Contrast-Induced Acute Kidney Injury in Patients with Heart Failure on Sodium-Glucose Cotransporter-2 Inhibitors Undergoing Radiocontrast Agent Invasive Procedures: A Propensity-Matched Analysis

(1) Background: This single-center retrospective study aimed to evaluate whether sodium-glucose cotransporter-2 inhibitors (SGLT2-i) therapy may have a nephroprotective effect to prevent contrast-induced acute kidney injury (CI-AKI) in patients with heart failure (HF) undergoing iodinated contrast medium (ICM) invasive procedures. (2) Methods: The population was stratified into SGLT2-i users and SGLT2-i non-users according to the chronic treatment with gliflozins. The primary endpoint was CI-AKI incidence during hospitalization. Secondary endpoints were all-cause mortality and the need for continuous renal replacement therapy (CRRT). (3) Results: In total, 86 patients on SGLT2-i and 179 patients not on SGLT2-i were enrolled. The incidence of CI-AKI in the gliflozin group was lower than in the non-user group (9.3 vs. 27.3%, p < 0.001), and these results were confirmed after propensity matching analysis. Multivariable logistic regression showed that only SGLT2-i treatment was an independent preventive factor for CI-AKI (OR: 0.41, 95% CI: 0.16-0.90, p = 0.045). The need for CRRT was reported only in five patients in the non-SGLT2-i-user group compared to zero patients in the gliflozin group (p = 0.05). (4) Conclusions: SGLT2-i therapy was associated with a lower risk of CI-AKI in patients with HF undergoing ICM invasive procedures.

A Clinical Workflow for Cost-Saving High-Rate Diagnosis of Genetic Kidney Diseases

SIGNIFICANCE STATEMENT

To optimize the diagnosis of genetic kidney disorders in a cost-effective manner, we developed a workflow based on referral criteria for in-person evaluation at a tertiary center, whole-exome sequencing, reverse phenotyping, and multidisciplinary board analysis. This workflow reached a diagnostic rate of 67%, with 48% confirming and 19% modifying the suspected clinical diagnosis. We obtained a genetic diagnosis in 64% of children and 70% of adults. A modeled cost analysis demonstrated that early genetic testing saves 20% of costs per patient. Real cost analysis on a representative sample of 66 patients demonstrated an actual cost reduction of 41%. This workflow demonstrates feasibility, performance, and economic effect for the diagnosis of genetic kidney diseases in a real-world setting.

BACKGROUND

Whole-exome sequencing (WES) increases the diagnostic rate of genetic kidney disorders, but accessibility, interpretation of results, and costs limit use in daily practice.

METHODS

Univariable analysis of a historical cohort of 392 patients who underwent WES for kidney diseases showed that resistance to treatments, familial history of kidney disease, extrarenal involvement, congenital abnormalities of the kidney and urinary tract and CKD stage ≥G2, two or more cysts per kidney on ultrasound, persistent hyperechoic kidneys or nephrocalcinosis on ultrasound, and persistent metabolic abnormalities were most predictive for genetic diagnosis. We prospectively applied these criteria to select patients in a network of nephrology centers, followed by centralized genetic diagnosis by WES, reverse phenotyping, and multidisciplinary board discussion.

RESULTS

We applied this multistep workflow to 476 patients with eight clinical categories (podocytopathies, collagenopathies, CKD of unknown origin, tubulopathies, ciliopathies, congenital anomalies of the kidney and urinary tract, syndromic CKD, metabolic kidney disorders), obtaining genetic diagnosis for 319 of 476 patients (67.0%) (95% in 21 patients with disease onset during the fetal period or at birth, 64% in 298 pediatric patients, and 70% in 156 adult patients). The suspected clinical diagnosis was confirmed in 48% of the 476 patients and modified in 19%. A modeled cost analysis showed that application of this workflow saved 20% of costs per patient when performed at the beginning of the diagnostic process. Real cost analysis of 66 patients randomly selected from all categories showed actual cost reduction of 41%.

CONCLUSIONS

A diagnostic workflow for genetic kidney diseases that includes WES is cost-saving, especially if implemented early, and is feasible in a real-world setting.

