Clinical course and management of children with IgA vasculitis with nephritis

BACKGROUND

IgA vasculitis is the most common vasculitis in children and is often complicated by acute nephritis (IgAVN). Risk of chronic kidney disease (CKD) among children with IgAVN remains unknown. This study aimed to describe the clinical management and kidney outcomes in a large cohort of children with IgAVN.

METHODS

This observational cohort study used the PEDSnet database to identify children diagnosed with IgAV between January 1, 2009, and February 29, 2020. Demographic and clinical characteristics were compared among children with and without kidney involvement. For children followed by nephrology, clinical course, and management patterns were described. Patients were divided into four categories based on treatment: observation, renin-angiotensin-aldosterone system (RAAS) blockade, corticosteroids, and other immunosuppression, and outcomes were compared among these groups.

RESULTS

A total of 6802 children had a diagnosis of IgAV, of whom 1139 (16.7%) were followed by nephrology for at least 2 visits over a median follow-up period of 1.7 years [0.4,4.2]. Conservative management was the most predominant practice pattern, consisting of observation in 57% and RAAS blockade in 6%. Steroid monotherapy was used in 29% and other immunosuppression regimens in 8%. Children receiving immunosuppression had higher rates of proteinuria and hypertension compared to those managed with observation (p < 0.001). At the end of follow-up, 2.6 and 0.5% developed CKD and kidney failure, respectively.

CONCLUSIONS

Kidney outcomes over a limited follow-up period were favorable in a large cohort of children with IgAV. Immunosuppressive medications were used in those with more severe presentations and may have contributed to improved outcomes. A higher resolution version of the Graphical abstract is available as Supplementary information.

CHIP protects against septic acute kidney injury by inhibiting NLRP3-mediated pyroptosis

Septic acute kidney injury (S-AKI), the most common type of acute kidney injury (AKI), is intimately related to pyroptosis and oxidative stress in its pathogenesis. Carboxy-terminus of Hsc70-interacting protein (CHIP), a U-box E3 ligase, modulates oxidative stress by degrading its targeted proteins. The role of CHIP in S-AKI and its relevance with pyroptosis have not been investigated. In this study, we showed that CHIP was downregulated in renal proximal tubular cells in lipopolysaccharide (LPS)-induced S-AKI. Besides, the extent of redox injuries in S-AKI was attenuated by CHIP overexpression or activation but accentuated by CHIP gene disruption. Mechanistically, our work demonstrated that CHIP interacted with and ubiquitinated NLRP3 to promote its proteasomal degradation, leading to the inhibition of NLRP3/ACS inflammasome-mediated pyroptosis. In summary, this study revealed that CHIP ubiquitinated NLRP3 to alleviate pyroptosis in septic renal injuries, suggesting that CHIP might be a potential therapeutic target for S-AKI.

Diarrhoea, vomiting and reduced wet nappies - a familiar story with unexpected twists

Vomiting and diarrhoea is a common presenting complaint in paediatrics. Most often it is due to a benign and self-limiting infectious illness. Here, we explore the diagnostic journey of a 7-month-old infant with these symptoms presenting in a secondary care hospital and the overnight clinical problem solving involved in tackling the unexpected complexities.

Effects of correction rate for severe hyponatremia in the intensive care unit on patient outcomes

PURPOSE

Limited evidence exists regarding outcomes associated with different correction rates of severe hyponatremia.

MATERIALS AND METHODS

This retrospective cohort analysis employed a multi-center ICU database to identify patients with sodium ≤120 mEq/L during ICU admission. We determined correction rates over the first 24 h and categorized them as rapid (> 8 mEq/L/day) or slow (≤ 8 mEq/L/day). The primary outcome was in-hospital mortality. Secondary outcomes included hospital-free days, ICU-free days, and neurological complications. We used inverse probability weighting for confounder adjustment.

RESULTS

Our cohort included 1024 patients; 451 rapid and 573 slow correctors. Rapid correction was associated with lower in-hospital mortality (absolute difference: -4.37%; 95% CI, -8.47 to -0.26%), longer hospital-free days (1.80 days; 95% CI, 0.82 to 2.79 days), and longer ICU-free days (1.16 days; 95% CI, 0.15 to 2.17 days). There was no significant difference in neurological complications (2.31%; 95% CI, -0.77 to 5.40%).

CONCLUSION

Rapid correction (>8 mEq/L/day) of severe hyponatremia within the first 24 h was associated with lower in-hospital mortality and longer ICU and hospital-free days without an increase in neurological complication. Despite major limitations, including the inability to identify the chronicity of hyponatremia, the results have important implications and warrant prospective studies.

