Targeting inflammatory monocytes by immune-modifying nanoparticles prevents acute kidney allograft rejection

A novel Si-based antioxidant agent attenuates antibody-mediated rejection in allogeneic rat kidney transplantation

Antibody-mediated rejection remains a leading cause of graft loss during kidney transplantation. Ischemia reperfusion injury (IRI) has been reported to promote T cell proliferation, leading to B cell activation and subsequent production of donor-specific antibodies, which target antigens on the vascular endothelium. We hypothesize that a novel therapeutic strategy targeting highly toxic reactive oxygen species could mitigate oxidative stress and immune responses associated with IRI. Our previous study demonstrated that oral administration of a silicon (Si)-based agent consistently generates substantial amounts of hydrogen, effectively suppressing IRI-induced oxidative stress and acute kidney injury in a rat renal clamp model. Here, we investigated the effect of the Si-based agent on immune responses in an allogeneic kidney transplant setting. Using both short-term and long-term evaluation models, we found that the Si-based agent suppressed oxidative stress and acquired immunity activation. Furthermore, early suppression of donor-specific antibody production and amelioration of chronic antibody-mediated rejection were observed. These findings indicate that the Si-based agent offers protective effects on graft function and survival, highlighting its potential clinical application to improve outcomes for kidney transplant recipients.

Targeted delivery of IL-21 neutralizing nanotherapeutics to lymph nodes and kidney allografts attenuates B cell alloimmunity

INTRODUCTION

Antibody-mediated rejection (ABMR) after allogeneic kidney transplantation is a substantial clinical problem for which there are no specific treatments. High endothelial venules (HEV) are specialized veins which are normally present only in lymph nodes (LN) facilitating immune cell entry. Here, we show that kidneys undergoing rejection develop HEV-like structures derived from host cells.

METHODS

We developed a nano-delivery system targeting HEVs to simultaneously deliver therapeutics to draining LN and kidney allografts.

RESULTS

Using this system, we preferentially delivered IL-21 neutralizing antibody (NP-HEV[ aIL21]) to draining LN and kidney allografts resulting in improved graft function and recipient survival. The NP-HEV[aIL21] system also decreased alloreactive B cell responses, donor-specific antibody production, and ABMR-like lesions in kidney grafts.

CONCLUSIONS

Our study provides a therapeutic strategy to selectively target distinct effector sites to attenuate B-cell alloimmunity while limiting effects of broad systemic immunosuppression in kidney transplantation.

Can mouse kidney transplant models inform mechanisms of injury and acceptance in clinical kidney transplantation?

Despite standard-of-care immunosuppression, acute rejection remains commonly observed in kidney transplants and leads to chronic graft injury and failure in many transplanted patients. Mechanisms underlying acute and chronic kidney graft injury are incompletely understood, undermining the development and implementation of therapeutic strategies to improve outcomes. This compels the use of preclinical kidney transplant models to identify components and mechanisms mediating acute and chronic graft injury. Mouse models have been instrumental in establishing basic principles of alloimmune responses and the rejection of heart allografts. There is increasing use of mouse models to extend these studies to kidney transplantation, but the relevance of the findings to clinical kidney transplants remains under scrutiny. Here, we discuss the strengths and weaknesses of mouse models of kidney allograft responses and injury. Although obvious weaknesses arise when considering the relevance to clinical kidney transplants, there are new models that recapitulate many features of kidney graft injury in the clinical scenario and have much to contribute to understanding innate and donor alloantigen-specific mechanisms underlying kidney allograft injury. As in most preclinical studies, the pertinent use of kidney allogeneic transplants in mice comes down to the judicious choice of test questions and the choice of appropriate donors and recipients for the chosen model.