Pre-Dialysis B-Line Quantification at Lung Ultrasound Is a Useful Method for Evaluating the Dry Weight and Predicting the Risk of Intradialytic Hypotension

Intradialytic hypotension (IDH) is a frequent and well-known complication of hemodialysis, occurring in about one third of patients. An integrated approach with different methods is needed to minimize IDH episodes and their complications. In this prospective observational study, recruited patients underwent a multiparametric evaluation of fluid status through a lung ultrasound (LUS) with the quantification of B-lines, a physical examination, blood pressure, NT-proBNP and chest X-rays. The evaluation took place immediately before and at the end of the dialysis session, and the patients were divided into IDH and no-IDH groups. We recruited a total of 107 patients. A pre-dialysis B-line number ≥ 15 showed a high sensitivity in fluid overload diagnosis (94.5%), even higher than a chest X-ray (78%) or physical examination (72%) alone. The identification at the beginning of dialysis of <8 B-lines in the overall cohort or <20 B-lines in patients with NYHA 3−4 class are optimal thresholds for identifying those patients at higher risk of experiencing an IDH episode. In the multivariable analysis, the NYHA class, a low pre-dialysis systolic BP and a low pre-dialysis B-line number were independent risk factors for IDH. At the beginning of dialysis, the B-line quantification at LUS is a valuable and reliable method for evaluating fluid status and predicting IDH episodes. A post-dialysis B-line number <5 may allow for an understanding of whether the IDH episode was caused by dehydration, probably due to due to an overestimation of the dry weight.

Differentiation of crescent-forming kidney progenitor cells into podocytes attenuates severe glomerulonephritis in mice

Crescentic glomerulonephritis is characterized by vascular necrosis and parietal epithelial cell hyperplasia in the space surrounding the glomerulus, resulting in the formation of crescents. Little is known about the molecular mechanisms driving this process. Inducing crescentic glomerulonephritis in two Pax2Cre reporter mouse models revealed that crescents derive from clonal expansion of single immature parietal epithelial cells. Preemptive and delayed histone deacetylase inhibition with panobinostat, a drug used to treat hematopoietic stem cell disorders, attenuated crescentic glomerulonephritis with recovery of kidney function in the two mouse models. Three-dimensional confocal microscopy and stimulated emission depletion superresolution imaging of mouse glomeruli showed that, in addition to exerting an anti-inflammatory and immunosuppressive effect, panobinostat induced differentiation of an immature hyperplastic parietal epithelial cell subset into podocytes, thereby restoring the glomerular filtration barrier. Single-cell RNA sequencing of human renal progenitor cells in vitro identified an immature stratifin-positive cell subset and revealed that expansion of this stratifin-expressing progenitor cell subset was associated with a poor outcome in human crescentic glomerulonephritis. Treatment of human parietal epithelial cells in vitro with panobinostat attenuated stratifin expression in renal progenitor cells, reduced their proliferation, and promoted their differentiation into podocytes. These results offer mechanistic insights into the formation of glomerular crescents and demonstrate that selective targeting of renal progenitor cells can attenuate crescent formation and the deterioration of kidney function in crescentic glomerulonephritis in mice.

MO910: Anti-COVID-19 Vaccination and Haemodialysis: Safety During the Haemodialysis Session

BACKGROUND AND AIMS

A complex interplay lies between COVID-19 infection and kidney disease. Patients with COVID-19 are at an increased risk of acute kidney injury (AKI), while CKD patients represent a population at a high risk of mortality from COVID-19 [1]. For 3 years, our hospital has been running an intradyalitic vaccination project (HBV, Haemophylus, Pneumococcus, Influenza) for haemodialysis patients. No data regarding the anti-COVID-19 vaccination administered during the dialysis session are available yet. This is a safety study aimed at defining the feasibility of this vaccination protocol.

METHOD

A total of 186 haemodialysis patients from 3 centres were vaccinated with the Spikevax-Moderna vaccine (Fig. 1). According to Italian law, patients with a COVID-19 infection in the previous 12 months received only one dose. The administration was performed between 1 and 2 h after the start of the dialysis session. Data regarding mild adverse events were collected. In 117 patients, a titration of the anti-RBD S1 antibodies of the virus spike antigen was performed 1 month after the completion of the vaccination [2]. Therefore, a new titration was obtained after 3 months in 50 patients.

