Islet transplantation in the twenty-first century

Deficiency of Atf3, an adaptive-response gene, protects islets and ameliorates inflammation in a syngeneic mouse transplantation model

AIMS/HYPOTHESIS

Islet transplantation is a potential therapeutic option for type 1 diabetes. However, the need for multiple donors per patient and heavy immunosuppression of the recipients limit its use. The goal of this study was to test whether the gene encoding activating transcription factor 3 (ATF3), a stress-inducible pro-apoptotic gene, plays a role in graft rejection in islet transplantation.

METHODS

We compared wild-type (WT) and Atf3 knockout (KO) islets in vitro using stress paradigms relevant to islet transplantation: isolation, inflammation and hypoxia. We also compared the WT and KO islets in vivo using a syngeneic mouse transplantation model.

RESULTS

ATF3 was induced in all three stress paradigms and played a deleterious role in islet survival, as evidenced by the lower viability of WT islets compared with KO islets. ATF3 upregulated various downstream target genes in a stress-dependent manner. These target genes can be classified into two functional groups: (1) apoptosis (Noxa [also known as Pmaip1] and Bnip3), and (2) immunomodulation (Tnfalpha [also known as Tnf], Il-1beta [also known as Il1b], Il-6 [also known as Il6] and Ccl2 [also known as Mcp-1]). In vivo, Atf3 KO islets performed better than WT islets after transplantation, as evidenced by better glucose homeostasis in the recipients and the reduction of the following variables in the KO grafts: caspase 3 activation, macrophage infiltration and expression of the above apoptotic and immunomodulatory genes.

CONCLUSIONS/INTERPRETATION

ATF3 plays a role in islet graft rejection by contributing to islet cell death and inflammatory responses at the graft sites. Silencing the ATF3 gene may provide therapeutic benefits in islet transplantation.

Polyglycolic Acid-islet grafts improve blood glucose and insulin concentrations in rats with induced diabetes

Pancreatic islet transplantation is a promising therapeutic treatment for type 1 diabetes mellitus. In the present study, we cocultured islets with or without a polyglycolic acid (PGA) fibrous scaffold for 5 days and transplanted the PGA-islet grafts into the leg muscles of Wistar rats with streptozotocin-induced diabetes; controls were injected with saline. The results showed that the blood glucose concentrations of the group given islets embedded with the PGA scaffold were lower than those without the scaffold or controls. On the other hand, the insulin content of the PGA-islet group was higher at all 5 time points compared with the insulin contents of the other 2 groups. After transplantation, many islets in the PGA-islet grafts showed normal morphology (as seen under the scanning electron microscope) and were surrounded by red blood cells. A fibrous extracellular matrix was visible around the PGA-islet grafts. These results demonstrated that PGA-islet grafts improved blood glucose and insulin concentrations in rats with induced diabetes.

[Cellular transplantation laboratory: a new field of action for nurses]

This article presents the experience of a nurse at a cellular transplantation laboratory. This laboratory goal is to isolate insulin producing cells for human transplantation. The nurse, as a member of an interdisciplinary team, took part in the planning of all work processes: working procedures and team training. The main activities under the nurse responsibilities include contamination control, on-the-job training and evaluation of the Quality of the procedures developed by the interdisciplinary team. Results have shown the effectiveness of the nurses' work in this new field.

Co-Expression of Vascular Endothelial Growth Factor and Interleukin-1 Receptor Antagonist Improves Human Islet Survival and Function

PURPOSE

Ex vivo gene therapy approaches can improve the outcome of islet transplantation for treating type I diabetes. We have previously shown the improvement in islet function and vascularization following ex vivo transfection for human vascular endothelial growth factor (hVEGF) gene expression. In this study, we tested the hypothesis that co-expression of two genes, which target different challenges faced by islets post-transplantation, supplement each other to improve the survival and function of islets. We determined whether there is an additive effect of hVEGF and human interleukin-1 receptor antagonist (hIL-1Ra) gene expression in human islets.

MATERIALS AND METHODS

Human islets were co-infected with adenoviral vectors encoding hVEGF and hIL-1Ra. Islets were then incubated with a cocktail of inflammatory cytokines (IL-1beta+TNFalpha+IFNgamma), and islet viability and function were determined. In vivo function was evaluated by transplanting islets under the kidney capsules of streptozotocin-induced non-obese diabetic severe combined immunodeficient (NOD-SCID) mice.

