Encapsulation of pancreatic islet with HMGB1 fragment for attenuating inflammation

Challenges and opportunities in the islet transplantation microenvironment: a comprehensive summary of inflammatory cytokine, immune cells, and vascular endothelial cells

It is now understood that islet transplantation serves as a β-cell replacement therapy for type 1 diabetes. Many factors impact the survival of transplanted islets, especially those related to the microenvironment. This review explored microenvironmental components, including vascular endothelial cells, inflammatory cytokines, and immune cells, and their profound effects on post-islet transplantation survival rates. Furthermore, it revealed therapeutic strategies aimed at targeting these elements. Current evidence suggests that vascular endothelial cells are pivotal in facilitating vascularization and nutrient supply and establishing a new microcirculation network for transplanted islets. Consequently, preserving the functionality of vascular endothelial cells emerges as a crucial strategy to enhance the survival of islet transplantation. Release of cytokines will lead to activation of immune cells and production and release of further cytokines. While immune cells hold undeniable significance in regulating immune responses, their activation can result in rejection reactions. Thus, establishing immunological tolerance within the recipient's body is essential for sustaining graft functionality. Indeed, future research endeavors should be directed toward developing precise strategies for modulating the microenvironment to achieve higher survival rates and more sustained transplantation outcomes. While acknowledging certain limitations inherent to this review, it provides valuable insights that can guide further exploration in the field of islet transplantation. In conclusion, the microenvironment plays a paramount role in islet transplantation. Importantly, we discuss novel perspectives that could lead to broader clinical applications and improved patient outcomes in islet transplantation.

Recent advances in endocrine organoids for therapeutic application

The endocrine system, consisting of the hypothalamus, pituitary, endocrine glands, and hormones, plays a critical role in hormone metabolic interactions. The complexity of the endocrine system is a significant obstacle to understanding and treating endocrine disorders. Notably, advances in endocrine organoid generation allow a deeper understanding of the endocrine system by providing better comprehension of molecular mechanisms of pathogenesis. Here, we highlight recent advances in endocrine organoids for a wide range of therapeutic applications, from cell transplantation therapy to drug toxicity screening, combined with development in stem cell differentiation and gene editing technologies. In particular, we provide insights into the transplantation of endocrine organoids to reverse endocrine dysfunctions and progress in developing strategies for better engraftments. We also discuss the gap between preclinical and clinical research. Finally, we provide future perspectives for research on endocrine organoids for the development of more effective treatments for endocrine disorders.

Enhancing longevity of immunoisolated pancreatic islet grafts by modifying both the intracapsular and extracapsular environment

Type 1 diabetes mellitus (T1DM) is a chronic metabolic disease characterized by autoimmune destruction of pancreatic β cells. Transplantation of immunoisolated pancreatic islets might treat T1DM in the absence of chronic immunosuppression. Important advances have been made in the past decade as capsules can be produced that provoke minimal to no foreign body response after implantation. However, graft survival is still limited as islet dysfunction may occur due to chronic damage to islets during islet isolation, immune responses induced by inflammatory cells, and nutritional issues for encapsulated cells. This review summarizes the current challenges for promoting longevity of grafts. Possible strategies for improving islet graft longevity are also discussed, including supplementation of the intracapsular milieu with essential survival factors, promotion of vascularization and oxygenation near capsules, modulation of biomaterials, and co-transplantation of accessory cells. Current insight is that both the intracapsular as well as the extracapsular properties should be improved to achieve long-term survival of islet-tissue. Some of these approaches reproducibly induce normoglycemia for more than a year in rodents. Further development of the technology requires collective research efforts in material science, immunology, and endocrinology. STATEMENT OF SIGNIFICANCE: Islet immunoisolation allows for transplantation of insulin producing cells in absence of immunosuppression and might facilitate the use of xenogeneic cell sources or grafting of cells obtained from replenishable cell sources. However, a major challenge to date is to create a microenvironment that supports long-term graft survival. This review provides a comprehensive overview of the currently identified factors that have been demonstrated to be involved in either stimulating or reducing islet graft survival in immunoisolating devices and discussed current strategies to enhance the longevity of encapsulated islet grafts as treatment for type 1 diabetes. Although significant challenges remain, interdisciplinary collaboration across fields may overcome obstacles and facilitate the translation of encapsulated cell therapy from the laboratory to clinical application.

Engineering Islets From Stem Cells: The Optimal Solution for the Treatment of Diabetes?

