Cathepsin C is a novel mediator of podocyte and renal injury induced by hyperglycemia

A growing body of evidence suggests a role of proteolytic enzymes in the development of diabetic nephropathy. Cathepsin C (CatC) is a well-known regulator of inflammatory responses, but its involvement in podocyte and renal injury remains obscure. We used Zucker rats, a genetic model of metabolic syndrome and insulin resistance, to determine the presence, quantity, and activity of CatC in the urine. In addition to the animal study, we used two cellular models, immortalized human podocytes and primary rat podocytes, to determine mRNA and protein expression levels via RT-PCR, Western blot, and confocal microscopy, and to evaluate CatC activity. The role of CatC was analyzed in CatC-depleted podocytes using siRNA and glycolytic flux parameters were obtained from extracellular acidification rate (ECAR) measurements. In functional analyses, podocyte and glomerular permeability to albumin was determined. We found that podocytes express and secrete CatC, and a hyperglycemic environment increases CatC levels and activity. Both high glucose and non-specific activator of CatC phorbol 12-myristate 13-acetate (PMA) diminished nephrin, cofilin, and GLUT4 levels and induced cytoskeletal rearrangements, increasing albumin permeability in podocytes. These negative effects were completely reversed in CatC-depleted podocytes. Moreover, PMA, but not high glucose, increased glycolytic flux in podocytes. Finally, we demonstrated that CatC expression and activity are increased in the urine of diabetic Zucker rats. We propose a novel mechanism of podocyte injury in diabetes, providing deeper insight into the role of CatC in podocyte biology.

APOL1 Kidney-Risk Variants Induce Mitochondrial Fission

Introduction

APOL1 G1 and G2 nephropathy-risk variants cause mitochondrial dysfunction and contribute to kidney disease. Analyses were performed to determine the genetic regulation of APOL1 and elucidate potential mechanisms in APOL1-nephropathy.

Methods

A global gene expression analysis was performed in human primary renal tubule cell lines derived from 50 African American individuals. Follow-up gene knock out, cell-based rescue, and microscopy experiments were performed.

Results

APOL1 genotypes did not alter APOL1 expression levels in the global gene expression analysis. Expression quantitative trait locus (eQTL) analysis in polyinosinic-polycytidylic acid (poly IC)–stimulated renal tubule cells revealed that single nucleotide polymorphism (SNP) rs513349 adjacent to BAK1 was a trans eQTL for APOL1 and a cis eQTL for BAK1; APOL1 and BAK1 were co-expressed in cells. BAK1 knockout in a human podocyte cell line resulted in diminished APOL1 protein, supporting a pivotal effect for BAK1 on APOL1 expression. Because BAK1 is involved in mitochondrial dynamics, mitochondrial morphology was examined in primary renal tubule cells and HEK293 Tet-on cells of various APOL1 genotypes. Mitochondria in APOL1 wild-type (G0G0) tubule cells maintained elongated morphology when stimulated by low-dose poly IC, whereas those with G1G1, G2G2, and G1G2 genotypes appeared to fragment. HEK293 Tet-on cells overexpressing APOL1 G0, G1, and G2 were created; G0 cells appeared to promote mitochondrial fusion, whereas G1 and G2 induced mitochondrial fission. The mitochondrial dynamic regulator Mdivi-1 significantly preserved cell viability and mitochondrial cristae structure and reversed mitochondrial fission induced by overexpression of G1 and G2.

Conclusion

Results suggest the mitochondrial fusion/fission pathway may be a therapeutic target in APOL1-nephropathy.

A role for OCRL in glomerular function and disease

BACKGROUND

Lowe syndrome and Dent-2 disease are caused by mutations in the OCRL gene, which encodes for an inositol 5-phosphatase. The renal phenotype associated with OCRL mutations typically comprises a selective proximal tubulopathy, which can manifest as Fanconi syndrome in the most extreme cases.

METHODS

Here, we report a 12-year-old male with nephrotic-range proteinuria and focal segmental glomerulosclerosis on renal biopsy. As a glomerular pathology was suspected, extensive investigation of tubular function was not performed.

RESULTS

Surprisingly, whole exome sequencing identified a genetic variant in OCRL (c1467-2A>G) that introduced a novel splice mutation leading to skipping of exon 15. In situ hybridisation of adult human kidney tissue and zebrafish larvae showed OCRL expression in the glomerulus, supporting a role for OCRL in glomerular function. In cultured podocytes, we found that OCRL associated with the linker protein IPIP27A and CD2AP, a protein that is important for maintenance of the podocyte slit diaphragm.

