Multi-omics and imaging mass cytometry characterization of human kidneys to identify pathways and phenotypes associated with impaired kidney function

Despite the recent advances in our understanding of the role of lipids, metabolites, and related enzymes in mediating kidney injury, there is limited integrated multi-omics data identifying potential metabolic pathways driving impaired kidney function. The limited availability of kidney biopsies from living donors with acute kidney injury has remained a major constraint. Here, we validated the use of deceased transplant donor kidneys as a good model to study acute kidney injury in humans and characterized these kidneys using imaging and multi-omics approaches. We noted consistent changes in kidney injury and inflammatory markers in donors with reduced kidney function. Neighborhood and correlation analyses of imaging mass cytometry data showed that subsets of kidney cells (proximal tubular cells and fibroblasts) are associated with the expression profile of kidney immune cells, potentially linking these cells to kidney inflammation. Integrated transcriptomic and metabolomic analysis of human kidneys showed that kidney arachidonic acid metabolism and seven other metabolic pathways were upregulated following diminished kidney function. To validate the arachidonic acid pathway in impaired kidney function we demonstrated increased levels of cytosolic phospholipase A2 protein and related lipid mediators (prostaglandin E2) in the injured kidneys. Further, inhibition of cytosolic phospholipase A2 reduced injury and inflammation in human kidney proximal tubular epithelial cells in vitro. Thus, our study identified cell types and metabolic pathways that may be critical for controlling inflammation associated with impaired kidney function in humans.

Treatment of unstable spinopelvic fractures: outcome of three surgical techniques-a retrospective single-center case series

PURPOSE

The aim of our retrospective study is to analyze how spinopelvic dissociations (SPDs) were treated in a single center trying to better understand how to improve surgical and non-surgical options.

METHODS

Twenty patients of a single center surgically treated for SPDs between 2013 and 2021 were retrospectively included in this study. Three surgical techniques have been used: modified triangular stabilization, triangular stabilization and double iliac screws stabilization. Follow-up was assessed for up to 11.6 ± 9.9 months through ODI, MRS, NRS, IIEF or FSFI, a CT scan and whole spine X-ray examination.

RESULTS

Twenty patients were admitted to our ER for traumatic spinopelvic dissociation. Surgical treatment for spinopelvic dissociation has been performed on average 11.5 ± 6.7 days after the trauma event. Eighteen fractures were C3 type and two C2 types. Neurological examination showed nerve root injury (N2) in 5 patients, incomplete spinal cord injury (N3) in 4 patients and cauda equina syndrome in two patients (N4). In case of neurologic deficits, routinary nerve decompression was performed. Three different surgical techniques have been used: 8 triangular fixations (Group 1), 6 modified triangular stabilization (Group 2) and 6 double iliac screws triangular fixation (Group 3).

CONCLUSION

In patients with post-traumatic neurological deficit, decompression surgery and fracture reduction seem to be associated with clinical improvement; however, sexual disorders seem to be less responsive to the treatment. Some open stabilization techniques, such as the double iliac screw, could help in restoring the sagittal balance in case of severe deformities.

FC080: A Systems Nephrology Framework for the Molecular Classification of Chronic Kidney Disease

BACKGROUND

Conventional stratification by clinical and histopathological phenotypes only approximates the heterogeneity of chronic kidney disease (CKD) and is insufficient to drive discovery of disease-modifying therapies or predict clinical outcomes. Recent advances in molecular stratification offer a mechanistic approach to disease classification but are limited by the availability of rich patient cohort datasets [1]. The National Unified Renal Translational Research Enterprise (NURTuRE) is a unique prospective cohort study for CKD and idiopathic nephrotic syndrome that comprises bio-banked patient samples from a broad range of clinical diagnoses and kidney functional states. Access to diagnostic biopsies and biofluids enables in-depth histological and molecular analysis and offers unique opportunities for a mechanistic disease understanding. Importantly, anonymized rich clinical data are available through the UK Renal Registry, allowing for a comprehensive view on CKD heterogeneity. Here we used unsupervised molecular clustering and dimensionality reduction to integrate and visualize the complex relationship between molecular, morphological and clinical data in this large cohort. We aim to generate mechanistic disease understanding for patient-centric, integrated target and biomarker discovery that will enable the development of novel precision treatments.

