Characterization of the Role of Major Histocompatibility Complex in Type 1 Diabetes Recurrence after Islet Transplantation

Alpha-Lipoic Acid Inhibits Spontaneous Diabetes and Autoimmune Recurrence in Non-Obese Diabetic Mice by Enhancing Differentiation of Regulatory T Cells and Showed Potential for Use in Cell Therapies for the Treatment of Type 1 Diabetes

Type 1 diabetes (T1D) is caused by the destruction of β cells in pancreatic islets by autoimmune T cells. Islet transplantation has been established as an effective treatment for T1D. However, the survival of islet grafts is often disrupted by recurrent autoimmunity. Alpha-lipoic acid (ALA) has been reported to have immunomodulatory effects and, therefore, may have therapeutic potential in the treatment of T1D. In this study, we investigated the therapeutic potential of ALA in autoimmunity inhibition. We treated non-obese diabetic (NOD) mice with spontaneous diabetes and islet-transplantation mice with ALA. The onset of diabetes was decreased and survival of the islet grafts was extended. The populations of Th1 cells decreased, and regulatory T cells (Tregs) increased in ALA-treated mice. The in vitro Treg differentiation was significantly increased by treatment with ALA. The adoptive transfer of ALA-differentiated Tregs into NOD recipients improved the outcome of the islet grafts. Our results showed that in vivo ALA treatment suppressed spontaneous diabetes and autoimmune recurrence in NOD mice by inhibiting the Th1 immune response and inducing the differentiation of Tregs. Our study also demonstrated the therapeutic potential of ALA in Treg-based cell therapies and islet transplantation used in the treatment of T1D.

Reversal of autoimmunity by mixed chimerism enables reactivation of β cells and transdifferentiation of α cells in diabetic NOD mice

Type 1 diabetes (T1D) results from the autoimmune destruction of β cells, so cure of firmly established T1D requires both reversal of autoimmunity and restoration of β cells. It is known that β cell regeneration in nonautoimmune diabetic mice can come from differentiation of progenitors and/or transdifferentiation of α cells. However, the source of β cell regeneration in autoimmune nonobese diabetic (NOD) mice remains unclear. Here, we show that, after reversal of autoimmunity by induction of haploidentical mixed chimerism, administration of gastrin plus epidermal growth factor augments β cell regeneration and normalizes blood glucose in the firmly established diabetic NOD mice. Using transgenic NOD mice with inducible lineage-tracing markers for insulin-producing β cells, Sox9+ ductal progenitors, Nestin+ mesenchymal stem cells, and glucagon-producing α cells, we have found that both reactivation of dysfunctional low-level insulin expression (insulinlo) β cells and neogenesis contribute to the regeneration, with the latter predominantly coming from transdifferentiation of α cells. These results indicate that, after reversal of autoimmunity, reactivation of β cells and transdifferentiation of α cells can provide sufficient new functional β cells to reach euglycemia in firmly established T1D.

Stem Cell Therapies for Treating Diabetes: Progress and Remaining Challenges

Restoration of insulin independence and normoglycemia has been the overarching goal in diabetes research and therapy. While whole-organ and islet transplantation have become gold-standard procedures in achieving glucose control in diabetic patients, the profound lack of suitable donor tissues severely hampers the broad application of these therapies. Here, we describe current efforts aimed at generating a sustainable source of functional human stem cell-derived insulin-producing islet cells for cell transplantation and present state-of-the-art efforts to protect such cells via immune modulation and encapsulation strategies.

Modulation by melatonin of the pathogenesis of inflammatory autoimmune diseases

Melatonin is the major secretory product of the pineal gland during the night and has multiple activities including the regulation of circadian and seasonal rhythms, and antioxidant and anti-inflammatory effects. It also possesses the ability to modulate immune responses by regulation of the T helper 1/2 balance and cytokine production. Autoimmune diseases, which result from the activation of immune cells by autoantigens released from normal tissues, affect around 5% of the population. Activation of autoantigen-specific immune cells leads to subsequent damage of target tissues by these activated cells. Melatonin therapy has been investigated in several animal models of autoimmune disease, where it has a beneficial effect in a number of models excepting rheumatoid arthritis, and has been evaluated in clinical autoimmune diseases including rheumatoid arthritis and ulcerative colitis. This review summarizes and highlights the role and the modulatory effects of melatonin in several inflammatory autoimmune diseases including multiple sclerosis, systemic lupus erythematosus, rheumatoid arthritis, type 1 diabetes mellitus, and inflammatory bowel disease.

