BACKGROUND:Neonatal porcine islets (NPIs) can mature into a mixed population of endocrine cells that can restore glucose control in mice, pigs, and non-human primates, representing a potential alternative islet source for clinical beta cell replacement therapy. However, it remains unclear how conditions in the recipient influence the maturation and function of these cells. Here, we investigated the impact of host sex on NPIs implanted under the kidney capsule of male and female B6.129S7-Rag1tm1Mom (B6/Rag-/-) mice. METHODS:Diabetic mice were transplanted with 3000 NPIs under the kidney capsule. All mice were monitored for reversal of hyperglycemia and glucose clearance at 8- and 20-weeks post-transplant. Grafts were assessed for cell composition and insulin content. RESULTS:Female mice demonstrated improved glucose clearance at 8- and 20-weeks post-transplant compared to their male counterparts. Improved glucose clearance correlated with accelerated diabetes reversal in females (8 weeks vs. 12 weeks in males) and increased rates of euglycemic achievement (17/18 in females vs. 14/19 in males). However, grafts collected from male mice exhibited an increased percentage of insulin-positive cells as well as increased insulin content. CONCLUSION:The sex of the host influences the outcomes of NPI transplantation, showcasing the relevance of understanding the role of sex as a biological variable in islet transplantation.

Beta cell replacement therapies utilizing the subcutaneous space have inherent advantages to other sites: the potential for increased accessibility, noninvasive monitoring, and graft extraction. Site prevascularization has been developed to enhance islet survivability in the subcutaneous zone while minimizing potential foreign body immune responses. Molecular communication between the host and prevascularized implant site remains ill-defined. Poly(ethylene oxide)s (PEOs) of various hydrated radii (i.e., similar to 11-62 & Aring;) were injected into prevascularized subcutaneous sites in C57BL/6 mice, and the clearance and organ biodistribution were characterized. Prevascularization formed a barrier that confined the molecules compared with the unmodified site. Molecular clearance from the prevascularized site was inversely proportional to the molecular weight. The upper limit in molecular size for entering the vasculature to be cleared was determined to be 35 kDa MW PEO. These findings provide insight into the impact of vascularization on molecular retention at the injection site and the effect of molecular size on the mobility of hydrophilic molecules from the prevascularized site to the host. This information is necessary for optimizing the transplantation site for increasing the beta cell graft survival.

Type 1 diabetes mellitus (T1DM) is a growing global health concern that affects approximately 8.5 million individuals worldwide. T1DM is characterized by an autoimmune destruction of pancreatic β cells, leading to a disruption in glucose homeostasis. Therapeutic intervention for T1DM requires a complex regimen of glycaemic monitoring and the administration of exogenous insulin to regulate blood glucose levels. Advances in continuous glucose monitoring and algorithm-driven insulin delivery devices have improved the quality of life of patients. Despite this, mimicking islet function and complex physiological feedback remains challenging. Pancreatic islet transplantation represents a potential functional cure for T1DM but is hindered by donor scarcity, variability in harvested cells, aggressive immunosuppressive regimens and suboptimal clinical outcomes. Current research is directed towards generating alternative cell sources, improving transplantation methods, and enhancing cell survival without chronic immunosuppression. This Review maps the progress in cell replacement therapies for T1DM and outlines the remaining challenges and future directions. We explore the state-of-the-art strategies for generating replenishable β cells, cell delivery technologies and local targeted immune modulation. Finally, we highlight relevant animal models and the regulatory aspects for advancing these technologies towards clinical deployment. Type 1 diabetes mellitus affects 8.5 million people globally and is characterized by autoimmune destruction of pancreatic β cells. This Review discusses cell replacement therapies for T1DM and outlines the challenges and future directions

