An animal model of glomerular light-chain-associated amyloidogenesis depicts the crucial role of lysosomes

Features that characterize monoclonal light chain ("myeloma") cast nephropathy with immunofluorescence challenges and emphasis on electron microscopy

Renal disease is a common cause of morbidity and mortality in patients with plasma cell dyscrasias. The serum-free light chain assay is used in patients, mostly older, with unexplained acute kidney injury to screen for potential myeloma cast nephropathy. This study consists of a systematic review of diagnostic features in myeloma cast nephropathy. The morphological features of tubular casts in patients with multiple myeloma have not been systematically analyzed. This study focuses on the morphology of these casts, emphasizing ultrastructural features, in a series of 23 patients with light chain ("myeloma") cast nephropathy and compared them with casts in 10 patients with various diseases. The immunofluorescence data were correlated with morphological findings to provide diagnostic assessments and practice guidelines. The ultrastructural features identified as diagnostic of casts associated with myeloma included: amyloid and crystals in the casts, multiple well-defined fracture planes forming a complex jigsaw puzzle arrangement of cast contents, indicative of the fragility of the immunoglobulin light chains involved, and reactive tubular cells lining the tubules with the casts. These features were seen in 95.2% of MCN cases and none of the casts in other renal conditions. Myeloma casts exhibited light chain monoclonality in a significant percentage of the MCN cases and often no staining for IgA or IgM. In contrast, the majority of non-myeloma casts stained for both kappa and lambda light chains, lgA, and lgM, and showed ultrastructurally a rather uniform finely to coarsely granular electron density occasionally admixed with cellular debris.

Macrophages in the reticuloendothelial system inhibit early induction stages of mouse apolipoprotein A-II amyloidosis

Amyloidosis refers to a group of degenerative diseases that are characterized by the deposition of misfolded protein fibrils in various organs. Deposited amyloid may be removed by a phagocyte-dependent innate immune system; however, the precise mechanisms during disease progression remain unclear. We herein investigated the properties of macrophages that contribute to amyloid degradation and disease progression using inducible apolipoprotein A-II amyloidosis model mice. Intravenously injected AApoAII amyloid was efficiently engulfed by reticuloendothelial macrophages in the liver and spleen and disappeared by 24 h. While cultured murine macrophages degraded AApoAII via the endosomal-lysosomal pathway, AApoAII fibrils reduced cell viability and phagocytic capacity. Furthermore, the depletion of reticuloendothelial macrophages before the induction of AApoAII markedly increased hepatic and splenic AApoAII deposition. These results highlight the physiological role of reticuloendothelial macrophages in the early stages of pathogenesis and suggest the maintenance of phagocytic integrity as a therapeutic strategy to inhibit disease progression.

Understanding AL amyloidosis with a little help from in vivo models

Monoclonal immunoglobulin (Ig) light chain amyloidosis (AL) is a rare but severe disease that may occur when a B or plasma cell clone secretes an excess of free Ig light chains (LCs). Some of these LCs tend to aggregate into organized fibrils with a β-sheet structure, the so-called amyloid fibrils, and deposit into the extracellular compartment of organs, such as the heart or kidneys, causing their dysfunction. Recent findings have confirmed that the core of the amyloid fibrils is constituted by the variable (V) domain of the LCs, but the mechanisms underlying the unfolding and aggregation of this fragment and its deposition are still unclear. Moreover, in addition to the mechanical constraints exerted by the massive accumulation of amyloid fibrils in organs, the direct toxicity of these variable domain LCs, full-length light chains, or primary amyloid precursors (oligomers) seems to play a role in the pathogenesis of the disease. Many in vitro studies have focused on these topics, but the variability of this disease, in which each LC presents unique properties, and the extent and complexity of affected organs make its study in vivo very difficult. Accordingly, several groups have focused on the development of animal models for years, with some encouraging but mostly disappointing results. In this review, we discuss the experimental models that have been used to better understand the unknowns of this pathology with an emphasis on in vivo approaches. We also focus on why reliable AL amyloidosis animal models remain so difficult to obtain and what this tells us about the pathophysiology of the disease.

