Expression of Gremlin, a Bone Morphogenetic Protein Antagonist, in Human Diabetic Nephropathy (original) (raw)
Related papers
Nephrology Dialysis Transplantation, 2008
Background. Recent evidence in vitro and in vivo suggests that gremlin, a bone morphogenetic protein antagonist, is participating in tubular epithelial mesenchymal transition (EMT) in diabetic nephropathy as a downstream mediator of TGF-b. Since EMT also occurs in parietal epithelial glomerular cells (PECs) leading to crescent formation, we hypothesized that gremlin could participate in this process. With this aim we studied its expression in 30 renal biopsies of patients with pauci-immune crescentic nephritis. Methods. Gremlin was detected by in situ hybridization (ISH) and immunohistochemistry (IMH) and TGF-b by ISH and Smads by southwestern histochemistry (SWH). Phosphorylated Smad2, CTGF, BMP-7, PCNA, a-SMA, synaptopodin, CD-68, and phenotypic markers of PECs (cytokeratin, E-cadherin), were detected by IMH. In cultured human monocytes, gremlin and CTGF induction by TGF-b was studied by western blot. Results. We observed strong expression of gremlin mRNA and protein in cellular and fibrocellular crescents corresponding to proliferating PECs and monocytes, in co-localization with TGF-b. A marked over-expression of gremlin was also observed in tubular and infiltrating interstitial cells, correlating with tubulointerstitial fibrosis (r ¼ 0.59; P < 0.01). A nuclear Smad activation in the same tubular cells, that are expressing TGF-b and gremlin, was detected. In human cultured monocytes, TGF-b induced gremlin production while CTGF expression was not detected. Conclusion. We postulate that gremlin may play a role in the fibrous process in crescentic nephritis, both in glomerular crescentic and tubular epithelial cells. The co-localization of gremlin and TGF-b expression found in glomeruli and tubular cells suggest that gremlin may be important in mediating some of the pathological effects of TGF-b.
Tubular Overexpression of Gremlin in Transgenic Mice Aggravates Renal Damage in Diabetic Nephropathy
American Journal of Physiology - Renal Physiology, 2015
Diabetic nephropathy (DN) is currently a leading cause of end-stage renal failure worldwide. Gremlin was identified as a gene differentially expressed in mesangial cells exposed to high glucose and in experimental diabetic kidneys. We have described that Gremlin is highly expressed in biopsies from patients with diabetic nephropathy, predominantly in areas of tubulointerstitial fibrosis. In streptozotocin (STZ)-induced experimental diabetes, Gremlin deletion using Grem1 heterozygous knockout mice or by gene silencing, ameliorates renal damage. To study the in vivo role of Gremlin in renal damage, we developed a diabetic model induced by STZ in transgenic (TG) mice expressing human Gremlin in proximal tubular epithelial cells. The albuminuria/creatinuria ratio, determined at week 20 after treatment, was significantly increased in diabetic mice but with no significant differences between transgenic (TG/STZ) and wild-type mice (WT/STZ). To assess the level of renal damage, kidney tissu...
Nephrology Dialysis Transplantation, 2007
Background. Recent evidence in vitro and in vivo suggests that gremlin, a bone morphogenetic protein antagonist, is participating in tubular epithelial mesenchymal transition (EMT) in diabetic nephropathy as a downstream mediator of TGF-b. Since EMT also occurs in parietal epithelial glomerular cells (PECs) leading to crescent formation, we hypothesized that gremlin could participate in this process. With this aim we studied its expression in 30 renal biopsies of patients with pauci-immune crescentic nephritis. Methods. Gremlin was detected by in situ hybridization (ISH) and immunohistochemistry (IMH) and TGF-b by ISH and Smads by southwestern histochemistry (SWH). Phosphorylated Smad2, CTGF, BMP-7, PCNA, a-SMA, synaptopodin, CD-68, and phenotypic markers of PECs (cytokeratin, E-cadherin), were detected by IMH. In cultured human monocytes, gremlin and CTGF induction by TGF-b was studied by western blot. Results. We observed strong expression of gremlin mRNA and protein in cellular and fibrocellular crescents corresponding to proliferating PECs and monocytes, in co-localization with TGF-b. A marked over-expression of gremlin was also observed in tubular and infiltrating interstitial cells, correlating with tubulointerstitial fibrosis (r ¼ 0.59; P < 0.01). A nuclear Smad activation in the same tubular cells, that are expressing TGF-b and gremlin, was detected. In human cultured monocytes, TGF-b induced gremlin production while CTGF expression was not detected. Conclusion. We postulate that gremlin may play a role in the fibrous process in crescentic nephritis, both in glomerular crescentic and tubular epithelial cells. The co-localization of gremlin and TGF-b expression found in glomeruli and tubular cells suggest that gremlin may be important in mediating some of the pathological effects of TGF-b.
