Project description:Kidney fibrosis is characterized by expansion and activation of platelet-derived growth factor receptor-β (PDGFR-β) positive mesenchymal cells. To study the consequences of PDGFR-ß activation, we developed a model of primary renal fibrosis using transgenic mice with PDGFR-β activation specifically in renal mesenchymal cells, driving their pathological proliferation and phenotypic switch towards myofibroblasts. This resulted in progressive mesangioproliferative glomerulonephritis, mesangial sclerosis and interstitial fibrosis with progressive anemia due to loss of erythropoietin production by fibroblasts. We used microarrays to compare wildtype animals (Foxd1_wt Pdgfrb_wt) to animals with constitutive mesenchymal PDGFR-β activation (Foxd1_mt Pdgfrb V536A) in the kidney to identify target genes of PDGFR-β signaling.
Project description:Kidney fibrosis is characterized by expansion and activation of platelet-derived growth factor receptor-? (PDGFR-?) positive mesenchymal cells. To study the consequences of PDGFR-ß activation, we developed a model of primary renal fibrosis using transgenic mice with PDGFR-? activation specifically in renal mesenchymal cells, driving their pathological proliferation and phenotypic switch towards myofibroblasts. This resulted in progressive mesangioproliferative glomerulonephritis, mesangial sclerosis and interstitial fibrosis with progressive anemia due to loss of erythropoietin production by fibroblasts. Fibrosis induced secondary tubular epithelial injury at later stages, coinciding with microinflammation and aggravated the progression of hypertensive and obstructive nephropathy. Inhibition of PDGFR activation reversed fibrosis more effectively in the tubulointerstitium compared to glomeruli. Gene expression signatures in mice with PDGFR-? activation resembled those found in patients. In conclusion, PDGFR-? activation alone is sufficient to induce progressive renal fibrosis and failure mimicking key aspects of chronic kidney disease in humans. Our data provide direct proof that fibrosis per se can drive chronic organ damage and establish a model of primary fibrosis allowing specific studies targeting fibrosis progression and regression.
Project description:Kidney fibrosis is characterized by expansion and activation of platelet-derived growth factor receptor-β (PDGFR-β)-positive mesenchymal cells. To study the consequences of PDGFR-β activation, we developed a model of primary renal fibrosis using transgenic mice with PDGFR-β activation specifically in renal mesenchymal cells, driving their pathological proliferation and phenotypic switch toward myofibroblasts. This resulted in progressive mesangioproliferative glomerulonephritis, mesangial sclerosis, and interstitial fibrosis with progressive anemia due to loss of erythropoietin production by fibroblasts. Fibrosis induced secondary tubular epithelial injury at later stages, coinciding with microinflammation, and aggravated the progression of hypertensive and obstructive nephropathy. Inhibition of PDGFR activation reversed fibrosis more effectively in the tubulointerstitium compared to glomeruli. Gene expression signatures in mice with PDGFR-β activation resembled those found in patients. In conclusion, PDGFR-β activation alone is sufficient to induce progressive renal fibrosis and failure, mimicking key aspects of chronic kidney disease in humans. Our data provide direct proof that fibrosis per se can drive chronic organ damage and establish a model of primary fibrosis allowing specific studies targeting fibrosis progression and regression.
Project description:The scaffold protein synectin plays a critical role in the trafficking and regulation of membrane receptor pathways. As the platelet derived growth factor receptor (PDGFR) pathway is essential for hepatic stellate cell (HSC) activation and liver fibrosis, we sought to determine the role of synectin on the PDGFR pathway in HSC. To study the role of synectin in the development of liver fibrosis, mice with selective deletion of synectin from HSC were generated and found to be protected from fibrosis. RNAseq revealed that knockdown of synectin in HSC demonstrated reductions in the fibrosis pathway of genes including PDGFR-β, but not PDGFR-α. Chromatin Immunoprecipitation assay of the PDGFR-β promoter upon synectin knockdown revealed a pattern of histone marks associated with decreased transcription, dependent on p300. In contradistinction, synectin was found to regulate PDGFR-α through an alternative mechanism: protection from autophagic degradation. Site directed mutagenesis revealed that ubiquitination of specific PDGFR-α lysine residues is responsible for its autophagic degradation. Furthermore, functional studies showed decreased PDGF dependent proliferation and migration after synectin knockdown. Finally, human cirrhotic livers demonstrated increased synectin expression. This work provides insight into differential transcriptional and post-translational mechanisms of synectin regulation of PDGFRs, which are critical to fibrogenesis.