CONCLUSION

Taken together, this work suggests a previously under-appreciated role for OCRL in glomerular function and highlights the importance of investigating tubular function in patients with persistent proteinuria.

Alterations in plasma membrane ion channel structures stimulate NLRP3 inflammasome activation in APOL1 risk milieu

We evaluated alterations in the structural configurations of channels and activation of nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome formation in apolipoprotein L1 (APOL1) risk and nonrisk milieus. APOL1G1- and APOL1G2-expressing podocytes (PD) displayed enhanced K⁺ efflux, induction of pyroptosis, and escalated transcription of interleukin (IL)-1β and IL-18. APOL1G1- and APOL1G2-expressing PD promoted the transcription as well as translation of proteins involved in the formation of inflammasomes. Since glyburide (a specific inhibitor of K⁺ efflux channels) inhibited the transcription of NLRP3, IL-1β, and IL-18, the role of K⁺ efflux in the activation of inflammasomes in APOL1 risk milieu was implicated. To evaluate the role of structural alterations in K⁺ channels in plasma membranes, bioinformatics studies, including molecular dynamic simulation, were carried out. Superimposition of bioinformatics reconstructions of APOL1G0, G1, and G2 showed several aligned regions. The analysis of pore-lining residues revealed that Ser342 and Tyr389 are involved in APOL1G0 pore formation and the altered conformations resulting from the Ser342Gly and Ile384Met mutation in the case of APOLG1 and deletion of the Tyr389 residue in the case of APOL1G2 are expected to alter pore characteristics, including K⁺ ion selectivity. Analysis of multiple membrane (lipid bilayer) models of interaction with the peripheral protein, integral membrane protein, and multimer protein revealed that for an APOL1 multimer model, APOL1G0 is not energetically favorable while the APOL1G1 and APOL1G2 moieties favor the insertion of multiple ion channels into the lipid bilayer. We conclude that altered pore configurations carry the potential to facilitate K⁺ ion transport in APOL1 risk milieu.

Molecular Analysis of Goodpasture's Disease Following Hematopoietic Stem Cell Transplant in a Pediatric Patient, Recalls the Conformeropathy of Wild-Type Anti-GBM Disease

Background: Goodpasture's disease (GP) is mediated by autoantibodies that bind the glomerular and alveolar basement membrane, causing rapidly progressive glomerulonephritis with or without pulmonary hemorrhage. The autoantibodies bind neoepitopes formed upon disruption of the quaternary structure of α345NC1 hexamer, a critical structural domain of α345 collagen IV scaffolds. Hexamer disruption leads to a conformational changes that transitions α3 and α5NC1 subunits into immunogens, however, the trigger remains unknown. This contrasts with another anti-GBM disease, Alports' post-transplant nephritis (APTN), where the pathogenic alloantibody binds directly to native NC1 hexamer. The current report includes the first study of antigenic specificity and allo-incompatability in anti-GBM disease occurring after allogeneic haematopoietic stem cell transplant (HSCT).

Results: The anti-GBM antibodies were found to be directed predominantly against the E_A epitope of the α3 NC1 monomer of collagen IV and developed rapidly in patient serum reaching peak level within 5 weeks. Autoantibody binding to native α345NC1 hexamer was minimal; however, binding was greatly increased upon dissociation of the native hexamer. There were no polymorphic genetic differences between donor and recipient collagen IV genes which would be predicted to cause a significant NC1 conformational change or to provide a target for antibody binding. Both patient and donor possessed the Goodpasture's susceptibility HLA-allele DRB1^*1501.

Conclusions: The current report includes the first in-depth study of allo-incompatability and antigenic specificity in anti-GBM disease occurring after allogeneic haematopoietic stem cell transplant (HSCT). No polymorphic genetic differences were identified between donor and recipient collagen IV genes which would be predicted to provide a target for antibody binding. Furthermore, autoantibody binding to native α345NC1 hexamer was minimal, increasing greatly upon dissociation of the native hexamer, resembling wild-type GP diseases and marking this as the first example of a post-HSCT conformeropathy.

Podocyte RhoGTPases: new therapeutic targets for nephrotic syndrome?