Glomerulopathic Light Chain-Mesangial Cell Interactions: Sortilin-Related Receptor (SORL1) and Signaling

INTRODUCTION

Deciphering the intricacies of the interactions of glomerulopathic Ig light chains with mesangial cells is key to delineate signaling events responsible for the mesangial pathologic alterations that ensue.

METHODS

Human mesangial cells, caveolin 1 (CAV1), wild type (WT) ,and knockout (KO), were incubated with glomerulopathic light chains purified from the urine of patients with light chain-associated (AL) amyloidosis or light chain deposition disease. Associated signaling events induced by surface interactions of glomerulopathic light chains with caveolins and other membrane proteins, as well as the effect of epigallocatechin-3-gallate (EGCG) on the capacity of mesangial cells to intracellularly process AL light chains were investigated using a variety of techniques, including chemical crosslinking with mass spectroscopy, immunofluorescence, and ultrastructural immunolabeling.

RESULTS

Crosslinking experiments provide evidence suggesting that sortilin-related receptor (SORL1), a transmembrane sorting receptor that regulates cellular trafficking of proteins, is a component of the receptor on mesangial cells for glomerulopathic light chains. Colocalization of glomerulopathic light chains with SORL1 in caveolae and also in lysosomes when light chain internalization occurred, was documented using double immunofluorescence and immunogold labeling ultrastructural techniques. It was found that EGCG directly blocks c-Fos cytoplasmic to nuclei signal translocation after interactions of AL light chains with mesangial cells, resulting in a decrease in amyloid formation.

CONCLUSION

Our findings document for the first time a role for SORL1 linked to glomerular pathology and signaling events that take place when certain monoclonal light chains interact with mesangial cells. This finding may lead to novel therapies for treating renal injury caused by glomerulopathic light chains.

Identification of critical amino acid residues in the regulatory N-terminal domain of PMEL

The pigment cell-specific protein PMEL forms a functional amyloid matrix in melanosomes onto which the pigment melanin is deposited. The amyloid core consists of a short proteolytic fragment, which we have termed the core-amyloid fragment (CAF) and perhaps additional parts of the protein, such as the PKD domain. A highly O-glycosylated repeat (RPT) domain also derived from PMEL proteolysis associates with the amyloid and is necessary to establish the sheet-like morphology of the assemblies. Excluded from the aggregate is the regulatory N-terminus, which nevertheless must be linked in cis to the CAF in order to drive amyloid formation. The domain is then likely cleaved away immediately before, during, or immediately after the incorporation of a new CAF subunit into the nascent amyloid. We had previously identified a 21 amino acid long region, which mediates the regulatory activity of the N-terminus towards the CAF. However, many mutations in the respective segment caused misfolding and/or blocked PMEL export from the endoplasmic reticulum, leaving their phenotype hard to interpret. Here, we employ a saturating mutagenesis approach targeting the motif at single amino acid resolution. Our results confirm the critical nature of the PMEL N-terminal region and identify several residues essential for PMEL amyloidogenesis.