RESULTS

Of the 117 patients, 65 (55.5%) were male, with a mean age of 69.2 ± 13.1 years. Of these, 25 patients (21.3%) showed mild adverse events without compromising dialysis administration. No serious adverse events took place. Seroconversion was noticed in 111 patients (94.9%) after 1 month, with a mean anti-RBD S1 antibody titer of 751.1 ± 610.5 BAU/mL. When a new titration was performed after 3 months, the titer decreased to 203.1 ± 134.3 BAU/mL (t-test; P = 0.005).

CONCLUSION

Intradialytic vaccination is a procedure with an excellent safety profile that may be implemented in dialysis settings. Further studies should be permormed to confirm these results.

MO1057: Cost-Analysis of a Clinical Workflow for Diagnosis of Inherited Kidney Diseases

BACKGROUND AND AIMS

In the last decade, the use of whole-exome sequencing techniques (WES) has provided many insights into inherited kidney diseases that are thought to represent at least 10%–15% of cases of end-stage CKD [1]. However, among others, cost concerns limit the widespread of genomics use in daily practice [1, 2]. Publicly funded genomic testing is restricted in most health care systems [2]. Consequently, the evaluation of cost-effectiveness is urgently required in order to establish genomic sequencing as a standard diagnostic test for nephropathic patients.

The aim of this study was to perform a cost-analysis of genetic testing use in a diagnostic workflow.

METHOD

We recently set up a diagnostic workflow for the selection of patients that should undergo genetic testing in the suspicion of a genetic disease. This algorithm is applied by a network of nephrology centres on the regional territory. Selected patients are referred to a tertiary centre, Meyer University Hospital of Florence (Italy), for genetic diagnosis by WES.

We enrolled paediatric and adult patients referred to the outpatient service based on the pre-specified clinical criteria. All the patients underwent genetic testing from 2018 to June 2021.

We conducted a cost-analysis in two parts: (1) assessment of the cost-effectiveness cut-off; and (2) exploratory modeled cost-analysis using WES in different phases of the diagnostic trajectory.

As a surrogate of the cost-effectiveness analysis, we calculated the cost-effectiveness cut-off, indicating the amount of expenses for diagnostic examinations at which WES sequencing would be cost-effective.

For the exploratory cost-analysis, we defined two diagnostic trajectories: Model I, considering an ideal complete diagnostic pathway and late use of WES; and Model II, considering an early use of WES allowing to save a certain number of examinations. Genomic and non-genomic investigations were obtained from local practice, available clinical evidence and guidelines. We then calculated the cost per diagnosis according to each Model for different clinical categories and for the whole study population using the diagnostic rates of this study.

We considered only direct medical costs, based on the regional health reimbursement system, which is comprehensive of materials and human resources. The prices are expressed in euros. The analysis was conducted from a regional healthcare system perspective.

RESULTS

The analysis included 402 patients. WES performed after the standard non-conclusive diagnostic work-up (at a mean cost of €2992/patient) resulted in cost-effectiveness at a cost of &lt;€2004/patient in the study population. Looking at different clinical categories, WES was cost-effective at a cost ranging from €3336 to €770.

Overall, the exploratory cost-analysis showed Model II as cost reducing in comparison to Model I. The mean cost per diagnosis in Model I with late use of WES was estimated at €7700. Early use of WES in Model II had an estimated cost per diagnosis of €6340, leading to a cost saving of €1360/patient tested. Regarding the single clinical categories, the highest cost saving per diagnosis was obtained in podocytopathies (Model I: €13.010 versus Model II: €7261). The early use of WES produced a slight increase in estimated costs per diagnosis for tubulopathies, as well as for ciliopathies, while for syndromic CKD and metabolic kidney disorders, the costs per diagnosis did not result in major changes.

CONCLUSION

Early use of WES in the diagnostic pathway of inherited diseases, guided by a framework of specific criteria, is feasible and has the potential to produce substantial cost savings in healthcare.

