Counterpoint: clinical islet transplantation: not ready for prime time

Immunosuppression With CD40 Costimulatory Blockade Plus Rapamycin for Simultaneous Islet-Kidney Transplantation in Nonhuman Primates

The lack of a reliable immunosuppressive regimen that effectively suppresses both renal and islet allograft rejection without islet toxicity hampers a wider clinical application of simultaneous islet-kidney transplantation (SIK). Seven MHC-mismatched SIKs were performed in diabetic cynomolgus monkeys. Two recipients received rabbit antithymocyte globulin (ATG) induction followed by daily tacrolimus and rapamycin (ATG/Tac/Rapa), and five recipients were treated with anti-CD40 monoclonal antibody (mAb) and rapamycin (aCD40/Rapa). Anti-inflammatory therapy, including anti-interleukin-6 receptor mAb and anti-tumor necrosis factor-α mAb, was given in both groups. The ATG/Tac/Rapa recipients failed to achieve long-term islet allograft survival (19 and 26 days) due to poor islet engraftment and cytomegalovirus pneumonia. In contrast, the aCD40/Rapa regimen provided long-term islet and kidney allograft survival (90, 94, >120, >120, and >120 days), with only one recipient developing evidence of allograft rejection. The aCD40/Rapa regimen was also tested in four kidney-alone transplant recipients. All four recipients achieved long-term renal allograft survival (100% at day 120), which was superior to renal allograft survival (62.9% at day 120) with triple immunosuppressive regimen (tacrolimus, mycophenolate mofetil, and steroids). The combination of anti-CD40 mAb and rapamycin is an effective and nontoxic immunosuppressive regimen that uses only clinically available agents for kidney and islet recipients.

Attainment of metabolic goals in the integrated UK islet transplant program with locally isolated and transported preparations

The objective was to determine whether metabolic goals have been achieved with locally isolated and transported preparations over the first 3 years of the UK's nationally funded integrated islet transplant program. Twenty islet recipients with C-peptide negative type 1 diabetes and recurrent severe hypoglycemia consented to the study, including standardized meal tolerance tests. Participants received a total of 35 infusions (seven recipients: single graft; 11 recipients: two grafts: two recipients: three grafts). Graft function was maintained in 80% at [median (interquartile range)] 24 (13.5-36) months postfirst transplant. Severe hypoglycemia was reduced from 20 (7-50) episodes/patient-year pretransplant to 0.3 (0-1.6) episodes/patient-year posttransplant (p < 0.001). Resolution of impaired hypoglycemia awareness was confirmed [pretransplant: Gold score 6 (5-7); 24 (13.5-36) months: 3 (1.5-4.5); p < 0.03]. Target HbA1c of <7.0% was attained/maintained in 70% of recipients [pretransplant: 8.0 (7.0-9.6)%; 24 (13.5-36) months: 6.2 (5.7-8.4)%; p < 0.001], with 60% reduction in insulin dose [pretransplant: 0.51 (0.41-0.62) units/kg; 24 (13.5-36) months: 0.20 (0-0.37) units/kg; p < 0.001]. Metabolic outcomes were comparable 12 months posttransplant in those receiving transported versus only locally isolated islets [12 month stimulated C-peptide: transported 788 (114-1764) pmol/L (n = 9); locally isolated 407 (126-830) pmol/L (n = 11); p = 0.32]. Metabolic goals have been attained within the equitably available, fully integrated UK islet transplant program with both transported and locally isolated preparations.

Safety and tolerability of the T-cell depletion protocol coupled with anakinra and etanercept for clinical islet cell transplantation

BACKGROUND

Islet cell transplantation (ICT) is a promising approach to cure patients with type 1 diabetes. We have implemented a new immunosuppression protocol with antithymoglobulin plus anti-inflammatory agents of anakinra and eternacept for induction and tacrolimus plus mycophenolate mofetil for maintenance [T-cell depletion with anti-inflammatory (TCD-AI) protocol], resulting in successful single-donor ICT.

METHODS

Eight islet recipients with type 1 diabetes reported adverse events (AEs) monthly. AEs were compared between three groups: first infusion with the TCD-AI protocol (TCD-AI-1st) and first and second infusion with the Edmonton-type protocol (Edmonton-1st and Edmonton-2nd).

