Novel Application of Localized Nanodelivery of Anti-Interleukin-6 Protects Organ Transplant From Ischemia-Reperfusion Injuries

Application of nanomaterials in heart transplantation: a narrative review

Background and Objective

Heart transplantation (HT) is a therapeutic option for end-stage heart disease. Still, it faces many challenges, especially the shortage of donor sources and the poor durability of grafts, which are the two critical issues. In this review, we generalize the application of existing nanomedicine technologies in donor management as well as prevention and diagnosis of post-transplantation complications, also including the current preclinical studies of nanomaterials in cardiac tissue engineering and gene-editing xeno-donor grafts. Finally, we discuss the remaining problems and future directions of nanomaterials in the field of HT.

Methods

A narrative review using current search of the most recent literature on the topic. The terms "nanomaterials", "nano medicine'', "Heart transplantation (HT)", "Nano-drug delivery system (NDDS)" or their combination were searched in PubMed and Google Scholar. The specified timeframe began from 1990, and we prioritized publications mainly from the last 10 years.

Key Content and Findings

Nano-systems integrating therapeutic and diagnostic functions have been applied to cardiovascular diseases (CVDs) with their unique advantages in multiple fields such as drug delivery, tissue engineering, gene editing, imaging, biomarker editing, and many other aspects. In terms of transplantation, the preservation, transportation, and pretreatment of donor hearts machine perfusion (MP) provide the possibility for nano-systems with unique features, and therapeutic and diagnostic functions to be directly and passively targeted in order to improve the functional status of the transplanted organs or to increase the ability to tolerate the graft of patients. The development of nano-imaging, nanosensor, and nano biomarker technologies are also being applied to monitor the status of transplant recipients for early prevention and treatment of post-transplantation-related complications. Nanomaterials combined with cardiac tissue engineering and gene editing technologies could also expand graft sources and alleviate donor shortages.

Conclusions

Although the overall research on nanomaterial applications in the field of HT is in its infancy, its role in improving the prognosis of transplant recipients and breaking the current dilemma of HT is clear. However, before nanotechnologies can be translated into clinical applications in the future, they must be aimed at ensuring the drug delivery system's safety and pose a challenge in the direction of the ability to intervene with multiple drugs in combination.

Modulatory immune responses in fungal infection associated with organ transplant - advancements, management, and challenges

Organ transplantation stands as a pivotal achievement in modern medicine, offering hope to individuals with end-stage organ diseases. Advancements in immunology led to improved organ transplant survival through the development of immunosuppressants, but this heightened susceptibility to fungal infections with nonspecific symptoms in recipients. This review aims to establish an intricate balance between immune responses and fungal infections in organ transplant recipients. It explores the fundamental immune mechanisms, recent advances in immune response dynamics, and strategies for immune modulation, encompassing responses to fungal infections, immunomodulatory approaches, diagnostics, treatment challenges, and management. Early diagnosis of fungal infections in transplant patients is emphasized with the understanding that innate immune responses could potentially reduce immunosuppression and promise efficient and safe immuno-modulating treatments. Advances in fungal research and genetic influences on immune-fungal interactions are underscored, as well as the potential of single-cell technologies integrated with machine learning for biomarker discovery. This review provides a snapshot of the complex interplay between immune responses and fungal infections in organ transplantation and underscores key research directions.

A new paradigm in transplant immunology: At the crossroad of synthetic biology and biomaterials

Solid organ transplant (SOT) recipients require meticulously tailored immunosuppressive regimens to minimize graft loss and mortality. Traditional approaches focus on inhibiting effector T cells, while the intricate and dynamic immune responses mediated by other components remain unsolved. Emerging advances in synthetic biology and material science have provided novel treatment modalities with increased diversity and precision to the transplantation community. This review investigates the active interface between these two fields, highlights how living and non-living structures can be engineered and integrated for immunomodulation, and discusses their potential application in addressing the challenges in SOT clinical practice.