FC071: An HDAC Inhibitor Attenuates Crescentic Glomerulonephritis and Avoid Chronic Kidney Disease Enhancing Podocyte Progenitor Differentiation

BACKGROUND AND AIMS

Crescentic glomerulonephritis (crescentic GN) encompasses a group of diverse disorders characterized by the presence of massive hyperplasia of parietal epithelial cells (PEC) as the main histopathological lesion at kidney biopsy. It is associated with a rapid decline in kidney function. Typically, crescent formation is the consequence of diverse upstream pathomechanisms involving the specific activation of PEC. PEC normally reside peacefully along Bowman capsule and represent in part renal progenitor cells (RPC). Previous studies observed RPC markers in crescents from patients with different types of glomerulonephritis. Similarities between stem cell niches of bone marrow and kidney, prompted us to hypothesized that crescents result from monoclonal expansion of a single RPC clone conceptually similar to monoclonal diseases originating from hematopoietic stem cells. According to this analogy, we further hypothesized that drugs known to cure monoclonal disease of the hematopoietic stem cells by enforcing their terminal differentiation could also attenuate crescentic glomerulonephritis.

METHOD

To address this hypothesis, we established a crescentic GN disease model in a conditional transgenic mouse based on the mT/mG and the Confetti reporter that allows lineage tracing and clonal analysis of RPCs. Animals were treated with known pharmacological inhibitors of clonal stem cell proliferation in myeloproliferative disorders. Crescentic lesions were characterized by super-resolution STED microscopy. Finally, we employed single cell RNA sequencing of human renal progenitor cultures to identify the immature progenitor subset-generating crescent in human to identify putative new biomarkers of crescentic GN to validate in biopsy of patients.

RESULTS

We observed that the crescentic lesions originated from the clonal expansion of single RPC, thus suggesting a clonal stem cell disorder. Therefore, we administrated a series of drugs known to ameliorates myeloproliferative neoplasms to our crescentic GN mouse model as potential therapeutic agents. Treatment with one of the compounds induced a reduction in both proteinuria and crescent formation. STED super-resolution imaging of glomeruli showed that this compound turned the uncontrolled hyperplasia of a specific immature PEC subset into a controlled differentiation into podocytes thereby restoring the injured glomerular filtration barrier. Moreover, delayed drug administration still induced proteinuria remission and avoided long-term development of chronic kidney disease (CKD), an effect associated to a continued generation of new podocytes and crescent regression over time.

Single cell RNA sequencing of human RPC identified a new marker of the crescent-generating progenitor cells. Expression of this marker in biopsies of patients with crescentic GN associated with progression toward end stage kidney disease. Treatment of human PEC with the drug that in in vivo experiments showed a therapeutic effect on crescentic GN reduced proliferation of the immature progenitor subset promoting their differentiation into podocytes.

CONCLUSION

These results demonstrate that glomerular hyperplastic lesions derive from clonal amplification of a RPC subset and that shifting proliferation to podocyte differentiation reverses improves clinical outcome and avoid CKD.

FC036: A Clinical Workflow for Selection of Patients and Cost-Efficient Diagnosis of Genetic Kidney Diseases

BACKGROUND AND AIMS

With the spread of whole-exome sequencing techniques (WES), genetic kidney diseases are increasingly recognized across all age groups. However, accessibility, interpretation of results and costs limit the widespread of genomics use in daily practice [1]. In the very last years, first experiences in the implementation of renal genetic services have been started [2]. In this work, we explored the feasibility and diagnostic performance of a service delivery model based on a territorial network for patients’ selection, followed by referral to the renal genetic clinic of a tertiary centre for WES, results interpretation and counseling. We hypothesized that higher diagnostic yield and cost-effectiveness could be achieved by implementing a workflow that could solve three problems: (1) Give clear indications to the nephrologist about which patients with kidney diseases should undergo genetic testing, (2) Increase the rate and accuracy of genetic testing and evaluate the clinical impact and (3) Identify the kidney diseases for which early genetic testing is not only clinically, but also economically convenient for the healthcare provider based on pre-specified clinical criteria for tertiary centre referral.

METHOD

We set up a multi-step diagnostic workflow. We established specific clinical criteria for evaluation of patients who should undergo genetic testing on the suspicion of a genetic disease by a network of nephrology centres. Patients selected were referred to a tertiary centre for genetic diagnosis by WES, reverse-phenotyping and multidisciplinary board analysis.