RESULTS

The incidence of symptomatic AEs within the initial three months in the TCD-AI-1st group was less than in the Edmonton-1st and Edmonton-2nd groups, with a marginally significant difference (mean ± SE: 5.5 ± 0.3, 7.5 ± 0.5, and 8.3 ± 1.3, respectively; p = 0.07). A significant reduction in liver enzyme elevation after ICT was found in the TCD-AI-1st group compared with the Edmonton-1st and Edmonton-2nd groups (p < 0.05). Because of AEs, all patients in the Edmonton protocol eventually converted to the TCD-AI protocol, whereas all patients tolerated the TCD-AI protocol.

CONCLUSIONS

TCD-AI protocol can be tolerated for successful ICT, although this study includes small cohort, and large population trial should be taken.

Potential role of mesenchymal stromal cells in pancreatic islet transplantation

Pancreatic islet transplantation is an attractive option for treatment of type 1 diabetes mellitus but maintaining long term islet function remains challenging. Mesenchymal stromal cells (MSCs), derived from bone marrow or other sources, are being extensively investigated in the clinical setting for their immunomodulatory and tissue regenerative properties. Indeed, MSCs have been already tested in some feasibility studies in the context of islet transplantation. MSCs could be utilized to improve engraftment of pancreatic islets by suppressing inflammatory damage and immune mediated rejection. In addition to their immunomodulatory effects, MSCs are known to provide a supportive microenvironmental niche by secreting paracrine factors and depositing extracellular matrix. These properties could be used for in vivo co-transplantation to improve islet engraftment, or for in vitro co-culture to prime freshly isolated islets prior to implantation. Further, tissue specific pancreatic islet derived MSCs may open new opportunities for its use in islet transplantation as those cells might be more physiological to pancreatic islets.

The influence of porcine pancreas digestion parameters and islet histomorphology on islet isolation outcome

Transplantation of the pig islets of Langerhans is considered as the future treatment for patients suffering from type Idiabetes mellitus. Despite the adaptation of modified Ricordi method and highly purified collagenase, the results of pancreas digestions are precarious. Selection of proper donor and optimal digestion procedure are fundamental. The aim of this study was to assess the impact of pancreas procuring parameters on pig islets yield. The pancreata were harvested from 69 market sows weighting over 150 kg. After intraductal injection of cold collagenase solution pancreata were transported in UW solution or under conditions of two layer method (TLM). In laboratory pancreata were digested at 37°C according to Ricordi isolation method or stationary in the bottle. The particular parameters of isolation procedure were considered as substantial. Pig weight, volume of infused collagenase solution, TLM application and pancreas dividing before digestion positively affected islet yield. Additionally, the influence of pancreatic islet tissue histomorphology on isolation outcome was studied. Proper donor selection as well as adequate digestion parameters could improve pig islet recovery during islet isolation.

Assessment of beta cell viability

This unit contains detailed protocols for the simultaneous identification of the human pancreatic β cells and determination of their viability by flow cytometry. The enumeration of β cells is based on the ability of the cell-permeable form of the zinc-selective dye, FluoZin-3-AM, to bind intracellular labile zinc stored at higher levels in these cells than any other types of cells in the body. Although staining of intracellular labile zinc by FluoZin-3-AM is dependent on the metabolic activity of β cells, co-staining with a mitochondrial transmembrane potential indicator allows the accurate determination of viability. Simultaneous measurement of intracellular antioxidant thiols is also compatible with the detection of β cells containing metabolically active mitochondria. The method for assessing the mitochondrial functionality by flow cytometry described herein is simple to perform and sufficient to detect the viability of β cells in human islet preparations.