Diabetes is a metabolic disease characterized by insulin deficiency. Bioengineering of stem cells with the aim to restore insulin production and glucose regulation has the potential to cure diabetic patients. In this review, we focus on the recent developments for bioengineering of induced pluripotent stem cells (iPSCs), mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), and pancreatic progenitor cells in view of generating insulin producing and glucose regulating cells for β-cell replacement therapies. Recent clinical trials using islet cells derived from stem cells have been initiated for the transplantation into diabetic patients, with crucial bottlenecks of tumorigenesis, post-transplant survival, genetic instability, and immunogenicity that should be further optimized. As a new approach given high expectations, bioengineered islets from stem cells occupies considerable potential for the future clinical application and addressing the treatment dilemma of diabetes.

Facilitating islet transplantation using a three-step approach with mesenchymal stem cells, encapsulation, and pulsed focused ultrasound

BACKGROUND

The aim of this study was to examine the effect of a three-step approach that utilizes the application of adipose tissue-derived mesenchymal stem cells (AD-MSCs), encapsulation, and pulsed focused ultrasound (pFUS) to help the engraftment and function of transplanted islets.

METHODS

In step 1, islets were co-cultured with AD-MSCs to form a coating of AD-MSCs on islets: here, AD-MSCs had a cytoprotective effect on islets; in step 2, islets coated with AD-MSCs were conformally encapsulated in a thin layer of alginate using a co-axial air-flow method: here, the capsule enabled AD-MSCs to be in close proximity to islets; in step 3, encapsulated islets coated with AD-MSCs were treated with pFUS: here, pFUS enhanced the secretion of insulin from islets as well as stimulated the cytoprotective effect of AD-MSCs.

RESULTS

Our approach was shown to prevent islet death and preserve islet functionality in vitro. When 175 syngeneic encapsulated islets coated with AD-MSCs were transplanted beneath the kidney capsule of diabetic mice, and then followed every 3 days with pFUS treatment until day 12 post-transplantation, we saw a significant improvement in islet function with diabetic animals re-establishing glycemic control over the course of our study (i.e., 30 days). In addition, our approach was able to enhance islet engraftment by facilitating their revascularization and reducing inflammation.

CONCLUSIONS

This study demonstrates that our clinically translatable three-step approach is able to improve the function and viability of transplanted islets.

Co-Microencapsulation of Islets and MSC CellSaics, Mosaic-Like Aggregates of MSCs and Recombinant Peptide Pieces, and Therapeutic Effects of Their Subcutaneous Transplantation on Diabetes

The subcutaneous transplantation of microencapsulated islets has been extensively studied as a therapeutic approach for type I diabetes. However, due to the lower vascular density and strong inflammatory response in the subcutaneous area, there have been few reports of successfully normalized blood glucose levels. To address this issue, we developed mosaic-like aggregates comprised of mesenchymal stem cells (MSCs) and recombinant peptide pieces called MSC CellSaics, which provide a continuous release of angiogenic factors and anti-inflammatory cytokines. Our previous report revealed that the diabetes of immunodeficient diabetic model mice was reversed by the subcutaneous co-transplantation of the MSC CellSaics and rat islets. In this study, we focused on the development of immune-isolating microcapsules to co-encapsulate the MSC CellSaics and rat islets, and their therapeutic efficiency via subcutaneous transplantation into immunocompetent diabetic model mice. As blood glucose level was monitored for 28 days following transplantation, the normalization rate of the new immuno-isolating microcapsules was confirmed to be significantly higher than those of the microcapsules without the MSC CellSaics, and the MSC CellSaics transplanted outside the microcapsules (p < 0.01). Furthermore, the number of islets required for the treatment was reduced. In the stained sections, a larger number/area of blood vessels was observed around the new immuno-isolating microcapsules, which suggests that angiogenic factors secreted by the MSC CellSaics through the microcapsules function locally for their enhanced efficacy.