Trained immunity - basic concepts and contributions to immunopathology

Trained immunity is a functional state of the innate immune response and is characterized by long-term epigenetic reprogramming of innate immune cells. This concept originated in the field of infectious diseases - training of innate immune cells, such as monocytes, macrophages and/or natural killer cells, by infection or vaccination enhances immune responses against microbial pathogens after restimulation. Although initially reported in circulating monocytes and tissue macrophages (termed peripheral trained immunity), subsequent findings indicate that immune progenitor cells in the bone marrow can also be trained (that is, central trained immunity), which explains the long-term innate immunity-mediated protective effects of vaccination against heterologous infections. Although trained immunity is beneficial against infections, its inappropriate induction by endogenous stimuli can also lead to aberrant inflammation. For example, in systemic lupus erythematosus and systemic sclerosis, trained immunity might contribute to inflammatory activity, which promotes disease progression. In organ transplantation, trained immunity has been associated with acute rejection and suppression of trained immunity prolonged allograft survival. This novel concept provides a better understanding of the involvement of the innate immune response in different pathological conditions, and provides a new framework for the development of therapies and treatment strategies that target epigenetic and metabolic pathways of the innate immune system.

The multifunctional roles of autophagy in the innate immune response: Implications for regulation of transplantation rejection

Organ transplantation is the main treatment for end-stage organ failure, which has rescued tens of thousands of lives. Immune rejection is the main factor affecting the survival of transplanted organs. How to suppress immune rejection is an important goal of transplantation research. A graft first triggers innate immune responses, leading to graft inflammation, tissue injury and cell death, followed by adaptive immune activation. At present, the importance of innate immunity in graft rejection is poorly understood. Autophagy, an evolutionarily conserved intracellular degradation system, is proven to be involved in regulating innate immune response following graft transplants. Moreover, there is evidence indicating that autophagy can regulate graft dysfunction. Although the specific mechanism by which autophagy affects graft rejection remains unclear, autophagy is involved in innate immune signal transduction, inflammatory response, and various forms of cell death after organ transplantation. This review summarizes how autophagy regulates these processes and proposes potential targets for alleviating immune rejection.

Targeting IL-6 to prevent cardiac allograft rejection

Outcomes following heart transplantation remain suboptimal with acute and chronic rejection being major contributors to poor long-term survival. IL-6 is increasingly recognized as a critical pro-inflammatory cytokine involved in allograft injury and has been shown to play a key role in regulating the inflammatory and alloimmune responses following heart transplantation. Therapies that inhibit IL-6 signaling have emerged as promising strategies to prevent allograft rejection. Here, we review experimental and pre-clinical evidence that supports the potential use of IL-6 signaling blockade to improve outcomes in heart transplant recipients.

Aging Affects the Role of Myeloid-Derived Suppressor Cells in Alloimmunity

Myeloid-derived suppressor cells (MDSC) are defined as a group of myeloid cells with potent immunoregulatory functions that have been shown to be involved in a variety of immune-related diseases including infections, autoimmune disorders, and cancer. In organ transplantation, MDSC promote tolerance by modifying adaptive immune responses. With aging, however, substantial changes occur that affect immune functions and impact alloimmunity. Since the vast majority of transplant patients are elderly, age-specific modifications of MDSC are of relevance. Furthermore, understanding age-associated changes in MDSC may lead to improved therapeutic strategies. Here, we provide a comprehensive update on the effects of aging on MDSC and discuss potential consequences on alloimmunity.

Nanotherapeutics in transplantation: How do we get to clinical implementation?

Patients undergoing organ transplantation transition from one life-altering issue (organ dysfunction) to a lifelong commitment-immunosuppression. Regimens of immunosuppressive agents (ISAs) come with significant side effects and comorbidities. Recently, the use of nanoparticles (NPs) as a solution to the problems associated with the long-term and systemic use of ISAs in transplantation has emerged. This minireview describes the role of NPs in organ transplantation and discusses obstacles to clinical implementation and pathways to clinical translation.

Intra-Organ Delivery of Nanotherapeutics for Organ Transplantation

Targeted delivery of therapeutics through the use of nanoparticles (NPs) has emerged as a promising method that increases their efficacy and reduces their side effects. NPs can be tailored to localize to selective tissues through conjugation to ligands that bind cell-specific receptors. Although the vast majority of nanodelivery platforms have focused on cancer therapy, efforts have begun to introduce nanotherapeutics to the fields of immunology as well as transplantation. In this review, we provide an overview from a clinician's perspective of current nanotherapeutic strategies to treat solid organ transplants with NPs during the time interval between organ harvest from the donor and placement into the recipient, an innovative technology that can provide major benefits to transplant patients. The use of ex vivo normothermic machine perfusion (NMP), which is associated with preserving the function of the organ following transplantation, also provides an ideal opportunity for a localized, sustained, and controlled delivery of nanotherapeutics to the organ during this critical time period. Here, we summarize previous endeavors to improve transplantation outcomes by treating the organ with NPs prior to placement in the recipient. Investigations in this burgeoning field of research are promising, but more extensive studies are needed to overcome the physiological challenges to achieving effective nanotherapeutic delivery to transplanted organs discussed in this review.