Triptolide ameliorates autoimmune diabetes and prolongs islet graft survival in nonobese diabetic mice

OBJECTIVES

Triptolide (TPL) possesses profound immunosuppressive effects and has potential in allograft transplantation. We investigated whether TPL treatment prevents autoimmune diabetes in nonobese diabetic (NOD) mice and prolongs the survival of islet grafts against autoimmune attack or allograft rejection.

METHODS

Diabetic incidence was monitored in TPL-treated NOD mice. Nonobese diabetic or BALB/c islets were transplanted into diabetic recipients treated with TPL. Different T-cell subsets in grafts or spleen were analyzed. The proliferation, apoptosis, cytokines, and activities of AKT, NFκB, and caspases 3, 8, and 9 of T cells were determined.

RESULTS

Diabetic incidence was reduced and inflammatory cytokines were decreased in islets and spleen under TPL treatment. T-cell proliferation was reduced and the survival of syngeneic or allogeneic grafts was significantly increased in TPL-treated mice. The populations of CD4, CD8, CD4CD69, CD8CD69, and interferon-γ-producing T cells in islet grafts and spleen were reduced. Triptolide treatment increased the apoptosis of T cells in the spleen of recipients. Levels of phosphorylated protein kinase B and phosphorylated inhibitor of kappa B in splenocytes were reduced and caspases 3, 8, and 9 were increased in TPL-treated mice.

CONCLUSIONS

Triptolide treatment not only reduced the diabetic incidence in NOD mice but also prolonged the survival of syngeneic or allogeneic grafts.

A theranostic small interfering RNA nanoprobe protects pancreatic islet grafts from adoptively transferred immune rejection

Islet transplantation has recently emerged as an acceptable clinical modality for restoring normoglycemia in patients with type 1 diabetes mellitus (T1DM). The long-term survival and function of islet grafts is compromised by immune rejection-related factors. Downregulation of factors that mediate immune rejection using RNA interference holds promise for improving islet graft resistance to damaging factors after transplantation. Here, we used a dual-purpose therapy/imaging small interfering (si)RNA magnetic nanoparticle (MN) probe that targets β(2) microglobulin (B2M), a key component of the major histocompatibility class I complex (MHC I). In addition to serving as a siRNA carrier, this MN-siB2M probe enables monitoring of graft persistence noninvasively using magnetic resonance imaging (MRI). Human islets labeled with these MNs before transplantation into B2M (null) NOD/scid mice showed significantly improved preservation of graft volume starting at 2 weeks, as determined by longitudinal MRI in an adoptive transfer model (P < 0.05). Furthermore, animals transplanted with MN-siB2M-labeled islets demonstrated a significant delay of up to 23.8 ± 4.8 days in diabetes onset after the adoptive transfer of T cells relative to 6.5 ± 4.5 days in controls. This study demonstrated that our approach could protect pancreatic islet grafts from immune rejection and could potentially be applied to allotransplantation and prevention of the autoimmune recurrence of T1DM in islet transplantation or endogenous islets.

Making the most of major histocompatibility complex molecule multimers: applications in type 1 diabetes

Classical major histocompatibility complex (MHC) class I and II molecules present peptides to cognate T-cell receptors on the surface of T lymphocytes. The specificity with which T cells recognize peptide-MHC (pMHC) complexes has allowed for the utilization of recombinant, multimeric pMHC ligands for the study of minute antigen-specific T-cell populations. In type 1 diabetes (T1D), CD8+ cytotoxic T lymphocytes, in conjunction with CD4+ T helper cells, destroy the insulin-producing β cells within the pancreatic islets of Langerhans. Due to the importance of T cells in the progression of T1D, the ability to monitor and therapeutically target diabetogenic clonotypes of T cells provides a critical tool that could result in the amelioration of the disease. By administering pMHC multimers coupled to fluorophores, nanoparticles, or toxic moieties, researchers have demonstrated the ability to enumerate, track, and delete diabetogenic T-cell clonotypes that are, at least in part, responsible for insulitis; some studies even delay or prevent diabetes onset in the murine model of T1D. This paper will provide a brief overview of pMHC multimer usage in defining the role T-cell subsets play in T1D etiology and the therapeutic potential of pMHC for antigen-specific identification and modulation of diabetogenic T cells.

