Novel pathologic scoring tools predict end-stage kidney disease in light chain (AL) amyloidosis

Spatial resolution of renal amyloid deposits through MALDI-MSI: a combined digital and molecular approach to monoclonal gammopathies

AIMS

Identification and characterisation of monoclonal gammopathies of renal significance (MGRS) is critical for therapeutic purposes. Amyloidosis represents one of the most common forms of MGRS, and renal biopsy remains the gold standard for their classification, although mass spectrometry has shown greater sensitivity in this area.

METHODS

In the present study, a new in situ proteomic technique, matrix-assisted laser desorption/ionisation mass spectrometry imaging (MALDI-MSI), is investigated as an alternative to conventional laser capture microdissection MS for the characterisation of amyloids. MALDI-MSI was performed on 16 cases (3 lambda light chain amyloidosis (AL), 3 AL kappa, 3 serum amyloid A amyloidosis (SAA), 2 lambda light chain deposition disease (LCDD), 2 challenging amyloid cases and 3 controls). Analysis began with regions of interest labelled by the pathologist, and then automatic segmentation was performed.

RESULTS

MALDI-MSI correctly identified and typed cases with known amyloid type (AL kappa, AL lambda and SAA). A 'restricted fingerprint' for amyloid detection composed of apolipoprotein E, serum amyloid protein and apolipoprotein A1 showed the best automatic segmentation performance (area under the curve >0.7).

CONCLUSIONS

MALDI-MSI correctly assigned minimal/challenging cases of amyloidosis to the correct type (AL lambda) and identified lambda light chains in LCDD cases, highlighting the promising role of MALDI-MSI for amyloid typing.

Tubular basement membrane amyloid deposition: is it an indicator of renal progression in light chain amyloidosis?

In light chain amyloidosis (LA), the massive glomerular and vascular amyloid deposition leading to interstitial fibrosis/tubular atrophy (IFTA) is thought to be responsible for renal failure. The amyloid deposition in the interstitium and the tubular basement membrane (TBM) has received less attention in the study of LA. We, therefore, collected clinical and laboratory data on patients diagnosed with LA in our Nephrology Department and studied amyloid deposition in the TBM. Twelve LA patients were diagnosed by renal biopsy during a seven-year period. In 4 of the 12, amyloid deposition could also be detected in the TBM. In our first case of a patient with diabetes mellitus, non-amyloid fibrils resembling 'diabetic fibrillosis' were also seen by electron microscopy. Despite the double damage, IFTA was negligible, blood vessels were unaffected, and the glomerular deposition was segmental. In the other three cases, significant (>50%) IFTA and a severely reduced estimated glomerular filtration rate were already detected at the time of diagnosis and amyloid deposition was also observed in the blood vessels. These findings indicate the importance of TBM amyloid deposition in the progression of renal disease. This may represent a late-stage presentation of the disease with a heavy LC burden.

Congo Red Staining in Digital Pathology: The Streamlined Pipeline for Amyloid Detection Through Congo Red Fluorescence Digital Analysis