Beta cell replacement therapies can restore glycemic control to select individuals living with type 1 diabetes. However, the obligation of lifelong immunosuppression restricts cell therapies from replacing exogenous insulin administration. Encapsulation strategies can reduce the inherent adaptive immune response; however, few are successfully translated into clinical testing. Herein, we evaluated if the conformal coating of islets with poly(N-vinylpyrrolidone) (PVPON) and tannic acid (TA) (PVPON/TA) could preserve murine and human islet function while conferring islet allograft protection. In vitro function was evaluated using static glucose-stimulated insulin secretion, oxygen consumption rates, and islet membrane integrity. In vivo function was evaluated by transplanting human islets into diabetic immunodeficient B6.129S7-Rag1tm1Mom/J (Rag-/-) mice. The immunoprotective capacity of the PVPON/TA-coating was assessed by transplanting BALB/c islets into diabetic C57BL/6 mice. Graft function was evaluated by non-fasting blood glucose measurements and glucose tolerance testing. Both coated and non-coated murine and human islets exhibited indistinguishable in vitro potency. PVPON/TA-coated and control human islets were able to restore euglycemia post-transplant. The PVPON/TA-coating as monotherapy and adjuvant to systemic immunosuppression reduced intragraft inflammation and delayed murine allograft rejection. This study demonstrates that PVPON/TA-coated islets may be clinically relevant as they retain their in vitro and in vivo function while modulating post-transplant immune responses.

Background: Islet transplantation is an effective means for a subset of people living with type 1 diabetes to achieve insulin independence; however, lifelong systemic immunosuppression required to subvert the immune response remains a major barrier to patient inclusion. Herein, we explore the use of a localized drug delivery system to preserve murine islet allograft function, reducing the need for toxic systemic immunosuppression. Our previous work demonstrated that localized delivery of dexamethasone eluting microparticles reduced intragraft proinflammatory cytokine expression and prolonged the function of murine islet allografts. Thus, we present our efforts in optimizing a microparticle formulation that encapsulates rapamycin (rapa), a more potent immunosuppressant employed in clinical islet transplantation. Localized delivery of rapa may be an attractive strategy to provide islet allograft protection while minimizing the diabetogenic effects of high-dose systemic rapa. Methods: Rapa was encapsulated via a modified single emulsion solvent evaporation technique. Utilizing Food and Drug Administration-approved poly(lactide-co-glycolide) (PLGA), we formed microparticles with an 87.3 ± 2.1 % rapa encapsulation efficiency. We assessed the in vitro and in vivo effects of our rapa-eluting microparticles on islets with the Seahorse XF24 assay and murine islet transplant models, respectively. Rodents with streptozotocin-induced diabetes were transplanted with microparticles and islets isolated from naïve BALB/c mice. Recipients included BALB/c (syngeneic) and C57BL/6 (allogeneic) mice. Results: Microparticles showed sustained in vitro rapa release for up to 35 days. Human islets co-cultured 24 hrs with rapa-microparticles (1.0 and 2.0 mg) demonstrated comparable mitochondrial potency and glucose-stimulated respiration to untreated islets, while 25 nM rapa incubation blunted the glucose response and increased proton leak. Syngeneic islets co-transplanted with a 0.1 mg/kg dose of rapa-microparticles (1.0 mg; n=3) under the kidney capsule all achieved euglycemia and a 0.2 mg/kg rapa-microparticles (2.0 mg; n=8) demonstrated partial graft function (3 of 8). Islet allograft recipients receiving 0.1 mg/kg rapa-microparticles (n=6) demonstrated prolonged allograft survival compared to empty microparticles recipients (n=4; P<0.01). Rapa-microparticles + CTLA-4-Ig (n=6) resulted in 100% allograft survival at 100 days compared to 38% empty microparticles + CTLA-4-Ig (n=8; P<0.05). Conclusion: Our novel rapa-eluting microparticles prolonged allograft function and worked synergistically with CTLA-4-Ig therapy. Further validating our findings in a humanized mouse model can help us study rapa-microparticles tolerogenic effects in the context of the human immune system. Collectively, localized drug delivery has the potential to alter the immune environment, protect grafts, and may serve as a safe adjuvant approach in clinical islet transplantation.Juvenile Diabetes Research Foundation (2-SRA-2019-779-S-B). Juvenile Diabetes Research Foundation (JDRF) Career Development Award (5-CDA-2020-945-A-N). ARP is also a Canada Research Chair in Cell Therapies for Diabetes, and as such, this research was undertaken, in part, thanks to funding from the Canada Research Chairs Program.