METHODS

Diagnostic kidney biopsies were obtained from the NURTuRE biobank. Samples from 286 patients comprising 16 primary diagnoses were RNA-sequenced and passed extended control of library quality and composition. Self-organizing maps (SOM) as implemented in the OposSOM R package were used for unsupervised clustering of transcriptomes, after adjusting for batch effects and sex. We used PHATE dimensionality reduction to visualize global data structure with the aim to project clinical, morphological and molecular data onto the resulting nonlinear disease trajectories.

RESULTS

Unsupervised clustering of kidney transcriptomes inferred five groups with distinct molecular landscapes (F, E, C, A and AB) that were generally consistent with molecular clusters previously described for CKD.1 Correlation of metagenes revealed a highly polarized global data structure with cluster C connecting F and E with the opposing clusters A and AB. Gene set enrichment analysis suggested that the polarization results from strong opposing metabolic and immune signatures, likely reflecting tubular atrophy, immune response and infiltration (Figure 1A). Consistently, cluster identity was independent of primary diagnosis but aligned with disease progression as reflected by kidney function decline (eGFR), increasing inflammation (CRP) and age range (Figure 1B). PHATE dimensionality reduction revealed complex nonlinear relations of transcriptomes aligned with disease progression and interpreted as molecular disease trajectories partitioned by SOM clusters (Figure 1C). We are now integrating real-world data, including longitudinal kidney function and free-text histopathology reports, and are expanding the molecular analysis by proteomics and genomics. Initial exploration of histopathology and eGFR series suggests a nonrandom distribution of morphological risk factors and disease progression rates across molecular clusters and trajectories, highlighting unique opportunities for drug discovery.

CONCLUSIONS

Molecular stratification aligns with disease progression irrespective of clinical diagnosis, reflecting common cellular and molecular mechanisms of disease associated with kidney function decline and substantial morphological changes. Further integration of complementary datasets, including clinical time series, histopathology and multiomics, will enable mechanistic interpretation of molecular clusters and trajectories with the goal of identifying novel, targetable drivers of CKD in well-defined patient subsets.

FC080: A Systems Nephrology Framework for the Molecular Classification of Chronic Kidney Disease

BACKGROUND

Conventional stratification by clinical and histopathological phenotypes only approximates the heterogeneity of chronic kidney disease (CKD) and is insufficient to drive discovery of disease-modifying therapies or predict clinical outcomes. Recent advances in molecular stratification offer a mechanistic approach to disease classification but are limited by the availability of rich patient cohort datasets [1]. The National Unified Renal Translational Research Enterprise (NURTuRE) is a unique prospective cohort study for CKD and idiopathic nephrotic syndrome that comprises bio-banked patient samples from a broad range of clinical diagnoses and kidney functional states. Access to diagnostic biopsies and biofluids enables in-depth histological and molecular analysis and offers unique opportunities for a mechanistic disease understanding. Importantly, anonymized rich clinical data are available through the UK Renal Registry, allowing for a comprehensive view on CKD heterogeneity. Here we used unsupervised molecular clustering and dimensionality reduction to integrate and visualize the complex relationship between molecular, morphological and clinical data in this large cohort. We aim to generate mechanistic disease understanding for patient-centric, integrated target and biomarker discovery that will enable the development of novel precision treatments.

METHODS

Diagnostic kidney biopsies were obtained from the NURTuRE biobank. Samples from 286 patients comprising 16 primary diagnoses were RNA-sequenced and passed extended control of library quality and composition. Self-organizing maps (SOM) as implemented in the OposSOM R package were used for unsupervised clustering of transcriptomes, after adjusting for batch effects and sex. We used PHATE dimensionality reduction to visualize global data structure with the aim to project clinical, morphological and molecular data onto the resulting nonlinear disease trajectories.