Prevention of vascular-allograft rejection by protecting the endothelial glycocalyx with immunosuppressive polymers

Systemic immunosuppression for the mitigation of immune rejection after organ transplantation causes adverse side effects and constrains the long-term benefits of the transplanted graft. Here we show that protecting the endothelial glycocalyx in vascular allografts via the enzymatic ligation of immunosuppressive glycopolymers under cold-storage conditions attenuates the acute and chronic rejection of the grafts after transplantation in the absence of systemic immunosuppression. In syngeneic and allogeneic mice that received kidney transplants, the steric and immunosuppressive properties of the ligated polymers largely protected the transplanted grafts from ischaemic reperfusion injury, and from immune-cell adhesion and thereby immunocytotoxicity. Polymer-mediated shielding of the endothelial glycocalyx following organ procurement should be compatible with clinical procedures for transplant preservation and perfusion, and may reduce the damage and rejection of transplanted organs after surgery.

Biologics and their delivery systems: Trends in myocardial infarction

Cardiovascular disease is the leading cause of death around the world, in which myocardial infarction (MI) is a precipitating event. However, current therapies do not adequately address the multiple dysregulated systems following MI. Consequently, recent studies have developed novel biologic delivery systems to more effectively address these maladies. This review utilizes a scientometric summary of the recent literature to identify trends among biologic delivery systems designed to treat MI. Emphasis is placed on sustained or targeted release of biologics (e.g. growth factors, nucleic acids, stem cells, chemokines) from common delivery systems (e.g. microparticles, nanocarriers, injectable hydrogels, implantable patches). We also evaluate biologic delivery system trends in the entire regenerative medicine field to identify emerging approaches that may translate to the treatment of MI. Future developments include immune system targeting through soluble factor or chemokine delivery, and the development of advanced delivery systems that facilitate the synergistic delivery of biologics.

Biomaterials-Based Opportunities to Engineer the Pulmonary Host Immune Response in COVID-19

The COVID-19 pandemic caused by the global spread of the SARS-CoV-2 virus has led to a staggering number of deaths worldwide and significantly increased burden on healthcare as nations scramble to find mitigation strategies. While significant progress has been made in COVID-19 diagnostics and therapeutics, effective prevention and treatment options remain scarce. Because of the potential for the SARS-CoV-2 infections to cause systemic inflammation and multiple organ failure, it is imperative for the scientific community to evaluate therapeutic options aimed at modulating the causative host immune responses to prevent subsequent systemic complications. Harnessing decades of expertise in the use of natural and synthetic materials for biomedical applications, the biomaterials community has the potential to play an especially instrumental role in developing new strategies or repurposing existing tools to prevent or treat complications resulting from the COVID-19 pathology. Leveraging microparticle- and nanoparticle-based technology, especially in pulmonary delivery, biomaterials have demonstrated the ability to effectively modulate inflammation and may be well-suited for resolving SARS-CoV-2-induced effects. Here, we provide an overview of the SARS-CoV-2 virus infection and highlight current understanding of the host's pulmonary immune response and its contributions to disease severity and systemic inflammation. Comparing to frontline COVID-19 therapeutic options, we highlight the most significant untapped opportunities in immune engineering of the host response using biomaterials and particle technology, which have the potential to improve outcomes for COVID-19 patients, and identify areas needed for future investigations. We hope that this work will prompt preclinical and clinical investigations of promising biomaterials-based treatments to introduce new options for COVID-19 patients.

Exosomes derived from MSC pre-treated with oridonin alleviates myocardial IR injury by suppressing apoptosis via regulating autophagy activation