Intra-hepatic islet transplantation for type-1 diabetes is limited by the need for multiple infusions and poor islet viability post-transplantation. The development of alternative transplantation sites is necessary to improve islet survival, and facilitate monitoring and retrieval. We tested a clinically proven Biodegradable Temporizing Matrix (BTM), a polyurethane-based scaffold, to generate a well vascularized intracutaneous ‘neo-dermis’ within the skin for islet transplantation. In murine models, BTM did not impair syngeneic islet renal-subcapsular transplant viability or function, and facilitated diabetes cure for over 150 days. Further, BTM supported functional neonatal porcine islet transplants into RAG-1-/- mice for 400 days. Hence, BTM is non-toxic for islets. two-photon intravital imaging used to map vessel growth through time identified dense vascular networks, with significant collagen deposition and increases in vessel mass up to 30 days post-BTM implantation. In a pre-clinical porcine skin model, BTM implants created a highly-vascularized intracutaneous site by day 7 post-implantation. When syngeneic neonatal porcine islets were transplanted intracutaneously the islets remained differentiated as insulin producing cells, maintained normal islet architecture, secreted c-peptide, and survived for over 100 days. Here we show that BTM facilitates formation of an islet-supportive intracutaneous ‘neo-dermis’ in a porcine pre-clinical model, as an alternative islet transplant site.

Pancreatic islet transplantation is an effective strategy for restoring glucose regulation for highly selected patients with type 1 diabetes. However, an undesirable level of islet cell death is caused by oxidative stress that occurs during islet isolation, culture, and transplantation. The loss of islets throughout the transplantation procedure often necessitates multiple human donors per recipient to achieve insulin independence. Administration of exogenous antioxidants has shown promise in both preserving islet cell viability and functionality post‐transplantation. Herein, thioketal (TK) antioxidant is evaluated using neonatal porcine islets and Beta‐TC‐6 cells exposed to H 2 O 2 for changes in membrane integrity, oxygen consumption rates, and lipid peroxidation. Diabetic BALB/c mice are transplanted with a marginal dose of syngeneic islets, ±48‐h TK pre‐treatment, under the kidney capsule. Graft function is measured by nonfasting blood glucose and glucose tolerance testing. It is found that 200 µM of TK was not cytotoxic, reduced reactive oxygen species‐mediated oxidative islet damage, preserved in vitro islet cell functionality, and facilitated superior murine syngeneic marginal islet mass engraftment. These results demonstrate that the antioxidant attributes of TK reduce the deleterious effects of reactive oxygen species experienced in vitro and enhance marginal islet mass transplant outcomes.

Neonatal porcine islets (NPIs) are a source of islets for xenotransplantation. In the pig, the pancreatic lobes remain separate, thus, when optimizing NPI isolation, the pancreatic lobes included in the pancreatic digest should be specified. These lobes are the duodenal (DL), splenic (SL) and connecting (CL) lobe that correspond to the head, body-tail, and uncinate process of the human pancreas. In this study we are the first to evaluate all three neonatal porcine pancreatic lobes and NPIs isolated from these lobes. We report, a significant difference in endocrine and progenitor cell composition between lobes, and observed pancreatic duct glands (PDG) within the mesenchyme surrounding exocrine ducts in the DL and CL. Following in vitro differentiation, NPIs isolated from each lobe differed significantly in the percent increase of endocrine cells and final cell composition. Compared to other recipients, diabetic immunodeficient mice transplanted with NPIs isolated from the SL demonstrated euglycemic control as early as 4 weeks (p < 0.05) and achieved normoglycemia by 6 weeks post-transplant (p < 0.01). For the first time we report significant differences between the neonatal porcine pancreatic lobes and demonstrate that NPIs from these lobes differ in xenograft function.

One strategy to prevent islet rejection is to create a favorable immune-protective local environment at the transplant site. Herein, we utilize localized cyclosporine A (CsA) delivery to islet grafts via poly(lactic-co-glycolic acid) (PLGA) microparticles to attenuate allograft rejection. CsA-eluting PLGA microparticles were prepared using a single emulsion (oil-in-water) solvent evaporation technique. CsA microparticles alone significantly delayed islet allograft rejection compared to islets alone (p < 0.05). Over 50% (6/11) of recipients receiving CsA microparticles and short-term cytotoxic T lymphocyte-associated antigen 4-Ig (CTLA4-Ig) therapy displayed prolonged allograft survival for 214 days, compared to 25% (2/8) receiving CTLA4-Ig alone. CsA microparticles alone and CsA microparticles + CTLA4-Ig islet allografts exhibited reduced T-cell (CD4+ and CD8+ cells, p < 0.001) and macrophage (CD68+ cells, p < 0.001) infiltration compared to islets alone. We observed the reduced mRNA expression of proinflammatory cytokines (IL-6, IL-10, INF-γ, and TNF-α; p < 0.05) and chemokines (CCL2, CCL5, CCL22, and CXCL10; p < 0.05) in CsA microparticles + CTLA4-Ig allografts compared to islets alone. Long-term islet allografts contained insulin+ and intra-graft FoxP3+ T regulatory cells. The rapid rejection of third-party skin grafts (C3H) in islet allograft recipients suggests that CsA microparticles + CTLA4-Ig therapy induced operational tolerance. This study demonstrates that localized CsA drug delivery plus short-course systemic immunosuppression promotes an immune protective transplant niche for allogeneic islets.

