Deletion of the Tensin2 SH2-PTB domain, but not the loss of its PTPase activity, induces podocyte injury in FVB/N mouse strain

Automated scoring of glomerular injury in TNS2-deficient nephropathy

Several artificial intelligence (AI) systems have been developed for glomerular pathology analysis in clinical settings. However, the application of AI systems in nonclinical fields remains limited. In this study, we trained a convolutional neural network model, which is an AI algorithm, to classify the severity of Tensin 2 (TNS2)-deficient nephropathy into seven categories. A dataset consisting of 803 glomerular images was generated from kidney sections of TNS2-deficient and wild-type mice. Manual evaluations of the images were conducted to assess their glomerular injury scores. The trained AI achieved approximately 70% accuracy in predicting the glomerular injury score for TNS2-deficient nephropathy. However, the AI achieved approximately 100% accuracy when considering predictions within one score of the true label as correct. The AI's predicted mean score closely matched the true mean score. In conclusion, while the AI model may not replace human judgment entirely, it can serve as a reliable second assessor in scoring glomerular injury, offering potential benefits in enhancing the accuracy and objectivity of such assessments.

Tensins in Kidney Function and Diseases

Tensins are focal adhesion proteins that regulate various biological processes, such as mechanical sensing, cell adhesion, migration, invasion, and proliferation, through their multiple binding activities that transduce critical signals across the plasma membrane. When these molecular interactions and/or mediated signaling are disrupted, cellular activities and tissue functions are compromised, leading to disease development. Here, we focus on the significance of the tensin family in renal function and diseases. The expression pattern of each tensin in the kidney, their roles in chronic kidney diseases, renal cell carcinoma, and their potentials as prognostic markers and/or therapeutic targets are discussed in this review.

Genetic background strongly influences the transition to chronic kidney disease of adriamycin nephropathy in mice

Animal models of podocytopathy and chronic kidney diseases (CKD) help elucidate these pathologies. Adriamycin (ADR)-induced nephropathy is a common rodent model of podocytopathy. BALB/c mice are sensitive to ADR, whereas C57BL/6 (B6) mice, the most commonly used strain, are resistant to ADR. Therefore, mouse strains with the B6 genetic background cannot be used as an ADR nephropathy model. We previously generated DNA-dependent protein kinase catalytic subunit (Prkdc) mutant B6 mice (B6-Prkdc^R2140C) carrying the R2140C mutation that causes ADR nephropathy. However, whether ADR nephropathy in the novel strain progresses to CKD after ADR administration has not been evaluated. Therefore, we examined whether the B6-Prkdc^R2140C mice develop CKD after ADR administration. We also evaluated whether differences existed in the genetic background in ADR nephropathy by comparing the B6-Prkdc^R2140C mice with BALB/c mice. Our findings demonstrated that B6-Prkdc^R2140C progresses to CKD and is resistant to nephropathy compared with the BALB/c mice. The B6-Prkdc^R2140C and BALB/c mice differed in the expression of genes related to inflammatory mediators, and further analysis is required to identify factors that contribute to resistance to nephropathy.

Tensin 2-deficient nephropathy - mechanosensitive nephropathy, genetic susceptibility

Tensin 2 (TNS2), a focal adhesion protein, is considered to anchor focal adhesion proteins to β integrin as an integrin adaptor protein and/or serve as a scaffold to facilitate the interactions of these proteins. In the kidney, TNS2 localizes to the basolateral surface of glomerular epithelial cells, i.e., podocytes. Loss of TNS2 leads to the development of glomerular basement membrane lesions and abnormal accumulation of extracellular matrix in maturing glomeruli during the early postnatal stages. It subsequently results in podocyte foot process effacement, eventually leading to glomerulosclerosis. Histopathological features of the affected glomeruli in the middle stage of the disease include expansion of the mesangial matrix without mesangial cell proliferation. In this review, we provide an overview of TNS2-deficient nephropathy and discuss the potential mechanism underlying this mechanosensitive nephropathy, which may be applicable to other glomerulonephropathies, such as CD151-deficient nephropathy and Alport syndrome. The onset of TNS2-deficient nephropathy strictly depends on the genetic background, indicating the presence of critical modifier genes. A better understanding of molecular mechanisms of mechanosensitive nephropathy may open new avenues for the management of patients with glomerulonephropathies.

