Pancreatic islet surface bioengineering with a heparin-incorporated starPEG nanofilm

Engineered inulin-based hybrid biomaterials for augmented immunomodulatory responses

Modified biopolymers that are based on prebiotics have been found to significantly contribute to immunomodulatory events. In recent years, there has been a growing use of modified biomaterials and polymer-functionalized nanomaterials in the treatment of various tumors by activating immune cells. However, the effectiveness of immune cells against tumors is hindered by several biological barriers, which highlights the importance of harnessing prebiotic-based biopolymers to enhance host defenses against cancer, thus advancing cancer prevention strategies. Inulin, in particular, plays a crucial role in activating immune cells and promoting the secretion of cytokines. Therefore, this mini-review aims to emphasize the importance of inulin in immunomodulatory responses, the development of inulin-based hybrid biopolymers, and the role of inulin in enhancing immunity and modifying cell surfaces. Furthermore, we discuss the various approaches of chemical modification for inulin and their potential use in cancer treatment, particularly in the field of cancer immunotherapy.

Replenishable prevascularized cell encapsulation devices increase graft survival and function in the subcutaneous space

Beta cell replacement therapy (BCRT) for patients with type 1 diabetes (T1D) improves blood glucose regulation by replenishing the endogenous beta cells destroyed by autoimmune attack. Several limitations, including immune isolation, prevent this therapy from reaching its full potential. Cell encapsulation devices used for BCRT provide a protective physical barrier for insulin-producing beta cells, thereby protecting transplanted cells from immune attack. However, poor device engraftment posttransplantation leads to nutrient deprivation and hypoxia, causing metabolic strain on transplanted beta cells. Prevascularization of encapsulation devices at the transplantation site can help establish a host vascular network around the implant, increasing solute transport to the encapsulated cells. Here, we present a replenishable prevascularized implantation methodology (RPVIM) that allows for the vascular integration of replenishable encapsulation devices in the subcutaneous space. Empty encapsulation devices were vascularized for 14 days, after which insulin-producing cells were inserted without disrupting the surrounding vasculature. The RPVIM devices were compared with nonprevascularized devices (Standard Implantation Methodology [SIM]) and previously established prevascularized devices (Standard Prevascularization Implantation Methodology [SPVIM]). Results show that over 75% of RPVIM devices containing stem cell-derived insulin-producing beta cell clusters showed a signal after 28 days of implantation in subcutaneous space. Notably, not only was the percent of RPVIM devices showing signal significantly greater than SIM and SPVIM devices, but the intraperitoneal glucose tolerance tests and histological analyses showed that encapsulated stem-cell derived insulin-producing beta cell clusters retained their function in the RPVIM devices, which is crucial for the successful management of T1D.

Pharmacology of Heparin and Related Drugs: An Update

Heparin has been used extensively as an antithrombotic and anticoagulant for close to 100 years. This anticoagulant activity is attributed mainly to the pentasaccharide sequence, which potentiates the inhibitory action of antithrombin, a major inhibitor of the coagulation cascade. More recently it has been elucidated that heparin exhibits anti-inflammatory effect via interference of the formation of neutrophil extracellular traps and this may also contribute to heparin's antithrombotic activity. This illustrates that heparin interacts with a broad range of biomolecules, exerting both anticoagulant and nonanticoagulant actions. Since our previous review, there has been an increased interest in these nonanticoagulant effects of heparin, with the beneficial role in patients infected with SARS2-coronavirus a highly topical example. This article provides an update on our previous review with more recent developments and observations made for these novel uses of heparin and an overview of the development status of heparin-based drugs. SIGNIFICANCE STATEMENT: This state-of-the-art review covers recent developments in the use of heparin and heparin-like materials as anticoagulant, now including immunothrombosis observations, and as nonanticoagulant including a role in the treatment of SARS-coronavirus and inflammatory conditions.

