Long-Term Survival and Induction of Operational Tolerance to Murine Islet Allografts by Co-Transplanting Cyclosporine A Microparticles and CTLA4-Ig.

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.

Heterogenous expression of endocrine and progenitor cells within the neonatal porcine pancreatic lobes-Implications for neonatal porcine islet xenotransplantation.

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.

MNK2 deficiency potentiates β-cell regeneration via translational regulation.

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.

Bioabsorption of Subcutaneous Nanofibrous Scaffolds Influences the Engraftment and Function of Neonatal Porcine Islets.

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.

Xenotransplantation of tannic acid-encapsulated neonatal porcine islets decreases proinflammatory innate immune responses.

Background: Islet transplantation with neonatal porcine islets (NPIs) is a promising treatment for type 1 diabetes (T1D), but immune rejection poses a major hurdle for clinical use. Innate immune-derived reactive oxygen species (ROS) synthesis can facilitate islet xenograft destruction and enhance adaptive immune responses.

Methods: To suppress ROS-mediated xenograft destruction, we utilized nanothin encapsulation materials composed of multilayers of tannic acid (TA), an antioxidant, and a neutral polymer, poly(N-vinylpyrrolidone) (PVPON).

Reinforcing one-carbon metabolism via folic acid/Folr1 promotes β-cell differentiation.

Diabetes can be caused by an insufficiency in β-cell mass. Here, we performed a genetic screen in a zebrafish model of β-cell loss to identify pathways promoting β-cell regeneration. We found that both folate receptor 1 (folr1) overexpression and treatment with folinic acid, stimulated β-cell differentiation in zebrafish.

Selection of a novel AAV2/TNFAIP3 vector for local suppression of islet xenograft inflammation.

Background: Neonatal porcine islets (NPIs) can restore glucose control in mice, pigs, and non-human primates, representing a potential abundant alternative islet supply for clinical beta cell replacement therapy. However, NPIs are vulnerable to inflammatory insults that could be overcome with genetic modifications. Here, we demonstrate in a series of proof-of-concept experiments the potential of the cytoplasmic ubiquitin-editing protein A20, encoded by the TNFAIP3 gene, as an NPI cytoprotective gene.

Impact of donor and prolonged cold ischemia time of neonatal pig pancreas on neonatal pig islet transplant outcome.

Background: Genetically modified pigs (GMP) have been developed to alleviate the shortage of donors in human islet transplantation and rejection. In this study, we characterized and compared the islets from GalTKO, GalTKO/hCD46, GalTKO/hCD46/hCD39, and wild-type (WT) neonatal pigs.

Methods: Islets were isolated from GMP and WT pig pancreases that have been packaged with ice pack for at least 24 hours.

Current State and Evidence of Cellular Encapsulation Strategies in Type 1 Diabetes.

Islet cell replacement therapies represent an effective way to restore physiologic glycemic control in patients with type 1 diabetes (T1DM) and severe hypoglycemia. Despite being able to provide long-term insulin independence, patients still require lifelong immunosuppression, which has myriad detrimental effects including an increased risk for opportunistic infections and some types of cancer. This vital issue precludes widespread application of these therapies as a true cure for T1DM.

Co-transplantation of human adipose-derived mesenchymal stem cells with neonatal porcine islets within a prevascularized subcutaneous space augments the xenograft function.

Background: Cell transplantation has been widely recognized as a curative treatment strategy for variety of diseases including type I diabetes (T1D). Broader patient inclusion for this therapeutic option is restricted by a limited supply of healthy human islet donors and significant loss of islets immediately postintrahepatic transplant due to immune activation. Neonatal porcine islets (NPIs) are a potential ubiquitous β-cell source for treating T1D.

Fibrin supports subcutaneous neonatal porcine islet transplantation without the need for pre-vascularization.

Background: Neonatal porcine islets (NPIs) are a promising tissue source for clinical islet xenotransplantation. To facilitate graft monitoring and recovery if needed, an extra-hepatic transplant site would be optimal. In addition, islet transplantation into the portal vein has been associated with life-threatening intraperitoneal bleeding, portal vein thrombosis, hepatic steatosis, and loss of islet graft function.

Co-localized immune protection using dexamethasone-eluting micelles in a murine islet allograft model.

The broad application of ß cell transplantation for type 1 diabetes is hindered by the requisite of lifelong systemic immunosuppression. This study examines the utility of localized islet graft drug delivery to subvert the inflammatory and adaptive immune responses. Herein, we have developed and characterized dexamethasone (Dex) eluting Food and Drug Administration-approved micro-Poly(lactic-co-glycolic acid) micelles and examined their efficacy in a fully major histocompatibility complex-mismatch murine islet allograft model.