Transplantation of pancreatic islets represents a proven therapeutic strategy to restore physiologic glycemic control for patients with type 1 diabetes mellitus (T1DM) who experience life-threatening severe hypoglycemia unawareness. However, limiting factors prevent islet transplantation from replacing insulin therapy, including donor shortage and lifelong immunosuppression. Islet encapsulation has the potential to reduce the immune reaction. We hypothesize that conformal islet coating with poly(N-vinylpyrrolidone) (PVPON) and tannic acid (TA) PVPON/TA will enhance the engraftment efficacy of human islet xenografts, as well as murine islet allografts.

Insulin replacement therapy is the mainstay treatment option for type 1 diabetes; however, when this fails to adequately maintain glucose homeostasis, islet transplantation can provide a solution. Shortages and the heterogenicity of human islet donors lead to the desire for an alternative, such as the use of xenografts, particularly porcine islets. Incremental improvements in immunosuppression, islet isolation, and xenograft characterization over the past thirty years have led to the feasibility of this solution. Engraftment of porcine islets can be facilitated through combinations of immunosuppressive reagents, macro or microencapsulation of islet grafts, and the use of genetically modified porcine islets, which are more compatible with the human body, both with respect to the immune system, and to the structure of insulin. Herein, we review the current advancements that may position porcine islet xenotransplantation to become a feasible clinical option for the treatment of type 1 diabetes.

Regenerating pancreatic β-cells is a potential curative approach for diabetes. We previously identified the small molecule CID661578 as a potent inducer of β-cell regeneration, but its target and mechanism of action have remained unknown. We now screened 257 million yeast clones and determined that CID661578 targets MAP kinase-interacting serine/threonine kinase 2 (MNK2), an interaction we genetically validated in vivo. CID661578 increased β-cell neogenesis from ductal cells in zebrafish, neonatal pig islet aggregates and human pancreatic ductal organoids. Mechanistically, we found that CID661578 boosts protein synthesis and regeneration by blocking MNK2 from binding eIF4G in the translation initiation complex at the mRNA cap. Unexpectedly, this blocking activity augmented eIF4E phosphorylation depending on MNK1 and bolstered the interaction between eIF4E and eIF4G, which is necessary for both hypertranslation and β-cell regeneration. Taken together, our findings demonstrate a targetable role of MNK2-controlled translation in β-cell regeneration, a role that warrants further investigation in diabetes.

The subcutaneous space is currently being pursued as an alternative transplant site for ß-cell replacement therapies due to its retrievability, minimally invasive procedure and potential for graft imaging. However, implantation of ß-cells into an unmodified subcutaneous niche fails to reverse diabetes due to a lack of adequate blood supply. Herein, poly (ε-caprolactone) (PCL) and poly (lactic-co-glycolic acid) (PLGA) polymers were used to make scaffolds and were functionalized with peptides (RGD (Arginine-glycine-aspartate), VEGF (Vascular endothelial growth factor), laminin) or gelatin to augment engraftment. PCL, PCL + RGD + VEGF (PCL + R + V), PCL + RGD + Laminin (PCL + R + L), PLGA and PLGA + Gelatin (PLGA + G) scaffolds were implanted into the subcutaneous space of immunodeficient Rag mice. After four weeks, neonatal porcine islets (NPIs) were transplanted within the lumen of the scaffolds or under the kidney capsule (KC). Graft function was evaluated by blood glucose, serum porcine insulin, glucose tolerance tests, graft cellular insulin content and histologically. PLGA and PLGA + G scaffold recipients achieved significantly superior euglycemia rates (86% and 100%, respectively) compared to PCL scaffold recipients (0% euglycemic) (* p < 0.05, ** p < 0.01, respectively). PLGA scaffolds exhibited superior glucose tolerance (* p < 0.05) and serum porcine insulin secretion (* p < 0.05) compared to PCL scaffolds. Functionalized PLGA + G scaffold recipients exhibited higher total cellular insulin contents compared to PLGA-only recipients (* p < 0.05). This study demonstrates that the bioabsorption of PLGA-based fibrous scaffolds is a key factor that facilitates the function of NPIs transplanted subcutaneously in diabetic mice.