Renal amyloidosis is a rare condition caused by the progressive accumulation of misfolded proteins within glomeruli, vessels, and interstitium, causing functional decline and requiring prompt treatment due to its significant morbidity and mortality. Congo red (CR) stain on renal biopsy samples is the gold standard for diagnosis, but the need for polarized light is limiting the digitization of this nephropathology field. This study explores the feasibility and reliability of CR fluorescence on virtual slides (CRFvs) in evaluating the diagnostic accuracy and proposing an automated digital pipeline for its assessment. Whole-slide images from 154 renal biopsies with CR were scanned through a Texas red fluorescence filter (NanoZoomer S60, Hamamatsu) at the digital Nephropathology Center of the Istituto di Ricovero e Cura a Carattere Scientifico San Gerardo, Monza, Italy, and evaluated double-blinded for the detection and quantification through the amyloid score and a custom ImageJ pipeline was built to automatically detect amyloid-containing regions. Interobserver agreement for CRFvs was optimal (k = 0.90; 95% CI, 0.81-0.98), with even better concordance when consensus-based CRFvs evaluation was compared to the standard CR birefringence (BR) (k = 0.98; 95% CI, 0.93-1). Excellent performance was achieved in the assessment of amyloid score overall by CRFvs (weighted k = 0.70; 95% CI, 0.08-1), especially within the interstitium (weighted k = 0.60; 95% CI, 0.35-0.84), overcoming the misinterpretation of interstitial and capsular collagen BR. The application of an automated digital pathology pipeline (Streamlined Pipeline for Amyloid detection through CR fluorescence Digital Analysis, SPADA) further increased the performance of pathologists, leading to a complete concordance with the standard BR. This study represents an initial step in the validation of CRFvs, demonstrating its general reliability in a digital nephropathology center. The computational method used in this study has the potential to facilitate the integration of spatial omics and artificial intelligence tools for the diagnosis of amyloidosis, streamlining its detection process.

Precise diagnosis and typing of early-stage renal immunoglobulin-derived amyloidosis by label-free quantification of parallel reaction monitoring-based targeted proteomics

BACKGROUND

Early diagnosis and typing are crucial for improving the prognosis of patients with renal amyloidosis. Currently, Untargeted proteomics based precise diagnosis and typing of amyloid deposits are crucial for guiding patient management. Although untargeted proteomics achieve ultra-high-throughput by selecting the most abundant eluting cationic peptide precursors in series for tandem MS events, it lacks in sensitivity and reproducibility, which may not be suitable for early-stage renal amyloidosis with minor damages. Here, we aimed to develop parallel reaction monitoring (PRM)-based targeted proteomics to achieve high sensitivity and specificity by determining absolute abundances and codetecting all transitions of highly repeatable peptides of preselected amyloid signature and typing proteins in identifying early-stage renal immunoglobulin-derived amyloidosis.

METHODS AND RESULTS

In 10 discovery cohort cases, Congo red-stained FFPE slices were micro-dissected and analyzed by data-dependent acquisition-based untargeted proteomics for preselection of typing specific proteins and peptides. Further, a list of proteolytic peptides from amyloidogenic proteins and internal standard proteins were quantified by PRM-based targeted proteomics to validate performance for diagnosis and typing in 26 validation cohort cases. The diagnosis and typing effectiveness of PRM-based targeted proteomics in 10 early-stage renal amyloid cases was assessed via a comparison with untargeted proteomics. A peptide panel of amyloid signature proteins, immunoglobulin light chain and heave chain in PRM-based targeted proteomics showed significantly distinguishing ability and amyloid typing performance in patients. The diagnostic algorithm of targeted proteomics with a low amount of amyloid deposits in early-stage renal immunoglobulin-derived amyloidosis showed better performance than untargeted proteomics in amyloidosis typing.

CONCLUSIONS

This study demonstrates that the utility of these prioritized peptides in PRM-based targeted proteomics ensure high sensitivity and reliability for identifying early-stage renal amyloidosis. Owing to the development and clinical application of this method, rapid acceleration of the early diagnosis, and typing of renal amyloidosis is expected.