This workflow has been applied to pediatric and adult patients with kidney diseases belonging to eight clinical categories (Podocytopathies, Collagenopathies, Tubulopathies, Unknown familial nephropathies, Ciliopathies, Congenital anomalies of the kidney and urinary tract, Syndromic chronic kidney disease and Metabolic kidney disorders). We recorded clinical-laboratory-radiological information of patients included. We also performed a cost-analysis of the diagnostic workflow modelling the possible economic saving using it.

RESULTS

We included 402 patients, of note, 188 patients were female (46.8%) and 132 patients (33%) were &gt;16 years of age. We obtained a global diagnostic yield of 69.2% (278–402), with category-specific diagnostic rates ranging from 38.5% to 87%. By reverse phenotyping, we reclassified diagnoses in 74–278 (26.6%) patients, thus increasing diagnostic accuracy. Overall, reverse phenotyping increased the diagnostic rate in an average of 20% of cases, irrespective of the age at clinical onset of the disease. Diagnostic yield was independent of the age at the onset of kidney disease. Genetic testing was offered as cascade screening to 67 families, providing a genetic diagnosis in 62 family members with previously unsuspected or unspecified kidney disorders. The clinical work-up changed and was redirected on average in 50% of patients. In 11.5% of patients, the results of genetic testing helped in guiding kidney transplant decisions. Finally, cost-analysis showed that our workflow is cost-efficient allowing to potentially save a mean of 1360 euros per patient.

CONCLUSION

Ordering genetic testing, interpreting results, counselling patients and their families, and tailoring clinical management (i.e. personalized nephrology) is feasible and saves costs in a real-world setting.

OUP accepted manuscript

Podocytopathies are glomerular disorders in which podocyte injury drives proteinuria and progressive kidney disease. They encompass a broad spectrum of aetiologies, resulting in pathological pictures of minimal-changes, focal segmental glomerulosclerosis, diffuse mesangial sclerosis or collapsing glomerulopathy. Despite improvement in classifying podocytopathies as a distinct group of disorders, the histological definition fails to capture the relevant biological heterogeneity underlying each case, manifesting as extensive variability in disease progression and response to therapies. Increasing evidence suggests that podocytopathies can result from a single causative factor or a combination of multiple genetic and/or environmental risk factors with different relative contributions, identifying complex physiopathological mechanisms. Consequently, the diagnosis can still be challenging. In recent years, significant advances in genetic, microscopy and biological techniques revolutionized our understanding of the molecular mechanisms underlying podocytopathies, pushing nephrologists to integrate innovative information with more conventional data obtained from kidney biopsy in the diagnostic workflow. In this review, we will summarize current approaches in the diagnosis of podocytopathies, focusing on strategies aimed at elucidating the aetiology underlying the histological picture. We will provide several examples of an integrative view of traditional concepts and new data in patients with suspected podocytopathies, along with a perspective on how a reclassification could help to improve not only diagnostic pathways and therapeutic strategies, but also the management of disease recurrence after kidney transplantation. In the future, the advantages of precision medicine will probably allow diagnostic trajectories to be increasingly focused, maximizing therapeutic results and long-term prognosis.

The Impact of the SARS-CoV-2 Pandemic on Healthcare Provision in Italy to non-COVID Patients: a Systematic Review

BACKGROUND

Italy has been one of the countries most affected by the SARS-CoV-2 pandemic, and the regional healthcare system has had to quickly adapt its organization to meet the needs of infected patients. This has led to a drastic change in the routine management of non-communicable diseases with a potential long-term impact on patient health care. Therefore, we investigated the management of non-COVID-19 patients across all medical specialities in Italy.

METHODS

A PRISMA guideline-based systematic review of the literature was performed using PubMed, Embase, and Scopus, restricting the search to the main outbreak period in Italy (from February 20 to June 25 2020). We selected articles in English or Italian that detailed changes in the Italian hospital care for non-COVID-19 patients due to the pandemic. Our keywords included all medical specialities combined with our geographical focus (Italy) and COVID-19.

RESULTS

Of the 4643 potentially eligible studies identified by the search, 247 were included. A decrease in the management of emergencies in non-COVID patients was found together with an increase in mortality. Similarly, non-deferrable conditions met a tendency toward decreased diagnosis. All specialities have been affected by the re-organization of healthcare provision in the hub-and-spoke system and have benefited from telemedicine.

