reliable criterion for pancreas allograft rejection. They are more sensitive than vascular changes and more specific than cellular infiltration of acinar tissue, which may also occur in infection.

Morphology of acute rejection and corresponding cytological findings in exocrine secretion after pancreas transplantation in the rat.

Reliable and timely rejection diagnosis still represents a major problem of pancreas allotransplantation. The aim of this study was to confirm the clinical findings of exocrine function impairment and pancreatic juice cytology during rejection, to refine the latter by means of flow cytometry, and to correlate these changes with graft histology. Heterotopic pancreatic transplants were performed in a modified technique in Lewis rats rendered diabetic by means of streptozotocin from LEW donors (group I, n = 10), Brown Norway rats without immunosuppression (group II, n = 16), and from BN rats where recipients were given cyclosporine 12 mg/kg/BW (group III, n = 10). Pancreatic juice was obtained by daily aspiration from a self-made fully implantable catheter reservoir system. In group II animals acute rejection diagnosed on histomorphological grounds was clearly associated with a decrease in the amount of exocrine secretion and its enzyme content from day 8 on. In contrast to groups I and III, a significant increase in lymphocytes in the pancreatic juice up to 13.5% occurred in group II between days 5 and 7. Activated lymphocytes increased from 7% to 13%, pan-T cells from 193 to 340 events. Histology revealed three distinct phases of acute rejection--phase I: diffuse infiltration of acinar structures; phase II: destruction of interlobular ducts; phase III: vasculitis associated with islet cell damage. The anatomy of the pancreas with the slackness of its highly vascularized interstitial connective tissue facilitates early infiltration of inflammatory cells and migration of these cells into the lumen of the pancreatic duct. Thus pancreatic juice cytology together with an impaired exocrine graft function is highly indicative of acute rejection.

A technique of pancreas transplantation in the rat securing pancreatic juice for monitoring.

In order to study exocrine pancreas graft function and cytological findings, a technique of vascularized pancreas transplantation with special reference to a pancreatic juice collecting system has been developed in the rat model. For this purpose, a catheter is introduced into the common bile duct, which is ligated close to the duodenum, thus covering all pancreatic ducts. This catheter is connected to a reservoir implanted subcutaneously, from which pancreatic juice can easily be aspirated. The amount of 0.7-1.2 cc of juice produced over a 24-h period has proven to be sufficient for various analyses and cytological examination.

[A technique for pancreatic juice collection in the rat]. / Technik der Pankreassaftgewinnung bei der Ratte.

Monitoring of exocrine graft function and pancreatic juice cytology have proved to be a reliable method of detection of pancreas allograft rejection. In order to confirm these clinical findings and to define further parameters, experimental work is still needed. The rat was chosen for these experiments and a technique of pancreatic juice procurement developed. In five animals a fully implantable closed reservoir-catheter system was used. For the prevention of bacterial contamination it was necessary to install a mixture of antibiotics and culture medium into the reservoir. Pancreatic juice was procured daily under general anaesthesia. During the observation time of 14 days no further complications were encountered with the exception of one catheter dislocation. The mean amount of juice of 1 cc per day has proved to be sufficient for various enzyme estimations as well as for juice cytology.

A new technique for venous anastomosis of pancreatic allografts.

Venous thrombosis is still a frequent cause of graft loss after pancreas transplantation where the portal vein is used for revascularisation. It is known that an increase in velocity of venous flow decreases the incidence of thrombosis. According to the equation of continuity, the flow velocity in the portal vein should decrease to 25% as compared with that in the splenic vein. Based on the rheological considerations we started to use the superior mesenteric vein, the diameter of which is similar to that of the splenic vein, for revascularisation of pancreas transplants after sewing the portal vein closed at its origin. This technique has been applied in 12 consecutive pancreatic transplants. Two patients died of a cerebrovascular accident and myocardial infarction, respectively. The only single pancreatic graft was lost due to rejection. The remaining 9 patients are alive and well between 2 and 23 months with normally functioning grafts. Another advantage of this technique is that a full-length portal vein can be left with the liver graft in the event of simultaneous liver and pancreas procurement.