This study aimed to investigate the molecular mechanisms underlying the role of bone marrow mesenchymal stem cells (BMMSCs)‐derived exosomes in ischaemia/reperfusion (IR)‐induced damage, and the role of oridonin in the treatment of IR. Exosomes were isolated from BMMSCs. Western blot analysis was done to examine the expression of proteins including CD63, CD8, apoptotic‐linked gene product 2 interacting protein X (AliX), Beclin‐1, ATG13, B‐cell lymphoma‐2 (Bcl‐2), apoptotic peptidase activating factor 1 (Apaf1) and Bcl2‐associated X (Bax) in different treatment groups. Accordingly, the expression of CD63, CD81 and AliX was higher in BMMSCs‐EXOs and IR + BMMSCs‐EXOs + ORI groups compared with that in the BMMSCs group. And BMMSCs‐derived exosomes inhibited the progression of IR‐induced myocardial damage, while this protective effect was boosted by the pre‐treatment with oridonin. Moreover, Beclin‐1, ATG13 and Bcl‐2 were significantly down‐regulated while Apaf1 and Bax were significantly up‐regulated in IR rats. And the presence of BMMSCs‐derived exosomes partly alleviated IR‐induced dysregulation of these proteins, while the oridonin pre‐treatment boosted the effect of these BMMSCs‐derived exosomes. The inhibited proliferation and promoted apoptosis of H9c2 cells induced by hypoxia/reperfusion (HR) were mitigated by the administration of BMMSCs‐derived exosomes. Meanwhile, HR also induced down‐regulation of Beclin‐1, ATG13 and Bcl‐2 expression and up‐regulation of Apaf1 and Bax, which were mitigated by the administration of BMMSCs‐derived exosomes. And oridonin pre‐treatment boosted the effect of BMMSCs‐derived exosomes. In conclusion, our results validated that BMMSCs‐derived exosomes suppressed the IR‐induced damages by participating in the autophagy process, while the pre‐treatment with oridonin could boost the protective effect of BMMSCs‐derived exosomes.

Nanotechnology Solutions for Controlled Cytokine Delivery: An Applied Perspective

Around 200 cytokines with roles in cell signaling have been identified and studied, with the vast majority belonging to the four-α-helix bundle family. These proteins exert their function by binding to specific receptors and are implicated in many diseases. The use of several cytokines as therapeutic targets has been approved by the FDA, however their rapid clearance in vivo still greatly limits their efficacy. Nano-based drug delivery systems have been widely applied in nanomedicine to develop safe, specific and controlled delivery techniques. Nevertheless, each nanomaterial has its own specifications and their suitability towards the biochemical and biophysical properties of the selected drug needs to be determined, weighing in the final choice of the ideal nano drug delivery system. Nanoparticles remain the most used vehicle for cytokine delivery, where polymeric carriers represent the vast majority of the studied systems. Liposomes and gold or silica nanoparticles are also explored and discussed in this review. Additionally, surface functionalization is of great importance to facilitate the attachment of a wide variety of molecules and modify features such as bioavailability. Since the monitoring of cytokine levels has an important role in early clinical diagnosis and for assessing therapeutic efficacy, nanotechnological advances are also valuable for nanosensor development.

Nanotechnology Applications in Transplantation Medicine

A recent technological advance that shows promise for applications in health care, including transplantation medicine, is the implementation of nanoparticles. Nanoparticles can be composed of a variety of organic or inorganic materials and confer many advantages over conventional treatments available, such as low toxicity, low-effective dosage required, and a high degree of manipulability. Although also used for imaging and diagnostics, nanoparticles' utility as a drug or genetic delivery system is of particular interest in transplantation medicine. Currently, researchers are exploring options to integrate nanoparticles into both diagnostics and therapy for both grafts ex-situ before transplantation and for patients following transplantation. These studies have demonstrated that nanoparticles can mitigate damage to organs and patients through a large variety of mechanisms-ranging from the induction of cellular genetic changes to the enhancement of immunosuppressive drug delivery. Specifically, with the advent of machine perfusion preservation ex vivo, treatment of the graft became a very attractive approach and nanoparticles have great potential. However, before nanoparticles can be translated into clinical use, their short-term and long-term toxicity must be thoroughly characterized, especially with regards to their interactions with other biological molecules present in the human body.

Reactive Oxygen Species (ROS)-Responsive Nanomedicine for Solving Ischemia-Reperfusion Injury

Ischemia-reperfusion injury (IRI) is a severe condition for most organs, which could occur in various tissues including brain, heart, liver, and kidney, etc. As one of the major hazards, reactive oxygen species (ROS) is excessively generated after IRI, which causes severe damage inside tissues and further induces the following injury via inflammatory response. However, current medical strategies could not thoroughly diagnose and prevent this disease, eventually leading to severe sequelae by missing the best time point for therapy. In the past decade, various nanoparticles that could selectively respond to ROS have been developed and applied in IRI. These advanced nanomedicines have shown efficient performance in detecting and treating a series of IRI (e.g., acute kidney injury, acute liver injury, and ischemic stroke, etc.), which are well-summarized in the current review. In addition, the nano-platforms (e.g., anti-IL-6 antibody, rapamycin, and hydrogen sulfide delivering nanoparticles, etc.) for preventing IRI during organ transplantation have also been included. Moreover, the development and challenges of ROS-responsive nanomedicine are systematically discussed for guiding the future direction.