Engineered Nanoparticles for Theranostic Applications in Kidney Repair

Kidney diseases are characterized by their intricate nature and complexity, posing significant challenges in their treatment and diagnosis. Nanoparticles (NPs), which can be further classified as synthetic and biomimetic NPs, have emerged as promising candidates for treating various diseases. In recent years, the development of engineered nanotherapeutics has focused on targeting damaged tissues and serving as drug delivery vehicles. Additionally, these NPs have shown superior sensitivity and specificity in diagnosis and imaging, thus providing valuable insights for the early detection of diseases. This review aims to focus on the application of engineered synthetic and biomimetic NPs in kidney diseases in the aspects of treatment, diagnosis, and imaging. Notably, the current perspectives and challenges are evaluated, which provide inspiration for future research directions, and encourage the clinical application of NPs in this field.

Nanoparticle-assisted Targeting Delivery Technologies for Preventing Organ Rejection

Although organ transplantation is a life-saving medical procedure, the challenge of posttransplant rejection necessitates safe and effective immune modulation strategies. Nanodelivery approaches may have the potential to overcome the limitations of small-molecule immunosuppressive drugs, achieving efficacious treatment options for transplant tolerance without compromising overall host immunity. This review highlights recent advances in biomaterial-assisted formulations and technologies for targeted nanodrug delivery with transplant organ- or immune cell-level precision for treating graft rejection after transplantation. We provide an overview of the mechanism of transplantation rejection, current clinically approved immunosuppressive drugs, and their relevant limitations. Finally, we discuss the targeting principles and advantages of organ- and immune cell-specific delivery technologies. The development of biomaterial-assisted novel therapeutic strategies holds considerable promise for treating organ rejection and clinical translation.

Regulatory B Cells Expressing Granzyme B from Tolerant Renal Transplant Patients: Highly Differentiated B Cells with a Unique Pathway with a Specific Regulatory Profile and Strong Interactions with Immune System Cells

The aim of our study was to determine whether granzyme B-expressing regulatory B cells (GZMB+ B cells) are enriched in the blood of transplant patients with renal graft tolerance. To achieve this goal, we analysed two single-cell RNA sequencing (scRNAseq) datasets: (1) peripheral blood mononuclear cells (PBMCs), including GZMB+ B cells from renal transplant patients, i.e., patients with stable graft function on conventional immunosuppressive treatment (STA, n = 3), drug-free tolerant patients (TOL, n = 3), and patients with antibody-mediated rejection (ABMR, n = 3), and (2) ex-vivo-induced GZMB+ B cells from these groups. In the patient PBMCs, we first showed that natural GZMB+ B cells were enriched in genes specific to Natural Killer (NK) cells (such as NKG7 and KLRD1) and regulatory B cells (such as GZMB, IL10, and CCL4). We performed a pseudotemporal trajectory analysis of natural GZMB+ B cells and showed that they were highly differentiated B cells with a trajectory that is very different from that of conventional memory B cells and linked to the transcription factor KLF13. By specifically analysing GZMB+ natural B cells in TOLs, we found that these cells had a very specific transcriptomic profile associated with a reduction in the expression of HLA molecules, apoptosis, and the inflammatory response (in general) in the blood and that this signature was conserved after ex vivo induction, with the induction of genes associated with migration processes, such as CCR7, CCL3, or CCL4. An analysis of receptor/ligand interactions between these GZMB+/- natural B cells and all of the immune cells present in PBMCs also demonstrated that GZMB+ B cells were the B cells that carried the most ligands and had the most interactions with other immune cells, particularly in tolerant patients. Finally, we showed that these GZMB+ B cells were able to infiltrate the graft under inflammatory conditions, thus suggesting that they can act in locations where immune events occur.

The Potential Role of the Leucocyte Immunoglobulin-Like Receptors in Kidney Transplant Rejection: A Mini Review

Antibody-mediated rejection (ABMR) remains one of the main causes of long-term graft failure after kidney transplantation, despite the development of powerful immunosuppressive therapy. A detailed understanding of the complex interaction between recipient-derived immune cells and the allograft is therefore essential. Until recently, ABMR mechanisms were thought to be solely caused by adaptive immunity, namely, by anti-human leucocyte antigen (HLA) donor-specific antibody. However recent reports support other and/or additive mechanisms, designating monocytes/macrophages as innate immune contributors of ABMR histological lesions. In particular, in mouse models of experimental allograft rejection, monocytes/macrophages are readily able to discriminate non-self via paired immunoglobulin receptors (PIRs) and thus accelerate rejection. The human orthologs of PIRs are leukocyte immunoglobulin-like receptors (LILRs). Among those, LILRB3 has recently been reported as a potential binder of HLA class I molecules, shedding new light on LILRB3 potential as a myeloid mediator of allograft rejection. In this issue, we review the current data on the role of LILRB3 and discuss the potential mechanisms of its biological functions.

