Integration of Islet/Beta-Cell Transplants with Host Tissue Using Biomaterial Platforms

Recent progress in modeling and treating diabetes using stem cell-derived islets

Stem cell-derived islets (SC-islets) offer the potential to be an unlimited source of cells for disease modeling and the treatment of diabetes. SC-islets can be genetically modified, treated with chemical compounds, or differentiated from patient derived stem cells to model diabetes. These models provide insights into disease pathogenesis and vulnerabilities that may be targeted to provide treatment. SC-islets themselves are also being investigated as a cell therapy for diabetes. However, the transplantation process is imperfect; side effects from immunosuppressant use have reduced SC-islet therapeutic potential. Alternative methods to this include encapsulation, use of immunomodulating molecules, and genetic modification of SC-islets. This review covers recent advances using SC-islets to understand different diabetes pathologies and as a cell therapy.

3D printed VEGF-CPO biomaterial scaffold to promote subcutaneous vascularization and survival of transplanted islets for the treatment of diabetes

Diabetes is a complex metabolic disease and islet transplantation is a promising approach for the treatment of diabetes. Unfortunately, the transplanted islets at the subcutaneous site are also affected by various adverse factors such as poor vascularization and hypoxia. In this study, we utilize biocompatible copolymers l-lactide and D,l-lactide to manufacture a biomaterial scaffold with a mesh-like structure via 3D printing technology, providing a material foundation for encapsulating pancreatic islet cells. The scaffold maintains the sustained release of vascular endothelial growth factor (VEGF) and a slow release of oxygen from calcium peroxide (CPO), thereby regulating the microenvironment for islet survival. This helps to improve insufficient subcutaneous vascularization and reduce islet death due to hypoxia post-transplantation. By pre-implanting VEGF-CPO scaffolds subcutaneously into diabetic rats, a sufficiently vascularized site is formed, thereby ensuring early survival of transplanted islets. In a word, the VEGF-CPO scaffold shows good biocompatibility both in vitro and in vivo, avoids the adverse effects on the implanted islets, and displays promising clinical transformation prospects.

Revolutionizing pancreatic islet organoid transplants: Improving engraftment and exploring future frontiers

Type-1 Diabetes Mellitus (T1DM) manifests due to pancreatic beta cell destruction, causing insulin deficiency and hyperglycaemia. Current therapies are inadequate for brittle diabetics, necessitating pancreatic islet transplants, which however, introduces its own set of challenges such as paucity of donors, rigorous immunosuppression and autoimmune rejection. Organoid technology represents a significant stride in the field of regenerative medicine and bypasses donor-based approaches. Hence this article focuses on strategies enhancing the in vivo engraftment of islet organoids (IOs), namely vascularization, encapsulation, immune evasion, alternative extra-hepatic transplant sites and 3D bioprinting. Hypoxia-induced necrosis and delayed revascularization attenuate organoid viability and functional capacity, alleviated by the integration of diverse cell types e.g., human amniotic epithelial cells (hAECs) and human umbilical vein endothelial cells (HUVECs) to boost vascularization. Encapsulation with biocompatible materials and genetic modifications counters immune damage, while extra-hepatic sites avoid surgical complications and immediate blood-mediated inflammatory reactions (IBMIR). Customizable 3D bioprinting may help augment the viability and functionality of IOs. While the clinical translation of IOs faces hurdles, preliminary results show promise. This article underscores the importance of addressing challenges in IO transplantation to advance their use in treating type 1 diabetes effectively.

Potential effects of biomaterials on macrophage function and their signalling pathways

The use of biomaterials in biomedicine and healthcare has increased in recent years. Macrophages are the primary immune cells that induce inflammation and tissue repair after implantation of biomaterials. Given that macrophages exhibit high heterogeneity and plasticity, the influence of biomaterials on macrophage phenotype should be considered a crucial evaluation criterion during the development of novel biomaterials. This review provides a comprehensive summary of the physicochemical, biological, and dynamic characteristics of biomaterials that drive the regulation of immune responses in macrophages. The mechanisms involved in the interaction between macrophages and biomaterials, including endocytosis, receptors, signalling pathways, integrins, inflammasomes and long non-coding RNAs, are summarised in this review. In addition, research prospects of the interaction between macrophages and biomaterials are discussed. An in-depth understanding of mechanisms underlying the spatiotemporal changes in macrophage phenotype induced by biomaterials and their impact on macrophage polarization can facilitate the identification and development of novel biomaterials with superior performance. These biomaterials may be used for tissue repair and regeneration, vaccine or drug delivery and immunotherapy.

Automated high-throughput, high-content 3D imaging of intact pancreatic islets

Diabetes poses a global health crisis affecting individuals across age groups and backgrounds, with a prevalence estimate of 700 million people worldwide by 2045. Current therapeutic strategies primarily rely on insulin therapy or hypoglycemic agents, which fail to address the root cause of the disease - the loss of pancreatic insulin-producing beta-cells. Therefore, bioassays that recapitulate intact islets are needed to enable drug discovery for beta-cell replenishment, protection from beta-cell loss, and islet-cell interactions. Standard cancer insulinoma beta-cell lines MIN6 and INS-1 have been used to interrogate beta-cell metabolic pathways and function but are not suitable for studying proliferative effects. Screening using primary human/rodent intact islets offers a higher level of physiological relevance to enhance diabetes drug discovery and development. However, the 3-dimensionality of intact islets have presented challenges in developing robust, high-throughput assays to detect beta-cell proliferative effects. Established methods rely on either dissociated islet cells plated in 2D monolayer cultures for imaging or reconstituted pseudo-islets formed in round bottom plates to achieve homogeneity. These approaches have significant limitations due to the islet cell dispersion process. To address these limitations, we have developed a robust, intact ex vivo pancreatic islet bioassay in 384-well format that is capable of detecting diabetes-relevant endpoints including beta-cell proliferation, chemoprotection, and islet spatial morphometrics.

