Surgical removal of the pancreas with one-step autotransplantation of isolated Langerhans islets into the hepatic portal system in the pig.

INTRODUCTION: Autotransplantation of isolated Langerhans islets is regarded as the only way to prevent iatrogenic diabetes in patients who had been scheduled for pancreatectomy due to painful chronic pancreatitis. A sufficient number of Langerhans islets capable of secretory activity need to be transplanted to maintain normoglycemia after the surgical procedure. In order to optimize all stages, including collection, storage, isolation and transplantation of pancreatic islets, a reproducible animal-based experimental model should be developed before a new method is introduced into clinical practice. OBJECTIVES: The aim of the present study was to develop a reproducible autogenic model-based method for collection, conservation and isolation of porcine pancreas so that transplantation of isolated pancreatic islets could be performed and postoperative normoglycemia achieved. MATERIAL AND METHODS: Pigs were subjected to total pancreatectomy with simultaneous splenectomy and without removal of the duodenum. The collected pancreas was stored in the University of Wisconsin solution with the addition of pentoxifylline (PTX) until the isolation procedure (<4 hours). Efficacy of isolation was evaluated based on the number, quality and viability of obtained islets. Following autotransplantation into the liver, secretory activity of the islets was assessed intravitally by serum glucose monitoring. RESULTS: The islet yield per gram of pancreas was 1452 (standard deviation [SD] +/- 125) for the PTX group and 384 (SD +/- 115) for the control non-PTX group (p<0.01). Viability of islets for individual isolations did not reveal any statistically significant differences between groups and was estimated at 85-93%. Three out of five animals demonstrated normoglycemia with features of neoangiogenesis in the islets transplanted into the liver, which was confirmed by histological examination. One animal developed hyperglycemia up to 430 mg/dl, and histological image showed intensive apoptosis and degranulation in the transplanted islets. CONCLUSIONS: Efficacy of the isolation method was confirmed by achieving normoglycemia after autotransplantation of pancreatic islets into the liver, while histological examination showed hepatic vascularization to be the most appropriate location for an autogenic graft. PTX presence in the preserving solution for the pancreas storage produced the cytoprotective effect, which directly correlated with the islet yield.

Allogeneic transplantation of isolated islet cells in clinical practice.

The only clinically acceptable radical treatment for patients with insulin-dependent diabetes mellitus is a whole pancreas transplantation, or alternatively an infusion of isolated islet cells into the hepatic portal venous system. Allogeneic transplantation of isolated islet cells is a procedure used only in a highly specific group of recipients, whereas intensive insulin treatment still remains the best therapy to achieve glycemia control in most patients with type 1 diabetes. Two groups of allograft recipients should be taken into consideration when scheduled for islet cell transplantation. The first group comprises allogeneic kidney recipients with a stabilized graft function for >6 months who receive chronic immunosuppression and require transplantation for end-stage renal disease caused by diabetic nephropathy. The second group consists of patients with unsatisfactory glycemic control despite insulin therapy, life-threatening hypoglycemic episodes and a rapid progression of long-term complications. Despite increasingly beneficial outcomes, islet cell transplantation has several limitations. Maintaining normoglycemia without exogenous insulin administration and appropriate selection of immunosuppressive agents to prolong graft survival are the major challenges. The aim of related studies has been to optimize all phases of islet cell transplantation in order to achieve total insulin independence and prolong graft survival.

TransEndoscopic Gastric SubMucosa Islet Transplantation (eGSM-ITx) in pigs with streptozotocine induced diabetes - technical aspects of the procedure - preliminary report.