Relationship between the microenvironment and survival in kidney transplantation: a bibliometric analysis from 2013 to 2023

Background

Kidney transplantation is considered the most effective treatment for end-stage renal failure. Recent studies have shown that the significance of the immune microenvironment after kidney transplantation in determining prognosis of patients. Therefore, this study aimed to conduct a bibliometric analysis to provide an overview of the knowledge structure and research trends regarding the immune microenvironment and survival in kidney transplantation.

Methods

Our search included relevant publications from 2013 to 2023 retrieved from the Web of Science core repository and finally included 865 articles. To perform the bibliometric analysis, we utilized tools such as VOSviewer, CiteSpace, and the R package "bibliometrix". The analysis focused on various aspects, including country, author, year, topic, reference, and keyword clustering.

Results

Based on the inclusion criteria, a total of 865 articles were found, with a trend of steady increase. China and the United States were the countries with the most publications. Nanjing Medical University was the most productive institution. High-frequency keywords were clustered into 6 areas, including kidney transplantation, transforming growth factor β, macrophage, antibody-mediated rejection, necrosis factor alpha, and dysfunction. Antibody mediated rejection (2019-2023) was the main area of research in recent years.

Conclusion

This groundbreaking bibliometric study comprehensively summarizes the research trends and advances related to the immune microenvironment and survival after kidney transplantation. It identifies recent frontiers of research and highlights promising directions for future studies, potentially offering fresh perspectives to scholars in the field.

Immune landscape of the kidney allograft in response to rejection

Preventing kidney graft dysfunction and rejection is a critical step in addressing the nationwide organ shortage and improving patient outcomes. While kidney transplants (KT) are performed more frequently, the overall number of patients on the waitlist consistently exceeds organ availability. Despite improved short-term outcomes in KT, comparable progress in long-term allograft survival has not been achieved. Major cause of graft loss at 5 years post-KT is chronic allograft dysfunction (CAD) characterized by interstitial fibrosis and tubular atrophy (IFTA). Accordingly, proactive prevention of CAD requires a comprehensive understanding of the immune mechanisms associated with either further dysfunction or impaired repair. Allograft rejection is primed by innate immune cells and carried out by adaptive immune cells. The rejection process is primarily facilitated by antibody-mediated rejection (ABMR) and T cell-mediated rejection (TCMR). It is essential to better elucidate the actions of individual immune cell subclasses (e.g. B memory, Tregs, Macrophage type 1 and 2) throughout the rejection process, rather than limiting our understanding to broad classes of immune cells. Embracing multi-omic approaches may be the solution in acknowledging these intricacies and decoding these enigmatic pathways. A transition alongside advancing technology will better allow organ biology to find its place in this era of precision and personalized medicine.

Clodronate is not protective in lethal viral encephalitis despite substantially reducing inflammatory monocyte infiltration in the CNS