RESULTS

Unsupervised clustering of kidney transcriptomes inferred five groups with distinct molecular landscapes (F, E, C, A and AB) that were generally consistent with molecular clusters previously described for CKD.1 Correlation of metagenes revealed a highly polarized global data structure with cluster C connecting F and E with the opposing clusters A and AB. Gene set enrichment analysis suggested that the polarization results from strong opposing metabolic and immune signatures, likely reflecting tubular atrophy, immune response and infiltration (Figure 1A). Consistently, cluster identity was independent of primary diagnosis but aligned with disease progression as reflected by kidney function decline (eGFR), increasing inflammation (CRP) and age range (Figure 1B). PHATE dimensionality reduction revealed complex nonlinear relations of transcriptomes aligned with disease progression and interpreted as molecular disease trajectories partitioned by SOM clusters (Figure 1C). We are now integrating real-world data, including longitudinal kidney function and free-text histopathology reports, and are expanding the molecular analysis by proteomics and genomics. Initial exploration of histopathology and eGFR series suggests a nonrandom distribution of morphological risk factors and disease progression rates across molecular clusters and trajectories, highlighting unique opportunities for drug discovery.

CONCLUSIONS

Molecular stratification aligns with disease progression irrespective of clinical diagnosis, reflecting common cellular and molecular mechanisms of disease associated with kidney function decline and substantial morphological changes. Further integration of complementary datasets, including clinical time series, histopathology and multiomics, will enable mechanistic interpretation of molecular clusters and trajectories with the goal of identifying novel, targetable drivers of CKD in well-defined patient subsets.

Synthesis of Taurine Analogues. Part 1: 2-Aminosulfonic Acids from Alkene–sulfur Monochloride Adducts

(±) Trans-2-aminocyclohexanesulfonic acid and (±) trans-2-aminocyclopentanesulfonic acid were prepared respectively from cyclohexene and cyclopentene by sulfur monochloride addition, followed by oxidation to 2-chlorosulfonic acid and substitution of chlorine.

CXCL12 blockade preferentially regenerates lost podocytes in cortical nephrons by targeting an intrinsic podocyte-progenitor feedback mechanism

Insufficient podocyte regeneration after injury is a central pathomechanism of glomerulosclerosis and chronic kidney disease. Podocytes constitutively secrete the chemokine CXCL12, which is known to regulate homing and activation of stem cells; hence we hypothesized a similar effect of CXCL12 on podocyte progenitors. CXCL12 blockade increased podocyte numbers and attenuated proteinuria in mice with Adriamycin-induced nephropathy. Similar studies in lineage-tracing mice revealed enhanced de novo podocyte formation from parietal epithelial cells in the setting of CXCL12 blockade. Super-resolution microscopy documented full integration of these progenitor-derived podocytes into the glomerular filtration barrier, interdigitating with tertiary foot processes of neighboring podocytes. Quantitative 3D analysis revealed that conventional 2D analysis underestimated the numbers of progenitor-derived podocytes. The 3D analysis also demonstrated differences between juxtamedullary and cortical nephrons in both progenitor endowment and Adriamycin-induced podocyte loss, with more robust podocyte regeneration in cortical nephrons with CXCL12 blockade. Finally, we found that delayed CXCL12 inhibition still had protective effects. In vitro studies found that CXCL12 inhibition uncoupled Notch signaling in podocyte progenitors. These data suggest that CXCL12-driven podocyte-progenitor feedback maintains progenitor quiescence during homeostasis, but also limits their intrinsic capacity to regenerate lost podocytes, especially in cortical nephrons. CXCL12 inhibition could be an innovative therapeutic strategy in glomerular disorders.

Gene expression profiling of the Notch-AhR-IL22 axis at homeostasis and in response to tissue injury

