In Vitro Assessment of Human Islet Vulnerability to Instant Blood-Mediated Inflammatory Reaction (IBMIR) and Its Use to Demonstrate a Beneficial Effect of Tissue Culture

Clinically available immunosuppression averts rejection but not systemic inflammation after porcine islet xenotransplant in cynomolgus macaques

A safe, efficacious, and clinically applicable immunosuppressive regimen is necessary for islet xenotransplantation to become a viable treatment option for diabetes. We performed intraportal transplants of wild-type adult porcine islets in 25 streptozotocin-diabetic cynomolgus monkeys. Islet engraftment was good in 21, partial in 3, and poor in 1 recipient. Median xenograft survival was 25 days with rapamycin and CTLA4Ig immunosuppression. Adding basiliximab induction and maintenance tacrolimus to the base regimen significantly extended median graft survival to 147 days (p < .0001), with three animals maintaining insulin-free xenograft survival for 265, 282, and 288 days. We demonstrate that this regimen suppresses non-Gal anti-pig antibody responses, circulating effector memory T cell expansion, effector function, and infiltration of the graft. However, a chronic systemic inflammatory state manifested in the majority of recipients with long-term graft survival indicated by increased neutrophil to lymphocyte ratio, IL-6, MCP-1, CD40, and CRP expression. This suggests that this immunosuppression regimen fails to regulate innate immunity and resulting inflammation is significantly associated with increased incidence and severity of adverse events making this regimen unacceptable for translation. Additional studies are needed to optimize a maintenance regimen for regulating the innate inflammatory response.

Differential cytokine expression in direct and indirect co-culture of islets and mesenchymal stromal cells

BACKGROUND

Transplantation of allogenic Langerhans islets (ISL) has been employed as an alternative to pancreas transplantation to provide endogenous supply of insulin and treat hypoglycemia unawareness in type 1 diabetes. Nevertheless, the process of islets isolation exposes the islets to hypoxia and other aggressive conditions that results in the recover of less than half of the islets present in the pancreas. Several studies demonstrated that co-culturing islets with mesenchymal stromal cells (MSC) before implantation enhances islets survival and function and this effect is mediated by cytokines. However, it remains unclear if the profile of cytokines secreted by MSC in co-culture with islets changes upon the type of co-culture: direct and indirect.

MATERIALS AND METHODS

In 3 series of experiments with human islets of 3 different donors, we compared the levels of a panel of cytokines measured in the supernatant of ISL cultured alone, Wharton Jelly MSC (WJMSC) cultured alone, direct co-culture of ISL-WJMSC and indirect co-culture using a permeable transwell membrane to separate ISL and WJMSC.

RESULTS

Comparing the profile of cytokines secreted by islets alone with islets in direct co- culture with WJMSC, we found higher expression of IL1b, IL17, IFγ, IL4, IL10, IL13, Granulocyte-macrophage colony-stimulating factor (GMCSF) and Leptin, in the supernatant of the co-cultures. In contrast, when comparing islets cultured alone with islets in indirect co-culture with MSC, we found no significant differences in the levels of cytokines we analyzed.

CONCLUSION

Direct contact between human WJMSC and pancreatic islets is required for elevated expression of a range of immune cytokines, including both those considered inflammatory, and anti-inflammatory.

Use of Culture to Reach Metabolically Adequate Beta-cell Dose by Combining Donor Islet Cell Isolates for Transplantation in Type 1 Diabetes Patients

BACKGROUND

Clinical islet transplantation is generally conducted within 72 hours after isolating sufficient beta-cell mass. A preparation that does not meet the sufficient dose can be cultured until this is reached after combination with subsequent ones. This retrospective study examines whether metabolic outcome is influenced by culture duration.

METHODS

Forty type 1 diabetes recipients of intraportal islet cell grafts under antithymocyte globulin induction and mycophenolate mofetil-tacrolimus maintenance immunosuppression were analyzed. One subgroup (n = 10) was transplanted with preparations cultured for ≥96 hours; in the other subgroup (n = 30) grafts contained similar beta-cell numbers but included isolates that were cultured for a shorter duration. Both subgroups were compared by numbers with plasma C-peptide ≥0.5 ng/mL, low glycemic variability associated with C-peptide ≥1.0 ng/mL, and with insulin independence.