Nephron Experimental Nephrology, 2012
brotic genes, such as TGF-β 1 , and augmented the production of ECM proteins, including type I collagen. The blockade of endogenous Gremlin with small interfering RNA inhibited TGF-β 1 -induced ECM upregulation. In tubular epithelial cells Gremlin also increased profibrotic genes and caused EMT changes: phenotypic modulation to myofibroblast-like morphology, loss of epithelial markers and in duction of mesenchymal markers. Moreover, Gremlin gene silencing inhibited TGF-β 1 -induced EMT changes. Conclusions: Gremlin directly activates profibrotic events in cul tured renal fibroblasts and tubular epithelial cells. Moreover, endogenous Gremlin blockade inhibited TGF-β-mediated matrix production and EMT, suggesting that Gremlin could be a novel therapeutic target for renal fibrosis.
PLoS ONE, 2010
Diabetic nephropathy is a complex and poorly understood disease process, and our current treatment options are limited. It remains critical, then, to identify novel therapeutic targets. Recently, a developmental protein and one of the bone morphogenetic protein antagonists, Gremlin, has emerged as a novel modulator of diabetic nephropathy. The high expression and strong co-localization with transforming growth factor-b1 in diabetic kidneys suggests a role for Gremlin in the pathogenesis of diabetic nephropathy. We have constructed a gremlin siRNA plasmid and have examined the effect of Gremlin inhibition on the progression of diabetic nephropathy in a mouse model. CD-1 mice underwent uninephrectomy and STZ treatment prior to receiving weekly injections of the plasmid. Inhibition of Gremlin alleviated proteinuria and renal collagen IV accumulation 12 weeks after the STZ injection and inhibited renal cell proliferation and apoptosis. In vitro experiments, using mouse mesangial cells, revealed that the transfect ion of gremlin siRNA plasmid reversed high glucose induced abnormalities, such as increased cell proliferation and apoptosis and increased collagen IV production. The decreased matrix metalloprotease level was partially normalized by transfection with gremlin siRNA plasmid. Additionally, we observed recovery of bone morphogenetic protein-7 signaling activity, evidenced by increases in phosphorylated Smad 5 protein levels. We conclude that inhibition of Gremlin exerts beneficial effects on the diabetic kidney mainly through maintenance of BMP-7 activity and that Gremlin may serve as a novel therapeutic target in the management of diabetic nephropathy.
Transplantation Proceedings, 2008
Background. Chronic allograft nephropathy (CAN) is the most frequent cause of chronic dysfunction and late loss of renal allografts. Epithelial mesenchymal transition (EMT) has been identified as responsible for the presence of activated interstitial fibroblasts (myofibroblasts) and transforming growth factor beta (TGF-)/Smad is the key signaling mediator. It has been proposed that the bone morphogenetic protein 7 (BMP-7) antagonist, Gremlin, could participate in EMT, as a downstream mediator of TGF-. Methods. We evaluated 33 renal allograft biopsies, 16 of which showed CAN, versus 17 controls. By in situ hybridization we studied the expression of TGF- and Gremlin mRNA. Gremlin, BMP-7, E-cadherin, and ␣-smooth muscle actin (␣-SMA) proteins were evaluated by immunohistochemistry and Smad3 activation by Southwestern. In cultured human tubuloepithelial cells (HK2 cell line), Gremlin induction by TGF- was studied by confocal microscopy. Results. Among renal biopsies of transplanted patients with CAN, we detected upregulation of TGF- in colocalization with Gremlin (RNA and protein), mainly in areas of tubulointerstitial fibrosis. In the same tubules, we observed decreased expression of E-cadherin and induction of vimentin and ␣-SMA. BMP-7 was significantly decreased in the CAN biopsies. In addition, HK2 stimulated with TGF- (1 ng/mL) induced Gremlin production at 72 hours. Conclusion. We postulated that Gremlin is a downstream mediator of TGF-, suggesting a role for Gremlin in EMT observed in CAN.