Notch and interleukin-22 (IL-22) signaling are known to regulate tissue homeostasis and respond to injury in humans and mice, and the induction of endogenous aryl hydrocarbon receptor (Ahr) ligands through Notch links the two pathways in a hierarchical fashion. However in adults, the species-, organ- and injury-specific gene expression of the Notch-AhR-IL22 axis components is unknown. We therefore performed gene expression profiling of DLL1, DLL3, DLL4, DLK1, DLK2, JAG1, JAG2, Notch1, Notch2, Notch3, Notch4, ADAM17/TNF-α ADAM metalloprotease converting enzyme (TACE), PSEN1, basigin (BSG)/CD147, RBP-J, HES1, HES5, HEY1, HEYL, AHR, ARNT, ARNT2, CYP1A1, CYP24A1, IL-22, IL22RA1, IL22RA2, IL10RB, and STAT3 under homeostatic conditions in ten mature murine and human organs. Additionally, the expression of these genes was assessed in murine models of acute sterile inflammation and progressive fibrosis. We show that there are organ-specific gene expression profiles of the Notch-AhR-IL22 axis in humans and mice. Although there is an overall interspecies congruency, specific differences between human and murine expression signatures do exist. In murine tissues with AHR/ARNT expression CYP1A1 and IL-22 were correlated with HES5 and HEYL expression, while in human tissues no such correlation was found. Notch and AhR signaling are involved in renal inflammation and fibrosis with specific gene expression changes in each model. Despite the presence of all Notch pathway molecules in the kidney and a model-specific induction of Notch ligands, IL-22 was only up-regulated in acute inflammation, but rapidly down-regulated during regeneration. This implies that for targeting injury responses, e.g. via IL-22, species-specific differences, injury type and time points have to be considered.

Immunomodulatory Molecule IRAK-M Balances Macrophage Polarization and Determines Macrophage Responses during Renal Fibrosis

Activation of various innate immune receptors results in IL-1 receptor-associated kinase (IRAK)-1/IRAK-4-mediated signaling and secretion of proinflammatory cytokines such as IL-12, IL-6, or TNF-α, all of which are implicated in tissue injury and elevated during tissue remodeling processes. IRAK-M, also known as IRAK-3, is an inhibitor of proinflammatory cytokine and chemokine expression in intrarenal macrophages. Innate immune activation contributes to both acute kidney injury and tissue remodeling that is associated with chronic kidney disease (CKD). Our study assessed the contribution of macrophages in CKD and the role of IRAK-M in modulating disease progression. To evaluate the effect of IRAK-M in chronic renal injury in vivo, a mouse model of unilateral ureteral obstruction (UUO) was employed. The expression of IRAK-M increased within 2 d after UUO in obstructed compared with unobstructed kidneys. Mice deficient in IRAK-M were protected from fibrosis and displayed a diminished number of alternatively activated macrophages. Compared to wild-type mice, IRAK-M-deficient mice showed reduced tubular injury, leukocyte infiltration, and inflammation following renal injury as determined by light microscopy, immunohistochemistry, and intrarenal mRNA expression of proinflammatory and profibrotic mediators. Taken together, these results strongly support a role for IRAK-M in renal injury and identify IRAK-M as a possible modulator in driving an alternatively activated profibrotic macrophage phenotype in UUO-induced CKD.

Systems biology analysis reveals role of MDM2 in diabetic nephropathy

To derive new insights in diabetic complications, we integrated publicly available human protein-protein interaction (PPI) networks with global metabolic networks using metabolomic data from patients with diabetic nephropathy. We focused on the participating proteins in the network that were computationally predicted to connect the urine metabolites. MDM2 had the highest significant number of PPI connections. As validation, significant downregulation of MDM2 gene expression was found in both glomerular and tubulointerstitial compartments of kidney biopsy tissue from 2 independent cohorts of patients with diabetic nephropathy. In diabetic mice, chemical inhibition of MDM2 with Nutlin-3a led to reduction in the number of podocytes, increased blood urea nitrogen, and increased mortality. Addition of Nutlin-3a decreased WT1⁺ cells in embryonic kidneys. Both podocyte- and tubule-specific MDM2-knockout mice exhibited severe glomerular and tubular dysfunction, respectively. Interestingly, the only 2 metabolites that were reduced in both podocyte and tubule-specific MDM2-knockout mice were 3-methylcrotonylglycine and uracil, both of which were also reduced in human diabetic kidney disease. Thus, our bioinformatics tool combined with multi-omics studies identified an important functional role for MDM2 in glomeruli and tubules of the diabetic nephropathic kidney and links MDM2 to a reduction in 2 key metabolite biomarkers.