Project description:Chronic kidney disease (CKD) is one of the fastest growing global causes of death, estimated to rank among the top five by 2040 (Foreman et al, 2018). This illustrates current pitfalls in diagnosis and management of CKD. Advanced CKD requires renal function replacement by dialysis or transplantation. However, earlier CKD stages, even when renal function is still normal, are already associated with an increased risk of premature death (Perez-Gomez et al, 2019). Thus, novel approaches to diagnose and treat CKD are needed. The histopathological hallmark of CKD is kidney fibrosis, which is closely associated with local inflammation and loss of kidney parenchymal cells. Thus, kidney fibrosis is an attractive process to develop tests allowing an earlier diagnosis of CKD and represents a potential therapeutic target to slow CKD progression or promote regression.
Project description:Kidney fibrosis results in progressive loss of function, ultimately leading to kidney failure, for which there are limited effective therapeutic strategies. The transcription factor, Forkhead box P2 (Foxp2), has been implicated in organ development and tumorigenesis through its association with the epithelial-to-mesenchymal transition (EMT) process. In this study, we uncovered a novel role of Foxp2 in kidney fibrosis. Expression of Foxp2 was upregulated in kidney tubules from both human chronic glomerulonephritides and animal models of chronic kidney disease. In vitro, Foxp2 was induced in tubular epithelial cells via TGF-β/Smad3 signaling while knockdown of Foxp2 suppressed TGF-β-induced EMT and accumulation of extracellular matrix proteins. In vivo, tubule-specific deletion of Foxp2 attenuated kidney inflammation and tubulointerstitial fibrosis in murine unilateral ureteral obstruction and unilateral ischemic-reperfusion models of progressive CKD, which were accompanied by reduction in cell cycle arrest. Mechanistically, overexpression of Foxp2 inhibited tubular cell proliferation with induction of G2/M cell cycle arrest. Using chromatin-immunoprecipitation sequencing, we identified Foxp2 target genes that are enriched in PI3K/Akt and TGF-β signaling pathways, and further revealed that Foxp2 directly regulated the transcriptional activities of collagen-1, E-cadherin and p21 that are involved in EMT and cell cycle arrest, thereby promoting the profibrotic process. Collectively, our findings provide novel evidence that Foxp2 regulates TGF-β-induced EMT and cell cycle arrest, the key signaling pathways of kidney fibrosis, and suggest that Foxp2 may be a potential therapeutic target for kidney fibrosis.
Project description:Patients with chronic kidney disease (CKD) are at markedly increased risk of disability, hospitalization, and death. Impaired physical function, which is common in CKD, is a major risk factor for these poor outcomes. CKD patients perform substantially below age-predicted norms on a variety of clinically relevant physical performance tests. Altered muscle physiology is an important cause of these functional deficits. We recently described skeletal muscle fibrosis in the vastus lateralis muscle of patients with severely impaired kidney function. Greater severity of fibrosis was associated with lower leg extension strength and reduced endurance capacity, suggesting that muscle fibrosis in CKD patients is functionally significant. An important unanswered question is whether muscle fibrosis in CKD is a slowly progressive process beginning with early loss of kidney function, or a complication observed only with severe disease. Here, we examined the associations of estimated glomerular filtration rate (a measure of kidney function) with measures of fibrosis across a broad range of kidney function, and tested the effect of receiving treatment with dialysis. We also integrated muscle transcriptomic analyses to provide further insight into this novel aspect of muscle pathology in CKD.
Project description:Kidney fibrosis, characterized by excessive extracellular matrix (ECM) deposition, is a progressive disease that, despite affecting 10% of the population, lacks specific treatments and suitable biomarkers. Aimed at unraveling disease mechanisms and identifying potential therapeutic targets, this study presents a comprehensive, time-resolved multi-omics analysis of kidney fibrosis using an in vitro model system based on human kidney PDGFRβ+ mesenchymal cells. Using computational network modeling we integrated transcriptomics, proteomics, phosphoproteomics, and secretomics with imaging of the extracellular matrix (ECM). We quantified over 14,000 biomolecules across seven time points following TGF-β stimulation, revealing distinct temporal patterns in the expression and activity of known and potential novel renal fibrosis markers and modulators. The resulting time-resolved multi-omic network models allowed us to propose mechanisms related to fibrosis progression through early transcriptional reprogramming. Using siRNA knockdowns and phenotypic assays, we validated predictions and elucidated regulatory mechanisms underlying kidney fibrosis. Notably, we demonstrate that several early-activated transcription factors, including FLI1 and E2F1, act as negative regulators of collagen deposition and propose underlying molecular mechanisms. This work advances our understanding of the pathogenesis of kidney fibrosis and provides a valuable resource for the organ fibrosis research community.