CTLA4-Ig prolongs survival of microencapsulated neonatal porcine islet xenografts in diabetic NOD mice.
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Abatacept↗
Biomedical subjects
G S Korbutt
Publications and source records attributed to G S Korbutt.
Survival and function of syngeneic rat islet grafts placed within the thymus versus under the kidney capsule.
The role of the thymus in the ongoing acquisition of tolerance to self antigens has made it an attractive site for islet transplantation. Several studies have reported survival of rodent islet allografts in the thymus without requiring the long-term use of immunosuppressive agents; however, the degree of glucose homeostasis in the intrathymic islet transplant recipients has not been examined. We transplanted 500, 1000, or 2000 syngeneic islets into the thymus of streptozotocin-induced diabetic Wistar-Furth rats, and compared the metabolic response of these recipients with animals receiving 2000 syngeneic islets under the kidney capsule. Three of four recipients which received 2000 islets under the kidney capsule achieved normoglycemia (< or =8.4 mmol/L) within 1 wk and all animals became normoglycemic within 2 wk posttransplantation. In contrast, intrathymic implantation of 2000 islets induced normoglycemia in only one of six recipients during the same time interval, and when this number was reduced to 1000 or 500 islets, none of the recipients (n = 6) normalized within 1 wk posttransplantation. Animals that received an intrathymic transplant were glucose intolerant compared to normal controls and animals with subcapsular islet transplant. Removal of the graft-bearing organs resulted in hyperglycemia in all cases, and examination of the grafts revealed the presence of numerous well-granulated insulin-containing cells in both sites. The cellular insulin content of the subcapsular grafts (67.4 +/- 12.1 microg; n = 4) was significantly higher (p < or =0.05) than what was extracted from intrathymic grafts (9.5 +/- 1.2 microg from 1000 islets; n = 3 and 20.0 +/- 4.6 microg from 2000 islets; n = 3). We conclude that 2000 syngeneic islets implanted either in the thymus or beneath the kidney capsule can normalize hyperglycemia in streptozotocin-diabetic rats; however, normal glucose tolerance was not established in intrathymic islet recipients, suggesting that a higher number of islets may be necessary to achieve normal glucose homeostasis.
Animals↗
Intraductal collagenase delivery into the human pancreas using syringe loading or controlled perfusion.
Effective intraductal delivery of the enzyme collagenase into the pancreas is crucial to the subsequent ability to isolate viable islets. Most clinical islet transplant centers load the enzyme into the pancreas by retrograde injection using a syringe following cannulation of the pancreatic duct. An alternative approach is to perfuse the pancreas via the pancreatic duct with collagenase solution using a recirculating perfusion device system. This provides control over perfusion pressures and collagenase temperature. This study reports on our evaluation of the delivery of Liberase-HI into the pancreas of 14 consecutive adult multiorgan cadaveric donors. Alternate glands were procured and processed using an identical protocol with the exception of collagenase delivery. The first group of pancreases was loaded using the perfusion technique where cold (4 degrees C) Liberase-HI was perfused at 80 mmHg for 5 min after which the pressure was increased to 180 mmHg. The collagenase solution was then slowly warmed to 35 degrees C, transferred to the dissociation chamber and mechanically dissociated, and then purified using discontinuous gradients of Ficoll. Pancreases in the second group were loaded with collagenase (28-32 degrees C) using the syringe technique before mechanical dissociation and purification. There were no significant differences in pancreas cold ischemia, donor age, body mass index, maximum blood glucose, or serum amylase of the donors between the two groups. Mean collagenase digestion time in the digestion chamber was not different between the two groups; however, the amount of undigested tissue remaining after dissociation was significantly higher in the syringe-loaded group (15.3 +/- 2.6 g vs. 4.6 +/- 2.1 g, mean +/- SEM, p < 0.05). Postdigestion recovery of islets was 471 +/- 83 x 10(3) IE in the perfusion group compared with 391 +/- 57 x 10(3) IE for the syringe-loaded group. Postpurification recovery was higher in the perfused group (379 +/- 45 vs. 251 +/- 28 x 10(3) IE, p < 0.05, two-tailed paired t-test). No difference in in vitro islet viability was observed between the two groups following glucose perifusion with the calculated stimulation index of 4.6 +/- 0.6 for the perfusion group and 4.2 +/- 0.7 for the syringe-loaded group. Controlled perfusion via the pancreatic duct allows the effective delivery of the enzyme achieving maximal distension to all regions of the pancreas leading to an increased recovery of the islets with no detrimental effect on subsequent in vitro islet function.
Adenosine↗