RESULTS

Infection of human islets with Adv-hVEGF and/or Adv-hIL-1Ra inhibited expression of inducible nitric oxide synthase (iNOS), decreased the production of nitric oxide (NO), and prevented the loss of in vitro glucose-stimulated insulin response and viability. Moreover, co-expression of hVEGF and hIL-1Ra reduced the blood glucose level of mice, and increased the level of blood insulin and c-peptide upon glucose challenge.

CONCLUSIONS

Our results indicated that co-expression of genes that target different insults to transplanted islets can improve the outcome of islet transplantation better than either gene alone.

Intracerebral xenotransplantation of semipermeable membrane- encapsuled pancreatic islets

AIM: To identify the decreasing effect of xenotransplantion in combination with privileged sites on rejection and death of biological semipermeable membrane-(BSM) encapsulated implanted islets.

METHODS: After the BSM experiment in vitro, BSM-encapsulated SD rat’s islet-like cell clusters (ICCs) were xenotransplanted into normal dog’s brain. Morphological changes were observed under light and transmission electron microscope. The islets and apoptosis of implanted B cells were identified by insulin-TUNEL double staining.

RESULTS: The BSM used in our study had a favorable permeability, some degree of rigidity, lighter foreign body reaction and toxicity. The grafts consisted of epithelioid cells and loose connective tissue. Severe infiltration of inflammatory cells was not observed. The implanted ICCs were identified 2 mo later and showed typical apoptosis.

CONCLUSION: BSM xenotransplantation in combination with the privileged site can inhibit the rejection of implanted heterogeneous ICCs, and death of implanted heterogeneous B cells is associated with apoptosis.

Establishing an islet transplantation program in a developing country

Diabetes is an emerging epidemic throughout the world. In our city alone, there are approximately 25,000 known diabetics (5% to 10% type 1) among a total population of 1.7 million inhabitants, and the incidence is increasing among all age groups. Islet transplantation is a potential treatment for type 1 diabetes mellitus. For this reason, we intended to establish an islet transplantation program. This required competent and well-trained professionals, a specially planned facility adhering to rigid regulations regarding safety and sterility, and a detailed study of the ethical laws and rules involving transplantation. In this article, we describe the process including any difficulties or barriers encountered due to limited resources in a developing country. We also describe all stages of personnel training and the necessary equipment and work area of a similar specialized center following the guidelines of the Brazilian National Agency for Health Care. Finally, we discuss our expectations for the initial phase of our islet transplantation program.

Inflammation-mediated dysfunction and apoptosis in pancreatic islet transplantation: implications for intrahepatic grafts

Recent advances in clinical protocols have improved the outcomes of pancreatic islet transplantation (PIT), yet PIT recipients typically require pancreatic islet grafts derived from multiple donors to achieve insulin independence. This along with experimental models of syngeneic PIT, showing that up to 60% of pancreatic islet tissue undergoes apoptosis within the first several days post-transplantation, strongly suggest the involvement of nonalloantigen-specific, inflammatory events in partial destruction of the graft following PIT. Interleukin-1beta appears to be among the most important inflammatory mediators, causing pancreatic islet dysfunction and apoptosis through the up-regulation of inducible nitric oxide (NO) synthase and cyclooxygenase-2. Kupffer cells secrete many molecules, including cytokines, NO, and free radicals, which are known to be directly toxic to the pancreatic islets, and depletion or inhibition of Kupffer cells improves outcomes following experimental PIT. Immediately after transplantation, the pancreatic islets are perfused only by portal vein blood until the process of angiogenesis restores arterial blood flow some 7-10 days later. This delayed vascularization may have implications for the expression of leukocyte adhesion molecules, the effects of free radicals, and the role of ischemia-reperfusion injury. Finally, in the immediate post-transplant period, hepatocytes may contribute to pancreatic islet injury through the production of NO. This paper reviews literature regarding the inflammatory events that follow PIT as well as the pathogenesis of diabetes and the pathophysiology of hepatic ischemia-reperfusion and their relation to the survival and function of intrahepatic pancreatic islet grafts.