Renal Expression of Light Chain Binding Proteins

Overproduction of human light chains (LCs) and immunoglobulins can result in various forms of renal disease such as cast nephropathy, monoclonal immunoglobulin deposition disease, LC proximal tubulopathy, AL amyloidosis, and crystal storing histiocytosis. This is caused by cellular uptake of LCs and overwhelmed intracellular transport and degradation in patients with high urine LC concentrations. LC kappa and lambda purification was evaluated by sodium dodecyl sulfate gel electrophoresis. LC and myeloma protein binding to immobilized renal proteins was measured by enzyme-linked immunosorbent assay (ELISA). The human protein microarray (HuProt™) was screened with purified kappa and lambda LC. Identified LC partners were subsequently analyzed in silico for renal expression sites using protein databases, Human Protein Atlas, UniProt, and Bgee. Binding of urinary LCs and immunoglobulins to immobilized whole renal proteins from 22 patients with myeloma or plasma cell dyscrasia was shown by ELISA. Forty lambda and 23 kappa interaction partners were identified from HuProt™ array screens, of which 21 were shared interactors. Among the total of 42 interactors, 12 represented cell surface proteins. Lambda binding signals were approximately 40% higher than kappa signals. LC interaction with renal cells and disease-causing pathologies are more complex than previously thought. It involves an extended spectrum of proteins expressed throughout the nephron, and their identification has been enabled by recently developed methods of protein analysis such as protein microarray screening. Further biochemical studies on interacting proteins are warranted to elucidate their clinical relevance.

Myeloma cast nephropathy with diffuse amyloid casts without systemic amyloidosis: two cases report

Background

Multiple myeloma (MM) is a plasma-cell derived hematologic malignant disease. The malignant proliferating plasma cells secrete massive monoclonal immunoglobulins which lead to various pathologic types of renal injury. Myeloma cast nephropathy (MCN) is the most common histopathologic lesion with the worst renal prognosis. Rarely, the free light chains in the protein casts can form amyloid fibrils. Here, we reported two rare cases of MCN with diffuse amyloid casts.

Case presentation

Case 1: A 54-year-old Chinese man presented with a 4-year history of multiple myeloma, proteinuria and hematuria. He had monoclonal IgAλ plus free λ spike in both serum and urine. He had been on chemotherapy for 4 years and maintained normal serum creatinine until 11 months ago. Then, his renal function deteriorated and he went on hemodialysis 4 months before admission. Renal biopsy showed diffuse amyloid casts in the tubular lumens, without any obvious amyloid deposits in other kidney compartments or signs of extra-renal amyloidosis. The amyloid fibrils formed around mononuclear cells which were CD68 negative. According to the morphology and location, these mononuclear cells were considered as tubular epithelial cells. The patient was maintained on chemotherapy and hemodialysis. He died 8 months after renal biopsy.

Case 2: A 58-year-old Chinese man presented with a one-and-a-half-year history of proteinuria and slowly rising serum creatinine. He had monoclonal IgDλ spike in both serum and urine. Amyloid casts were observed in the tubular lumens and mononuclear cells could be identified in the center of some casts. There were no amyloid deposits in other kidney compartments and no sign of systemic amyloidosis. The patient also had fine granular deposits along the tubular basement membrane with λ linear staining along tubular basement membrane suggesting light chain deposition disease. He was treated with bortezomib-based chemotherapy followed by lenalidomide-based chemotherapy and achieved very good partial remission (VGPR). After 27 months of follow-up, the patient still showed no signs of systemic amyloidosis.

Conclusions

These 2 cases of MCN with diffuse amyloid casts have different histopathologic characteristics from the usual myeloma casts and tubular epithelial cells might play important roles in the pathogenesis.

Renal amyloidosis with emphasis on the diagnostic role of electron microscopy

Our understanding of renal diseases with structured deposits has improved in the last two decades with the development of new diagnostic techniques that also changed the role of ultrastructural pathology in diagnostic decision-making. This review article addresses the current role of electron microscopy in the evaluation of structured deposits and discusses the impact of new developments. The diagnosis in a subset of structured deposits, amyloidosis, relies on morphologic and tinctorial characteristics at the light microscopic level. Congo red staining of tissue with demonstrable birefringence upon polarization has been regarded as the mainstay during tissue evaluation; however, there are pitfalls that must be considered, and electron microscopy remains a crucial adjunct investigative tool. Ultrastructurally the amyloid fibrils are unique with their characteristic appearance. They are randomly arranged, rigid, criss-crossing, non-branching, 7-15 nm (0.07-0.15 um) in diameter and of variable length. The morphology of fibrils is very similar in the different types of amyloidosis. By scanning electron microscopy amyloid fibrils appear artfully displayed. Immunofluorescence and immunohistochemical stains can be used to characterize the type of amyloidosis while mass spectroscopy is extremely useful in cases where typing of the amyloid using the above-mentioned techniques is difficult or equivocal.