Podocytes, or glomerular epithelial cells, form the final layer in the glomerular capillary wall of the kidney. Along with the glomerular basement membrane and glomerular endothelial cells, they make up the glomerular filtration barrier which allows the passage of water and small molecules and, in healthy individuals, prevents the passage of albumin and other key proteins. The podocyte is a specialised and terminally differentiated cell with a specific cell morphology that is largely dependent on a highly dynamic underlying cytoskeletal network and that is essential for maintaining glomerular function and integrity in healthy kidneys. The RhoGTPases (RhoA, Rac1 and Cdc42), which act as molecular switches that regulate actin dynamics, are known to play a crucial role in maintaining the cytoskeletal and molecular integrity of the podocyte foot processes in a dynamic manner. Recently, novel protein interaction networks that regulate the RhoGTPases in the podocyte and that are altered by disease have been discovered. This review will discuss these networks and their potential as novel therapeutic targets in nephrotic syndrome. It will also discuss the evidence that they are direct targets for (a) steroids, the first-line agents for the treatment of nephrotic syndrome, and (b) certain kinase inhibitors used in cancer treatment, leading to nephrotoxicity.

The TRAPP complex mediates secretion arrest induced by stress granule assembly

The TRAnsport Protein Particle (TRAPP) complex controls multiple membrane trafficking steps and is strategically positioned to mediate cell adaptation to diverse environmental conditions, including acute stress. We have identified the TRAPP complex as a component of a branch of the integrated stress response that impinges on the early secretory pathway. The TRAPP complex associates with and drives the recruitment of the COPII coat to stress granules (SGs) leading to vesiculation of the Golgi complex and arrest of ER export. The relocation of the TRAPP complex and COPII to SGs only occurs in cycling cells and is CDK1/2-dependent, being driven by the interaction of TRAPP with hnRNPK, a CDK substrate that associates with SGs when phosphorylated. In addition, CDK1/2 inhibition impairs TRAPP complex/COPII relocation to SGs while stabilizing them at ER exit sites. Importantly, the TRAPP complex controls the maturation of SGs. SGs that assemble in TRAPP-depleted cells are smaller and are no longer able to recruit RACK1 and Raptor, two TRAPP-interactive signaling proteins, sensitizing cells to stress-induced apoptosis.

A Composite Hydrogel Scaffold Permits Self-Organization and Matrix Deposition by Cocultured Human Glomerular Cells

3D scaffolds provide cells with a spatial environment that more closely resembles that of in vivo tissue, when compared to 2D culture on a plastic substrate. However, many scaffolding materials commonly used in tissue engineering tend to exhibit anisotropic morphologies that exhibit a narrow range of fiber diameters and pore sizes, which do not recapitulate extracellular matrices. In this study, a fibrin hydrogel is formed within the interstitial spaces of an electrospun poly(glycolic) acid (PGA) monolith to generate a composite, bimodal scaffold for the coculture of kidney glomerular cell lines. This new scaffold exhibits multiple fiber morphologies, containing both PGA microfibers (14.5 ± 2 µm) and fibrin gel nanofibers (0.14 ± 0.09 µm), which increase the compressive Young's modulus beyond that of either of the constituents. The composite structure provides an enhanced 3D environment that increases proliferation and adhesion of immortalized human podocytes and glomerular endothelial cells. Moreover, the micro/nanoscale fibrous morphology promotes motility and reorganization of the glomerular cells into glomerulus-like structures, resulting in the deposition of organized collagen IV; the primary component of the glomerular basement membrane (GBM).

Disruption of MAGI2-RapGEF2-Rap1 signaling contributes to podocyte dysfunction in congenital nephrotic syndrome caused by mutations in MAGI2

The essential role of membrane associated guanylate kinase 2 (MAGI2) in podocytes is indicated by the phenotypes of severe glomerulosclerosis of both MAGI2 knockout mice and in patients with congenital nephrotic syndrome (CNS) caused by mutations in MAGI2. Here, we show that MAGI2 forms a complex with the Rap1 guanine nucleotide exchange factor, RapGEF2, and that this complex is lost when expressing MAGI2 CNS variants. Co-expression of RapGEF2 with wild-type MAGI2, but not MAGI2 CNS variants, enhanced activation of the small GTPase Rap1, a central signaling node in podocytes. In mice, podocyte-specific RapGEF2 deletion resulted in spontaneous glomerulosclerosis, with qualitative glomerular features comparable to MAGI2 knockout mice. Knockdown of RapGEF2 or MAGI2 in human podocytes caused similar reductions in levels of Rap1 activation and Rap1-mediated downstream signaling. Furthermore, human podocytes expressing MAGI2 CNS variants show severe abnormalities of cellular morphology and dramatic loss of actin cytoskeletal organization, features completely rescued by pharmacological activation of Rap1 via a non-MAGI2 dependent upstream pathway. Finally, immunostaining of kidney sections from patients with congenital nephrotic syndrome and MAGI2 mutations showed reduced podocyte Rap1-mediated signaling. Thus, MAGI2-RapGEF2-Rap1 signaling is essential for normal podocyte function. Hence, disruption of this pathway is an important cause of the renal phenotype induced by MAGI2 CNS mutations.