CONCLUSIONS

Our work highlights the changes in the Italian public healthcare system to tackle the developing health crisis due to the COVID-19 pandemic. The findings of our review may be useful to analyse future directions for the healthcare system in the case of new pandemic scenarios.

FC 038CRESCENTS DERIVE FROM SINGLE PODOCYTE PROGENITORS AND A DRUG ENHANCING THEIR DIFFERENTIATION ATTENUATES RAPIDLY PROGRESSIVE GLOMERULONEPHRITIS

Background and Aims

Rapidly progressive glomerulonephritis (RPGN) encompasses a group of diverse disorders characterized by the presence of massive hyperplasia of parietal epithelial cells (PEC) as the main histopathological lesion at kidney biopsy. It is associated with a rapid decline in kidney function referred to altogether as rapidly progressive glomerulonephritis. Typically, crescent formation is the consequence of diverse upstream pathomechanisms involving the specific activation of PEC. PEC normally reside peacefully along Bowman capsule and represent in part renal progenitor cells (RPC). Previous studies observed RPC markers in crescents from patients with different types of glomerulonephritis. Similarities between stem cell niches of bone marrow and kidney, prompted us to hypothesized that crescents result from monoclonal expansion of a single RPC clone conceptually similar to monoclonal diseases originating from hematopoietic stem cells. According to this analogy, we further hypothesized that drugs known to cure monoclonal disease of the hematopoietic stem cells by enforcing their terminal differentiation could also attenuate crescentic glomerulonephritis.

Method

To address this hypothesis, we established a RPGN disease model in a conditional transgenic mouse based on the mT/mG and the Confetti reporter that allows lineage tracing and clonal analysis of RPCs. Animals were treated with known pharmacological inhibitors of clonal stem cell proliferation in myeloproliferative disorders. Crescentic lesions were characterized by super-resolution STED microscopy. Finally, we employed single cell RNA sequencing of human renal progenitor cultures to identify the immature progenitor subset-generating crescent in human to identify putative new biomarker(s) of RPNG to validate in biopsy of patients.

Results

We observed that the crescentic lesions originated from the clonal expansion of single RPC, thus suggesting a clonal stem cell disorder. Therefore, we administrated a series of drugs known to ameliorates myeloproliferative neoplasms to our RPGN mouse model as potential therapeutic agents. In particular, treatment with one of the compounds induced a reduction in both proteinuria and crescent formation. 3D confocal microscopy and STED super-resolution imaging of glomeruli showed that this compound turned the uncontrolled hyperplasia of a specific immature PEC subset into a controlled differentiation into new podocytes thereby restoring the injured glomerular filtration barrier.

Single cell RNA sequencing of human renal progenitor cultures identified a new marker of the crescent-generating progenitor cells. Expression of this marker in biopsies of patients with rapidly progressive glomerulonephritis associated with progression toward end stage kidney disease. Treatment of human PEC with the drug that in in vivo experiments showed a therapeutic effect on RPGN reduced proliferation of the immature progenitor subset promoting their differentiation into podocytes.

Conclusion

These results demonstrate that glomerular hyperplastic lesions derive from clonal amplification of a RPC subset and that shifting proliferation to podocyte differentiation reverses crescent formation and improves clinical outcome.

Threatening drug-drug interaction in a kidney transplant patient with coronavirus disease 2019 (COVID-19)

During the novel coronavirus pandemic, organ transplant recipients represent a frail susceptible category due to long-term immunosuppressive therapy. For this reason, clinical manifestations may differ from general population and different treatment approaches may be needed. We present the case of a 36-year-old kidney-transplanted woman affected by Senior-Loken syndrome diagnosed with COVID-19 pneumonia after a contact with her positive mother. Initial symptoms were fatigue, dry cough, and coryza; she never had fever nor oxygen supplementation. Hydroxychloroquine and lopinavir/ritonavir were started, and the antiviral drug was replaced with darunavir/cobicistat after 2 days for diarrhea. Immunosuppressant levels were closely monitored, and we observed very high tacrolimus trough levels despite initial dose reduction. The patient was left with steroid therapy alone. The peculiarity of clinical presentation and the management difficulties represent the flagship of our case report. We stress the need for guidelines in transplant recipients with COVID-19 infection with particular regard to the management of therapy.