Prebiotic inulin nanocoating for pancreatic islet surface engineering

Pancreatic islet surface engineering has been proposed as an "easy-to-adopt" approach to enhance post-transplantation islet engraftment for treatment against diabetes. Inulin is an FDA-approved dietary prebiotic with reported anti-diabetic, anti-inflammatory, anti-hypoxic and pro-angiogenic properties. We therefore assessed whether inulin would be a viable option for islet surface engineering. Inulin was oxidized to generate inulin-CHO, which would bind to the cell membrane via covalent bond formation between -CHO and -NH₂ across the islet cell membrane. In vitro assessments demonstrated enhanced islet viability and better glucose-induced insulin secretion from inulin-coated (5 mg mL^-1) islets, which was accompanied by enhanced revascularization, shown as significantly enhanced tube formation and branching of islet endothelial MS1 cells following co-culture with inulin-coated islets. Reduction of cytokine-induced cell death was also observed from inulin-coated islets following exposure to pro-inflammatory cytokine LPS. LPS-induced ROS production was significantly dampened by 44% in inulin-coated islets when compared to controls. RNA-seq analysis of inulin-coated and control islets identified expression alterations of genes involved in islet function, vascular formation and immune regulation, supporting the positive impact of inulin on islet preservation. In vivo examination using streptozotocin (STZ)-induced hyperglycemic mice further showed moderately better maintained plasma glucose levels in mice received transplantation of inulin-coated islets, attributable to ameliorated CD45⁺ immune cell infiltration and improved in vivo graft vascularization. We therefore propose islet surface engineering with inulin as safe and beneficial, and further assessment is required to verify its applicability in clinical islet transplantation.

Decellularized Matrix Bioscaffolds: Implementation of Native Microenvironment in Pancreatic Tissue Engineering

ABSTRACT

Type 1 diabetes is an autoimmune disease, and its incidence is usually estimated in the range of 5% to 10%. Currently, the administration of exogenous insulin is the standard of care therapy. However, this therapy is not effective in some patients who may develop some chronic complications. Islet transplantation into the liver is another therapy with promising outcomes; however, the long-term efficacy of this therapeutic option is limited to a small number of patients. Because native extracellular matrix (ECM) components provide a suitable microenvironment for islet functions, engineering a 3-dimensional construct that recapitulates the native pancreatic environment could address these obstacles. Many attempts have been conducted to mimic an in vivo microenvironment to increase the survival of islets or islet-like clusters. With the advent of decellularization technology, it is possible to use a native ECM in organ engineering. Pancreatic decellularized bioscaffold provides proper cell-cell and cell-ECM interactions and retains growth factors that are critical in the determination of cell fate within a native organ. This review summarizes the current knowledge of decellularized matrix technology and addresses its possible limitations before use in the clinic.

Modulating the foreign body response of implants for diabetes treatment

Diabetes Mellitus is a group of diseases characterized by high blood glucose levels due to patients' inability to produce sufficient insulin. Current interventions often require implants that can detect and correct high blood glucose levels with minimal patient intervention. However, these implantable technologies have not reached their full potential in vivo due to the foreign body response and subsequent development of fibrosis. Therefore, for long-term function of implants, modulating the initial immune response is crucial in preventing the activation and progression of the immune cascade. This review discusses the different molecular mechanisms and cellular interactions involved in the activation and progression of foreign body response (FBR) and fibrosis, specifically for implants used in diabetes. We also highlight the various strategies and techniques that have been used for immunomodulation and prevention of fibrosis. We investigate how these general strategies have been applied to implants used for the treatment of diabetes, offering insights on how these devices can be further modified to circumvent FBR and fibrosis.

Cell microencapsulation technologies for sustained drug delivery: Latest advances in efficacy and biosafety

The development of cell microencapsulation systems began several decades ago. However, today few systems have been tested in clinical trials. For this reason, in the last years, researchers have directed efforts towards trying to solve some of the key aspects that still limit efficacy and biosafety, the two major criteria that must be satisfied to reach the clinical practice. Regarding the efficacy, which is closely related to biocompatibility, substantial improvements have been made, such as the purification or chemical modification of the alginates that normally form the microspheres. Each of the components that make up the microcapsules has been carefully selected to avoid toxicities that can damage the encapsulated cells or generate an immune response leading to pericapsular fibrosis. As for the biosafety, researchers have developed biological circuits capable of actively responding to the needs of the patients to precisely and accurately release the demanded drug dose. Furthermore, the structure of the devices has been subject of study to adequately protect the encapsulated cells and prevent their spread in the body. The objective of this review is to describe the latest advances made by scientist to improve the efficacy and biosafety of cell microencapsulation systems for sustained drug delivery, also highlighting those points that still need to be optimized.