RESULTS

The subgroup with all cells cultured ≥96 hours exhibited longer C-peptide ≥0.5 ng/mL (103 versus 48 mo; P = 0.006), and more patients with low glycemic variability and C-peptide ≥1.0 ng/mL, at month 12 (9/10 versus 12/30; P = 0.005) and 24 (7/10 versus 6/30; P = 0.007). In addition, 9/10 became insulin-independent versus 15/30 (P = 0.03). Grafts with all cells cultured ≥96 hours did not contain more beta cells but a higher endocrine purity (49% versus 36%; P = 0.03). In multivariate analysis, longer culture duration and older recipient age were independently associated with longer graft function.

CONCLUSIONS

Human islet isolates with insufficient beta-cell mass for implantation within 72 hours can be cultured for 96 hours and longer to combine multiple preparations in order to reach the desired beta-cell dose and therefore result in a better metabolic benefit.

A Strategy to Simultaneously Cure Type 1 Diabetes and Diabetic Nephropathy by Transplant of Composite Islet-Kidney Grafts

In recent years islet cell transplant has proven itself to be a viable clinical option for a select group of diabetic patients. Graft loss after transplant however continues to hinder the long-term success of the procedure. Transplanting the islets as a pre-vascularized composite islet-kidney graft has emerged as a relevant solution. Much groundbreaking research has been done utilizing this model in conjunction with strategies aimed towards islet cell survival and prolongation of function in the host. Transplanting the islet cells as a prevascularized graft under the capsule of the donor kidney as a composite islet-kidney graft has been shown to provide long term durable blood glucose control in large animal studies by limiting graft apoptosis as well as providing a physical barrier against the host immune response. While promising, this technique is limited by long term immunosuppression requirements of the host with its well-known adverse sequelae. Research into tolerance inducing strategies of the host to the allogeneic and xenogeneic islet-kidney graft has shown much promise in the avoidance of long-term immunosuppression. In addition, utilizing xenogeneic tissue grafts could provide a near-limitless supply of organs. The islet-kidney model could provide a durable and long-term cure for diabetes. Here we summarize the most recent data, as well as groundbreaking strategies to avoid long term immunosuppression and promote graft acceptance.

Protection of Pancreatic Islets Using Theranostic Silencing Nanoparticles in a Baboon Model of Islet Transplantation

The long-term success of pancreatic islet transplantation (Tx) as a cure for type 1 diabetes remains limited. Islet loss after Tx related to apoptosis, inflammation, and other factors continues to limit Tx efficacy. In this project, we demonstrate a novel approach aimed at protecting islets before Tx in nonhuman primates (NHPs) (baboons) by silencing a gene (caspase-3) responsible for induction of apoptosis. This was done using siRNA (siCas-3) conjugated to magnetic nanoparticles (MNs). In addition to serving as carriers for siCas-3, these nanoparticles also act as reporters for MRI, so islets labeled with MN-siCas-3 can be monitored in vivo after Tx. In vitro studies showed the antiapoptotic effect of MN-siCas-3 on islets in culture, resulting in minimal islet loss. For in vivo studies, donor baboon islets were labeled with MN-siCas-3 and infused into recipient diabetic subjects. A dramatic reduction in insulin requirements was observed in animals transplanted with even a marginal number of labeled islets compared with controls. By demonstrating the protective effect of MN-siCas-3 in the challenging NHP model, this study proposes a novel strategy to minimize the number of donor islets required from either cadaveric or living donors.

Glycaemic control in diabetic rats treated with islet transplantation using plasma combined with hydroxypropylmethyl cellulose hydrogel