BACKGROUND: Islets and pancreas transplantation have become standard treatments of patients with diabetic complications. However pancreas transplantation is associated with high incidence of complications and the long-term results of islet transplantation are still unsatisfactory. Loss of pancreatic islets grafts is caused not only by immunological reactions but also due to the site of grafting and IBMIR. Gastric submucosal space could be an alternative site for transplantation. The aim of this study was to assess the possibility of endoscopic islets transplantation into the gastric submucosa-its efficacy and potential complications.
MATERIAL/METHOD: 20 Landrace pigs weighing 19-24 kg were obtained for the study. Seven animals were controls (C-group) and 13 formed the transplantation group (TX group). In both groups diabetes was induced by streptozotocine (stz) infusion at a dose of 200 mg/kg. At 7 days post stz infusion pigs of both groups underwent endoscopy-in group C to assess the feasibility of gastroscopic examination under general anaesthesia in pigs with diabetes and to study the influence of basiliximab infusion on pigs, in the Tx-group to perform endoscopic submucosal islet transplantation (eGSM-ITx). Immunosuppression consisted of tacrolimus 0.2 mg/kg and sirolimus 6 mg/m(2). At 7 days post transplantation, control gastroscopy was performed to assess the gastric mucosa and to obtain biopsies for histopathology. 10 to 30 days after eGSM-ITx, magnetic resonance (MRI) scan was performed. Stomach and pancreas were obtained at autopsy for histopathology. Glycemia was assessed twice daily during the experiment. For 10 days after diabetes induction (up to three days after eGSM-ITx) in both groups, insulin was given to reach glycemia between 150-200 mg/dl, after that period insulin was given only when glycemia exceeded 600 mg/dl.
RESULTS: There were no differences in insulin requirement and glycemia up to the day of eGSM-ITx between the groups. Tx-group animals received a mean of 6000+/-3170 IEQ/kg. Tx-group animals had a significantly lower insulin requirement and significantly lower mean glycemia since the first day post transplantation. C-group animals all required insulin once daily to keep glycemia below 600 mg/dl. There were no signs of perforation, ulceration or bleeding after eGSM-ITx on gastroscopy and histopathological examination. MRI scans revealed unspecific thickening of gastric wall at sites of islet deposition.
CONCLUSIONS: Transendoscopic islets transplantation into gastric submucosa is feasible and a safe procedure in an experimental animal setting. Its potential for clinical application in human subjects needs further studies.

Highly selective intraportal transplantation of pancreatic islets.

BACKGROUND: Histological assessment of intraportally transplanted islets in experimental rodent models is limited by the wide dissemination of islets throughout the liver. We describe a technique of highly selective intraportal islet transplantation, which increases the density of transplanted islets and hence facilitates their histological analysis and validate this model as a means of quantitative histological analysis of islet graft survival. We also compared the number of islets visualized histologically with that of nonabsorbable dextran beads, representing the number of transplanted islets there would have been if there had been no graft loss. MATERIALS AND METHODS: Diabetic Lewis rats or nondiabetic Sprague-Dawley rats were transplanted with 500 or 1000 syngeneic islets or an equivalent number of beads either into the main branch (MB), or selectively into the right branch (RB) of the portal vein. RESULTS: Islet transplantation led to an identical fall in blood glucose levels whichever technique was used. The graft area and number of islets recovered for histological analysis was 3- to 4-fold higher when islets were transplanted using the RB technique. Quantitative histological graft analysis demonstrated that 46% to 61% of intraportally transplanted islets were lost compared with corresponding bead graft sizes. Fewer islets were lost when a greater islet mass was transplanted. CONCLUSIONS: Selective islet transplantation increases the concentration of islets and hence facilitates islet recovery after intraportal transplantation without detrimental effects on transplantation outcome. This technique, when combined with bead transplantation and digital image analysis, provides an accurate method for estimating the number of islets surviving intra-portal transplantation.

Time course of islet loss after intraportal transplantation.

A high percentage of islets fail to survive intraportal transplantation, but the absolute amount and time course of this loss are uncertain. We have devised a technique to directly quantitate the number of surviving islets using simultaneous selective transplantation of islets and inert beads into the posterior lobes of the liver. Islet:bead ratio did not change significantly within the first 2 hours, but fell progressively thereafter, giving calculated islet survival rates of 89, 43, and 66% at days 1, 7 and 28, respectively. This technique provides a baseline from which to develop strategies to improve the survival of intraportally transplanted islets.