Calponin 2 regulates ketogenesis to mitigate acute kidney injury

Calponin 2 (CNN2) is a prominent actin stabilizer. It regulates fatty acid oxidation (FAO) by interacting with estrogen receptor 2 (ESR2) to determine kidney fibrosis. However, whether CNN2 is actively involved in acute kidney injury (AKI) remains unclear. Here, we report that CNN2 was induced in human and animal kidneys after AKI. Knockdown of CNN2 preserved kidney function, mitigated tubular cell death and inflammation, and promoted cell proliferation. Distinct from kidney fibrosis, proteomics showed that the key elements in the FAO pathway have few changes during AKI, but we identified that 3-hydroxymethylglutaryl-CoA synthase 2 (Hmgcs2), a rate-limiting enzyme of endogenous ketogenesis that promotes cell self-renewal, was markedly increased in CNN2 knockdown kidneys. The ketone bodies β-hydroxybutyrate and ATP production were increased in CNN2 knockdown mice. Mechanistically, CNN2 interacts with ESR2 to negatively regulate activities of mitochondrial sirtuin 5. Activated sirtuin 5 subsequently desuccinylates Hmgcs2 to produce energy for mitigating AKI. Understanding CNN2-mediated discrete fine-tuning of protein posttranslational modification is critical to optimize organ performance after AKI.

Transcending boundaries: Unleashing the potential of multi-organ point-of-care ultrasound in acute kidney injury

Acute kidney injury (AKI) is a clinical syndrome characterized by a rapid increase in serum creatinine levels or a decrease in urine output or both. In spite of thorough history-taking, physical examination, and laboratory analysis, there are limitations in the diagnostic process and clinical monitoring of AKI. Point-of-care ultrasonography (POCUS), a limited ultrasound study performed by clinicians at the bedside, has emerged as a valuable tool in different clinical settings. In this discussion, we explore the potential of POCUS performed by nephrologists to address specific questions encountered in the diagnosis and management of AKI patients. POCUS not only aids in excluding hydronephrosis but also provides real-time insights into hemodynamics, enabling formulation of individualized treatment plans. Further studies are required to assess the impact of multi-organ POCUS on pragmatic patient outcomes related to AKI, as well as its potential in risk stratification and identification of different levels of AKI severity and pathophysiological signatures.

A phase I study of autologous mesenchymal stromal cells for severe steroid-dependent nephrotic syndrome

BACKGROUNDSevere forms of idiopathic nephrotic syndrome (INS) require prolonged immunosuppressive therapies and repeated courses of high-dose glucocorticoids. Mesenchymal stromal cells (MSCs) have promising immunomodulatory properties that may be employed therapeutically to reduce patient exposure to medications and their side effects.METHODSWe performed a phase I open-label trial assessing safety and feasibility of autologous bone marrow-derived MSCs (BM-MSCs) in children and young adults with severe forms of steroid-dependent nephrotic syndrome. Following autologous BM-MSC preparation and infusion, oral immunosuppression was tapered. Safety, efficacy, and immunomodulatory effects in vivo were monitored for 12 months.RESULTSSixteen patients (10 children, 6 adults) were treated. Adverse events were limited and not related to BM-MSC infusions. All patients relapsed during follow-up, but in the 10 treated children, time to first relapse was delayed (P = 0.02) and number of relapses was reduced (P = 0.002) after BM-MSC infusion, compared with the previous 12 months. Cumulative prednisone dose was also reduced at 12 months compared with baseline (P < 0.05). No treatment benefit was observed in adults.In children, despite tapering of immunosuppression, clinical benefit was mirrored by a significant reduction in total CD19+, mature, and memory B cells and an increase in regulatory T cells in vivo up to 3-6 months following BM-MSC infusionCONCLUSIONTreatment with autologous BM-MSCs is feasible and safely reduces relapses and immunosuppression at 12 months in children with severe steroid-dependent INS. Immunomodulatory studies suggest that repeating MSC infusions at 3-6 months may sustain benefit.TRIAL REGISTRATIONEudraCT 2016-004804-77.FUNDINGAIFA Ricerca Indipendente 2016-02364623.

The effect of dehydration, hyperchloremia and volume of fluid resuscitation on acute kidney injury in children admitted to hospital with diabetic ketoacidosis

BACKGROUND

Acute kidney injury (AKI) is a recognized comorbidity in pediatric diabetic ketoacidosis (DKA), although the exact etiology is unclear. The unique physiology of DKA makes dehydration assessments challenging, and these patients potentially receive excessive amounts of intravenous fluids (IVF). We hypothesized that dehydration is over-estimated in pediatric DKA, leading to over-administration of IVF and hyperchloremia that worsens AKI.

