Pancreas and islet transplantation. I. Experimental studies

Lessons learned from more than 1,000 pancreas transplants at a single institution

OBJECTIVE

To determine outcome in diabetic pancreas transplant recipients according to risk factors and the surgical techniques and immunosuppressive protocols that evolved during a 33-year period at a single institution.

SUMMARY BACKGROUND DATA

Insulin-dependent diabetes mellitus is associated with a high incidence of management problems and secondary complications. Clinical pancreas transplantation began at the University of Minnesota in 1966, initially with a high failure rate, but outcome improved in parallel with other organ transplants. The authors retrospectively analyzed the factors associated with the increased success rate of pancreas transplants.

METHODS

From December 16, 1966, to March 31, 2000, the authors performed 1,194 pancreas transplants (111 from living donors; 191 retransplants): 498 simultaneous pancreas-kidney (SPK) and 1 simultaneous pancreas-liver transplant; 404 pancreas after kidney (PAK) transplants; and 291 pancreas transplants alone (PTA). The analyses were divided into five eras: era 0, 1966 to 1973 (n = 14), historical; era 1, 1978 to 1986 (n = 148), transition to cyclosporine for immunosuppression, multiple duct management techniques, and only solitary (PAK and PTA) transplants; era 2, 1986 to 1994 (n = 461), all categories (SPK, PAK, and PTA), predominantly bladder drainage for graft duct management, and primarily triple therapy (cyclosporine, azathioprine, and prednisone) for maintenance immunosuppression; era 3, 1994 to 1998 (n = 286), tacrolimus and mycophenolate mofetil used; and era 4, 1998 to 2000 (n = 275), use of daclizumab for induction immunosuppression, primarily enteric drainage for SPK transplants, pretransplant immunosuppression in candidates awaiting PTA.

RESULTS

Patient and primary cadaver pancreas graft functional (insulin-independence) survival rates at 1 year by category and era were as follows: SPK, era 2 (n = 214) versus eras 3 and 4 combined (n = 212), 85% and 64% versus 92% and 79%, respectively; PAK, era 1 (n = 36) versus 2 (n = 61) versus 3 (n = 84) versus 4 (n = 92), 86% and 17%, 98% and 59%, 98% and 76%, and 98% and 81%, respectively; in PTA, era 1 (n = 36) versus 2 (n = 72) versus 3 (n = 30) versus 4 (n = 40), 77% and 31%, 99% and 50%, 90% and 67%, and 100% and 88%, respectively. In eras 3 and 4 combined for primary cadaver SPK transplants, pancreas graft survival rates were significantly higher with bladder drainage (n = 136) than enteric drainage (n = 70), 82% versus 74% at 1 year (P =.03). Increasing recipient age had an adverse effect on outcome only in SPK recipients. Vascular disease was common (in eras 3 and 4, 27% of SPK recipients had a pretransplant myocardial infarction and 40% had a coronary artery bypass); those with no vascular disease had significantly higher patient and graft survival rates in the SPK and PAK categories. Living donor segmental pancreas transplants were associated with higher technically successful graft survival rates in each era, predominately solitary (PAK and PTA) in eras 1 and 2 and SPK in eras 3 and 4. Diabetic secondary complications were ameliorated in some recipients, and quality of life studies showed significant gains after the transplant in all recipient categories.

CONCLUSIONS

Patient and graft survival rates have significantly improved over time as surgical techniques and immunosuppressive protocols have evolved. Eventually, islet transplants will replace pancreas transplants for suitable candidates, but currently pancreas transplants can be applied and should be an option at all stages of diabetes. Early transplants are preferable for labile diabetes, but even patients with advanced complications can benefit.

Blood flow measurements in autotransplanted pancreatic islets of the rat. Impairment of the blood perfusion of the graft during hyperglycemia

No information is available on the rate of blood flow in transplanted islets. In this study, adult rats were partially depancreatized, and islets from the excised pancreas were then isolated, maintained for 7 d in tissue culture, and subsequently transplanted back to the animal, beneath the renal capsule. Some rats were rendered diabetic with streptozotocin before transplantation. A month after transplantation the blood flow of the grafts was measured by a microsphere technique. Autotransplantation to streptozotocin-diabetic rats of approximately 500 islets did not revert the hyperglycemia, and the blood flow of these grafts was approximately 25% of that in the normoglycemic-transplanted rats. However, in insulin-treated diabetic rats the blood flow of the pancreatic graft was similar to that in the normoglycemic rats. The present results suggest that the blood flow in transplanted islets is markedly diminished by hyperglycemia and that this can be enhanced by insulin administration.

Metabolic control of type I (insulin dependent) diabetes after pancreas transplantation

A study was conducted of the circadian hormonal and metabolic patterns of 10 type I (insulin dependent) uraemic diabetic patients after pancreas and renal transplantation. A single 24 hour profile was obtained in each patient following as closely as possible his or her normal daily routine two to 15 months after transplantation. None of the patients were using insulin at the time of the study. Compared with a group of six normal subjects the transplant recipients had mildly raised blood glucose concentrations, hyperinsulinaemia between meals and at night, delayed postprandial insulin peaks, mild hyperketonaemia, and normal blood lactate and plasma glucagon concentrations. The findings showed that successful pancreas transplantation results in disappearance of the need for insulin and return to normal or near normal of the metabolic abnormalities of diabetes. The minor differences observed in comparison with normal hormonal and metabolic homoeostasis were probably due to intrinsic (reduced islet mass, denervation, peripheral hormone delivery) and environmental (immunosuppression, relatively impaired renal function) factors.