Novel challenges in the management of immunoglobulin light chain amyloidosis: from the bench to the bedside

INTRODUCTION

Immunoglobulin light chain (AL) amyloidosis is one of the most frequent systemic amyloidosis in Western countries. It is caused by a B-cell clone producing a misfolded light chain (LC) that deposits in organs.

AREAS COVERED

The review examines recent findings on pathophysiology and clinical management of AL amyloidosis. It contains an update on the recent hot topics as novel therapeutic approaches, definition of relapse, and hematologic response assessment. To review literature on AL amyloidosis, a bibliographic search was performed using PubMed.

EXPERT OPINION

Due to the proteotoxicity of amyloidogenic LCs, the therapeutic goal is a rapid and profound decrease in their concentration. The standard treatment is a risk-adapted chemotherapy targeting the B-cell clone. Novel, promising drugs, as daratumumab, are currently under evaluation in newly-diagnosed and relapsed/refractory patients. New sensitive techniques, as mass spectrometry approach and bone marrow minimal residual disease assessment, are available to evaluate depth of response. After first-line therapy, increase in LC concentration may precede worsening of organ dysfunction and should be considered carefully. Further clarification of molecular mechanisms of the disease are shedding light on new possible therapeutic targets. Innovative treatment strategies and novel technologies will improve our ability to treat AL amyloidosis, preventing organ deterioration.

Understanding Mesangial Pathobiology in AL-Amyloidosis and Monoclonal Ig Light Chain Deposition Disease

Patients with plasma cell dyscrasias produce free abnormal monoclonal Ig light chains that circulate in the blood stream. Some of them, termed glomerulopathic light chains, interact with the mesangial cells and trigger, in a manner dependent of their structural and physicochemical properties, a sequence of pathological events that results in either light chain–derived (AL) amyloidosis (AL-Am) or light chain deposition disease (LCDD). The mesangial cells play a key role in the pathogenesis of both diseases. The interaction with the pathogenic light chain elicits specific cellular processes, which include apoptosis, phenotype transformation, and secretion of extracellular matrix components and metalloproteinases. Monoclonal light chains associated with AL-Am but not those producing LCDD are avidly endocytosed by mesangial cells and delivered to the mature lysosomal compartment where amyloid fibrils are formed. Light chains from patients with LCDD exert their pathogenic signaling effect at the cell surface of mesangial cells. These events are generic mesangial responses to a variety of adverse stimuli, and they are similar to those characterizing other more frequent glomerulopathies responsible for many cases of end-stage renal disease. The pathophysiologic events that have been elucidated allow to propose future therapeutic approaches aimed at preventing, stopping, ameliorating, or reversing the adverse effects resulting from the interactions between glomerulopathic light chains and mesangium.

Macrophage-Mediated Phagocytosis and Dissolution of Amyloid-Like Fibrils in Mice, Monitored by Optical Imaging