Prospective, single-centre, randomised controlled trial to evaluate the efficacy and safety of ischaemia-free liver transplantation (IFLT) in the treatment of end-stage liver disease

INTRODUCTION

During conventional liver transplantation (CLT), ischaemia-reperfusion injury (IRI) is inevitable and is associated with complications such as early allograft dysfunction (EAD), primary non-function and ischaemic-type biliary lesions. We have established a novel procedure called ischaemia-free liver transplantation (IFLT). The results from a pilot study suggest that IFLT might prevent IRI and yield better transplant outcomes than CLT. The purpose of this study was to further assess the efficacy and safety of IFLT versus CLT in patients with end-stage liver disease.

METHODS AND ANALYSIS

This is an investigator-initiated, open-label, phase III, prospective, single-centre randomised controlled trial on the effects of IFLT in patients with end-stage liver disease. Adult patients (aged 18-75 years) eligible for liver transplantation will be screened for participation in this trial and will be randomised between the IFLT group (n=34) and the CLT group (n=34). In the IFLT group, the donor liver will be procured, preserved and implanted with continuous normothermic machine perfusion (NMP). In the CLT group, the donor liver will be procured after a fast cold flush, preserved in 0°C-4°C solution and implanted under hypothermic and hypoxic conditions. Patients in both groups will be managed according to the standard protocol of our centre. The primary end point is the incidence of EAD after liver transplantation. Intraoperative and postoperative parameters of donor livers and recipients will be observed and recorded, and postoperative liver graft function, complications and recipient and graft survival will be evaluated. After a 12-month follow-up of the last enrolled recipient, the outcomes will be analysed to evaluate the safety and efficacy of IFLT versus CLT in patients with end-stage liver disease.

ETHICS AND DISSEMINATION

The protocol was reviewed and approved by the Ethics Committee of The First Affiliated Hospital of Sun Yat-sen University. The findings will be disseminated to the public through conference presentations and peer-reviewed scientific journals.

TRIAL REGISTRATION NUMBER

ChiCTR1900021158.

Application of PLGA nano/microparticle delivery systems for immunomodulation and prevention of allotransplant rejection

INTRODUCTION

Allograft transplantation is an effective end-point therapy to replace the function of an impaired organ. The main problem associated with allotransplantation is the induction of immune responses that results in acute and chronic graft rejection. To modulate the response of the immune system, transplant recipients generally take high dose immunosuppressant drugs for life. These drugs are associated with serious side effects such as infection with opportunistic pathogens and the development of neoplasia.

AREAS COVERED

We reviewed the obstacles to successful transplantation and PLGA-based strategies to reduce immune-mediated allograft rejection.

EXPERT OPINION

Biomaterial-based approaches using micro- and nanoparticles such as poly (lactic-co-glycolic acid) (PLGA) can be used to achieve controlled release of drugs. This approach decreases the required effective dose of drugs and enables local delivery of these agents to specific tissues and cells, whilst decreasing systemic effects.

Nanodelivery of Mycophenolate Mofetil to the Organ Improves Transplant Vasculopathy

Inflammation occurring within the transplanted organ from the time of harvest is an important stimulus of early alloimmune reactivity and promotes chronic allograft rejection. Chronic immune-mediated injury remains the primary obstacle to the long-term success of organ transplantation. However, organ transplantation represents a rare clinical setting in which the organ is accessible ex vivo, providing an opportunity to use nanotechnology to deliver therapeutics directly to the graft. This approach facilitates the directed delivery of immunosuppressive agents (ISA) to target local pathogenic immune responses prior to the transplantation. Here, we have developed a system of direct delivery and sustained release of mycophenolate mofetil (MMF) to treat the donor organ prior to transplantation. Perfusion of a donor mouse heart with MMF-loaded PEG-PLGA nanoparticles (MMF-NPs) prior to transplantation abrogated cardiac transplant vasculopathy by suppressing intragraft pro-inflammatory cytokines and chemokines. Our findings demonstrate that ex vivo delivery of an ISA to donor organs using a nanocarrier can serve as a clinically feasible approach to reduce transplant immunity.