Next generation sequencing and functional analysis of patient urine renal progenitor-derived podocytes to unravel the diagnosis underlying refractory lupus nephritis

Often the cause of refractory lupus nephritis (RLN) remains unclear. We performed next-generation sequencing for podocyte genes in an RLN patient and identified compound heterozygosity for APOL1 risk alleles G1 and G2 and a novel homozygous c.[1049C>T]+[1049C>T] NPHS1 gene variant of unknown significance. To test for causality renal progenitor cells isolated from urine of this patient were differentiated into podocytes in vitro. Podocytes revealed aberrant nephrin trafficking, cytoskeletal structure and lysosomal leakage, and increased detachment as compared with podocytes isolated from controls. Thus, lupus podocytopathy can be confirmed as a cause of RLN by functional genetics on patient-derived podocytes.

Intestinal Dysbiosis, Barrier Dysfunction, and Bacterial Translocation Account for CKD-Related Systemic Inflammation

CKD associates with systemic inflammation, but the underlying cause is unknown. Here, we investigated the involvement of intestinal microbiota. We report that collagen type 4 α3-deficient mice with Alport syndrome-related progressive CKD displayed systemic inflammation, including increased plasma levels of pentraxin-2 and activated antigen-presenting cells, CD4 and CD8 T cells, and Th17- or IFNγ-producing T cells in the spleen as well as regulatory T cell suppression. CKD-related systemic inflammation in these mice associated with intestinal dysbiosis of proteobacterial blooms, translocation of living bacteria across the intestinal barrier into the liver, and increased serum levels of bacterial endotoxin. Uremia did not affect secretory IgA release into the ileum lumen or mucosal leukocyte subsets. To test for causation between dysbiosis and systemic inflammation in CKD, we eradicated facultative anaerobic microbiota with antibiotics. This eradication prevented bacterial translocation, significantly reduced serum endotoxin levels, and fully reversed all markers of systemic inflammation to the level of nonuremic controls. Therefore, we conclude that uremia associates with intestinal dysbiosis, intestinal barrier dysfunction, and bacterial translocation, which trigger the state of persistent systemic inflammation in CKD. Uremic dysbiosis and intestinal barrier dysfunction may be novel therapeutic targets for intervention to suppress CKD-related systemic inflammation and its consequences.

Murine Double Minute-2 Inhibition Ameliorates Established Crescentic Glomerulonephritis

Rapidly progressive glomerulonephritis is characterized by glomerular necroinflammation and crescent formation. Its treatment includes unspecific and toxic agents; therefore, the identification of novel therapeutic targets is required. The E3-ubiquitin ligase murine double minute (MDM)-2 is a nonredundant element of NF-κB signaling and the negative regulator of tumor suppressor gene TP53-mediated cell cycle arrest and cell death. We hypothesized that the MDM2 would drive crescentic glomerulonephritis by NF-κB-dependent glomerular inflammation and by p53-dependent parietal epithelial cell hyperproliferation. Indeed, the pre-emptive MDM2 blockade by nutlin-3a ameliorated all aspects of crescentic glomerulonephritis. MDM2 inhibition had identical protective effects in Trp53-deficient mice, with the exception of crescent formation, which was not influenced by nutlin-3a treatment. In vitro experiments confirmed the contribution of MDM2 for induction of NF-κB-dependent cytokines in murine glomerular endothelial cells and for p53-dependent parietal epithelial cell proliferation. To evaluate MDM2 blockade as a potential therapeutic intervention in rapidly progressive glomerulonephritis, we treated mice with established glomerulonephritis with nutlin-3a. Delayed onset of nutlin-3a treatment was equally protective as the pre-emptive treatment in abrogating crescentic glomerulonephritis. Together, the pathogenic effects of MDM2 are twofold, that is, p53-independent NF-κB activation increasing intraglomerular inflammation and p53-dependent parietal epithelial cell hyperplasia and crescent formation. We therefore propose MDM2 blockade as a potential novel therapeutic strategy in rapidly progressive glomerulonephritis.