Light chain-associated amyloidosis is characterized by the extracellular deposition of amyloid fibrils in abdominothoracic organs, skin, soft tissue, and peripheral nerves. Phagocytic cells of the innate immune system appear to be ineffective at clearing the material; however, human light chain amyloid extract, injected subcutaneously into mice, is rapidly cleared in a process that requires neutrophil activity. To better elucidate the phagocytosis of light chain fibrils, a potential method of cell-mediated dissolution, amyloid-like fibrils were labeled with the pH-sensitive dye pHrodo red and a near infrared fluorophore. After injecting this material subcutaneously in mice, optical imaging was used to quantitatively monitor phagocytosis and dissolution of fibrils concurrently. Histologic evaluation of the residual fibril masses revealed the presence of CD68⁺, F4/80⁺, ionized calcium binding adaptor molecule 1^- macrophages containing Congo red-stained fibrils as well as neutrophil-associated proteins with no evidence of intact neutrophils. These data suggest an early infiltration of neutrophils, followed by extensive phagocytosis of the light chain fibrils by macrophages, leading to dissolution of the mass. Optical imaging of this novel murine model, coupled with histologic evaluation, can be used to study the cellular mechanisms underlying dissolution of synthetic amyloid-like fibrils and human amyloid extracts. In addition, it may serve as a test bed to evaluate investigational opsonizing agents that might serve as therapeutic agents for light chain-associated amyloidosis.

Bifunctional amyloid-reactive peptide promotes binding of antibody 11-1F4 to diverse amyloid types and enhances therapeutic efficacy

Amyloidosis is a malignant pathology associated with the formation of proteinaceous amyloid fibrils that deposit in organs and tissues, leading to dysfunction and severe morbidity. More than 25 proteins have been identified as components of amyloid, but the most common form of systemic amyloidosis is associated with the deposition of amyloid composed of Ig light chains (AL). Clinical management of amyloidosis focuses on reducing synthesis of the amyloid precursor protein. However, recently, passive immunotherapy using amyloid fibril-reactive antibodies, such as 11-1F4, to remove amyloid from organs has been shown to be effective at restoring organ function in patients with AL amyloidosis. However, 11-1F4 does not bind amyloid in all AL patients, as evidenced by PET/CT imaging, nor does it efficiently bind the many other forms of amyloid. To enhance the reactivity and expand the utility of the 11-1F4 mAb as an amyloid immunotherapeutic, we have developed a pretargeting "peptope" comprising a multiamyloid-reactive peptide, p5+14, fused to a high-affinity peptide epitope recognized by 11-1F4. The peptope, known as p66, bound the 11-1F4 mAb in vitro with subnanomolar efficiency, exhibited multiamyloid reactivity in vitro and, using tissue biodistribution and SPECT imaging, colocalized with amyloid deposits in a mouse model of systemic serum amyloid A amyloidosis. Pretreatment with the peptope induced 11-1F4 mAb accumulation in serum amyloid A deposits in vivo and enhanced 11-1F4-mediated dissolution of a human AL amyloid extract implanted in mice.

Immunoglobulin light chain amyloid aggregation

Light chain (AL) amyloidosis is a devastating, complex, and incurable protein misfolding disease. It is characterized by an abnormal proliferation of plasma cells (fully differentiated B cells) producing an excess of monoclonal immunoglobulin light chains that are secreted into circulation, where the light chains misfold, aggregate as amyloid fibrils in target organs, and cause organ dysfunction, organ failure, and death. In this article, we will review the factors that contribute to AL amyloidosis complexity, the findings by our laboratory from the last 16 years and the work from other laboratories on understanding the structural, kinetics, and thermodynamic contributions that drive immunoglobulin light chain-associated amyloidosis. We will discuss the role of cofactors and the mechanism of cellular damage. Last, we will review our recent findings on the high resolution structure of AL amyloid fibrils. AL amyloidosis is the best example of protein sequence diversity in misfolding diseases, as each patient has a unique combination of germline donor sequences and multiple amino acid mutations in the protein that forms the amyloid fibril.

Kidney disease models: tools to identify mechanisms and potential therapeutic targets

Acute kidney injury (AKI) and chronic kidney disease (CKD) are worldwide public health problems affecting millions of people and have rapidly increased in prevalence in recent years. Due to the multiple causes of renal failure, many animal models have been developed to advance our understanding of human nephropathy. Among these experimental models, rodents have been extensively used to enable mechanistic understanding of kidney disease induction and progression, as well as to identify potential targets for therapy. In this review, we discuss AKI models induced by surgical operation and drugs or toxins, as well as a variety of CKD models (mainly genetically modified mouse models). Results from recent and ongoing clinical trials and conceptual advances derived from animal models are also explored.