Islet transplantation is one of the most efficient cell therapies used in clinics and could treat a large proportion of patients with diabetes. However, it is limited by the high requirement of pancreas necessary to provide the sufficient surviving islet mass in the hepatic tissue and restore normoglycaemia. Reduction in organ procurement requirements could be achieved by extrahepatic transplantation using a biomaterial that enhances islet survival and function. We report a plasma-supplemented hydroxypropyl methylcellulose (HPMC) hydrogel, engineered specifically using a newly developed technique for intra-omental islet infusion, known as hOMING (h-Omental Matrix Islet filliNG). The HPMC hydrogel delivered islets with better performance than that of the classical intrahepatic infusion. After the validation of the HPMC suitability for islets in vivo and in vitro, plasma supplementation modified the rheological properties of HPMC without affecting its applicability with hOMING. The biomaterial association was proven to be more efficient both in vitro and in vivo, with better islet viability and function than that of the current clinical intrahepatic delivery technique. Indeed, when the islet mass was decreased by 25% or 35%, glycaemia control was observed in the group of plasma-supplemented hydrogels, whereas no regulation was observed in the hepatic group. Plasma gelation, observed immediately post infusion, decreased anoïkis and promoted vascularisation. To conclude, the threshold mass for islet transplantation could be decreased using HPMC-Plasma combined with the hOMING technique. The simplicity of the hOMING technique and the already validated use of its components could facilitate its transfer to clinics. STATEMENT OF SIGNIFICANCE: One of the major limitations for the broad deployment of current cell therapy for brittle type 1 diabetes is the islets' destruction during the transplantation process. Retrieved from their natural environment, the islets are grafted into a foreign tissue, which triggers massive cell loss. It is mandatory to provide the islets with an 3D environment specifically designed for promoting isletimplantation to improve cell therapy outcomes. For this aim, we combined HPMC and plasma. HPMC provides suitable rheological properties to the plasma to be injectable and be maintained in the omentum. Afterwards, the plasma polymerises around the graft in vivo, thereby allowing their optimal integration into their transplantation site. As a result, the islet mass required to obtain glycaemic control was reduced by 35%.

Does Islet Size Really Influence Graft Function After Clinical Islet Transplantation?

Background

It has been proposed that islet transplants comprised primarily of small rather than large islets may provide better graft function, due to their lower susceptibility to hypoxic damage. Our aim was to determine whether islet size correlated with in vivo graft function in islet transplant recipients with C peptide–negative type 1 diabetes when islets have undergone pretransplant islet culture.

Methods

Human pancreatic islets were isolated, cultured for 24 hours and infused by standardized protocols. Ninety-minute stimulated C-peptide concentrations were determined during a standard meal tolerance test 3 months posttransplant. The islet isolation index (IEq/islet number) was determined immediately after isolation and again before transplantation (after tissue culture). This was correlated with patient insulin requirement or stimulated C-peptide.

Results

Changes in insulin requirement did not significantly correlate with islet isolation index. Stimulated C-peptide correlated weakly with IEq at isolation (P = 0.40) and significantly with IEq at transplantation (P = 0.018). Stimulated C-peptide correlated with islet number at isolation (P = 0.013) and more strongly with the islet number at transplantation (P = 0.001). In contrast, the correlation of stimulated C-peptide and islet isolation index was weaker (P = 0.018), and this was poorer at transplantation (P = 0.034). Using linear regression, the strongest association with graft function was islet number (r = 0.722, P = 0.001). Islet size was not related to graft function after adjusting for islet volume or number.

Conclusions

These data show no clear correlation between islet isolation index and graft function; both small and large islets are suitable for transplantation, provided the islets have survived a short culture period postisolation.

By analyzing the insulin requirements from 25 islet transplantation recipients, Hughes et al determined the strongest association with graft function was islet number while islet size was not related to graft function after adjusting for islet volume or number.

Improvement of islet graft function using liraglutide is correlated with its anti-inflammatory properties

Background and Purpose

Liraglutide improves the metabolic control of diabetic animals after islet transplantation. However, the mechanisms underlying this effect remain unknown. The objective of this study was to evaluate the anti‐inflammatory and anti‐oxidative properties of liraglutide on rat pancreatic islets in vitro and in vivo.

Experimental Approach

In vitro, rat islets were incubated with 10 μmol·L⁻¹ liraglutide for 12 and 24 h. Islet viability functionality was assessed. The anti‐inflammatory properties of liraglutide were evaluated by measuring CCL2, IL‐6 and IL‐10 secretion and macrophage chemotaxis. The anti‐oxidative effect of liraglutide was evaluated by measuring intracellular ROS and the total anti‐oxidative capacity. In vivo, 1000 islets were cultured for 24 h with or without liraglutide and then transplanted into the liver of streptozotocin‐induced diabetic Lewis rats with or without injections of liraglutide. Effects of liraglutide on metabolic control were evaluated for 1 month.

Key Results

Islet viability and function were preserved and enhanced with liraglutide treatment. Liraglutide decreased CCL2 and IL‐6 secretion and macrophage activation after 12 h of culture, while IL‐10 secretion was unchanged. However, intracellular levels of ROS were increased with liraglutide treatment at 12 h. This result was correlated with an increase of anti‐oxidative capacity. In vivo, liraglutide decreased macrophage infiltration and reduced fasting blood glucose in transplanted rats.