Effects of heparin and derivatives on podocytes: An in vitro functional and morphological evaluation

Unfractionated heparin (UFH) and low molecular heparin derivatives (LMWH) display numerous biological properties in addition to their anticoagulant effects. However, due to the physicochemical heterogeneity of these drugs, a better understanding concerning their effects on human cells is clearly needed. Considering that heparins are mainly excreted by the kidney, we focused our attention on the effect of UFH and LMWH on human podocytes by functional and morphological/phenotypic in vitro analyses. We demonstrated that these products differentially modulate the permeability of podocyte monolayer to albumin. The functional perturbations observed were correlated to significant cellular morphological and cytoskeletal changes, as well as a decrease in the expression of proteins involved in podocyte adherence to the extracellular matrix or intercellular interactions. This point confirms that UFH and the different LMWHs exert specific effects on podocyte permeability and underlines the need of in vitro tests to evaluate new biological nonanticoagulant properties of LMWH.

TRPC6 Binds to and Activates Calpain, Independent of Its Channel Activity, and Regulates Podocyte Cytoskeleton, Cell Adhesion, and Motility

BACKGROUND

Mutations in the transient receptor potential channel 6 (TRPC6) gene are associated with an inherited form of FSGS. Despite widespread expression, patients with TRPC6 mutations do not present with any other pathologic phenotype, suggesting that this protein has a unique yet unidentified role within the target cell for FSGS, the kidney podocyte.

METHODS

We generated a stable TRPC6 knockout podocyte cell line from TRPC6 knockout mice. These cells were engineered to express wild-type TRPC6, a dominant negative TRPC6 mutation, or either of two disease-causing mutations of TRPC6, G109S or K874*. We extensively characterized these cells using motility, detachment, and calpain activity assays; immunofluorescence; confocal or total internal reflection fluorescence microscopy; and western blotting.

RESULTS

Compared with wild-type cells, TRPC6^-/- podocytes are less motile and more adhesive, with an altered actin cytoskeleton. We found that TRPC6 binds to ERK1/2 and the actin regulatory proteins, caldesmon (a calmodulin- and actin-binding protein) and calpain 1 and 2 (calcium-dependent cysteine proteases that control the podocyte cytoskeleton, cell adhesion, and motility via cleavage of paxillin, focal adhesion kinase, and talin). Knockdown or expression of the truncated K874* mutation (but not expression of the gain-of-function G019S mutation or dominant negative mutant of TRPC6) results in the mislocalization of calpain 1 and 2 and significant downregulation of calpain activity; this leads to altered podocyte cytoskeleton, motility, and adhesion-characteristics of TRPC6 ^-/- podocytes.

CONCLUSIONS

Our data demonstrate that independent of TRPC6 channel activity, the physical interaction between TRPC6 and calpain in the podocyte is important for cell motility and detachment and demonstrates a scaffolding role of the TRPC6 protein in disease.

Human Th17 cells produce a soluble mediator that increases podocyte motility via signaling pathways that mimic PAR-1 activation