Beta cell replacement therapy is a proven strategy to restore glycemic control, reduce hypoglycemic awareness and stabilize glycated hemoglobin (HbA1c) for a subset of patients with type 1 diabetes. However, the absence of an effective strategy to prevent islet allograft rejection and recurrent autoimmunity restricts patient inclusion and durable insulin independence. Herein, we explore the utility of islet graft localized cyclosporine A (CsA) delivery via co-transplanted drug-eluting poly(lactic-co-glycolic acid) (PLGA) microparticles to attenuate allograft rejection.

Pancreatic islet transplantation represents an attractive therapeutic strategy to restore physiologic blood glucose control to individuals with type 1 diabetes (T1D). This treatment modality is established as an effective means to achieve normoglycemia, prevent hypoglycemia, improve quality of life, and potentially protect against vascular complications of T1D.1 Despite clear progress in clinical islet transplantation, this approach is limited to those with life-threatening hypoglycemic unawareness.2 While both auto- and alloimmune-mediated rejection clearly contribute to long-term islet graft failure, accumulating evidence suggests that acute islet cell death, in the peritransplant and posttransplant periods, severely compromises engraftment.3 As a consequence, multiple organ donors are routinely required to achieve insulin independence with chronic life-long toxic immunosuppression, restricting this therapeutic option to a narrow range of T1D patients. While transplanting islets within the liver has been demonstrated as an efficient means of restoring glycemic control, the procedure often results in acute or gradual graft attrition and carries procedural risks. Moreover, intrahepatic transplantation does not permit retrieval of donor islets; the ability to recover the graft is also important for safety monitoring in efforts to replace donor-derived islets with human stem cell– or animal cell–derived pancreatic cells. In recent years, numerous investigators have defined signaling pathways that allow the efficient generation of pancreatic progenitor cells and improved their commitment in vitro to β-like cells, thus serving as a potentially unlimited supply of surrogate islets.4 As a means to minimize potential recipient risk in early clinical trials, the transplant site for stem cell–derived cell-based therapies should ideally exploit an approach that encapsulates the stem cells, is retrievable, and provides vascular support.5 The subcutaneous tissue is an auspicious extrahepatic site, based on its ability to house large transplant volumes, minimal invasiveness, and the capacity for graft excision if required. Inopportunely, subcutaneous engraftment is limited by its innate hypovascularity, leading to poor oxygenation, inadequate metabolic exchange, and subsequent loss of transplanted tissue.6 To address this challenge, researchers have used approaches to create a subcutaneous prevascularized bed through tissue engineering, which has enabled long-term islet engraftment. This technique preconditions the subcutaneous site into a more sustainable microenvironment, cloaking the graft in a vascular matrix while facilitating long-term reversal of diabetes posttransplant using rodent and human islets,7 and more recently human stem cell–derived pancreatic endoderm cells.8 However, a limitation of prevascularized strategies is the requirement of a 2-stage surgical procedure, one to prime the site and another to deliver the therapeutic cells. In contrast, cellular encapsulation technologies that do not rely on prevascularization are plagued by a delay in revascularization, reliance on acute passive diffusion for nutrient exchange, and the stimulation of a chronic foreign body reaction.9 In this issue of Transplantation, Takaichi et al10 present their findings exploring the efficacy of a vascularized human-induced pluripotent stem cell–derived β cells (hiPS β cells) spheroid modality, transplanted subcutaneously for the treatment of T1D. This present work is an expansion of their previous published observations with layer-by-layer constructed spheroids utilizing normal human dermal fibroblasts and human umbilical vein endothelial cells, now applied to pancreatic β cells. The topic of evaluating extrahepatic islet engraftment sites is of great importance as the feasibility of alternative cell sources (ie, stem cell–derived insulin producing cell products) are rapidly becoming a present reality. Again, while the infusion of islets into the liver continues to remain only transplant site to routinely reverse diabetes in clinical patients, this site may not indeed be suitable for alternative cells sources, namely due to the inability to retrieve the cellular graft should complications arise. Using either MIN-6- and hiPS-derived β-cell spheroids, the authors demonstrate that vascularized spheroids enhanced in vitro glucose-stimulated insulin secretion. Postsubcutaneous transplant, vascularized hiPS β-cell spheroid also significantly decreased daily nonfasting blood glucose levels as well as improved glucose tolerance during an intraperitoneal glucose tolerance test in diabetic immunodeficient mice compared with controls not implanted with the spheroid grafts. The authors make a persuasive argument that this improved metabolic outcome was the result of the hiPS β-cell spheroids increasing angiogenesis at the graft site without the need for prevascularization. A caveat to the author’s 3D vascularized spheroid approach is its inability to facilitate full engraftment and correction of diabetes, coupled with the limited biological replicates. We agree with the authors that the true translational potential of this cell replacement therapy can only be fully gauged with future optimized studies that demonstrate routine posttransplant normoglycemia in larger cohort of recipients. Nevertheless, this β-cell transplant modality does represent an important and innovative advancement as it demonstrates a “single step” approach to create a functional and vascularized subcutaneous β-cell transplant platform. While our expectations are tempered until future studies materialize, we remain optimistic that this innovation could lead to promising regenerative treatments for T1D.