Growth differentiation factor-15 is a new biomarker for survival and renal outcomes in light chain amyloidosis

GDF-15 level is a new prognostic factor for survival in AL amyloidosis, and its reduction after therapy is associated with better outcome. GDF-15 level is probably the strongest predictor for renal outcomes in patients with AL amyloidosis.

Stability and aggregation propensity do not fully account for the association of various germline variable domain gene segments with light chain amyloidosis

Variable domain (VL) gene segments exhibit variable tendencies to be associated with light chain amyloidosis (AL). While few of them are very frequent in AL and give rise to most of the amyloidogenic light chains compiled at the sequence databases, other are rarely found among the AL cases. To analyze to which extent these tendencies depend on folding stability and aggregation propensity of the germline VL protein, we characterized VL proteins encoded by four AL-associated germline gene segments and one not associated to AL. We found that the AL-associated germline rVL proteins differ widely in conformational stability and propensity to in vitro amyloid aggregation. While in vitro the amyloid formation kinetics of these proteins correlate well with their folding stabilities, the folding stability does not clearly correlate with their germline's frequencies in AL. We conclude that the association of the VL genes segments to amyloidosis is not determined solely by the folding stability and aggregation propensity of the germline VL protein. Other factors, such as the frequencies of destabilizing mutations and susceptibility to proteolysis, must play a role in determining the light chain amyloidogenicity.

Viewing Extrinsic Proteotoxic Stress Through the Lens of Amyloid Cardiomyopathy

Proteotoxicity refers to toxic stress caused by misfolded proteins of extrinsic or intrinsic origin and plays an integral role in the pathogenesis of cardiovascular diseases. Herein, we provide an overview of the current understanding of mechanisms underlying proteotoxicity and its contribution in the pathogenesis of amyloid cardiomyopathy.

Light chain amyloidosis: Where are the light chains from and how they play their pathogenic role?

Amyloid light-chain (AL) amyloidosis is a plasma-cell dyscrasia, as well as the most common type of systematic amyloidosis. Pathogenic plasma cells that have distinct cytogenetic and molecular properties secrete an excess amount of amyloidogenic light chains. Assisted by post-translational modifications, matrix components, and other environmental factors, these light chains undergo a conformational change that triggers the formation of amyloid fibrils that overrides the extracellular protein quality control system. Moreover, the amyloidogenic light-chain itself is cytotoxic. As a consequence, organ dysfunction is caused by both organ architecture disruption and the direct cytotoxic effect of amyloidogenic light chains. Here, we reviewed the molecular mechanisms underlying this sequence of events that ultimately leads to AL amyloidosis and also discuss current in vitro and in vivo models, as well as relevant novel therapeutic approaches.

Melanosomal formation of PMEL core amyloid is driven by aromatic residues

PMEL is a pigment cell protein that forms physiological amyloid in melanosomes. Many amyloids and/or their oligomeric precursors are toxic, causing or contributing to severe, incurable diseases including Alzheimer’s and prion diseases. Striking similarities in intracellular formation pathways between PMEL and various pathological amyloids including Aβ and PrP^Sc suggest PMEL is an excellent model system to study endocytic amyloid. Learning how PMEL fibrils assemble without apparent toxicity may help developing novel therapies for amyloid diseases. Here we identify the critical PMEL domain that forms the melanosomal amyloid core (CAF). An unbiased alanine-scanning screen covering the entire region combined with quantitative electron microscopy analysis of the full set of mutants uncovers numerous essential residues. Many of these rely on aromaticity for function suggesting a role for π-stacking in melanosomal amyloid assembly. Various mutants are defective in amyloid nucleation. This extensive data set informs the first structural model of the CAF and provides insights into how the melanosomal amyloid core forms.