A20 as an immune tolerance factor can determine islet transplant outcomes.

Islet transplantation can restore lost glycemic control in type 1 diabetes subjects but is restricted in its clinical application by a limiting supply of islets and the need for heavy immune suppression to prevent rejection. TNFAIP3, encoding the ubiquitin editing enzyme A20, regulates the activation of immune cells by raising NF-κB signaling thresholds. Here, we show that increasing A20 expression in allogeneic islet grafts resulted in permanent survival for ~45% of recipients, and > 80% survival when combined with subtherapeutic rapamycin.

Improved islet recovery and efficacy through co-culture and co-transplantation of islets with human adipose-derived mesenchymal stem cells.

Islet transplantation is an established clinical procedure for select patients with type 1 diabetes and severe hypoglycemia to stabilize glycemic control. Post-transplant, substantial beta cell mass is lost, necessitating multiple donors to maintain euglycemia. A potential strategy to augment islet engraftment is the co-transplantation of islets with multipotent mesenchymal stem cells to capitalize upon their pro-angiogenic and anti-inflammatory properties.

In vitro characterization of neonatal, juvenile, and adult porcine islet oxygen demand, β-cell function, and transcriptomes.

Background: There is currently a shortage of human donor pancreata which limits the broad application of islet transplantation as a treatment for type 1 diabetes. Porcine islets have demonstrated potential as an alternative source, but a study evaluating islets from different donor ages under unified protocols has yet to be conducted.

Methods: Neonatal porcine islets (NPI; 1-3 days), juvenile porcine islets (JPI; 18-21 days), and adult porcine islets (API; 2+ years) were compared in vitro, including assessments of oxygen consumption rate, membrane integrity determined by FDA/PI staining, β-cell proliferation, dynamic glucose-stimulated insulin secretion, and RNA sequencing.

Functional Maturation and In Vitro Differentiation of Neonatal Porcine Islet Grafts.

Background: There is a strong rationale to pursue the use of neonatal porcine islets (NPIs) as an unlimited source of islets for clinical xenotransplantation. Because NPIs are composed of immature insulin producing beta (ß) cells and ductal precursor cells, they provide an ideal model to examine culture conditions to enhance ß cell proliferation and/or ß cell neoformation from ductal cells. In an attempt to optimize the potential of NPIs as a source of ß cell grafts, we used an in vitro differentiation protocol and measured its effect on the functional maturation and differentiation of NPIs.

Ferroptosis-inducing agents compromise in vitro human islet viability and function.

Human islet transplantation has been hampered by donor cell death associated with the islet preparation procedure before transplantation. Regulated necrosis pathways are biochemically and morphologically distinct from apoptosis. Recently, ferroptosis was identified as a non-apoptotic form of iron-dependent regulated necrosis implicated in various pathological conditions.

Porcine Islet Xenografts: a Clinical Source of ß-Cell Grafts.

Purpose Of Review: Diabetes is medical and social burden affecting millions around the world. Despite intensive therapy, insulin fails to maintain adequate glucose homeostasis and often results in episodes of hypoglycemic unawareness. Islet transplantation is a propitious replacement therapy, and incremental improvements in islet isolation and immunosuppressive drugs have made this procedure a feasible option.

Cotransplantation of Mesenchymal Stem Cells With Neonatal Porcine Islets Improve Graft Function in Diabetic Mice.

Mesenchymal stem cells (MSCs) possess immunoregulatory, anti-inflammatory, and proangiogenic properties and, therefore, have the potential to improve islet engraftment and survival. We assessed the effect human bone marrow-derived MSCs have on neonatal porcine islets (NPIs) in vitro and determined islet engraftment and metabolic outcomes when cotransplanted in a mouse model. NPIs cocultured with MSCs had greater cellular insulin content and increased glucose-stimulated insulin secretion.

The effect of additive compounds on glycerol-induced damage to human chondrocytes.

High concentrations of cryoprotective agents are required for cryopreservation techniques such as vitrification. Glycerol is a common cryoprotective agent used in cryopreservation protocols but this agent is toxic at high concentrations. This work is an attempt to mitigate the toxic effects of high concentrations of glycerol on intact chondrocytes in human knee articular cartilage from total knee arthroplasty patients by simultaneous exposure to glycerol and a variety of additive compounds.