Introduction: Intrahepatic islet transplantation represents an effective therapeutic strategy to restore physiological insulin delivery in patients with Type 1 Diabetes. However, transplantation currently requires islets isolated from multiple donors, and results in an estimated 70% loss of transplanted β-cell mass acutely post-transplant. Necroptosis, a programmed and regulated form of necrotic cell death, occurs following cell damage or inflammation. The signaling cascade requires the involvement of receptor interacting protein kinase 1 and 3 (RIPK1 and RIPK3, respectively), which form the necrosome. Previous research has examined the function of necroptosis in other organ systems such as renal ischemia/reperfusion injury, however, the role of necroptosis in islets remains unexplored. Herein, we hypothesize that inhibition of RIPK1 and RIPK3 in islets, and subsequently, inhibition of the necrosome formation, will prevent necroptosis from occurring following transplant. Methods: Necrostatin-1s is an inhibitor of RIPK1 and necrostatin-1 is an inhibitor of both RIPK1 and RIPK3. Human islets and MIN6 cells were co-cultured in ± necrostatin-1s and ± necrostatin-1 for 24 and 48 hours at 37°C and 5% CO2, to determine their safety, efficacy, and optimal dose. Cells and islets were also co-cultured in ± Z-VAD-FMK, a pan-caspase inhibitor, to shunt cell death events away from apoptosis and towards necroptosis. In-vitro islet function was assessed by oxygen consumption rate, glucose stimulated insulin secretion, and cell membrane integrity. In-vivo islet function was assessed through human islet marginal mass transplantation (500 islet equivalents) under the kidney capsule of diabetic immunodeficient Rag-/- mice. Human islets were cultured for 48 hours in 100μM necrostatin-1s or necrostatin-1 ± Z-VAD-FMK prior to transplant. Graft function was assessed via measurement of non-fasting blood glucose, and intraperitoneal glucose tolerance testing (IPGTT). Results: When paired with a pan-caspase inhibitor, at 48 hours, cell membrane integrity of cells treated with necrostatin-1 is significantly increased, as compared with controls (p<0.001). Furthermore, post-transplant non-fasting blood glucose means and blood glucose area under the curve (AUC) calculated following IPGTT are lowest in mice transplanted with subtherapeutic doses of human islets treated with necrostatin-1 + ZVAD (p<0.05), and ZVAD alone (p<0.01), and are highest in mice transplanted with subtherapeutic doses of untreated human islets. Conclusions: The present results indicate the therapeutic potential of administration of combination therapy of an apoptosis and necroptosis inhibition in improving islet survival. Inhibition of necroptosis and apoptosis in conjunction may improve human marginal islet engraftment, leading to an increased rate of cell survival. Improvement of transplant outcomes could potentially lead to improved rates of single donor islet transplant success rates and increase graft durability. Furthermore, pre-treatment of islets alone, as opposed to systemic delivery of inhibitors, provides a safer translational pathway to clinical therapeutic use.