Conclusions and Implications

The beneficial effects of liraglutide on pancreatic islets appear to be linked to its anti‐inflammatory and anti‐oxidative properties. These findings indicated that analogues of glucagon‐like peptide‐1 could be used to improve graft survival.

Endocrine pancreas engineered using porcine islets and partial pancreatic scaffolds

OBJECTIVES

Because therapeutic options for severe diabetes are currently limited, there is a continuing need for new therapeutic strategies, especially in the field of regenerative medicine. Collaborative efforts across the fields of tissue engineering technology and islet biology may be able to create functionally engineered islets capable of restoring endocrine function in patients with insulin-dependent diabetes.

METHODS

This engineered scaffold was seeded with isolated primary porcine islets via the pancreatic duct using a multi-step infusion technique. Endocrine function of perfusion-cultured islets in the native scaffold was analyzed by immunohistochemical staining of insulin and glucagon as well as by the insulin stimulation test.

RESULTS

The pancreas in this large animal could be uniformly decellularized by perfusion with trypsin and TritonX-100 via the pancreatic duct, as shown by positive staining of extracellular matrix (ECM) components. These scaffolds derived from porcine pancreas were able to maintain the cellular integrity of islets that had repopulated the parenchymal space, which is fundamental for the restoration of endocrine function. Insulin release up to four days after islet infusion was maintained.

CONCLUSIONS

This scaffold from a large animal maintained islet survival and function in the short-term, retaining the cells as a solid organ in the parenchymal space after infusion through the pancreatic duct. These results suggest that this scaffold is suitable for further fabrication of fully functional bioengineered endocrine pancreases when implanted in vivo. Therefore, it may represent a key improvement in the field of beta-cell replacement therapy. Nonetheless, the facilitation of longer-term islet survival and studies of implantation in vivo is required for successful clinical translation.

Regenerative Therapy of Type 1 Diabetes Mellitus: From Pancreatic Islet Transplantation to Mesenchymal Stem Cells

Type 1 diabetes is an autoimmune disease resulting in the permanent destruction of pancreatic islets. Islet transplantation to portal vein provides an approach to compensate for loss of insulin producing cells. Clinical trials demonstrated that even partial islet graft function reduces severe hypoglycemic events in patients. However, therapeutic impact is restrained due to shortage of pancreas organ donors and instant inflammation occurring in the hepatic environment of the graft. We summarize on what is known about regenerative therapy in type 1 diabetes focusing on pancreatic islet transplantation and new avenues of cell substitution. Metabolic pathways and energy production of transplanted cells are required to be balanced and protection from inflammation in their intravascular bed is desired. Mesenchymal stem cells (MSCs) have anti-inflammatory features, and so they are interesting as a therapy for type 1 diabetes. Recently, they were reported to reduce hyperglycemia in diabetic rodents, and they were even discussed as being turned into endodermal or pancreatic progenitor cells. MSCs are recognized to meet the demand of an individual therapy not raising the concerns of embryonic or induced pluripotent stem cells for therapy.

Impact of Pancreatic Rat Islet Density on Cell Survival during Hypoxia

In bioartificial pancreases (BP), the number of islets needed to restore normoglycaemia in the diabetic patient is critical. However, the confinement of a high quantity of islets in a limited space may impact islet survival, particularly in regard to the low oxygen partial pressure (PO2) in such environments. The aim of the present study was to evaluate the impact of islet number in a confined space under hypoxia on cell survival. Rat islets were seeded at three different concentrations (150, 300, and 600 Islet Equivalents (IEQ)/cm(2)) and cultured in normal atmospheric pressure (160 mmHg) as well as hypoxic conditions (15 mmHg) for 24 hours. Cell viability, function, hypoxia-induced changes in gene expression, and cytokine secretion were then assessed. Notably, hypoxia appeared to induce a decrease in viability and increasing islet density exacerbated the observed increase in cellular apoptosis as well as the loss of function. These changes were also associated with an increase in inflammatory gene transcription. Taken together, these data indicate that when a high number of islets are confined to a small space under hypoxia, cell viability and function are significantly impacted. Thus, in order to improve islet survival in this environment during transplantation, oxygenation is of critical importance.