The versatile electric condition in mouse embryos for genome editing using a three-step square-wave pulse electroporator

Technique for Animal Knockout system by Electroporation (TAKE) is a simple and efficient method to generate genetically modified (GM) mice using the clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 (Cas9) systems. To reinforce the versatility of electroporation used for gene editing in mice, the electric condition was optimized for vitrified-warmed mouse embryos, and applied to the fresh embryos from widely used inbred strains (C57BL/6NCr, BALB/cCrSlc, FVB/NJcl, and C3H/HeJJcl). The electric pulse settings (poring pulse: voltage, 150 V; pulse width, 1.0 ms; pulse interval, 50 ms; number of pulses, +4; transfer pulse: voltage, 20 V; pulse width, 50 ms; pulse interval, 50 ms; number of pulses, ±5) were optimal for vitrified-warmed mouse embryos, which could efficiently deliver the gRNA/Cas9 complex into the zygotes without zona pellucida thinning process and edit the target locus. These electric condition efficiently generated GM mice in widely used inbred mouse strains. In addition, electroporation using the electrode with a 5 mm gap could introduce more than 100 embryos within 5 min without specific pretreatment and sophisticated technical skills, such as microinjection, and exhibited a high developmental rate of embryos and genome-editing efficiency in the generated offspring, leading to the rapid and efficient generation of genome editing mice. The electric condition used in this study is highly versatile and can contribute to understanding human diseases and gene functions by generating GM mice more easily and efficiently.

Functional, proteomic and phenotypic in vitro studies evidence podocyte injury after chronic exposure to heparin

Unfractionated heparin (UFH) is a widely used anticoagulant that possess numerous properties including anti-inflammatory, anti-viral, anti-angiogenesis, and anti-metastatic effects. The effect of this drug was evaluated on the podocyte, an important actor of the glomerular filtration. Using a functional approach, we demonstrate that heparin treatment leads to a functional podocyte perturbation characterized by the increase of podocyte monolayer permeability. This effect is enhanced with time of exposure. Proteomic study reveals that heparin down regulate focal adhesion and cytoskeletal protein expressions as well as the synthesis of glomerular basement membrane components. This study clearly demonstrates that UFH may affect podocyte function by altering cytoskeleton organization, cell-cell contacts and cell attachment.

A single amino acid substitution in PRKDC is a determinant of sensitivity to Adriamycin-induced renal injury in mouse

Adriamycin (ADR)-induced nephropathy is frequently utilized in rodent models of podocytopathy. However, the application of this model in mice is limited to a few strains, such as BALB/c mice. The most commonly used mouse strain, C57BL/6 (B6), is resistant to ADR-induced nephropathy, as are all mouse strains with a B6 genetic background. Reportedly, the R2140C variant of the Prkdc gene is the cause of susceptibility to ADR-induced nephropathy in mice. To verify this hypothesis, we produced Prkdc mutant B6 mice, termed B6-Prkdc^R2140C, that possess the R2140C mutation. After administration of ADR, B6-Prkdc^R2140C mice exhibited massive proteinuria and glomerular and renal tubular injuries. In addition, there was no significant difference in the severity between B6-Prkdc^R2140C and BALB/c. These findings demonstrated that B6-Prkdc^R2140C show ADR-induced nephropathy susceptibility at a similar level to BALB/c, and that the PRKDC R2140C variant causes susceptibility to ADR-induced nephropathy. In future studies, ADR-induced nephropathy may become applicable to various kinds of genetically modified mice with a B6 background by mating with B6-Prkdc^R2140C.

Tensins - emerging insights into their domain functions, biological roles and disease relevance

Tensins are a family of focal adhesion proteins consisting of four members in mammals (TNS1, TNS2, TNS3 and TNS4). Their multiple domains and activities contribute to the molecular linkage between the extracellular matrix and cytoskeletal networks, as well as mediating signal transduction pathways, leading to a variety of physiological processes, including cell proliferation, attachment, migration and mechanical sensing in a cell. Tensins are required for maintaining normal tissue structures and functions, especially in the kidney and heart, as well as in muscle regeneration, in animals. This Review discusses our current understanding of the domain functions and biological roles of tensins in cells and mice, as well as highlighting their relevance to human diseases.

Tensin2 is important for podocyte-glomerular basement membrane interaction and integrity of the glomerular filtration barrier

Tensin2 (Tns2), an integrin-linked protein, is enriched in podocytes within the glomerulus. Previous studies have revealed that Tns2-deficient mice exhibit defects of the glomerular basement membrane (GBM) soon after birth in a strain-dependent manner. However, the mechanisms for the onset of defects caused by Tns2 deficiency remains unidentified. Here, we aimed to determine the role of Tns2 using newborn Tns2-deficient mice and murine primary podocytes. Ultrastructural analysis revealed that developing glomeruli during postnatal nephrogenesis exhibited abnormal GBM processing due to ectopic laminin-α₂ accumulation followed by GBM thickening. In addition, analysis of primary podocytes revealed that Tns2 deficiency led to impaired podocyte-GBM interaction and massive expression of laminin-α₂ in podocytes. Our study suggests that weakened podocyte-GBM interaction due to Tns2 deficiency causes increased mechanical stress on podocytes by continuous daily filtration after birth, resulting in stressed podocytes ectopically producing laminin-α₂, which interrupts GBM processing. We conclude that Tns2 plays important roles in the podocyte-GBM interaction and maintenance of the glomerular filtration barrier.