Paraprotein-Related Kidney Disease: Kidney Injury from Paraproteins-What Determines the Site of Injury?

Disorders of plasma and B cells leading to paraproteinemias are associated with a variety of renal diseases. Understanding the mechanisms of injury and associated nephropathies provides a framework that aids clinicians in prompt diagnosis and appropriate adjunctive treatment of these disorders. Glomerular diseases that may be associated with paraproteinemias include amyloid deposition, monoclonal Ig deposition disease, proliferative GN with monoclonal Ig deposits, C3 glomerulopathy caused by alterations in the complement pathway, immunotactoid glomerulopathy, fibrillary GN, and cryoglobulinemia. Tubular lesions include the classic Fanconi syndrome, light-chain proximal tubulopathy, interstitial fibrosis, and cast nephropathy. These paraproteinemic renal diseases are distinct in their pathogenesis as well as their urinary and kidney biopsy findings. Renal pathology is usually initiated by deposition and direct involvement of the intact monoclonal Ig or Ig fragments with resident cells of the nephron. Our review summarizes current insights into the underlying molecular pathogenesis of these interesting kidney lesions.

Amyloid Fibres: Inert End-Stage Aggregates or Key Players in Disease?

The formation of amyloid fibres is a hallmark of amyloid disorders. Nevertheless, the lack of correlation between fibre load and disease as observed, for example, in Alzheimer's disease, means that fibres are considered secondary contributors to the onset of cellular dysfunction. Instead, soluble intermediates of amyloid assembly are often described as the agents of toxicity. Here, we discuss recent experimental discoveries which suggest that amyloid fibres should be considered as disease-relevant species that can mediate a range of pathological processes. These include disruption of biological membranes, secondary nucleation, amyloid aggregate transmission, and the disruption of protein homeostasis (proteostasis). Thus, a greater understanding of amyloid fibre biology could enhance prospects of developing therapeutic interventions against this devastating class of protein-misfolding disorders.

Mesangial cells as amyloid factory: a unique contribution of animal models

AL amyloidosis is a severe complication of plasma-cell disorders, secondary to monoclonal immunoglobulin light chain (LC) deposition in the kidney and other organs. Though the physicochemical properties of amyloid-forming monoclonal LCs have been demonstrated to be involved in their propensity to aggregate, it remains unclear where, when, and finally why amyloid fibrils are formed in vivo. Teng et al. shed light on this long-standing issue thanks to a new animal model.

Translational value of animal models of kidney failure

Acute kidney injury (AKI) and chronic kidney disease (CKD) are associated with decreased renal function and increased mortality risk, while the therapeutic armamentarium is unsatisfactory. The availability of adequate animal models may speed up the discovery of biomarkers for disease staging and therapy individualization as well as design and testing of novel therapeutic strategies. Some longstanding animal models have failed to result in therapeutic advances in the clinical setting, such as kidney ischemia-reperfusion injury and diabetic nephropathy models. In this regard, most models for diabetic nephropathy are unsatisfactory in that they do not evolve to renal failure. Satisfactory models for additional nephropathies are needed. These include anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, IgA nephropathy, anti-phospholipase-A2-receptor (PLA2R) membranous nephropathy and Fabry nephropathy. However, recent novel models hold promise for clinical translation. Thus, the AKI to CKD translation has been modeled, in some cases with toxins of interest for human CKD such as aristolochic acid. Genetically modified mice provide models for Alport syndrome evolving to renal failure that have resulted in clinical recommendations, polycystic kidney disease models that have provided clues for the development of tolvaptan, that was recently approved for the human disease in Japan; and animal models also contributed to target C5 with eculizumab in hemolytic uremic syndrome. Some ongoing trials explore novel concepts derived from models, such TWEAK targeting as tissue protection for lupus nephritis. We now review animal models reproducing diverse, genetic and acquired, causes of AKI and CKD evolving to kidney failure and discuss the contribution to clinical translation and prospects for the future.