Cold storage (8 C) of islets of Langerhans in a high-potassium "intracellular medium": near-normal insulin release and morphology after one week

Islets of Langerhans from ob/ob mice were microdissected and stored for one week at 8 C or 37 C in a high-potassium "intracellular medium" or in a traditional culture medium (RPMI 1640 +/- fetal calf serum). Subsequent glucose-stimulated insulin release and islet morphology were best preserved by 8 C-storage in the high-potassium "intracellular medium". This suggests that normal, adult, mammalian tissues which do not readily divide in vitro may be better preserved for short periods of time at refrigerator temperatures in a high-potassium medium than by conventional culture at 37 C in a tissue culture medium.

One hundred pancreas transplants at a single institution

Clinical pancreas transplantation at the University of Minnesota began in 1966. An initial series of 14 whole pancreas grafts was reported in part to the American Surgical Association in 1970. Only one patient survived for more than 1 year with a functioning graft. Twenty attempts at islet allotransplantation in the mid-1970s were unsuccessful. In 1978 we resumed performing pancreas transplants by the segmental technique, allowing the use of related donors. The current series (July 25, 1978 to December 20, 1983) includes 86 pancreas transplants (51 cadaver, 35 related) in 75 patients (41 with and 34 without previous kidney grafts). Variations in management of the pancreatic duct include three ligated, 15 duct-open, 39 duct-injected, and 29 pancreaticojejunostomies. The latter technique is currently preferred. Currently (April 1984) 61 patients are alive (81%), 24 have functioning grafts (32%), and 21 are insulin-independent (28%), three with open-duct grafts for 4.4 to 5.7 years, seven with silicone-injected grafts from 10 to 39 months, and 14 with pancreaticojejunostomies for 3 to 31 months; 15 of the grafts have functioned for greater than 1 year. Twenty-two of the grafts (25%) failed for technical reasons (thrombosis, infection, or ascites); 35 grafts functioned for 1 to 13 months before totally failing from either rejection, fibrosis, or recurrent disease; five patients died with functioning grafts. The graft survival rate has been higher for pancreases from related (15/35, 43% functioning) than from cadaver (9/51, 18% functioning) donors. The success rate has increased, e.g., 11/22 recipients of pancreas transplants in 1983 currently have functioning grafts (50%). Metabolic studies show most patients with functioning grafts to be euglycemic; however, three of 24 have chronic hyperglycemia unless supplemented with insulin, but they are no longer ketosis-prone. Glucose tolerance test results are normal or nearly normal in 12 and abnormal in 12 of the recipients with currently functioning grafts. Regression of diabetic nephropathy has been documented in two long-term recipients. Pancreas transplantation is currently applicable as treatment for selected diabetics who have demonstrated their propensity to develop serious secondary complications.

Pathology of the pancreas after intraductal neoprene injection in dogs and diabetic patients treated by pancreatic transplantation

The injection of neoprene into the pancreatic ducts of dogs has been used to destroy exocrine function prior to pancreatic transplantation. The subsequent histological changes and the evolution of lesions over a period of 3-36 months are described. Animals were sacrificed or biopsied at various intervals (3, 15 and 36 months) and the pancreases showed the disappearance of exocrine acini and changes of chronic pancreatitis. An immunoperoxidase procedure with insulin, glucagon, somatostatin and pancreatic polypeptide antisera was used to show the persistence of pancreatic endocrine cells. After the injections, sclerosis progressively increased and secondary lesions of the islets were seen, although functional islets persisted. This technique was then applied to pancreas transplantation in man. Eight transplants from seven diabetic patients were available for examination. In four cases, there were early technical failures, but four pancreatic transplants continued to function for 28-889 days until suppuration destroyed one of the grafts and the three other patients died. The persistence of endocrine cells in sclerotic tissue was observed in histological and immunopathological examinations.

Monolayer culture of neonatal pig pancreatic islet cells

Pancreatic islet cells from pigs (3-12 days old) were maintained in monolayer culture at 37 degrees C for greater than 30 days. Cultures were maintained in enriched Medium 199 with 5% fetal calf serum and with the glucose concentration being cycled between 11.10 and 27.75 mmol/l every 2 days. The presence of B cells in the cultures was demonstrated by insulin secretion into the culture medium, cell staining with aldehyde fuchsin and immunofluorescence. A cells in the cultures were monitored by glucagon secretion into the medium. The absence of exocrine cells was determined by the inability to detect alpha-amylase in the culture medium. Insulin secretion determined over a 34-day period, was found to diminish after 12 days in culture. The fall in levels of extractable B cell insulin with time correlated with the levels of insulin secreted into the medium. Response to short term glucose stimulation (2 h in serum-free medium) was determined on days 6, 10 and 12 in culture. Morphological changes appeared after 25 days in culture, although on day 33 insulin secretion was 62.5 microU X culture-1 X day-1. DNA synthesis (determined by 3H-thymidine incorporation and autoradiography) was demonstrated (day 12, 39.4 +/- 0.9 labelled cells/culture). These findings suggest that pig islet cell monolayer cultures are a useful tool for morphological and biochemical studies and that neonatal pig islets are a potential source of material for transplantation.