A New Islet Transplantation Method Combining Mesenchymal Stem Cells with Recombinant Peptide Pieces, Microencapsulated Islets, and Mesh Bags

Microencapsulated islet transplantation was widely studied as a promising treatment for type 1 diabetes mellitus. However, micro-encapsulated islet transplantation has the following problems—early dysfunction of the islets due to the inflammatory reaction at the transplantation site, and hyponutrition and hypoxia due to a lack of blood vessels around the transplantation site, and difficulty in removal of the islets. On the other hand, we proposed a cell transplantation technique called CellSaic, which was reported to enhance the vascular induction effect of mesenchymal stem cells (MSCs) in CellSaic form, and to enhance the effect of islet transplantation through co-transplantation. Therefore, we performed islet transplantation in diabetic mice by combining three components—microencapsulated islets, MSC-CellSaic, and a mesh bag that encapsulates them and enables their removal. Mesh pockets were implanted in the peritoneal cavity of Balb/c mice as implantation sites. After 4 weeks of implantation, a pocket was opened and transplanted with (1) pancreatic islets, (2) microencapsulated islets, and (3) microencapsulated islets + MSC-CellSaic. Four weeks of observation of blood glucose levels showed that the MSC-CellSaic co-transplant group showed a marked decrease in blood glucose levels, compared to the other groups. A three-component configuration of microcapsules, MSC-CellSaic, and mesh bag was shown to enhance the efficacy of islet transplantation.

The effect of preexisting HMGB1 within fetal bovine serum on murine pancreatic beta cell biology

High-mobility group box 1 (HMGB1) can act as a structural protein of the chromatin and at the same time as a mediator of the immune system. Its high correlation with the graft acceptance in pancreatic islet recipients makes it a biomarker in islet transplantation. With the suspicion that preexisting HMGB1 in the fetal bovine serum (FBS) would be detrimental to the viability and function of murine beta cells, HMGB1 was removed from FBS and its impact was investigated. Interestingly, the elimination of HMGB1 from FBS seemed unfavorable to the viability and function of cultured murine beta cells, suggesting that the preexisting HMGB1 in the FBS may be an indispensable component of islet cell culture.

The intraperitoneal space is more favorable than the subcutaneous one for transplanting alginate fiber containing iPS-derived islet-like cells

Introduction

Although immunosuppressants are required for current islet transplantation for type 1 diabetic patients, many papers have already reported encapsulation devices for islets to avoid immunological attack. The aim of this study is to determine the optimal number of cells and optimal transplantation site for human iPS-derived islet-like cells encapsulated in alginate fiber using diabetic model mice.

Methods

We used a suspension culture system for inducing islet-like cells from human iPS cells throughout the islet differentiation process. Islet-like spheroids were encapsulated in the alginate fiber, and cell transplantation experiments were performed with STZ-induced diabetic NOD/SCID mice. We compared the efficacy of transplanted cells between intraperitoneal and subcutaneous administration of alginate fibers by measuring blood glucose and human C-peptide levels serially in mice. Grafts were analyzed histologically, and gene expression in pancreatic β cells was also compared.

Results

We demonstrated the reversal of hyperglycemia in diabetic model mice after intraperitoneal administration of these fibers, but not with subcutaneous ones. Intraperitoneal fibers were easily retrieved without any adhesion. Although we detected human c-peptide in mice plasma after subcutaneous administration of these fibers, these fibers became encased by fibrous tissue.

Conclusions

These results suggest that the intraperitoneal space is favorable for islet-like cells derived from human iPS cells when encapsulated in alginate fiber.

Paving the way for successful islet encapsulation

Type 1 diabetes mellitus (T1DM) is a disorder that decimates pancreatic β-cells which produce insulin. Direct pancreatic islet transplantation cannot serve as a widespread therapeutic modality owing to the need for lifelong immunosuppression and donor shortage. Therefore, several encapsulation techniques have been developed to enclose the islets in semipermeable vehicles that will allow oxygen and nutrient input as well as insulin, other metabolites and waste output, while accomplishing immunoisolation. Although encapsulation technology continues to face significant obstacles, recent advances in material science, stem cell biology and immunology potentially serve as pathways to success. This review summarizes the accomplishments of the past 5 years.

Generation of Human Stem Cell-Derived Pancreatic Organoids (POs) for Regenerative Medicine