Cytotoxicity of crystals involves RIPK3-MLKL-mediated necroptosis

Crystals cause injury in numerous disorders, and induce inflammation via the NLRP3 inflammasome, however, it remains unclear how crystals induce cell death. Here we report that crystals of calcium oxalate, monosodium urate, calcium pyrophosphate dihydrate and cystine trigger caspase-independent cell death in five different cell types, which is blocked by necrostatin-1. RNA interference for receptor-interacting protein kinase 3 (RIPK3) or mixed lineage kinase domain like (MLKL), two core proteins of the necroptosis pathway, blocks crystal cytotoxicity. Consistent with this, deficiency of RIPK3 or MLKL prevents oxalate crystal-induced acute kidney injury. The related tissue inflammation drives TNF-α-related necroptosis. Also in human oxalate crystal-related acute kidney injury, dying tubular cells stain positive for phosphorylated MLKL. Furthermore, necrostatin-1 and necrosulfonamide, an inhibitor for human MLKL suppress crystal-induced cell death in human renal progenitor cells. Together, TNF-α/TNFR1, RIPK1, RIPK3 and MLKL are molecular targets to limit crystal-induced cytotoxicity, tissue injury and organ failure.

Kidney stone disease is caused by accumulation of oxalate crystals, which trigger tissue injury, inflammation and cell death. Mulay et al. show that crystals induce cell death in the kidney through necroptosis, and propose that this pathway may be a target for the treatment of crystal-induced disease.

Oxalate-induced chronic kidney disease with its uremic and cardiovascular complications in C57BL/6 mice

Chronic kidney disease (CKD) research is limited by the lack of convenient inducible models mimicking human CKD and its complications in experimental animals. We demonstrate that a soluble oxalate-rich diet induces stable stages of CKD in male and female C57BL/6 mice. Renal histology is characterized by tubular damage, remnant atubular glomeruli, interstitial inflammation, and fibrosis, with the extent of tissue involvement depending on the duration of oxalate feeding. Expression profiling of markers and magnetic resonance imaging findings established to reflect inflammation and fibrosis parallel the histological changes. Within 3 wk, the mice reproducibly develop normochromic anemia, metabolic acidosis, hyperkalemia, FGF23 activation, hyperphosphatemia, and hyperparathyroidism. In addition, the model is characterized by profound arterial hypertension as well as cardiac fibrosis that persist following the switch to a control diet. Together, this new model of inducible CKD overcomes a number of previous experimental limitations and should serve useful in research related to CKD and its complications.

PMA and crystal-induced neutrophil extracellular trap formation involves RIPK1-RIPK3-MLKL signaling

Neutrophil extracellular trap (NET) formation contributes to gout, autoimmune vasculitis, thrombosis, and atherosclerosis. The outside-in signaling pathway triggering NET formation is unknown. Here, we show that the receptor-interacting protein kinase (RIPK)-1-stabilizers necrostatin-1 or necrostatin-1s and the mixed lineage kinase domain-like (MLKL)-inhibitor necrosulfonamide prevent monosodium urate (MSU) crystal- or PMA-induced NET formation in human and mouse neutrophils. These compounds do not affect PMA- or urate crystal-induced production of ROS. Moreover, neutrophils of chronic granulomatous disease patients are shown to lack PMA-induced MLKL phosphorylation. Genetic deficiency of RIPK3 in mice prevents MSU crystal-induced NET formation in vitro and in vivo. Thus, neutrophil death and NET formation may involve the signaling pathway defining necroptosis downstream of ROS production. These data imply that RIPK1, RIPK3, and MLKL could represent molecular targets in gout or other crystallopathies.

Neutrophil Extracellular Trap-Related Extracellular Histones Cause Vascular Necrosis in Severe GN