Nanoscale Technologies for Prevention and Treatment of Heart Failure: Challenges and Opportunities

The adult myocardium has a limited regenerative capacity following heart injury, and the lost cells are primarily replaced by fibrotic scar tissue. Suboptimal efficiency of current clinical therapies to resurrect the infarcted heart results in injured heart enlargement and remodeling to maintain its physiological functions. These remodeling processes ultimately leads to ischemic cardiomyopathy and heart failure (HF). Recent therapeutic approaches (e.g., regenerative and nanomedicine) have shown promise to prevent HF postmyocardial infarction in animal models. However, these preclinical, clinical, and technological advancements have yet to yield substantial enhancements in the survival rate and quality of life of patients with severe ischemic injuries. This could be attributed largely to the considerable gap in knowledge between clinicians and nanobioengineers. Development of highly effective cardiac regenerative therapies requires connecting and coordinating multiple fields, including cardiology, cellular and molecular biology, biochemistry and chemistry, and mechanical and materials sciences, among others. This review is particularly intended to bridge the knowledge gap between cardiologists and regenerative nanomedicine experts. Establishing this multidisciplinary knowledge base may help pave the way for developing novel, safer, and more effective approaches that will enable the medical community to reduce morbidity and mortality in HF patients.

Anti-IL-6 eluting immunomodulatory biomaterials prolong skin allograft survival

A primary goal in the management of burn wounds is early wound closure. The use of skin allografts represents a lifesaving strategy for severe burn patients, but their ultimate rejection limits their potential efficacy and utility. IL-6 is a major pleiotropic cytokine which critically links innate and adaptive immune responses. Here, we devised anti-IL-6 receptor eluting gelatin methacryloyl (GelMA) biomaterials (GelMA/anti-IL-6), which were implanted at the interface between the wound beds and skin allografts. Our visible light crosslinked GelMA/anti-IL-6 immunomodulatory biomaterial (IMB) demonstrated a stable kinetic release profile of anti-IL-6. In addition, the incorporation of anti-IL-6 within the GelMA hydrogel had no effect on the mechanical properties of the hydrogels. Using a highly stringent skin transplant model, the GelMA/anti-IL-6 IMB almost doubled the survival of skin allografts. The use of GelMA/anti-IL-6 IMB was far superior to systemic anti-IL-6 receptor treatment in prolonging skin allograft survival. As compared to the untreated control group, skin from the GelMA/anti-IL-6 IMB group contained significantly fewer alloreactive T cells and macrophages. Interestingly, the environmental milieu of the draining lymph nodes (DLNs) of the mice implanted with the GelMA/anti-IL-6 IMB was also considerably less pro-inflammatory. The percentage of CD4⁺ IFNγ⁺ cells was much lower in the DLNs of the GelMA/anti-IL-6 IMB group in comparison to the GelMA group. These data highlight the importance of localized immune delivery in prolonging skin allograft survival and its potential utility in treating patients with severe burns.

Active targeted delivery of immune therapeutics to lymph nodes

PURPOSE OF REVIEW

Organ transplantation is a life-saving procedure and the only option for patients with end-organ failure. Immune therapeutics have been key to the success of organ transplantation. However, immune therapeutics are still unable to eliminate graft rejection and their toxicity has been implicated in poorer long-term transplant outcomes. Targeted nanodelivery has the potential to enhance not only the therapeutic index but also the bioavailability of the immune therapeutics. One of the key sites of immune therapeutics delivery is lymph node where the priming of immune cells occur. The focus of this review is on nanomedicine research to develop the targeted delivery of immune therapeutics to lymph nodes for controlling immune activation.

RECENT FINDINGS

As nanomedicine creates its niche in clinical care, it provides novel immunotherapy platforms for transplant recipients. Draining lymph nodes are the primary loci of immune activation and represent a formidable site for delivery of wide variety of immune therapeutics. There have been relentless efforts to improve the properties of nanomedicines, to have in-depth knowledge of antigen and drug loading, and, finally, to explore various routes of passive and active targeted delivery to lymph nodes.

SUMMARY

The application of nanotechnology principles in the delivery of immune therapeutics to the lymph node has created enormous excitement as a paradigm shifting approach that enables targeted delivery of a gamut of molecules to achieve a desired immune response. Therefore, innovative strategies that improve their efficacy while reducing their toxicity are among the highest unmet needs in transplantation.

FGF21 protects myocardial ischemia-reperfusion injury through reduction of miR-145-mediated autophagy

AIMS

Fibroblast growth factor 21 (FGF21) plays a critical role in protecting against myocardial ischemia/reperfusion (I/R) injury. However, the molecular mechanism is not completely understood. Here, we aimed to examine whether miRNA-145 (miR-145) is involved in FGF21 protection against myocardial I/R injury through angiopoietin-2 (Angpt2) and autophagy.