Insulin-dependent diabetes mellitus or type 1 diabetes mellitus (T1DM) is an auto-immune condition characterized by the loss of pancreatic β-cells. The curative approach for highly selected patients is the pancreas or the pancreatic islet transplantation. Nevertheless, these options are limited by a growing shortage of donor organs and by the requirement of immunosuppression.Xenotransplantation of porcine islets has been extensively investigated. Nevertheless, the strong xenoimmunity and the risk of transmission of porcine endogenous retroviruses, have limited their application in clinic. Generation of β-like cells from stem cells is one of the most promising strategies in regenerative medicine. Embryonic, and more recently, adult stem cells are currently the most promising cell sources exploited to generate functional β-cells in vitro. A number of studies demonstrated that stem cells could generate functional pancreatic organoids (POs), able to restore normoglycemia when implanted in different preclinical diabetic models. Nevertheless, a gradual loss of function and cell dead are commonly detected when POs are transplanted in immunocompetent animals. So far, the main issue to be solved is the post-transplanted islet loss, due to the host immune attack. To avoid this hurdle, nanotechnology has provided a number of polymers currently under investigation for islet micro and macro-encapsulation. These new approaches, besides conferring PO immune protection, are able to supply oxygen and nutrients and to preserve PO morphology and long-term viability.Herein, we summarize the current knowledge on bioengineered POs and the stem cell differentiation platforms. We also discuss the in vitro strategies used to generate functional POs, and the protocols currently used to confer immune-protection against the host immune attack (micro- and macro-encapsulation). In addition, the most relevant ongoing clinical trials, and the most relevant hurdles met to move towards clinical application are revised.

Encapsulated Islet Transplantation: Where Do We Stand?

Transplantation of pancreatic islets encapsulated within immuno-protective microcapsules is a strategy that has the potential to overcome graft rejection without the need for toxic immunosuppressive medication. However, despite promising preclinical studies, clinical trials using encapsulated islets have lacked long-term efficacy, and although generally considered clinically safe, have not been encouraging overall. One of the major factors limiting the long-term function of encapsulated islets is the host's immunological reaction to the transplanted graft which is often manifested as pericapsular fibrotic overgrowth (PFO). PFO forms a barrier on the capsule surface that prevents the ingress of oxygen and nutrients leading to islet cell starvation, hypoxia and death. The mechanism of PFO formation is still not elucidated fully and studies using a pig model have tried to understand the host immune response to empty alginate microcapsules. In this review, the varied strategies to overcome or reduce PFO are discussed, including alginate purification, altering microcapsule geometry, modifying alginate chemical composition, co-encapsulation with immunomodulatory cells, administration of pharmacological agents, and alternative transplantation sites. Nanoencapsulation technologies, such as conformal and layer-by-layer coating technologies, as well as nanofiber, thin-film nanoporous devices, and silicone based NanoGland devices are also addressed. Finally, this review outlines recent progress in imaging technologies to track encapsulated cells, as well as promising perspectives concerning the production of insulin-producing cells from stem cells for encapsulation.

Vitexin alleviates lipopolysaccharide‑induced islet cell injury by inhibiting HMGB1 release

Diabetes mellitus (DM) is a chronic metabolic disease, where the predominant pathogenesis is pancreatic β‑cells dysfunction or injury. It has been well established that inflammation leads to a gradual exhaustion of pancreatic β‑cell function with decreased β‑cell mass likely resulting from pancreatic β‑cells apoptosis or death. Vitexin, a major bioactive flavonoid compound in plants has numerous pharmacological properties, including antioxidant, anti‑inflammatory and antimyeloperoxidase. Whether vitexin can protect pancreatic β‑cells against lipopolysaccharide (LPS)‑induced pro‑inflammatory cytokine production and apoptosis has received little attention. The present study investigated the potential effects of vitexin on LPS‑induced pancreatic β‑cell injury and apoptosis. It was revealed that apoptosis and damage induced by LPS in islet tissue of rats and INS‑1 cells was significantly decreased in response to vitexin treatment. In addition, pretreatment with vitexin decreased the levels of the pro‑inflammatory cytokines tumor necrosis factor‑α and high mobility group box 1 (HMGB1) in LPS‑induced rats. Further experiments demonstrated that vitexin pretreatment suppressed the activation of P38 mitogen‑activated protein kinase signaling pathways in LPS‑induced INS‑1 cells. In conclusion, the results indicated that vitexin prevented LPS‑induced islet tissue damage in rats, and INS‑1 cells injury and apoptosis by inhibiting HMGB1 release. Therefore, the present study provided clear evidence indicating that vitexin may be a viable therapeutic strategy for the treatment of DM.