Severe GN involves local neutrophil extracellular trap (NET) formation. We hypothesized a local cytotoxic effect of NET-related histone release in necrotizing GN. In vitro, histones from calf thymus or histones released by neutrophils undergoing NETosis killed glomerular endothelial cells, podocytes, and parietal epithelial cells in a dose-dependent manner. Histone-neutralizing agents such as antihistone IgG, activated protein C, or heparin prevented this effect. Histone toxicity on glomeruli ex vivo was Toll-like receptor 2/4 dependent, and lack of TLR2/4 attenuated histone-induced renal thrombotic microangiopathy and glomerular necrosis in mice. Anti-glomerular basement membrane GN involved NET formation and vascular necrosis, whereas blocking NET formation by peptidylarginine inhibition or preemptive anti-histone IgG injection significantly reduced all aspects of GN (i.e., vascular necrosis, podocyte loss, albuminuria, cytokine induction, recruitment or activation of glomerular leukocytes, and glomerular crescent formation). To evaluate histones as a therapeutic target, mice with established GN were treated with three different histone-neutralizing agents. Anti-histone IgG, recombinant activated protein C, and heparin were equally effective in abrogating severe GN, whereas combination therapy had no additive effects. Together, these results indicate that NET-related histone release during GN elicits cytotoxic and immunostimulatory effects. Furthermore, neutralizing extracellular histones is still therapeutic when initiated in established GN.

Murine Double Minute-2 Prevents p53-Overactivation-Related Cell Death (Podoptosis) of Podocytes

Murine double minute-2 (MDM2), an E3 ligase that regulates the cell cycle and inflammation, is highly expressed in podocytes. In podocyte injury, MDM2 drives podocyte loss by mitotic catastrophe, but the function of MDM2 in resting podocytes has not been explored. Here, we investigated the effects of podocyte MDM2 deletion in vitro and in vivo. In vitro, MDM2 knockdown by siRNA caused increased expression of p53 and podocyte death, which was completely rescued by coknockdown of p53. Apoptosis, pyroptosis, pyronecrosis, necroptosis, ferroptosis, and parthanatos were excluded as modes of occurrence for this p53-overactivation-related cell death (here referred to as podoptosis). Podoptosis was associated with cytoplasmic vacuolization, endoplasmic reticulum stress, and dysregulated autophagy (previously described as paraptosis). MDM2 knockdown caused podocyte loss and proteinuria in a zebrafish model, which was consistent with the phenotype of podocyte-specific MDM2-knockout mice that also showed the aforementioned ultrastructual podocyte abnormalities before and during progressive glomerulosclerosis. The phenotype of both animal models was entirely rescued by codeletion of p53. We conclude that MDM2 maintains homeostasis and long-term survival in podocytes by preventing podoptosis, a p53-regulated form of cell death with unspecific features previously classified as paraptosis.

Toll-like receptor 4-induced IL-22 accelerates kidney regeneration

AKI involves early Toll-like receptor (TLR)-driven immunopathology, and resolution of inflammation is needed for rapid regeneration of injured tubule cells. Notably, activation of TLRs also has been implicated in epithelial repair. We hypothesized that TLR signaling drives tubule regeneration after acute injury through the induction of certain ILs. Systematic screening in vitro identified IL-22 as a candidate proregeneratory factor in primary tubular cell recovery, and IL-22 deficiency or IL-22 blockade impaired post-ischemic tubular recovery after AKI in mice. Interstitial mononuclear cells, such as dendritic cells and macrophages, were the predominant source of IL-22 secretion, whereas IL-22 receptor was expressed by tubular epithelial cells exclusively. Depleting IL-22-producing cells during the healing phase impaired epithelial recovery, which could be rescued entirely by reconstituting mice with IL-22. In vitro, necrotic tubular cells and oxidative stress induced IL-22 secretion selectively through TLR4. Although TLR4 blockade during the early injury phase prevented tubular necrosis and AKI, TLR4 blockade during the healing phase suppressed IL-22 production and impaired kidney regeneration. Taken together, these results suggest that necrotic cell-derived TLR4 agonists activate intrarenal mononuclear cells to secrete IL-22, which accelerates tubular regeneration and recovery in AKI.

Analysis of nucleic acid-induced nonimmune cell death in vitro

Foreign nucleic acids are recognized by germ-line-encoded receptors expressed in immune and nonimmune cells. Activation of the nucleic acid-specific pattern recognition receptors by foreign nucleic acid promotes production of inflammatory cytokines (mostly type I IFNs) and at the later stage leads to cell death. Here, we describe reliable and simple methods to quantify cell death caused by nucleic acid recognition. Additionally, we report two different methods to discriminate between two cell death modalities: apoptosis and necrosis.