METHODS

Retrospective cohort of all DKA inpatients at a tertiary pediatric hospital from 2014 to 2019. A total of 145 children were included; reasons for exclusion were pre-existing kidney disease or incomplete medical records. AKI was determined by change in creatinine during admission, and comparison to a calculated baseline value. Linear regression multivariable analysis was used to identify factors associated with AKI. True dehydration was calculated from patients' change in weight, as previously validated. Fluid over-resuscitation was defined as total fluids given above the true dehydration.

RESULTS

A total of 19% of patients met KDIGO serum creatinine criteria for AKI on admission. Only 2% had AKI on hospital discharge. True dehydration and high serum urea levels were associated with high serum creatinine levels on admission (p = 0.042; p < 0.001, respectively). Fluid over-resuscitation and hyperchloremia were associated with delayed kidney recovery (p < 0.001). Severity of initial AKI was associated with cerebral edema (p = 0.018).

CONCLUSIONS

Dehydration was associated with initial AKI in children with DKA. Persistent AKI and delay to recovery was associated with hyperchloremia and over-resuscitation with IVF, potentially modifiable clinical variables for earlier AKI recovery and reduction in long-term morbidity. This highlights the need to re-address fluid protocols in pediatric DKA. A higher resolution version of the Graphical abstract is available as Supplementary information.

Circulating extracellular vesicles in human cardiorenal syndrome promote renal injury in Kidney on Chip system

BACKGROUND

Cardiorenal syndrome (CRS)-renal injury during heart failure (HF)-is linked to higher morbidity. Whether circulating extracellular vesicles (EVs) and their RNA cargo directly impact its pathogenesis remains unclear.

METHODS

We investigated the role of circulating EVs from patients with CRS on renal epithelial/endothelial cells using a microfluidic kidney-on-chip model (KOC). The small RNA cargo of circulating EVs was regressed against serum creatinine to prioritize subsets of functionally relevant EV miRNAs and their mRNA targets investigated using in silico pathway analysis, human genetics, and interrogation of expression in the KOC model and in renal tissue. The functional effects of EV-RNAs on kidney epithelial cells were experimentally validated.

RESULTS

Renal epithelial and endothelial cells in the KOC model exhibited uptake of EVs from HF patients. HF-CRS EVs led to higher expression of renal injury markers (IL18, LCN2, HAVCR1) relative to non-CRS EVs. 15 EV-miRNAs were associated with creatinine, targeting 1143 gene targets specifying pathways relevant to renal injury, including TGF beta and AMPK signaling. We observed directionally consistent changes in the expression of TGF beta pathway members (BMP6, FST, TIMP3) in the KOC model exposed to CRS EVs, which were validated in epithelial cells treated with corresponding inhibitors and mimics of miRNAs. A similar trend was observed in renal tissue with kidney injury. Mendelian randomization suggested a role for FST in renal function.

CONCLUSION

Plasma EVs in CRS patients elicit adverse transcriptional and phenotypic responses in a KOC model by regulating biologically relevant pathways, suggesting a role for EVs in CRS.

Mice lacking γENaC palmitoylation sites maintain benzamil-sensitive Na+ transport despite reduced ENaC activity

Epithelial Na+ channels (ENaCs) control extracellular fluid volume by facilitating Na+ absorption across transporting epithelia. In vitro studies showed that Cys-palmitoylation of the γ ENaC subunit is a major regulator of channel activity. We tested whether γ subunit palmitoylation sites are necessary for channel function in vivo by generating mice lacking the palmitoylated cysteines (γC33A,C41A) using CRISPR-Cas9 technology. ENaCs in dissected kidney tubules from γC33A,C41A mice had reduced open probability compared to wild type (WT) littermates maintained on either standard or Na+-deficient diets. Male mutant mice also had higher aldosterone levels than WT littermates following Na+ restriction. However, γC33A,C41A mice did not have reduced amiloride-sensitive Na+ currents in the distal colon or benzamil-induced natriuresis compared to WT mice. We identified a second, larger conductance cation channel in the distal nephron with biophysical properties distinct from ENaC. The activity of this channel was higher in Na+-restricted γC33A,C41A versus WT mice and was blocked by benzamil, providing a possible compensatory mechanism for reduced prototypic ENaC function. We conclude that γ subunit palmitoylation sites are required for prototypic ENaC activity in vivo, but are not necessary for amiloride/benzamil-sensitive Na+ transport in the distal nephron or colon.