Amyloidosis: What does pathology offer? The evolving field of tissue biopsy

Since the mid-nineteenth century pathology has followed the convoluted story of amyloidosis, recognized its morphology in tissues and made identification possible using specific staining. Since then, pathology studies have made a significant contribution and advanced knowledge of the disease, so providing valuable information on the pathophysiology of amyloid aggregation and opening the way to clinical studies and non-invasive diagnostic techniques. As amyloidosis is a heterogeneous disease with various organ and tissue deposition patterns, histology evaluation, far from offering a simple yes/no indication of amyloid presence, can provide a wide spectrum of qualitative and quantitative information related to and changing with the etiology of the disease, the comorbidities and the clinical characteristics of patients. With the exception of cardiac transthyretin related amyloidosis cases, which today can be diagnosed using non-biopsy algorithms when stringent clinical criteria are met, tissue biopsy is still an essential tool for a definitive diagnosis in doubtful cases and also to define etiology by typing amyloid fibrils. This review describes the histologic approach to amyloidosis today and the current role of tissue screening biopsy or targeted organ biopsy protocols in the light of present diagnostic algorithms and various clinical situations, with particular focus on endomyocardial and renal biopsies. Special attention is given to techniques for typing amyloid fibril proteins, necessary for the new therapies available today for cardiac transthyretin related amyloidosis and to avoid patients receiving inappropriate chemotherapy in presence of plasma cell dyscrasia unrelated to amyloidosis. As the disease is still burdened with high mortality, the role of tissue biopsy in early diagnosis to assure prompt treatment is also mentioned.

Value of repeat renal biopsy in the evaluation of AL amyloidosis patients lacking renal response despite of complete hematologic remission: a case report and literature review

BACKGROUNDS

Published literatures on repeat renal biopsy of AL amyloidosis have basically reached a consensus that amyloid material deposit does not disappear or diminish after satisfactory hematologic response, regardless of renal response. However, the need of a repeat renal biopsy in such situation is still controversial.

CASE PRESENTATION

Here we reported a case of histologically confirmed λ Type renal AL amyloidosis who had been classified as Stage I and low risk at initial diagnosis. The patient received a total of six courses of CyBorD chemotherapy. She had achieved complete hematologic remission after two courses of chemotherapy but consistently had large amount of proteinuria over 10 g/day during follow up. A repeat renal biopsy was performed nine months after the first one and indicated mild to moderate increase of amyloid deposits as well as significant glomerulosclerosis and interstitial lesions, suggesting a lack of histological renal improvement despite her satisfactory hematologic response.

CONCLUSIONS

This case indicated renal involvement in AL amyloidosis could progress after successful hematologic treatment, and supported the value of repeat renal biopsy in the evaluation of AL amyloidosis patients lacking renal response despite of complete hematologic remission.

Restless Legs Syndrome Shows Increased Silent Postmortem Cerebral Microvascular Disease With Gliosis

Background

Patients with restless legs syndrome (RLS) have increased silent microvascular disease by magnetic resonance imaging. However, there has been no previous autopsy confirmation of these magnetic resonance imaging findings. RLS is also frequently associated with inflammatory and immunologically mediated medical disorders. The postmortem cortex in patients with RLS was therefore evaluated for evidence of microvascular and immunological changes.

Methods and Results

Ten microvascular injury samples of precentral gyrus in 5 patients with RLS (3 men, 2 women; mean age, 81 years) and 9 controls (2 men, 7 women; mean age, 90 years) were studied by hematoxylin and eosin stains in a blinded fashion. None of the subjects had a history of stroke or neurologic insults. In a similar manner, the following immunohistochemistry stains were performed: (1) glial fibrillary acidic protein (representing gliosis, reactive change of glial cells in response to damage); (2) CD3 (a T‐cell marker); (3) CD19 (a B‐cell marker); (4) CD68 (a macrophage marker); and (5) CD117 (a mast cell marker). Patients with RLS had significantly greater silent microvascular disease (P=0.015) and gliosis (P=0.003). T cells were increased in RLS compared with controls (P=0.009) and tended to colocalize with microvascular disease (P=0.003). Other markers did not differ. There was no correlation between microvascular lesion load and RLS severity or duration.

Conclusions

Patients with RLS had statistically significantly more silent cerebral microvascular disease and gliosis than controls compatible with previous magnetic resonance imaging studies and with studies showing a link between RLS and hypertension, clinical stroke, and cardiovascular disease. T‐cell invasion may be a secondary phenomenon.

