[Validation of the total morbidity score and investigation of the efficacy of methotrexate in localized scleroderma]. / Validierung des "Total Morbidity Scores" und Untersuchung der Wirksamkeit von Methotrexat bei der lokalisierten Sklerodermie.

BACKGROUND: Localized scleroderma is an autoimmune disease belonging to the group of collagenoses, which can manifest cutaneously and extracutaneously. The extracutaneous manifestations may have significant morbidity but are not considered in previous scoring systems. For this reason, another scoring system, the total morbidity score (TMS) was developed, which also takes into account the extracutaneous symptoms. METHOD: In the retrospective monocentric study at the Hamburg Center for Pediatric and Adolescent Rheumatology, the TMS was applied to patients from 2004-2019 suffering from localized scleroderma who had at least one control presentation. In addition, data were analyzed according to the previously established localized scleroderma cutaneous assessment tool (LoSCAT) scoring systems to ensure better comparability to the TMS. Furthermore, the score values were considered and compared during the course of treatment with methotrexate (MTX). RESULTS: Due to a lack of control presentations, data from 51 of the 95 patients with a confirmed diagnosis could be included in the retrospective evaluation. The treatment of these patients was considered over a period of 2 years, from the initial presentation over at least 3 further control presentations. The TMS total score remained largely constant. There was a weak correlation between the TMS total score and the localized scleroderma skin damage index (mLoSDI), which indicates the degree of damage. In addition, insignificant changes in the TMS total score were shown over time with MTX treatment (T1/T4: -0.007). DISCUSSION: The evaluation showed that the TMS total score is mainly fed by the extracutaneous manifestations, demonstrating the inaccuracy of previous scores. Another advantage of the TMS is that different scores are assigned depending on whether the feature is new, persistent, improving, or even worsening. The TMS is more time consuming to collect but enables a more accurate assessment of disease activity.

N-Degradomic Analysis Reveals a Proteolytic Network Processing the Podocyte Cytoskeleton.

Regulated intracellular proteostasis, controlled in part by proteolysis, is essential in maintaining the integrity of podocytes and the glomerular filtration barrier of the kidney. We applied a novel proteomics technology that enables proteome-wide identification, mapping, and quantification of protein N-termini to comprehensively characterize cleaved podocyte proteins in the glomerulus in vivo We found evidence that defined proteolytic cleavage results in various proteoforms of important podocyte proteins, including those of podocin, nephrin, neph1, α-actinin-4, and vimentin. Quantitative mapping of N-termini demonstrated perturbation of protease action during podocyte injury in vitro, including diminished proteolysis of α-actinin-4. Differentially regulated protease substrates comprised cytoskeletal proteins as well as intermediate filaments. Determination of preferential protease motifs during podocyte damage indicated activation of caspase proteases and inhibition of arginine-specific proteases. Several proteolytic processes were clearly site-specific, were conserved across species, and could be confirmed by differential migration behavior of protein fragments in gel electrophoresis. Some of the proteolytic changes discovered in vitro also occurred in two in vivo models of podocyte damage (WT1 heterozygous knockout mice and puromycin aminonucleoside-treated rats). Thus, we provide direct and systems-level evidence that the slit diaphragm and podocyte cytoskeleton are regulated targets of proteolytic modification, which is altered upon podocyte damage.

YAP-mediated mechanotransduction determines the podocyte's response to damage.

Podocytes are terminally differentiated cells of the kidney filtration barrier. They are subjected to physiological filtration pressure and considerable mechanical strain, which can be further increased in various kidney diseases. When injury causes cytoskeletal reorganization and morphological alterations of these cells, the filtration barrier may become compromised and allow proteins to leak into the urine (a condition called proteinuria). Using time-resolved proteomics, we showed that podocyte injury stimulated the activity of the transcriptional coactivator YAP and the expression of YAP target genes in a rat model of glomerular disease before the development of proteinuria. Although the activities of YAP and its ortholog TAZ are activated by mechanical stress in most cell types, injury reduced YAP and TAZ activity in cultured human and mouse podocyte cell lines grown on stiff substrates. Culturing these cells on soft matrix or inhibiting stress fiber formation recapitulated the damage-induced YAP up-regulation observed in vivo, indicating a mechanotransduction-dependent mechanism of YAP activation in podocytes. YAP overexpression in cultured podocytes increased the abundance of extracellular matrix-related proteins that can contribute to fibrosis. YAP activity was increased in mouse models of diabetic nephropathy, and the YAP target CTGF was highly expressed in renal biopsies from glomerular disease patients. Although overexpression of human YAP in mice induced mild proteinuria, pharmacological inhibition of the interaction between YAP and its partner TEAD in rats ameliorated glomerular disease and reduced damage-induced mechanosignaling in the glomeruli. Thus, perturbation of YAP-dependent mechanosignaling is a potential therapeutic target for treating some glomerular diseases.