Inhibition of retinoic acid signaling in proximal tubular epithelial cells protects against acute kidney injury

Retinoic acid receptor (RAR) signaling is essential for mammalian kidney development, but in the adult kidney is restricted to occasional collecting duct epithelial cells. We now show that there is widespread reactivation of RAR signaling in proximal tubular epithelial cells (PTECs) in human sepsis-associated acute kidney injury (AKI), and in mouse models of AKI. Genetic inhibition of RAR signaling in PTECs protected against experimental AKI but was unexpectedly associated with increased expression of the PTEC injury marker, Kim1. However, the protective effects of inhibiting PTEC RAR signaling were associated with increased Kim1 dependent apoptotic cell clearance, or efferocytosis, and this was associated with de-differentiation, proliferation, and metabolic reprogramming of PTECs. These data demonstrate the functional role that reactivation of RAR signaling plays in regulating PTEC differentiation and function in human and experimental AKI.

Severe kidney dysfunction in sialidosis mice reveals an essential role for neuraminidase 1 in reabsorption

Sialidosis is an ultrarare multisystemic lysosomal disease caused by mutations in the neuraminidase 1 (NEU1) gene. The severe Type II form of the disease, manifests with a prenatal/infantile or juvenile onset, bone abnormalities, severe neuropathology and visceromegaly. A subset of these patients presents with nephrosialidosis, characterized by abrupt onset of fulminant glomerular nephropathy. We studied the pathophysiological mechanism of the disease in two NEU1-deficient mouse models, a constitutive Neu1 knockout Neu1∆Ex3 and a conditional phagocyte-specific knockout Neu1Cx3cr1ΔEx3. Mice of both strains exhibited terminal urinary retention and severe kidney damage with elevated urinary albumin levels, loss of nephrons, renal fibrosis, presence of storage vacuoles and dysmorphic mitochondria in the intraglomerular and tubular cells. Glycoprotein sialylation in glomeruli, proximal and distal tubules was drastically increased including that of an endocytic reabsorption receptor megalin. The pool of megalin bearing O-linked glycans with terminal galactose residues, essential for protein targeting and activity, was reduced to below detection levels. Megalin levels were severely reduced, and the protein was directed to lysosomes instead of the apical membrane. Together, our results demonstrated that desialylation by NEU1 plays a crucial role in processing and cellular trafficking of megalin and that NEU1 deficiency in sialidosis impairs megalin-mediated protein reabsorption.

1,25-Dihydroxyvitamin D3 regulates furin-mediated FGF23 cleavage

Intact fibroblast growth factor 23 (iFGF23) is a phosphaturic hormone that is cleaved by furin into N-terminal and C-terminal fragments. Several studies have implicated vitamin D in regulating furin in infections. Thus, we investigated the effect of 1,25-dihydroxyvitamin D3 [1,25(OH)2D] and the vitamin D receptor (VDR) on furin-mediated iFGF23 cleavage. Mice lacking VDR (Vdr-/-) had a 25-fold increase in iFGF23 cleavage, with increased furin levels and activity compared with wild-type (WT) littermates. Inhibition of furin activity blocked the increase in iFGF23 cleavage in Vdr-/- animals and in a Vdr-knockdown osteocyte OCY454 cell line. Chromatin immunoprecipitation revealed VDR binding to DNA upstream of the Furin gene, with more transcription in the absence of VDR. In WT mice, furin inhibition reduced iFGF23 cleavage, increased iFGF23, and reduced serum phosphate levels. Similarly, 1,25(OH)2D reduced furin activity, decreased iFGF23 cleavage, and increased total FGF23. In a post hoc analysis of a randomized clinical trial, we found that ergocalciferol treatment, which increased serum 1,25(OH)2D, significantly decreased serum furin activity and iFGF23 cleavage, compared with placebo. Thus, 1,25(OH)2D inhibits iFGF23 cleavage via VDR-mediated suppression of Furin expression, thereby providing a mechanism by which vitamin D can augment phosphaturic iFGF23 levels.

Dietary potassium stimulates Ppp1Ca-Ppp1r1a dephosphorylation of kidney NaCl co-transporter and reduces blood pressure