Renal amyloidosis: validation of a proposed histological scoring system in an independent cohort

Background

In systemic amyloidosis, the kidney is frequently affected and renal involvement has a major impact on survival. Renal involvement is clinically characterized by decreased estimated glomerular filtration rate (eGFR) and proteinuria. The two most common renal amyloidosis types are light chain-related amyloidosis (AL) and serum amyloid A (AA) amyloidosis. Standardized histopathological scoring of amyloid deposits is crucial to assess disease progression. Therefore, we aimed to validate the proposed scoring system from Rubinstein et al. (Novel pathologic scoring tools predict end-stage kidney disease in light chain (AL) amyloidosis. Amyloid 2017; 24: 205–211) in an independent patient cohort.

Methods

We attempt to reproduce the scoring system, consisting of an amyloid score (AS) and a composite scarring injury score (CSIS), in a multicentre AL and AA case series. Additionally, we analysed all renal amyloidosis kidney biopsies performed in the Netherlands between 1993 and 2012.

Results

Similar to the original study, AS and CSIS correlated to eGFR (r = −0.45, P = 0.0061 and r = −0.60, P < 0.0001, respectively) but not to proteinuria at diagnosis. Furthermore, AS, but not CSIS, was associated with renal outcome. The scoring system was not reproducible in AA patients. The median incidence rate for renal amyloidosis in the Netherlands was 2.3 per million population per year, and increased during the study period.

Conclusions

In our AL case series and the original study, AS and CSIS were correlated to eGFR but not to proteinuria, and AS correlated with renal outcome. Overall, we regard this scoring system as competent for standardized histopathological assessment of amyloid deposits burden and thereby disease advancement in renal biopsies.

Development of model to predict end-stage renal disease after coronary artery bypass grafting: The ACHE score

Because end-stage renal disease (ESRD) increases the risks of morbidity and mortality, early detection and prevention of ESRD is a critical issue in clinical practice. However, no ESRD-prediction models have been developed or validated in patients undergoing coronary artery bypass grafting (CABG).This is a retrospective multicenter cohort study, recruited between January 2004 and December 2015. A cohort of 3089 patients undergoing CABG in two tertiary referral centers was analyzed to derive a risk-prediction model. The model was developed using Cox proportional hazard analyses, and its performance was assessed using C-statistics. The model was externally validated in an independent cohort of 279 patients.During the median follow-up of 6 years (maximum 13 years), ESRD occurred in 60 patients (2.0%). Through stepwise selection multivariate analyses, the following three variables were finally included in the ESRD-prediction model: postoperative Acute kidney injury, underlying Chronic kidney disease, and the number of antiHypertensive drugs (ACHE score). This model showed good performance in predicting ESRD with the following C-statistics: 0.89 (95% confidence interval [CI] 0.84-0.94) in the development cohort and 0.82 (95% CI 0.60-1.00) in the external validation cohort.The present ESRD-prediction model may be applicable to patients undergoing CABG, with the advantage of simplicity and preciseness.

Recent Advances in the Diagnosis, Risk Stratification, and Management of Systemic Light-Chain Amyloidosis

The term amyloidosis refers to a group of disorders in which protein fibrils accumulate in certain organs, disrupt their tissue architecture, and impair the function of the effected organ. The clinical manifestations and prognosis vary widely depending on the specific type of the affected protein. Immunoglobulin light-chain (AL) amyloidosis is the most common form of systemic amyloidosis, characterized by deposition of a misfolded monoclonal light-chain that is secreted from a plasma cell clone. Demonstrating amyloid deposits in a tissue biopsy stained with Congo red is mandatory for the diagnosis. Novel agents (proteasome inhibitors, immunomodulatory drugs, monoclonal antibodies, venetoclax) and autologous stem cell transplantation, used for eliminating the underlying plasma cell clone, have improved the outcome for low- and intermediate-risk patients, but the prognosis for high-risk patients is still grave. Randomized studies evaluating antibodies that target the amyloid deposits (PRONTO, VITAL) were recently stopped due to futility and currently there is an intensive search for novel treatment approaches to AL amyloidosis. Early diagnosis is of paramount importance for effective treatment and prognosis, due to the progressive nature of this disease.