Unusual exophytic subependymoma in the bulbo-cerebellar angle. Case report

Subependymoma was first described by Scheinker in 1945; it frequently occurs in the ventricles and rarely in the spinal canal representing 0.7% of all central nervous system tumours. Most of these intraventricular tumours are subclinical entities, remaining of small size and discovered at autopsy with 0.4%incidence. We report a case of subependymoma with a completely exophytic growth from the foramen of Luscka: only a similar one has been described in the literature but with a lesser cysternal involvement. Neuroradiological and anatomopathological features of subependymoma are discussed.

Genomic gain at 6p21: a new cryptic molecular rearrangement in secondary myelodysplastic syndrome and acute myeloid leukemia

Fluorescence in situ hybridization and comparative genomic hybridization characterized 6p rearrangements in eight primary and in 10 secondary myeloid disorders (including one patient with Fanconi anemia) and found different molecular lesions in each group. In primary disorders, 6p abnormalities, isolated in six patients, were highly heterogeneous with different breakpoints along the 6p arm. Reciprocal translocations were found in seven. In the 10 patients with secondary acute myeloid leukemia/myelodysplastic syndrome (AML/MDS), the short arm of chromosome 6 was involved in unbalanced translocations in 7. The other three patients showed full or partial trisomy of the 6p arm, that is, i(6)(p10) (one patient) and dup(6)(p) (two patients). In 5/7 patients with unbalanced translocations, DNA sequences were overrepresented at band 6p21 as either cryptic duplications (three patients) or cryptic low-copy gains (two patients). In the eight patients with cytogenetic or cryptic 6p gains, we identified a common overrepresented region extending for 5-6 megabases from the TNF gene to the ETV-7 gene. 6p abnormalities were isolated karyotype changes in four patients. Consequently, in secondary AML/MDS, we hypothesize that 6p gains are major pathogenetic events arising from acquired and/or congenital genomic instability.

Retrieval of broken pedicle screws by "friction" technique. Technical note

The authors describe a simple and fast technique for removal of deeply situated broken pedicle screw fragments. The screw fragments are removed using a fine-serrated, conically cored bit with a light rough inner surface that is mounted on a common slow-speed drill capable of rotating clockwise and counterclockwise. The cored head of the bit is pressed and engaged on the cut surface of the broken screw, and the drill is made to turn in counterclockwise rotation; this, by means of friction, causes the two surfaces to interlock, and consequently the broken screw fragment backs out. This technique was used to retrieve both broken titanium and stainless steel screws, and satisfying results were obtained. There were no complications associated with the application of the technique, and the pedicle as well as the screw hole were always preserved, offering, in the event that the vertebral instability continued, the possibility of applying a new screw of slightly larger diameter at the same screw hole. This technical application offers the opportunity of removing deeply situated screw fragments by using a simple technique while maintaining the vertebral pedicle and screw-hole integrity.

Fatty acid dietary intake and the risk of ischaemic stroke: a multicentre case-control study. UFA Study Group

A low dietary intake of unsaturated fatty acids has been found in male patients with stroke as compared with controls in Italy, and a high consumption of meat has been associated with an increased risk of stroke in Australia. We present a case-control study, comparing the unsaturated and saturated fatty acids content of red cell membranes (which reflects the dietary intake of saturated and unsaturated fats) in 89 patients with ischaemic stroke and 89 controls matched for age and sex. In univariate analysis, besides hypertension, atrial fibrillation, ischaemic changes in ECG and hypercholesterolaemia, stroke patients showed a lower level of oleic acid (P = 0.000), but a higher level of eicosatrienoic acid (P = 0.009). Conditional logistic regression (dependent variable; being a case) showed that the best model included atrial fibrillation, hypertension, oleic acid and eicosatrienoic acids. These results confirm a possible protective role of unsaturated fatty acids against vascular diseases; however, we did not find any difference in the content of omega3 acids, which have been considered in the past to protect against coronary heart disease. We conclude that the preceding diet of patients with ischaemic stroke may be poor in unsaturated fatty acids (namely, oleic acid), and this defect is independent of other vascular risk factors. Only further studies will show whether changes in diet and/or supplement of unsaturated fatty acids might reduce the incidence of ischaemic stroke.