Nano-structure of vitronectin/heparin on cell membrane for stimulating single cell in iPSC-derived embryoid body

Individual cell environment stimulating single cell is a suitable strategy for the generation of sophisticated multicellular aggregates with localized biochemical signaling. However, such strategy for induced pluripotent stem cell (iPSC)-derived embryoid bodies (EBs) is limited because the presence of external stimulation can inhibit spontaneous cellular communication, resulting in misdirection in the maturation and differentiation of EBs. In this study, a facile method of engineering the iPSC membrane to stimulate the inner cell of EBs while maintaining cellular activities is reported. We coated the iPSC surface with nanoscale extracellular matrix fabricated by self-assembly between vitronectin and heparin. This nano-coating allowed iPSC to retain its in vitro properties including adhesion capability, proliferation, and pluripotency during its aggregation. More importantly, the nano-coating did not induce lineage-specific differentiation but increased E-cadherin expression, resulting in promotion of development of EB. This study provides a foundation for future production of sophisticated patient-specific multicellular aggregates by modification of living cell membranes.

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VTN/HEP nano-coating acts as a flexible individual cellular environment

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VTN/HEP nano-coating stimulates embryoid body to promote its development

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VTN/HEP nano-coating preserves spontaneous cell aggregation

Toll-like receptor 2-modulating pectin-polymers in alginate-based microcapsules attenuate immune responses and support islet-xenograft survival

Encapsulation of pancreatic islets in alginate-microcapsules is used to reduce or avoid the application of life-long immunosuppression in preventing rejection. Long-term graft function, however, is limited due to varying degrees of host tissue responses against the capsules. Major graft-longevity limiting responses include inflammatory responses provoked by biomaterials and islet-derived danger-associated molecular patterns (DAMPs). This paper reports on a novel strategy for engineering alginate microcapsules presenting immunomodulatory polymer pectin with varying degrees of methyl-esterification (DM) to reduce these host tissue responses. DM18-pectin/alginate microcapsules show a significant decrease of DAMP-induced Toll-Like Receptor-2 mediated immune activation in vitro, and reduce peri-capsular fibrosis in vivo in mice compared to higher DM-pectin/alginate microcapsules and conventional alginate microcapsules. By testing efficacy of DM18-pectin/alginate microcapsules in vivo, we demonstrate that low-DM pectin support long-term survival of xenotransplanted rat islets in diabetic mice. This study provides a novel strategy to attenuate host responses by creating immunomodulatory capsule surfaces that attenuate activation of specific pro-inflammatory immune receptors locally at the transplantation site.

Multifunctional Islet Transplantation Hydrogel Encapsulating A20 High-Expressing Islets

Islet transplantation is regarded as the most promising treatment for type 1 diabetes (T1D). However, the function of grafted islet could be damaged on account of transplant rejection and/or hypoxia several years later after transplantation. We proposed a hypothetical functionalized hydrogel model, which encapsulates sufficient A20 high-expressing islets and supporting cells, and performs as a drug release system releasing immunosuppressants and growth factors, to improve the outcome of pancreatic islet transplantation. Once injected in vivo, the hydrogel can gel and offer a robust mechanical structure for the A20 high-expressing islets and supporting cells. The natural biomaterials (eg, heparin) added into the hydrogel provide adhesive sites for islets to promote islets’ survival. Furthermore, the hydrogel encapsulates various supporting cells, which can facilitate the vascularization and/or prevent the immune system attacking the islet graft. Based on the previous studies that generally applied one or two combined strategies to protect the function of islet graft, we designed this hypothetical multifunctional encapsulation hydrogel model with various functions. We hypothesized that the islet graft could survive and maintain its function for a longer time in vivo compared with naked islets. This hypothetical model has a limitation in terms of clinical application. Future development work will focus on verifying the function and safety of this hypothetical islet transplantation hydrogel model in vitro and in vivo.

Nanomedicine-Based Strategies for Diabetes: Diagnostics, Monitoring, and Treatment

Traditional methods for diabetes management require constant and tedious glucose monitoring (GM) and insulin injections, impacting quality of life. The global diabetic population is expected to increase to 439 million, with approximately US$490 billion in healthcare expenditures by 2030, imposing a significant burden on healthcare systems worldwide. Recent advances in nanotechnology have emerged as promising alternative strategies for the management of diabetes. For example, implantable nanosensors are being developed for continuous GM, new nanoparticle (NP)-based imaging approaches that quantify subtle changes in β cell mass can facilitate early diagnosis, and nanotechnology-based insulin delivery methods are being explored as novel therapies. Here, we provide a holistic summary of this rapidly advancing field compiling all aspects pertaining to the management of diabetes.