Bone marrow (BM)-derived monocytes induce inflammation and tissue damage in a range of pathologies. In particular, in a mouse model of West Nile virus (WNV) encephalitis (WNE), nitric oxide-producing, Ly6Chi inflammatory monocytes from the BM are recruited to the central nervous system (CNS) and contribute to lethal immune pathology. Reducing the migration of these cells into the CNS using monoclonal antibody blockade, immune-modifying particles or CSF-1R inhibitors reduces neuroinflammation, improving survival and/or clinical outcomes. Macrophages can also be targeted more broadly by administration of clodronate-encapsulated liposomes, which induce apoptosis in phagocytes. In this study, clodronate reduced the inflammatory infiltrate by 70% in WNE, however, surprisingly, this had no effect on disease outcome. More detailed analysis demonstrated a compensatory increase in neutrophils and enhanced activation status of microglia in the brain. In addition, we observed increased numbers of Ly6Chi BM monocytes with an increased proliferative capacity and expression of SCA-1 and CD16/32, potentially indicating output of immature cells from the BM. Once in the brain, these cells were more phagocytic and had a reduced expression of antigen-presenting molecules. Lastly, we show that clodronate also reduces non-myeloid cells in the spleen and BM, as well as ablating red blood cells and their proliferation. These factors likely impeded the therapeutic potential of clodronate in WNE. Thus, while clodronate provides an excellent system to deplete macrophages in the body, it has larger and broader effects on the phagocytic and non-phagocytic system, which must be considered in the interpretation of data.

Transcriptional and spatial profiling of the kidney allograft unravels a central role for FcyRIII+ innate immune cells in rejection

Rejection remains the main cause of premature graft loss after kidney transplantation, despite the use of potent immunosuppression. This highlights the need to better understand the composition and the cell-to-cell interactions of the alloreactive inflammatory infiltrate. Here, we performed droplet-based single-cell RNA sequencing of 35,152 transcriptomes from 16 kidney transplant biopsies with varying phenotypes and severities of rejection and without rejection, and identified cell-type specific gene expression signatures for deconvolution of bulk tissue. A specific association was identified between recipient-derived FCGR3A+ monocytes, FCGR3A+ NK cells and the severity of intragraft inflammation. Activated FCGR3A+ monocytes overexpressed CD47 and LILR genes and increased paracrine signaling pathways promoting T cell infiltration. FCGR3A+ NK cells overexpressed FCRL3, suggesting that antibody-dependent cytotoxicity is a central mechanism of NK-cell mediated graft injury. Multiplexed immunofluorescence using 38 markers on 18 independent biopsy slides confirmed this role of FcγRIII+ NK and FcγRIII+ nonclassical monocytes in antibody-mediated rejection, with specificity to the glomerular area. These results highlight the central involvement of innate immune cells in the pathogenesis of allograft rejection and identify several potential therapeutic targets that might improve allograft longevity.

Nanomedicine in kidney disease

PURPOSE OF REVIEW

The pathophysiological understanding of kidney-related disorders has profoundly increased; however, tissue-specific and cell-specific treatments in this field remain scarce. Advances in nanomedicine enable alteration of pharmacokinetics and targeted treatments improving efficiency and reducing toxicity. This review addresses recent developments of nanocarriers used for various purposes in the broad field of kidney disease, which may pave a path to new therapeutic and diagnostic solutions employing nanomedicine.

RECENT FINDINGS

Controlled delivery of antiproliferative medications enables improved treatment of polycystic kidney disease and fibrosis. Directed anti-inflammatory treatment mitigated glomerulonephritis and tubulointerstitial nephritis. Multiple injury pathways in AKI have been targeted, with therapeutic solutions for oxidative stress, mitochondrial dysfunction, local inflammation and improving self-repair mechanisms. In addition to such treatment development, noninvasive early detection methods (minutes after ischemic insult) have been demonstrated as well. Sustained release of therapies that reduce ischemia-reperfusion injury as well as new aspects for immunosuppression bring hope to improving kidney transplant outcomes. The latest breakthroughs in gene therapy are made achievable by engineering the targeted delivery of nucleic acids for new treatments of kidney disease.

SUMMARY

Recent advances in nanotechnology and pathophysiological understanding of kidney diseases show potential for translatable therapeutic and diagnostic interventions in multiple etiologies of kidney disease.