The Role of HMGB1 in the Pathogenesis of Type 2 Diabetes

Significance. With an alarming increase in recent years, diabetes mellitus has become a global challenge. Despite advances in treatment of diabetes mellitus, currently, medications available are unable to control the progression of diabetes and its complications. Growing evidence suggests that inflammation is an important pathogenic mediator in the development of diabetes mellitus. The perspectives including suggestions for new therapies involving the shift from metabolic stress to inflammation should be taken into account. Critical Issues. High-mobility group box 1 (HMGB1), a nonhistone nuclear protein regulating gene expression, was rediscovered as an endogenous danger signal molecule to trigger inflammatory responses when released into extracellular milieu in the late 1990s. Given the similarities of inflammatory response in the development of T2D, we will discuss the potential implication of HMGB1 in the pathogenesis of T2D. Importantly, we will summarize and renovate the role of HMGB1 and HMGB1-mediated inflammatory pathways in adipose tissue inflammation, insulin resistance, and islet dysfunction. Future Directions. HMGB1 and its downstream receptors RAGE and TLRs may serve as potential antidiabetic targets. Current and forthcoming projects in this territory will pave the way for prospective approaches targeting the center of HMGB1-mediated inflammation to improve T2D and its complications.

Islet-derived damage-associated molecular pattern molecule contributes to immune responses following microencapsulated neonatal porcine islet xenotransplantation in mice

BACKGROUND

Clinical allogeneic islet transplantation has become an attractive procedure for type 1 diabetes mellitus treatment. However, there is a severe shortage of human donors. Microencapsulated neonatal porcine islet (NPI) xenotransplantation may be an alternative transplantation procedure. Currently, the efficacy of microencapsulated NPI xenotransplantation into the peritoneal cavity is limited because of early non-function resulting from inflammation, which is a serious hindrance to promoting this procedure as a standard therapy. Previously, we have demonstrated that high-mobility group box 1 (HMGB1), a damage-associated molecular pattern (DAMP) molecule, was released from transplanted islets and triggered inflammatory reactions leading to early loss of intrahepatic syngeneic islet grafts in mice. In this study, we hypothesized that the inflammatory reaction in the peritoneal cavity following the transplantation of microencapsulated NPIs is more severe than that of empty capsules. Additionally, we predicted that HMGB1 released from transplanted microencapsulated NPIs triggers further inflammatory reactions in mice. Finally, we hypothesized that microencapsulated NPI xenotransplantation efficacy would be improved by treatment-targeting inflammatory reactions in a mouse model.

METHODS

A total of 10 000 empty capsules (alginate-poly-L-ornithine-alginate) or 10 000 IEQ microencapsulated NPIs were transplanted into the peritoneal cavity of streptozotocin-induced diabetic C57BL/6 mice.

RESULTS

The numbers of mononuclear cells in the peritoneal cavity following empty capsule or microencapsulated NPI transplantation were 4.8 × 10(6)  ± 0.9 × 10(6) and 13.6 × 10(6)  ± 3.0 × 10(6) , respectively (P < 0.05). Fluorescence-activated cell sorting (FACS) analysis revealed that tumor necrosis factor (TNF)-α-, interleukin (IL)-6-, interferon (IFN)-γ-, and/or IL-12-positive macrophages, neutrophils, and dendritic cells had infiltrated the peritoneal cavity after empty capsules or microencapsulated NPIs administration. IL-6 concentrations in the peritoneal lavage fluids on 7 days after empty capsule or microencapsulated NPI transplantation were 18.5 ± 10.0 and 157.4 ± 46.3 pg/ml, respectively (P < 0.001), while TNF-α concentrations were 4.6 ± 1.4 and 19.8 ± 8.4 pg/ml, respectively (P < 0.01). In addition, HMGB1 concentrations were 37.6 ± 6.6 and 117.4 ± 8.1 ng/ml, respectively (P < 0.0001). In vitro experiments revealed that the total amount of released HMGB1 into the culture medium of empty capsule (200 capsules/dish) and microencapsulated NPI (200 IEQ/dish) after hypoxic culture (1% O2 , 5% CO2 , and 94% N2 ) was 0 and 8.6 ± 2.2 ng, respectively (P < 0.001). FACS analysis revealed that TNF-α- and IL-6-positive macrophages were also observed in the peritoneal cavity following intraperitoneal injection of HMGB1 itself. Anti-TNF-α antibody treatment was associated with slightly prolonged graft survival and improved glucose tolerance 30 days after transplantation, but none of the recipients were remained normoglycemic.

CONCLUSIONS

In conclusion, early inflammatory reactions might be therapeutic targets for the prolongation of microencapsulated NPIs graft survival. Thus, treatment-targeting inflammation might improve the efficiency of clinical microencapsulated NPI xenotransplantation.