Transplantation of PEGylated islets enhances therapeutic efficacy in a diabetic nonhuman primate model

Islet cell transplantation can lead to insulin independence, reduced hypoglycemia, and amelioration of diabetes complications in patients with type 1 diabetes. The systemic delivery of anti-inflammatory agents, while considered crucial to limit the early loss of islets associated with intrahepatic infusion, increases the burden of immunosuppression. In an effort to decrease the pharmaceutical load to the patient, we modified the pancreatic islet surface with long-chain poly(ethylene glycol) (PEG) to mitigate detrimental host-implant interactions. The effect of PEGylation on islet engraftment and long-term survival was examined in a robust nonhuman primate model via three paired transplants of dosages 4300, 8300, and 10 000 islet equivalents per kg body weight. A reduced immunosuppressive regimen of anti-thymocyte globulin induction plus tacrolimus in the first posttransplant month followed by maintenance with sirolimus monotherapy was employed. To limit transplant variability, two of the three pairs were closely MHC-matched recipients and received MHC-disparate PEGylated or untreated islets isolated from the same donors. Recipients of PEGylated islets exhibited significantly improved early c-peptide levels, reduced exogenous insulin requirements, and superior glycemic control, as compared to recipients of untreated islets. These results indicate that this simple islet modification procedure may improve islet engraftment and survival in the setting of reduced immunosuppression.

Nanotechnology Approaches to Modulate Immune Responses to Cell-based Therapies for Type 1 Diabetes

Islet transplantation is a promising curative treatment option for type 1 diabetes (T1D) as it can provide physiological blood glucose control. The widespread utilization of islet transplantation is limited due to systemic immunosuppression requirements, persisting graft immunodestruction, and poor islet engraftment. Traditional macro- and micropolymeric encapsulation strategies can alleviate the need for antirejection immunosuppression, yet the increased graft volume and diffusional distances imparted by these coatings can be detrimental to graft viability and glucose control. Additionally, systemic administration of pro-engraftment and antirejection therapeutics leaves patients vulnerable to adverse off-target side effects. Nanoscale engineering techniques can be used to immunocamouflage islets, modulate the transplant microenvironment, and provide localized pro-engraftment cues. In this review, we discuss the applications of nanotechnology to advance the clinical potential of islet transplantation, with a focus on cell surface engineering, bioactive functionalization, and use of nanoparticles in T1D cell-based treatments.

Engineering Strategies to Improve Islet Transplantation for Type 1 Diabetes Therapy

Type 1 diabetes is an autoimmune disease in which the immune system attacks insulin-producing beta cells of pancreatic islets. Type 1 diabetes can be treated with islet transplantation; however, patients must be administered immunosuppressants to prevent immune rejection of the transplanted islets if they are not autologous or not engineered with immune protection/isolation. To overcome biological barriers of islet transplantation, encapsulation strategies have been developed and robustly investigated. While islet encapsulation can prevent the need for immunosuppressants, these approaches have not shown much success in clinical trials due to a lack of long-term insulin production. Multiple engineering strategies have been used to improve encapsulation and post-transplantation islet survival. In addition, more efficient islet cryopreservation methods have been designed to facilitate the scaling-up of islet transplantation. Other islet sources have been identified including porcine islets and stem cell-derived islet-like aggregates. Overall, islet-laden capsule transplantation has greatly improved over the past 30 years and is moving towards becoming a clinically feasible treatment for type 1 diabetes.

Polymeric Approaches to Reduce Tissue Responses Against Devices Applied for Islet-Cell Encapsulation

Immunoisolation of pancreatic islets is a technology in which islets are encapsulated in semipermeable but immunoprotective polymeric membranes. The technology allows for successful transplantation of insulin-producing cells in the absence of immunosuppression. Different approaches of immunoisolation are currently under development. These approaches involve intravascular devices that are connected to the bloodstream and extravascular devices that can be distinguished in micro- and macrocapsules and are usually implanted in the peritoneal cavity or under the skin. The technology has been subject of intense fundamental research in the past decade. It has co-evolved with novel replenishable cell sources for cure of diseases such as Type 1 Diabetes Mellitus that need to be protected for the host immune system. Although the devices have shown significant success in animal models and even in human safety studies most technologies still suffer from undesired tissue responses in the host. Here we review the past and current approaches to modulate and reduce tissue responses against extravascular cell-containing micro- and macrocapsules with a focus on rational choices for polymer (combinations). Choices for polymers but also choices for crosslinking agents that induce more stable and biocompatible capsules are discussed. Combining beneficial properties of molecules in diblock polymers or application of these molecules or other anti-biofouling molecules have been reviewed. Emerging are also the principles of polymer brushes that prevent protein and cell-adhesion. Recently also immunomodulating biomaterials that bind to specific immune receptors have entered the field. Several natural and synthetic polymers and even combinations of these polymers have demonstrated significant improvement in outcomes of encapsulated grafts. Adequate polymeric surface properties have been shown to be essential but how the surface should be composed to avoid host responses remains to be identified. Current insight is that optimal biocompatible devices can be created which raises optimism that immunoisolating devices can be created that allows for long term survival of encapsulated replenishable insulin-producing cell sources for treatment of Type 1 Diabetes Mellitus.