Consumption of low dietary potassium, common with ultra-processed foods, activates the thiazide-sensitive sodium chloride cotransporter (NCC) via the WNK-SPAK kinase pathway to induce salt retention and elevate blood pressure (BP). However, it remains unclear how high potassium "DASH-like" diets inactivate the cotransporter and whether this decreases BP. A transcriptomic screen identified Ppp1C⍺, encoding PP1A, as a potassium up-regulated gene, and its negative regulator, Ppp1r1a, as a potassium-suppressed gene in the kidney. PP1A directly binds to and dephosphorylates NCC when extracellular potassium is elevated. Using mice genetically engineered to constitutively activate the NCC-regulatory kinase SPAK and thereby eliminate the effects of the WNK-SPAK kinase cascade, we confirmed that PP1A dephosphorylates NCC directly in a potassium-regulated manner. Prior adaptation to a high potassium diet was required to maximally dephosphorylate NCC and lower BP in the constitutively active SPAK mice, and this was associated with potassium-dependent suppression of Ppp1r1a, and dephosphorylation of its cognate protein, Inhibitory Subunit 1 (I1). In conclusion, potassium-dependent activation of PP1A and inhibition of I1 drives NCC dephosphorylation, providing a mechanism to explain how high dietary K+ lowers BP. Shifting signaling of PP1A in favor of activation of WNK-SPAK may provide an improved therapeutic approach for treating salt-sensitive hypertension.

Clinical characteristics and outcomes of community acquired-acute kidney injury

PURPOSE

Published works have reported the impact of a nephrologist intervention on outcomes for patients with hospital-acquired acute kidney injury (HA-AKI), however little is known about the clinical characteristics of patients with community-acquired acute kidney injury (CA-AKI) and the impact of nephrology interventions on outcomes in these patients.

METHODS

A retrospective study on all adult patients admitted to a large tertiary care hospital in 2019 who were identified to have CA-AKI were followed from hospital admission to discharge. Clinical characteristics and outcomes of these patients were analysed by receipt of nephrology consultation. Statistical analysis included descriptive, simple Chi-squared/Fischer Exact test, independent samples t-test/Mann-Whitney U test and logistic regression.

RESULTS

182 patients fulfilled the study inclusion criteria. Mean age was 75 ± 14 years, 41% were female, 64% had stage 1 AKI on admission, 35% received nephrology input and 52% had achieved recovery of kidney function by discharge. Higher admission and discharge serum creatinine (SCr) (290.5 vs 159 and 173 vs 109 µmol/L respectively, p =  < 0.001), and younger age (68 vs 79, p =  < 0.001) were associated with nephrology consultations, whilst length of hospitalisation, mortality and rehospitalisation rates were not significantly different between the two groups. At least 65% were recorded to be on at least one nephrotoxic medication.

CONCLUSION

Our findings provide a snapshot of current practice where close to two-thirds of hospitalised patients with CA-AKI had a mild form of AKI that was associated with good clinical outcomes. While higher SCr on admission and younger age were predictors of receiving a nephrology consultation, nephrology consultations did not have any impact on outcomes.

Cape York Kidney Care: service description and baseline characteristics of a client-centred multidisciplinary specialist kidney health service in remote Australia

BACKGROUND

Chronic Kidney disease (CKD) is over-represented amongst First Nation people with more than triple the rate of CKD in those aged 15 years and over. The impact of colonisation, including harmful experiences of health practices and research, has contributed to these health inequities. Cape York Kidney Care (CYKC) has been created as an unique service which provides specialist care that aims to centre the client within a multidisciplinary team that is integrated within the primary care setting of the remote health clinics in six communities in western Cape York, Australia. This research aims to describe the Cape York Kidney Care service delivery model, and baseline service data, including aggregated client health measures.

METHODS

The model of care is described in detail. Review of the first 12 months of service provision has been undertaken with client demographic and clinical profile baseline data collected including kidney health measures. Participants are adults (> 18 years if age) with CKD grades 1-5. This data has been de-identified and aggregated.

RESULTS

CYKC reviewed 204 individuals, with 182 not previously been reviewed by specialist kidney health services. Three quarters of clients identified as Aboriginal. The average age was 55 with a high level of comorbidity, with majority having a history of hypertension and Type 2 diabetes (average Hba1c 8.2%). Just under one third had cardiovascular disease. A large proportion of people had either Grade 2 CKD (32%) or Grade 3 CKD (~ 30%), and over half had severely increased albuminuria (A3), with Type 2 diabetes being the predominant presumed cause of CKD. Most clients did not meet evidence-based targets for diabetes, blood pressure or lipids and half were self-reported smokers. The proportion of clients reviewed represents 6.2% of the adult population in the participating First Nation communities.

CONCLUSION

The CYKC model was able to target those clients at high risk of progression and increase the number of people with chronic kidney disease reviewed by specialist kidney services within community. Baseline data demonstrated a high burden of chronic disease that subsequently will increase risk of CKD progression and cardiovascular disease. People were seen to have more severe disease at younger ages, with a substantial number demonstrating risk factors for rapid progression of kidney disease including poorly controlled Type 2 diabetes and severely increased albuminuria. Further evaluation concerning implementation challenges, consumer and community satisfaction, and health outcomes is required.