P0384PROTEINURIA SELECTIVITY INDEX MAY PREDICT RITUXIMAB RESPONSE IN MCD AND FSGS

Background and Aims

Proteinuria selectivity index (PSI) predicts steroid responsiveness in minimal change disease (MCD) and focal segmental glomerulosclerosis (FSGS). Rituximab, a monoclonal antibody targeting CD20, has increasingly recognized as a potential therapy of idiopathic podocytopathies, such as MCD and FSGS, although the mechanism of action is still unrecognized and randomized controlled studies are still lacking. Currently, no tools are available to predict responsiveness to RTX. We explored the role of PSI as a potential predictor of RTX responsiveness in MCD and FSGS.

Method

We analysed cases of biopsy-proven MCD and FSGS followed at one single centre, who received RTX therapy. Baseline data, including proteinuria and PSI, were collected. Proteinuria was considered selective with PSI (clearance of urinary IgG/transferrin ratio) &lt;0.20. Complete remission (CR) was resolution of proteinuria and clinical symptoms, while partial remission (PR) was proteinuria decrease (&gt;50%) and substantial improvement of clinical symptoms.

Results

RTX was administered to 14 patients with MCD and 16 patients with FSGS and, of them, PSI was available before treatment for 10 and 14 patients, respectively. Baseline characteristics of the patients are shown in Table 1. Among the 24 cases with available PSI, CR was reported in 12 and PR in 5, while 9 did not respond to RTX. All patients who achieved CR and PR had selective proteinuria at baseline, while all patients with PSI &gt;0.20 did not respond to RTX (Figure 2). Median relapse-free survival was 25.4 months. Among responders, in 10 out of 19 patients (53%) the relapse occurred between 4 and 60 months from initial treatment. No potentially life-threatening adverse events have been observed.

Conclusion

Selective proteinuria before treatment can predict the response to RTX in adult patients with steroid-dependent and refractory forms of MCD and FSGS.

Aspects of energy-linked calcium accumulation by rat heart mitochondria

When intact rat heart mitochondria were pulsed with 150 nmol of CaCl2/mg of mitochondrial protein, only a marginal stimulation of the rate of oxygen consumption was observed. This result was obtained with mitochondria isolated in either the presence or absence of nagarse. In contrast, rat liver mitochondria under similar conditions demonstrated a rapid, reversible burst of respiration associated with energy-linked calcium accumulation. Direct analysis of calcium retention using 45Ca and Millipore filtration indicated that calcium was accumulated by heart mitochondria under the above conditions via a unique energy-dependent process. The rate of translocation by heart mitochondria was less than that of liver mitochondria; likewise the release of bound calcium back into the medium was also retarded. These results suggest that the slower accumulation and release of calcium is characteristic of heart mitochondria. The amound of calcium bound was independent of penetrant anions at low calcium concentrations. Above 100 nmol/mg of mitochondrial protein, the total calcium bound was increased by the presence of inorganic phosphate. Under nonrespiring conditions, a biphasic Scatchard plot indicative of binding sites with different affinities for Ca2+ was observed. The extrapolated constants are 7.5 nmol/mg bound with an apparent half-saturation value of 75 muM and 42.5 nmol/mg bound with half-saturation at 1.15 mM. The response of the reduced State 4 cytochrome b to pulsed additions of Ca2+ was used to calculate an energy-dependent half-saturation constant of 40 muM. When the concentration of free calcium was stabilized at low levels with Ca2+-EGTA buffers, the spectrophotometrically determined binding constant decreased two orders of magnitude to an apparent affinity of 4.16 X 10(-7) M. Primary of calcium transport over oxidative phosphorylation was not observed with heart mitochondria. The phosphorylation of ADP competed with Ca2+ accumulation, depressed the rates of cation transport, and altered the profile of respiration-linked H+ movements. Consistent with these result was the observation that with liver mitochondrial the magnitude of the cytochrome b oxidation-reduction shift was greater for Ca2+ than for ADP, whereas calcium responses never surpassed the ADP response in heart mitochondria. Furthermore, Mg2+ ingibited calcium accumulation by heart mitochondria while having only a slight effect upon calcium transport in liver mitochondria. The unique energetics of heart mitochondrial calcium transport are discussed relative to the regulated flux of cations during the cardiac excitation-relaxation cycle.