Increased numbers of low-oxygenated pancreatic islets after intraportal islet transplantation

OBJECTIVE

No previous study has measured the oxygenation of intraportally transplanted islets, although recent data suggest that insufficient engraftment may result in hypoxia and loss of islet cells.

RESEARCH DESIGN AND METHODS

After intraportal infusion into syngeneic mice, islet oxygenation was investigated in 1-day-old, 1-month-old, or 3-month-old grafts and compared with renal subcapsular grafts and native islets. Animals received an intravenous injection of pimonidazole for immunohistochemical detection of low-oxygenated islet cells (pO(2) <10 mmHg), and caspase-3 immunostaining was performed to assess apoptosis rates in adjacent tissue sections.

RESULTS

In the native pancreas of nontransplanted animals, ∼30% of the islets stained positive for pimonidazole. In 1-day-old and 1-month-old grafts, the percentage of pimonidazole-positive islets in the liver was twice that of native islets, whereas this increase was abolished in 3-month-old grafts. Beneath the renal capsule, pimonidazole accumulation was, however, similar to native islets at all time points. Apoptosis rates were markedly increased in 1-day-old intrahepatic grafts compared with corresponding renal islet grafts, which were slightly increased compared with native islets. One month posttransplantation renal subcapsular grafts had similar frequencies of apoptosis as native islets, whereas apoptosis in intraportally implanted islets was still high. In the liver, islet graft vascular density increased between 1 and 3 months posttransplantation, and apoptosis rates simultaneously dropped to values similar to those observed in native islets.

CONCLUSIONS

The vascular engraftment of intraportally transplanted islets is markedly delayed compared with renal islet grafts. The prolonged ischemia of intraportally transplanted islets may favor an alternative implantation site.

Adjuvant immunotherapy increases beta cell regenerative factor Reg2 in the pancreas of diabetic mice

Insulin-producing β cells can partially regenerate in adult pancreatic tissues, both in human and animal models of type 1 diabetes (T1D). Previous studies have shown that treatment with mycobacterial adjuvants such as CFA and bacillus Calmette-Guérin prevents induction and recurrence of T1D in NOD mice with partial recovery of β cell mass. In this study, we investigated factors involved in the regeneration of β cells in the pancreas of NOD mice during diabetes development and after treatment with adjuvants. The Regeneration (Reg) gene family is known to be involved in regeneration of various tissues including β cells. Reg2 expression was found to be upregulated in pancreatic islets both during diabetes development and as a result of adjuvant treatment in diabetic NOD mice and in C57BL/6 mice made diabetic by streptozotocin treatment. The upregulation of Reg2 by adjuvant treatment was independent of signaling through MyD88 and IL-6 because it was not altered in MyD88 or IL-6 knockout mice. We also observed upregulation of Reg2 in the pancreas of diabetic mice undergoing β cell regenerative therapy with exendin-4 or with islet neogenesis-associated protein. Reg2 expression following adjuvant treatment correlated with a reduction in insulitis, an increase in insulin secretion, and an increase in the number of small islets in the pancreas of diabetic NOD mice and with improved glucose tolerance tests in streptozotocin-treated diabetic C57BL/6 mice. In conclusion, adjuvant immunotherapy regulates T1D in diabetic mice and induces Reg2-mediated regeneration of β cells.