Extrahepatic transplantation of 3D cultured stem cell-derived islet organoids on microporous scaffolds

Stem cell differentiation methods have been developed to produce cells capable of insulin secretion which are showing promise in clinical trials for treatment of type-1 diabetes. Nevertheless, opportunities remain to improve cell maturation and function. Three-dimensional (3D) culture has demonstrated improved differentiation and metabolic function in organoid systems, with biomaterial scaffolds employed to direct cell assembly and facilitate cell-cell contacts. Herein, we investigate 3D culture of human stem cell-derived islet organoids, with 3D culture initiated at the pancreatic progenitor, endocrine progenitor, or immature β-cell stage. Clusters formed by reaggregation of immature β-cells could be readily seeded into the microporous poly(lactide-co-glycolide) scaffold, with control over cell number. Culture of islet organoids on scaffolds at the early to mid-stage beta cell progenitors had improved in vitro glucose stimulated insulin secretion relative to organoids formed at the pancreatic progenitor stage. Reaggregated islet organoids were transplanted into the peritoneal fat of streptozotocin-induced diabetic mice, which resulted in reduced blood glucose levels and the presence of systemic human C-peptide. In conclusion, 3D cell culture supports development of islet organoids as indicated by insulin secretion in vitro and supports transplantation to extrahepatic sites that leads to a reduction of hyperglycemia in vivo.

Fas Ligand-Modified Scaffolds Protect Stem Cell Derived β-Cells by Modulating Immune Cell Numbers and Polarization

Stem cell derived β-cells have demonstrated the potential to control blood glucose levels and represent a promising treatment for Type 1 diabetes (T1D). Early engraftment post-transplantation and subsequent maturation of these β-cells are hypothesized to be limited by the initial inflammatory response, which impacts the ability to sustain normoglycemia for long periods. We investigated the survival and development of immature hPSC-derived β-cells transplanted on poly(lactide-co-glycolide) (PLG) microporous scaffolds into the peritoneal fat, a site being considered for clinical translation. The scaffolds were modified with biotin for binding of a streptavidin-FasL (SA-FasL) chimeric protein to modulate the local immune cell responses. The presence of FasL impacted infiltration of monocytes and neutrophils and altered the immune cell polarization. Conditioned media generated from SA-FasL scaffolds explanted at day 4 post-transplant did not impact hPSC-derived β-cell survival and maturation in vitro, while these responses were reduced with conditioned media from control scaffolds. Following transplantation, β-cell viability and differentiation were improved with SA-FasL modification. A sustained increase in insulin positive cell ratio was observed with SA-FasL-modified scaffolds relative to control scaffolds. These results highlight that the initial immune response can significantly impact β-cell engraftment, and modulation of cell infiltration and polarization may be a consideration for supporting long-term function at an extrahepatic site.

Nanoparticle-Based Drug Delivery Systems for Induction of Tolerance and Treatment of Autoimmune Diseases

Autoimmune disease is a chronic inflammatory disease caused by disorders of immune regulation. Antigen-specific immunotherapy has the potential to inhibit the autoreactivity of inflammatory T cells and induce antigen-specific immune suppression without impairing normal immune function, offering an ideal strategy for autoimmune disease treatment. Tolerogenic dendritic cells (Tol DCs) with immunoregulatory functions play important roles in inducing immune tolerance. However, the effective generation of tolerogenic DCs in vivo remains a great challenge. The application of nanoparticle-based drug delivery systems in autoimmune disease treatment can increase the efficiency of inducing antigen-specific tolerance in vivo. In this review, we discuss multiple nanoparticles, with a focus on their potential in treatment of autoimmune diseases. We also discuss how the physical properties of nanoparticles influence their therapeutic efficacy.

Diabetes Mellitus Is a Chronic Disease that Can Benefit from Therapy with Induced Pluripotent Stem Cells

Diabetes mellitus (DM) is one of the main causes of morbidity and mortality, with an increasing incidence worldwide. The impact of DM on public health in developing countries has triggered alarm due to the exaggerated costs of the treatment and monitoring of patients with this disease. Considerable efforts have been made to try to prevent the onset and reduce the complications of DM. However, because insulin-producing pancreatic β-cells progressively deteriorate, many people must receive insulin through subcutaneous injection. Additionally, current therapies do not have consistent results regarding the prevention of chronic complications. Leveraging the approval of real-time continuous glucose monitors and sophisticated algorithms that partially automate insulin infusion pumps has improved glycemic control, decreasing the burden of diabetes management. However, these advances are facing physiologic barriers. New findings in molecular and cellular biology have produced an extraordinary advancement in tissue development for the treatment of DM. Obtaining pancreatic β-cells from somatic cells is a great resource that currently exists for patients with DM. Although this therapeutic option has great prospects for patients, some challenges remain for this therapeutic plan to be used clinically. The purpose of this review is to describe the new techniques in cell biology and regenerative medicine as possible treatments for DM. In particular, this review highlights the origin of induced pluripotent cells (iPSCs) and how they have begun to emerge as a regenerative treatment that may mitigate the pathology of this disease.