The specific pathogenesis of idiopathic nephrotic syndrome (NS) is poorly understood, and the role of immune mediators remains contentious. However, there is good evidence for the role of a circulating factor, and we recently postulated circulating proteases as candidate factors. Immunosuppressive therapy with glucocorticoids (GCs) and T cell inhibitors are widely used in the clinical treatment of NS. Given that T helper (CD4⁺) cells expressing IL-17A (so-called Th17 cells) have recently been reported to be resistant to GC treatment, and GC resistance remains a major challenge in the management of NS, we hypothesized that Th17 cells produce a circulating factor that is capable of signaling to the podocyte and inducing deleterious phenotypic changes. To test this, we generated human Th17 cells from healthy volunteers and added the supernatants from these T cell cultures to conditionally immortalized human podocytes in vitro. This demonstrated that podocytes treated with Th17 cell culture supernatant, as well as with patient disease plasma, showed significant stimulation of JNK and p38 MAPK pathways and an increase in motility, which was blocked using a JNK inhibitor. We have previously shown that nephrotic plasma elicits a podocyte response via protease-activated receptor-1 (PAR-1). Stimulation of PAR-1 in podocytes elicited the same signaling response as Th17 cell culture supernatant treatment. Equally, protease inhibitors with Th17 cell culture treatment blocked the signaling response. This was not replicated by the reagents added to Th17 cell cultures or by IL-17A. Hence, we conclude that an undefined soluble mediator produced by Th17 cells mimics the deleterious effect of PAR-1 activation in vitro. Given the association between pathogenic subsets of Th17 cells and GC resistance, these observations have potential therapeutic relevance for patients with NS.

Disrupted apolipoprotein L1-miR193a axis dedifferentiates podocytes through autophagy blockade in an APOL1 risk milieu

We hypothesized that a functional apolipoprotein LI (APOL1)-miR193a axis (inverse relationship) preserves, but disruption alters, the podocyte molecular phenotype through the modulation of autophagy flux. Podocyte-expressing APOL1G0 (G0-podocytes) showed downregulation but podocyte-expressing APOL1G1 (G1-podocytes) and APOL1G2 (G2-podocytes) displayed enhanced miR193a expression. G0-, G1-, and G2-podocytes showed enhanced expression of light chain (LC) 3-II and beclin-1, but a disparate expression of p62 (low in wild-type but high in risk alleles). G0-podocytes showed enhanced, whereas G1- and G2-podocytes displayed decreased, phosphorylation of Unc-51-like autophagy-activating kinase (ULK)1 and class III phosphatidylinositol 3-kinase (PI3KC3). Podocytes overexpressing miR193a (miR193a-podocytes), G1, and G2 showed decreased transcription of PIK3R3 (PI3KC3's regulatory unit). Since 3-methyladenine (3-MA) enhanced miR193a expression but inhibited PIK3R3 transcription, it appears that 3-MA inhibits autophagy and induces podocyte dedifferentiation via miR193a generation. miR193a-, G1-, and G2-podocytes also showed decreased phosphorylation of mammalian target of rapamycin (mTOR) that could repress lysosome reformation. G1- and G2-podocytes showed enhanced expression of run domain beclin-1-interacting and cysteine-rich domain-containing protein (Rubicon); however, its silencing prevented their dedifferentiation. Docking, protein-protein interaction, and immunoprecipitation studies with antiautophagy-related gene (ATG)14L, anti-UV radiation resistance-associated gene (UVRAG), or Rubicon antibodies suggested the formation of ATG14L complex I and UVRAG complex II in G0-podocytes and the formation of Rubicon complex III in G1- and G2-podocytes. These findings suggest that the APOL1 risk alleles favor podocyte dedifferentiation through blockade of multiple autophagy pathways.

Big data and stratified medicine: what does it mean for children?

Stratified medicine in paediatrics is increasingly becoming a reality, as our understanding of disease pathogenesis improves and novel treatment targets emerge. We have already seen some success in paediatrics in targeted therapies such as cystic fibrosis for specific cystic fibrosis transmembrane conductance regulator variants. With the increased speed and decreased cost of processing and analysing data from rare disease registries, we are increasingly able to use a systems biology approach (including '-omics') to screen across populations for molecules and genes of interest. Improving our understanding of the molecular mechanisms underlying disease, and how to classify patients according to these will lead the way for targeted therapies for individual patients. This review article will summarise how 'big data' and the 'omics' are being used and developed, and taking examples from paediatric renal medicine and rheumatology, demonstrate progress being made towards stratified medicine for children.