Melatonin prolongs islet graft survival in diabetic NOD mice

Islet transplantation has been established as a potential therapy for type 1 diabetes. However, inflammation, allorejection, and on-going autoimmune damage contribute to early graft loss and failure of islet transplantation. Melatonin is the major secretory product of the pineal gland during the dark period of each day and displays multifunctional properties including the regulation of circadian and seasonal rhythms, antioxidation reactions and immune modulation. Based on the immunosuppressive properties of melatonin, we investigated whether melatonin treatment prolonged the survival of islet grafts in non-obese diabetic (NOD) mice. The mean islet graft survival time was 7.33 +/- 1.51 and 7.75 +/- 2.66 days in untreated controls and in the solvent-treated animals, respectively. Strikingly, the mean survival time of islet grafts in recipients treated with melatonin (200 mg/kg/bw) was 17 +/- 7.76 days. Moreover, melatonin treatment reduced the proliferation of splenocytes in NOD mice. Using a T1 and T2 double transgenic mouse model, we found that T helper 1 (Th1) cells in mice treated with melatonin were significantly decreased. The reduction of Th1 cells and T cell proliferation may result from an increase in the immunosuppressive cytokine IL-10. Our results indicate that melatonin treatment suppresses autoimmune recurrence by inhibiting the proliferation of Th1 cells in NOD mice and thus prolongs the survival of syngeneic islet grafts.

CD4+ T cells are sufficient to elicit allograft rejection and major histocompatibility complex class I molecule is required to induce recurrent autoimmune diabetes after pancreas transplantation in mice

BACKGROUND

We characterized the role of T cell subsets and major histocompatibility complex molecules in allograft rejection and recurrence of autoimmune diabetes.

METHODS

Adoptive cell transfer and vascularized segmental pancreas transplantation were performed in mice.

RESULTS

In an alloimmune response model, transfer of nondiabetic CD4, but not CD8 T cells, elicited pancreas allograft rejection in streptozotocin (STZ)-induced diabetic NOD/scid mice. Pancreas allografts were acutely rejected in STZ-induced diabetic NOD/beta2m mice (confirmed the absence of major histocompatibility complex [MHC] class I and CD8 T cells) and permanently accepted in NOD/CIIT mice (confirmed the absence of MHC class II and CD4 T cells). The results suggest that rejection of pancreas allograft is CD4-dependent and MHC class I-independent. In the autoimmune diabetes model, whole spleen cells obtained from diabetic NOD mice induced autoimmune diabetes in NOD/scid and NOD/CIIT mice, but the onset of diabetes was delayed in NOD/beta2m mice. However, the purified diabetic T cells failed to elicit autoimmune diabetes in NOD/beta2m mice. NOD/scid and NOD/CIIT pancreas grafts were acutely destroyed whereas four of six NOD/beta2m pancreas grafts were permanently accepted in autoimmune diabetic NOD mice.

CONCLUSION

CD4 T cells are sufficient for the induction of allograft rejection, and MHC class I molecule is required to induce recurrent autoimmune diabetes after pancreas transplantation in mice.

Lessons on autoimmune diabetes from animal models

T1DM (Type I diabetes mellitus) results from selective destruction of the insulin-producing beta-cells of the pancreas by the immune system, and is characterized by hyperglycaemia and vascular complications arising from suboptimal control of blood glucose levels. The discovery of animal models of T1DM in the late 1970s and early 1980s, particularly the NOD (non-obese diabetic) mouse and the BB (BioBreeding) diabetes-prone rat, had a fundamental impact on our ability to understand the genetics, aetiology and pathogenesis of this disease. NOD and BB diabetes-prone rats spontaneously develop a form of diabetes that closely resembles the human counterpart. Early studies of these animals quickly led to the realization that T1DM is caused by autoreactive T-lymphocytes and revealed that the development of T1DM is controlled by numerous polymorphic genetic elements that are scattered throughout the genome. The development of transgenic and gene-targeting technologies during the 1980s allowed the generation of models of T1DM of reduced genetic and pathogenic complexity, and a more detailed understanding of the immunogenetics of T1DM. In this review, we summarize the contribution of studies in animal models of T1DM to our current understanding of four fundamental aspects of T1DM: (i) the nature of genetic elements affording T1DM susceptibility or resistance; (ii) the mechanisms underlying the development and recruitment of pathogenic autoreactive T-cells; (iii) the identity of islet antigens that contribute to the initiation and/or progression of islet inflammation and beta-cell destruction; and (iv) the design of avenues for therapeutic intervention that are rooted in the knowledge gained from studies of animal models. Development of new animal models will ensure continued progress in these four areas.