METHODS

We established a rat myocardial I/R model and H9c2 hypoxia/reoxygenation (H/R) model. After administration of FGF21 in the rat I/R model, the infarct size, morphological changes and apoptosis in myocardium were determined by 2,3,5-triphenyltetrazolium chloride (TTC), hematoxylin and eosin (HE), and Masson's trichrome staining, and TUNEL assay, respectively. The expression levels of miR-145 and Angpt2 were evaluated by quantitative real-time PCR (qRT-PCR), Western blotting and immunohistochemical (IHC) staining. The activity of lactate dehydrogenase (LDH), TNF-α and IL-6 were assayed. Using a dual-luciferase reporter system, the targeted role of miR-145 on Angpt2 was studied. After transfection with miR-145 inhibitor, H9c2 cells were subjected to stimulated H/R with or without FGF21 treatment. The expression of Angpt2 was assessed while cell apoptosis and cell migration assays were performed.

RESULTS

FGF21 significantly decreased infarction after I/R, ameliorated I/R-induced cell apoptosis, and inhibited I/R-induced LDH, TNF-α and IL-6 in serum. FGF21 inhibited I/R-induced decrease in miR-145 level, increase in Angpt2 expression and decrease in autophagy; FGF21 also upregulated LC3-B and Beclin1 levels. miR-145 directly targeted Angpt2. The roles of FGF21 in expression of miR-145 and Angpt2 and activation of autophagy after H/R were reversed by miR-145 inhibitor. In addition, the FGF21-inhibited cell apoptosis and FGF21-promoted migration after H/R were restored by miR-145 inhibitor.

CONCLUSION

FGF21 protects myocardial cells against I/R injury by promoting an increase in miR-145 levels and autophagy while inhibiting Angpt2 expression, suggesting a novel therapeutic strategy for protecting against myocardial I/R injury.

Donor IL-6 deficiency evidently reduces memory T cell responses in sensitized transplant recipients

BACKGROUND

Resistance of tolerance induction in sensitized transplantation is mainly caused by generation of memory T cells. It is unknown whether alteration of graft niche such as level of pro-inflammatory cytokines can affect generation of memory T cells.

METHODS

IL-6 deficient or wild-type (WT) C57BL/6 heart grafts were transplanted into pre-sensitized wild-type BALB/c recipients. Frequencies of memory T cells in the peripheral blood, grafts, and spleen were evaluated.

RESULTS

We revealed that deficiency of donor IL-6 could significant prolong sensitized allograft survival. Compared with counterpart of WT group, frequency of effector memory CD4 + T cells (CD4 + CD44 + CD62L-) in the peripheral blood was significantly lower in the IL-6 KO group (p = .026) at day 3 post-transplantation. Frequency of effector memory CD8 + T cells (CD8 + CD44 + CD62L-) in the peripheral blood was significantly lower in the IL-6 KO group (p < .0001) at day 3 post-transplant in comparison to that of WT group. No significant difference of central memory T cells was found between these groups. Histology demonstrated that deficiency of donor pro-inflammatory cytokine IL-6 (IL-6 KO group) preserved cardiac architecture with a mild infiltration of lymphocytes, whereas wild-type donor (control group) caused an evident lymphocytic infiltration within myocardial fibers of grafts and destruction of cardiac structure.

CONCLUSION

Deficiency of pro-inflammatory IL-6 of donor graft could effectively prolong sensitized allograft survival, which was caused by a remarkable decrease of peripheral memory T cells rather than central memory T cells. This unveiled mechanism of targeting IL-6 signaling pathway might provide a novel insight into preventing allograft rejection for sensitized transplant recipients.

Interleukin-6 Neutralization by Antibodies Immobilized at the Surface of Polymeric Nanoparticles as a Therapeutic Strategy for Arthritic Diseases

Arthritic diseases are disabling conditions affecting millions of patients worldwide. Pro-inflammatory cytokines, particularly interleukin-6 (IL-6), plays a crucial role in inflammation and cartilage destruction. Although the beneficial effects of antibody therapy, its efficacy is limited. Therefore, this work proposes the immobilization of antibodies at the surface of biodegradable polymeric nanoparticles (NPs) to capture and neutralize IL-6. Our system is intended to protect, extend and enhance the therapeutic efficacy after delivery. Chitosan-hyaluronic acid NPs are synthesized as a stable monodisperse population. After determining the maximum immobilization capacity (10 μg/mL), the capture ability was confirmed. Biological assays demonstrate the NPs cytocompatibility with human articular chondrocytes (hACs) and human macrophages. hACs stimulated with macrophage conditioned medium shows the beneficial role of IL-6 capture and neutralization. Biofunctionalized NPs exhibit a prolonged action and stronger efficacy than the free antibody. In conclusion, this system can be an effective and long lasting treatment for arthritic diseases.