Disruption of APOL1-miR193a Axis Induces Disorganization of Podocyte Actin Cytoskeleton

APOL1-miR193a axis participates in the preservation of molecular phenotype of differentiated podocytes (DPDs). We examined the hypothesis that APOL1 (G0) preserves, but APOL1 risk alleles (G1 and G2) disrupt APOL1-miR193a axis in DPDs. DPDG0s displayed down-regulation of miR193a, but upregulation of nephrin expression. DPDG1s/G2s exhibited an increase in miR193a and down-regulation of the expression of adherens complex's constituents (CD2AP, nephrin, and dendrin). DPDG0s showed decreased Cathepsin L, enhanced dynamin expressions, and the intact actin cytoskeleton. On the contrary, DPDG1s/G2s displayed an increase in Cathepsin L, but down-regulation of dynamin expressions and disorganization of the actin cytoskeleton. APOL1 silencing enhanced miR193a and Cathepsin L, but down-regulated dynamin expressions. DPDG1s/G2s displayed nuclear import of dendrin, indicating an occurrence of destabilization of adherens complexes in APOL1 risk milieu. These findings suggest that DPDG1s and DPDG2s developed disorganized actin cytoskeleton as a consequence of disrupted APOL1-miR193a axis. Interestingly, docking and co-labeling studies suggested an interaction between APOL1 and CD2AP. APOL1G1/G1 and APOL1G1/G2 transgenic mice displayed nuclear import of dendrin indicating destabilization of adherens complexes in podocytes; moreover, these mice showed a four-fold increase in urinary albumin to creatinine ratio and development of focal segmental glomerular lesions.

TBC1D8B Loss-of-Function Mutations Lead to X-Linked Nephrotic Syndrome via Defective Trafficking Pathways

Steroid-resistant nephrotic syndrome (SRNS) is characterized by high-range proteinuria and most often focal and segmental glomerulosclerosis (FSGS). Identification of mutations in genes causing SRNS has improved our understanding of disease mechanisms and highlighted defects in the podocyte, a highly specialized glomerular epithelial cell, as major factors in disease pathogenesis. By exome sequencing, we identified missense mutations in TBC1D8B in two families with an X-linked early-onset SRNS with FSGS. TBC1D8B is an uncharacterized Rab-GTPase-activating protein likely involved in endocytic and recycling pathways. Immunofluorescence studies revealed TBC1D8B presence in human glomeruli, and affected individual podocytes displayed architectural changes associated with migration defects commonly found in FSGS. In zebrafish we demonstrated that both knockdown and knockout of the unique TBC1D8B ortholog-induced proteinuria and that this phenotype was rescued by human TBC1D8B mRNA injection, but not by either of the two mutated mRNAs. We also showed an interaction between TBC1D8B and Rab11b, a key protein in vesicular recycling in cells. Interestingly, both internalization and recycling processes were dramatically decreased in affected individuals' podocytes and fibroblasts, confirming the crucial role of TBC1D8B in the cellular recycling processes, probably as a Rab11b GTPase-activating protein. Altogether, these results confirmed that pathogenic variations in TBC1D8B are involved in X-linked podocytopathy and points to alterations in recycling processes as a mechanism of SRNS.

Podocyte GSK3 is an evolutionarily conserved critical regulator of kidney function

Albuminuria affects millions of people, and is an independent risk factor for kidney failure, cardiovascular morbidity and death. The key cell that prevents albuminuria is the terminally differentiated glomerular podocyte. Here we report the evolutionary importance of the enzyme Glycogen Synthase Kinase 3 (GSK3) for maintaining podocyte function in mice and the equivalent nephrocyte cell in Drosophila. Developmental deletion of both GSK3 isoforms (α and β) in murine podocytes causes late neonatal death associated with massive albuminuria and renal failure. Similarly, silencing GSK3 in nephrocytes is developmentally lethal for this cell. Mature genetic or pharmacological podocyte/nephrocyte GSK3 inhibition is also detrimental; producing albuminuric kidney disease in mice and nephrocyte depletion in Drosophila. Mechanistically, GSK3 loss causes differentiated podocytes to re-enter the cell cycle and undergo mitotic catastrophe, modulated via the Hippo pathway but independent of Wnt-β-catenin. This work clearly identifies GSK3 as a critical regulator of podocyte and hence kidney function.

Effectiveness of premedication protocol using intravenous fentanyl to reduce pain associated with femoral artery closure device placement

AIM

To test the effectiveness of a premedication protocol using intravenous bolus of 100 μg fentanyl to reduce pain associated with femoral artery closure device placement for neuro-endovascular procedures.

MATERIALS AND METHODS

The severity of pain associated with femoral artery closure device placement was analysed using a numerical rating scale score ranging from 0 (no pain) to 10 (most severe pain) in two cohorts of consecutive adult patients (n=118), those who were (n=64) or were not (n=54) treated with premedication protocol. The primary endpoints were the proportion of patients with excellent (score ≤1) and failed pain control (score ≥8). Stepwise logistic regression analysis was performed to identify the effect of premedication on pain control after adjustment for potential confounders.