MARCO Inhibits Porcine Reproductive and Respiratory Syndrome Virus Infection through Intensifying Viral GP5-Induced Apoptosis

Studying viral glycoprotein-host membrane protein interactions contributes to the discovery of novel cell receptors or entry facilitators for viruses. Glycoprotein 5 (GP5), which is a major envelope protein of porcine reproductive and respiratory syndrome virus (PRRSV) virions, is a key target for the control of the virus. Here, the macrophage receptor with collagenous structure (MARCO), which is a member of the scavenger receptor family, was identified as one of the host interactors of GP5 through a DUALmembrane yeast two-hybrid screening. MARCO was specifically expressed on porcine alveolar macrophages (PAMs), and PRRSV infection downregulated MARCO expression both in vitro and in vivo. MARCO was not involved in viral adsorption and internalization processes, indicating that MARCO may not be a PRRSV-entry facilitator. Contrarily, MARCO served as a host restriction factor for PRRSV. The knockdown of MARCO in PAMs enhanced PRRSV proliferation, whereas overexpression suppressed viral proliferation. The N-terminal cytoplasmic region of MARCO was responsible for its inhibitory effect on PRRSV. Further, we found that MARCO was a proapoptotic factor in PRRSV-infected PAMs. MARCO knockdown weakened virus-induced apoptosis, whereas overexpression aggravated apoptosis. MARCO aggravated GP5-induced apoptosis, which may result in its proapoptotic function in PAMs. The interaction between MARCO and GP5 may contribute to the intensified apoptosis induced by GP5. Additionally, the inhibition of apoptosis during PRRSV infection weakened the antiviral function of MARCO, suggesting that MARCO inhibits PRRSV through the regulation of apoptosis. Taken together, the results of this study reveal a novel antiviral mechanism of MARCO and suggest a molecular basis for the potential development of therapeutics against PRRSV. IMPORTANCE Porcine reproductive and respiratory syndrome virus (PRRSV) has been one of the most serious threats to the global swine industry. Glycoprotein 5 (GP5) exposed on the surface of PRRSV virions is a major glycoprotein, and it is involved in viral entry into host cells. A macrophage receptor with collagenous structure (MARCO), which is a member of the scavenger receptor family, was identified to interact with PRRSV GP5 in a DUALmembrane yeast two-hybrid screening. Further investigation demonstrated that MARCO may not serve as a potential receptor to mediate PRRSV entry. Instead, MARCO was a host restriction factor for the virus, and the N-terminal cytoplasmic region of MARCO was responsible for its anti-PRRSV effect. Mechanistically, MARCO inhibited PRRSV infection through intensifying virus-induced apoptosis in PAMs. The interaction between MARCO and GP5 may contribute to GP5-induced apoptosis. Our work reveals a novel antiviral mechanism of MARCO and advances the development of control strategies for the virus.

The Response of Macrophages in Sepsis-Induced Acute Kidney Injury

Sepsis-induced acute kidney injury (SAKI) is common in critically ill patients and often leads to poor prognosis. At present, the pathogenesis of SAKI has not been fully clarified, and there is no effective treatment. Macrophages are immune cells that play an important role in the pathogenesis of SAKI. The phenotype and role of macrophages can vary from early to later stages of SAKI. Elucidating the role of macrophages in SAKI will be beneficial to its diagnosis and treatment. This article reviews past studies describing the role of macrophages in SAKI, with the aim of identifying novel therapeutic targets.

Nanomaterials and Their Impact on the Immune System

Nanomaterials have been the focus of intensive development and research in the medical and industrial sectors over the past several decades. Some studies have found that these compounds can have a detrimental impact on living organisms, including their cellular components. Despite the obvious advantages of using nanomaterials in a wide range of applications, there is sometimes skepticism caused by the lack of substantial proof that evaluates potential toxicities. The interactions of nanoparticles (NPs) with cells of the immune system and their biomolecule pathways are an area of interest for researchers. It is possible to modify NPs so that they are not recognized by the immune system or so that they suppress or stimulate the immune system in a targeted manner. In this review, we look at the literature on nanomaterials for immunostimulation and immunosuppression and their impact on how changing the physicochemical features of the particles could alter their interactions with immune cells for the better or for the worse (immunotoxicity). We also look into whether the NPs have a unique or unexpected (but desired) effect on the immune system, and whether the surface grafting of polymers or surface coatings makes stealth nanomaterials that the immune system cannot find and get rid of.