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.

Nanotechnology in cell replacement therapies for type 1 diabetes

Islet transplantation is a promising long-term, compliance-free, complication-preventing treatment for type 1 diabetes. However, islet transplantation is currently limited to a narrow set of patients due to the shortage of donor islets and side effects from immunosuppression. Encapsulating cells in an immunoisolating membrane can allow for their transplantation without the need for immunosuppression. Alternatively, "open" systems may improve islet health and function by allowing vascular ingrowth at clinically attractive sites. Many processes that enable graft success in both approaches occur at the nanoscale level-in this review we thus consider nanotechnology in cell replacement therapies for type 1 diabetes. A variety of biomaterial-based strategies at the nanometer range have emerged to promote immune-isolation or modulation, proangiogenic, or insulinotropic effects. Additionally, coating islets with nano-thin polymer films has burgeoned as an islet protection modality. Materials approaches that utilize nanoscale features manipulate biology at the molecular scale, offering unique solutions to the enduring challenges of islet transplantation.

Pancreatic islet surface engineering with a starPEG-chondroitin sulfate nanocoating

Islet transplantation is one of the most promising therapeutic options that could restore euglycaemia in type 1 diabetic individuals.

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.

Surface Engineering of Pancreatic Islets with a Heparinized StarPEG Nanocoating

Cell surface engineering can protect implanted cells from host immune attack. It can also reshape cellular landscape to improve graft function and survival post-transplantation. This protocol aims to achieve surface engineering of pancreatic islets using an ultrathin heparin-incorporated starPEG (Hep-PEG) nanocoating. To generate the Hep-PEG nanocoating for pancreatic islet surface engineering, heparin succinimidyl succinate (Heparin-NHS) was first synthesized by modification of its carboxylate groups using N-(3-dimethylamino propyl)-N'-ethyl carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS). The Hep-PEG mixture was then formed by crosslinking of the amino end-functionalized eight-armed starPEG (starPEG-(NH2)8) and Heparin-NHS. For islet surface coating, mouse islets were isolated via collagenase digestion and gradient purification using Histopaque. Isolated islets were then treated with ice cold Hep-PEG solution for 10 min to allow covalent binding between NHS and the amine groups of islet cell membrane. Nanocoating with the Hep-PEG incurs minimal alteration to islet size and volume and heparinization of the islets with Hep-PEG may also reduce instant blood-mediated inflammatory reaction during islet transplantation. This "easy-to-adopt" approach is mild enough for surface engineering of living cells without compromising cell viability. Considering that heparin has shown binding affinity to multiple cytokines, the Hep-PEG nanocoating also provides an open platform that enables incorporation of unlimited functional biological mediators and multi-layered surfaces for living cell surface bioengineering.

Polymeric nano-shielded islets with heparin-polyethylene glycol in a non-human primate model

Intraportal pancreatic islet transplantation incurs huge cell losses during its early stages due to instant blood-mediated inflammatory reactions (IBMIRs), which may also drive regulation of the adaptive immune system. Therefore, a method that evades IBMIR will improve clinical islet transplantation. We used a layer-by-layer approach to shield non-human primate (NHP) islets with polyethylene glycol (nano-shielded islets, NSIs) and polyethylene glycol plus heparin (heparin nano-shielded islets; HNSIs). Islets ranging from 10,000 to 20,000 IEQ/kg body weight were transplanted into 19 cynomolgus monkeys (n = 4, control; n = 5, NSI; and n = 10, HNSI). The mean C-peptide positive graft survival times were 68.5, 64 and 108 days for the control, NSI and HNSI groups, respectively (P = 0.012). HNSI also reduced the factors responsible for IBMIR in vitro. Based on these data, HNSIs in conjunction with clinically established immunosuppressive drug regimens will result in superior outcomes compared to those achieved with the current protocol for clinical islet transplantation.