RESULTS

The median numerical pain rating score at femoral artery closure device placement was significantly lower in patients treated with premedication protocol compared with those who underwent closure without premedication (1 versus 5, p<0.001). There was a significantly higher rate of excellent (56.2% versus 14.8%, p<0.001) and good (68.7% versus 31.2%, p<0.001) pain control at closure device placement among patients treated with premedication protocol. None of the patients treated with premedication protocol reported failed pain control compared with 33.4% of those who underwent closure device placement without premedication. In the multivariate analysis, treatment with the premedication protocol was significantly associated with an increased rate of excellent pain control (odds ratio 2.3; 95% confidence interval 1.9-3.1).

CONCLUSION

Premedication with intravenous fentanyl injection prior to femoral artery closure device placement can reduce the intensity of pain associated with closure.

Solution fibre spinning technique for the fabrication of tuneable decellularised matrix-laden fibres and fibrous micromembranes

Recreating tissue-specific microenvironments of the extracellular matrix (ECM) in vitro is of broad interest for the fields of tissue engineering and organ-on-a-chip. Here, we present biofunctional ECM protein fibres and suspended membranes, with tuneable biochemical, mechanical and topographical properties. This soft and entirely biologic membrane scaffold, formed by micro-nano-fibres using low voltage electrospinning, displays three unique characteristics for potential cell culture applications: high-content of key ECM proteins, single-layered mesh membrane, and flexibility for in situ integration into a range of device setups. Extracellular matrix (ECM) powder derived from urinary bladder, was used to fabricate the ECM-laden fibres and membranes. The highest ECM concentration in the dry protein fibre was 50 wt%, with the rest consisting of gelatin. Key ECM proteins, including collagen IV, laminin, and fibronectin, were shown to be preserved post the biofabrication process. The single fibre tensile Young's modulus can be tuned for over two orders of magnitude between ∼600 kPa and 50 MPa depending on the ECM content. Combining the fibre mesh printing with 3D printed or microfabricated structures, culture devices were constructed for endothelial layer formation, and a trans-membrane co-culture formed by glomerular cell types of podocytes and glomerular endothelial cells, demonstrating feasibility of the membrane culture. Our cell culture observation points to the importance of membrane mechanical property and re-modelling ability as a factor for soft membrane-based cell cultures. The ECM-laden fibres and membranes presented here would see potential applications in in vitro assays, and tailoring structure and biological functions of tissue engineering scaffolds.

STATEMENT OF SIGNIFICANCE

Recreating tissue-specific microenvironments of the extracellular matrix (ECM) is of broad interest for the fields of tissue engineering and organ-on-a-chip. Both the biochemical and biophysical signatures of the engineered ECM interplay to affect cell response. Currently, there are limited biomaterials processing methods which allow to design ECM membrane properties flexibly and rapidly. Solvents and additives used in many existing processes also induced unwanted ECM protein degradation and toxic residues. This paper presents a solution fibre spinning technique, where careful selection of the solution combination led to well-preserved ECM proteins with tuneable composition. This technique also provides a highly versatile approach to fabricate ECM fibres and membranes, leading to designable fibre Young's modulus for over two orders of magnitude.

Modulation of apolipoprotein L1-microRNA-193a axis prevents podocyte dedifferentiation in high-glucose milieu

The loss of podocyte (PD) molecular phenotype is an important feature of diabetic podocytopathy. We hypothesized that high glucose (HG) induces dedifferentiation in differentiated podocytes (DPDs) through alterations in the apolipoprotein (APO) L1-microRNA (miR) 193a axis. HG-induced DPD dedifferentiation manifested in the form of downregulation of Wilms' tumor 1 (WT1) and upregulation of paired box 2 (PAX2) expression. WT1-silenced DPDs displayed enhanced expression of PAX2. Immunoprecipitation of DPD cellular lysates with anti-WT1 antibody revealed formation of WT1 repressor complexes containing Polycomb group proteins, enhancer of zeste homolog 2, menin, and DNA methyltransferase (DNMT1), whereas silencing of either WT1 or DNMT1 disrupted this complex with enhanced expression of PAX2. HG-induced DPD dedifferentiation was associated with a higher expression of miR193a, whereas inhibition of miR193a prevented DPD dedifferentiation in HG milieu. HG downregulated DPD expression of APOL1. miR193a-overexpressing DPDs displayed downregulation of APOL1 and enhanced expression of dedifferentiating markers; conversely, silencing of miR193a enhanced the expression of APOL1 and preserved DPD phenotype. Moreover, stably APOL1G0-overexpressing DPDs displayed the enhanced expression of WT1 but attenuated expression of miR193a; nonetheless, silencing of APOL1 reversed these effects. Since silencing of APOL1 enhanced miR193a expression as well as dedifferentiation in DPDs, it appears that downregulation of APOL1 contributed to dedifferentiation of DPDs through enhanced miR193a expression in HG milieu. Vitamin D receptor agonist downregulated miR193a, upregulated APOL1 expression, and prevented dedifferentiation of DPDs in HG milieu. These findings suggest that modulation of the APOL1-miR193a axis carries a potential to preserve DPD molecular phenotype in HG milieu.