Ischemia augments alloimmune injury through IL-6-driven CD4+ alloreactivity

Ischemia reperfusion injuries (IRI) are unavoidable in solid organ transplantation. IRI augments alloimmunity but the mechanisms involved are poorly understood. Herein, we examined the effect of IRI on antigen specific alloimmunity. We demonstrate that ischemia promotes alloimmune activation, leading to more severe histological features of rejection, and increased CD4+ and CD8+ T cell graft infiltration, with a predominantly CD8+ IFNγ+ infiltrate. This process is dependent on the presence of alloreactive CD4+ T cells, where depletion prevented infiltration of ischemic grafts by CD8+ IFNγ+ T cells. IL-6 is a known driver of ischemia-induced rejection. Herein, depletion of donor antigen-presenting cells reduced ischemia-induced CD8+ IFNγ+ allograft infiltration, and improved allograft outcomes. Following prolonged ischemia, accelerated rejection was observed despite treatment with CTLA4Ig, indicating that T cell costimulatory blockade failed to overcome the immune activating effect of IRI. However, despite severe ischemic injury, treatment with anti-IL-6 and CTLA4Ig blocked IRI-induced alloimmune injury and markedly improved allograft survival. We describe a novel pathway where IRI activates innate immunity, leading to upregulation of antigen specific alloimmunity, resulting in chronic allograft injury. Based on these findings, we describe a clinically relevant treatment strategy to overcome the deleterious effect of IRI, and provide superior long-term allograft outcomes.

Organ preservation with targeted rapamycin nanoparticles: a pre-treatment strategy preventing chronic rejection in vivo

Hypothermic preservation is the standard of care for storing organs prior to transplantation. Endothelial and epithelial injury associated with hypothermic storage causes downstream graft injury and, as such, the choice of an ideal donor organ preservation solution remains controversial. Cold storage solutions, by design, minimize cellular necrosis and optimize cellular osmotic potential, but do little to assuage immunological cell activation or immune cell priming post transplantation. Thus, here we explore the efficacy of our previously described novel Targeted Rapamycin Micelles (TRaM) as an additive to standard-of-care University of Wisconsin preservation solution as a means to alter the immunological microenvironment post transplantation using in vivo models of tracheal and aortic allograft transplantation. In all models of transplantation, grafts pre-treated with 100 ng mL^-1 of TRaM augmented preservation solution ex vivo showed a significant inhibition of chronic rejection post-transplantation, as compared to UW augmented with free rapamycin at a ten-fold higher dose. Here, for the first time, we present a novel method of organ pretreatment using a nanotherapeutic-based cellular targeted delivery system that enables donor administration of rapamycin, at a ten-fold decreased dose during cold storage. Clinically, these pretreatment strategies may positively impact post-transplant outcomes and can be readily translated to clinical scenarios.

Harnessing Apoptotic Cells for Transplantation Tolerance: Current Status and Future Perspectives

PURPOSE OF REVIEW

The use of donor apoptotic cells is an emerging therapy for inducing transplantation tolerance. In this review, we will discuss current understanding of mechanisms of this approach, as well as crucial aspects necessary for successful translation of this approach to clinical transplantation.

RECENT FINDINGS

Transplantation tolerance by donor apoptotic cells is mediated by their homeostatic interaction with recipient phagocytes, and subsequent expansion of suppressor cell populations as well as inhibition of effector T cells via deletion and anergy. To ensure their tolerogenicity, it is critical to procure non-stressed donor cells, and to induce and arrest their apoptosis at the appropriate stage prior to their administration. Equally important is the monitoring of dynamics of recipient immunological status, and its influences on tolerance efficacy and longevity. Emerging concepts and technologies may significantly streamline tolerogen manufacture and delivery of this approach, and smooth its transition to clinical application.

SUMMARY

Hijacking homeostatic clearance of donor apoptotic cells is a promising strategy for transplantation tolerance. Timing is now mature for concerted efforts for transitioning this strategy to clinical transplantation.