[Small intestine, pancreas and islet cell transplantation]

The past decade has seen substantial improvements in patient and graft survival after intestinal transplantation. This improvement has been achieved by advances in donor and recipient selection, patient management, immunosuppression and surgical techniques. Intestinal transplantation is therefore considered a therapeutic option in the treatment of short bowel syndrome. Mile stones include the development of the calcineurin inhibitor Tacrolimus for immunosuppression as well as induction therapy using immune modulating substances like interleukin-2 receptor antagonists and antilymphocyte preparations. In addition to improvements in immunosuppression, antimicrobial prophylaxis and diagnosis of rejection, advances in surgical techniques have been crucial to achieving increased graft survival. Pancreas transplantation, generally with simultaneous kidney transplantation, is now available as a treatment option for patients with labile diabetes mellitus (usually type 1). Allogeneic islet transplantation was developed in the 1990s as a minimally invasive alternative to pancreas transplantation. Pancreatic islets are isolated enzymatically from the donor pancreas, in most cases infused into the portal vein and thus engrafted into the liver. Currently, technical and medical problems as well as high costs prevent the application of islet transplantation as a therapeutic option for a larger number of patients with diabetes mellitus.

Gut microbiota in health and disease

Gut microbiota is an assortment of microorganisms inhabiting the length and width of the mammalian gastrointestinal tract. The composition of this microbial community is host specific, evolving throughout an individual's lifetime and susceptible to both exogenous and endogenous modifications. Recent renewed interest in the structure and function of this "organ" has illuminated its central position in health and disease. The microbiota is intimately involved in numerous aspects of normal host physiology, from nutritional status to behavior and stress response. Additionally, they can be a central or a contributing cause of many diseases, affecting both near and far organ systems. The overall balance in the composition of the gut microbial community, as well as the presence or absence of key species capable of effecting specific responses, is important in ensuring homeostasis or lack thereof at the intestinal mucosa and beyond. The mechanisms through which microbiota exerts its beneficial or detrimental influences remain largely undefined, but include elaboration of signaling molecules and recognition of bacterial epitopes by both intestinal epithelial and mucosal immune cells. The advances in modeling and analysis of gut microbiota will further our knowledge of their role in health and disease, allowing customization of existing and future therapeutic and prophylactic modalities.

Islet transplantation: lessons learned since the Edmonton breakthrough

This work sought to summarize the main issues of the last decade in the field of clinical islet transplantation. Ten years ago in Edmonton, a new protocol initiated for islet transplantation brought a breakthrough to the field. The earlier, rather poor results were in a sharp contrast to the first published results of 100% insulin freedom at 1 year. However, later it became clear that the promising initial results decline with time; at around 5 years, only about 10% of the patients maintain freedom from external insulin. Despite that fact, a milestone was set and intensive research started worldwide. New hopes were raised for patients. Modifications of the original protocol have been implemented to improve clinical results; however, islet transplantation remains an experimental procedure to date.

Pancreas vs. islet transplantation: a call on the future

PURPOSE OF REVIEW

The aim of this article is to review recent reports on whole pancreas and islet cell transplantation. It focuses on 'what the call to the future looks like' for both therapies as treatment options for those type 1 diabetes patients who do not respond well to conventional therapy.

RECENT FINDINGS

The major benefit of pancreas transplantation is the reversal of diabetes improvement of diabetes complications. Although the procedure requires major surgery and life-long immunosuppression, it remains the gold standard for a specific population of patients who suffer from type 1 diabetes and who do not respond to conventional therapy. Allogeneic islet transplantation is a promising alternative to pancreas transplantation, but patient outcomes remain less than optimal and significant progress is required in order for this procedure to be considered a reliable therapy.

CONCLUSION

Several factors have to be taken into consideration before making the decision of which of these procedures would better suit a patient with type 1 diabetes.

5'-AZA induces Ngn3 expression and endocrine differentiation in the PANC-1 human ductal cell line

Neurogenin 3 is necessary for endocrine cell development in the embryonic pancreas and has been shown to induce transdifferentiation duct cells from adult pancreas toward a neuro-endocrine phenotype. Here we discovered that the demethylating agent 5'-Azadeoxycytidine (AZA) induced Ngn3 expression and endocrine differentiation from the PANC-1 human ductal cell line. The expression of markers specific to mature islet cells, i.e., glucagon and somatostatin, was also observed. In addition, we demonstrated that growth factors (betacellulin and soluble factors released during pancreas embryogenesis) increased the level of maturation. Our studies revealed that the PANC-1 model system may provide a basis for elucidating the ductal/endocrine differentiation.