Role of fungal-induced stress in biochemical and phytochemical profiling of Peganum harmala

The current study was designed to evaluate bioactive compounds under the influence of biotic stress on seedlings of Peganum harmala. Biologically active compounds were determined by using different techniques. The HPLC and GC-MS analyses detected the significant amount of phenolic acids and active biological compound. Total protein content, activity of proteases, α-amylases, catalases and peroxidases were observed to be accelerated under fungal stress. The seedling extracts exhibited prominent antifungal and antimicrobial activity against selected strains. The present study showed that P. harmala is a good candidate to be used in natural therapies and medicine.

A novel assay provides sensitive measurement of physiologically relevant changes in albumin permeability in isolated human and rodent glomeruli

Increased urinary albumin excretion is a key feature of glomerular disease but has limitations as a measure of glomerular permeability. Here we describe a novel assay to measure the apparent albumin permeability of single capillaries in glomeruli, isolated from perfused kidneys cleared of red blood cells. The rate of decline of the albumin concentration within the capillary lumen was quantified using confocal microscopy and used to calculate apparent permeability. The assay was extensively validated and provided robust, reproducible estimates of glomerular albumin permeability. These values were comparable with previous in vivo data, showing this assay could be applied to human as well as rodent glomeruli. To confirm this, we showed that targeted endothelial glycocalyx disruption resulted in increased glomerular albumin permeability in mice. Furthermore, incubation with plasma from patients with post-transplant recurrence of nephrotic syndrome increased albumin permeability in rat glomeruli compared to remission plasma. Finally, in glomeruli isolated from rats with early diabetes there was a significant increase in albumin permeability and loss of endothelial glycocalyx, both of which were ameliorated by angiopoietin-1. Thus, a glomerular permeability assay, producing physiologically relevant values with sufficient sensitivity to measure changes in glomerular permeability and independent of tubular function, was developed and validated. This assay significantly advances the ability to study biology and disease in rodent and human glomeruli.

Clinical genetic testing using a custom-designed steroid-resistant nephrotic syndrome gene panel: analysis and recommendations

BACKGROUND

There are many single-gene causes of steroid-resistant nephrotic syndrome (SRNS) and the list continues to grow rapidly. Prompt comprehensive diagnostic testing is key to realising the clinical benefits of a genetic diagnosis. This report describes a bespoke-designed, targeted next-generation sequencing (NGS) diagnostic gene panel assay to detect variants in 37 genes including the ability to identify copy number variants (CNVs).

METHODS

This study reports results of 302 patients referred for SRNS diagnostic gene panel analysis. Phenotype and clinical impact data were collected using a standard proforma. Candidate variants detected by NGS were confirmed by Sanger sequencing/Multiplex Ligation-dependent Probe Amplification with subsequent family segregation analysis where possible.

RESULTS

Clinical presentation was nephrotic syndrome in 267 patients and suspected Alport syndrome (AS) in 35. NGS panel testing determined a likely genetic cause of disease in 44/220 (20.0%) paediatric and 10/47 (21.3%) adult nephrotic cases, and 17/35 (48.6%) of haematuria/AS patients. Of 71 patients with genetic disease, 32 had novel pathogenic variants without a previous disease association including two with deletions of one or more exons of NPHS1 or NPHS2.

CONCLUSION

Gene panel testing provides a genetic diagnosis in a significant number of patients presenting with SRNS or suspected AS. It should be undertaken at an early stage of the care pathway and include the ability to detect CNVs as an emerging mechanism for genes associated with this condition. Use of clinical genetic testing after diagnosis of SRNS has the potential to stratify patients and assist decision-making regarding management.