Tubular Overexpression of Gremlin Induces Renal Damage Susceptibility in Mice
PLoS ONE, 2014
A growing number of patients are recognized worldwide to have chronic kidney disease. Glomerular and interstitial fibrosis are hallmarks of renal progression. However, fibrosis of the kidney remains an unresolved challenge, and its molecular mechanisms are still not fully understood. Gremlin is an embryogenic gene that has been shown to play a key role in nephrogenesis, and its expression is generally low in the normal adult kidney. However, gremlin expression is elevated in many human renal diseases, including diabetic nephropathy, pauci-immune glomerulonephritis and chronic allograft nephropathy. Several studies have proposed that gremlin may be involved in renal damage by acting as a downstream mediator of TGF-b. To examine the in vivo role of gremlin in kidney pathophysiology, we generated seven viable transgenic mouse lines expressing human gremlin (GREM1) specifically in renal proximal tubular epithelial cells under the control of an androgen-regulated promoter. These lines demonstrated 1.2-to 200-fold increased GREM1 expression. GREM1 transgenic mice presented a normal phenotype and were without proteinuria and renal function involvement. In response to the acute renal damage cause by folic acid nephrotoxicity, tubule-specific GREM1 transgenic mice developed increased proteinuria after 7 and 14 days compared with wild-type treated mice. At 14 days tubular lesions, such as dilatation, epithelium flattening and hyaline casts, with interstitial cell infiltration and mild fibrosis were significantly more prominent in transgenic mice than wild-type mice. Tubular GREM1 overexpression was correlated with the renal upregulation of profibrotic factors, such as TGF-b and aSMA, and with increased numbers of monocytes/macrophages and lymphocytes compared to wild-type mice. Taken together, our results suggest that GREM1-overexpressing mice have an increased susceptibility to renal damage, supporting the involvement of gremlin in renal damage progression. This transgenic mouse model could be used as a new tool for enhancing the knowledge of renal disease progression.
Allelic Depletion of grem1 Attenuates Diabetic Kidney Disease
Diabetes, 2009
OBJECTIVE Gremlin (grem1) is an antagonist of the bone morphogenetic protein family that plays a key role in limb bud development and kidney formation. There is a growing appreciation that altered grem1 expression may regulate the homeostatic constraints on damage responses in diseases such as diabetic nephropathy. RESEARCH DESIGN AND METHODS Here we explored whether knockout mice heterozygous for grem1 gene deletion (grem1+/−) exhibit protection from the progression of diabetic kidney disease in a streptozotocin-induced model of type 1 diabetes. RESULTS A marked elevation in grem1 expression was detected in the kidneys and particularly in kidney tubules of diabetic wild-type mice compared with those of littermate controls. In contrast, diabetic grem1+/− mice displayed a significant attenuation in grem1 expression at 6 months of diabetes compared with that in age- and sex-matched wild-type controls. Whereas the onset and induction of diabetes were similar between grem1+/− and wild-t...
Diabetologia, 2005
Aims/hypothesis: We quantified the glomerular expression of thrombospondin-1 (THBS1, also known as TSP-1), transforming growth factor beta 1 (TGFB1, also known as TGF-β1) and connective tissue growth factor (CTGF) at each stage of diabetic nephropathy. We also examined the roles of THBS1 and CTGF in mediating high-glucose-and glycated-albumin-induced synthesis of the matrix protein, fibronectin, by mesangial cells. Methods: THBS1, latent and active TGFB1, and CTGF, were detected by immunohistochemistry and in situ hybridisation in biopsies from 19 insulin-dependent diabetic patients with incipient, manifest and advanced diabetic nephropathy, and in 11 control kidneys. Findings were quantified by image analysis. Human mesangial cells were cultured with normal or high glucose, albumin or glycated albumin (Amadori product), +/−THBS1 or CTGF antisense oligonucleotides, or with peptide W, an inhibitor of TGFB1 bioactivation by THBS1. Proteins were measured by western blot analysis or ELISA. Results: In glomeruli of normal kidneys, mRNA and protein levels for THBS1, latent-TGFB1 and CTGF were low. They were increased in the incipient stage of diabetic nephropathy, predominantly in mesangial areas, with further increases at later stages of the disease. Little or no active TGFB1 immunostaining was detected prior to manifest diabetic nephropathy. In contrast to high-glucose conditions, increases in fibronectin synthesis that were stimulated by glycated albumin were not dependent on THBS1 activation of latent TGFB1. However, increased fibronectin synthesis in both conditions required CTGF. Conclusions/interpretation: Increased glomerular expression of all three factors occurs from the earliest stage of diabetic nephropathy. In contrast to THBS1, CTGF is required for mesangial synthesis of fibronectin stimulated by high glucose or glycated albumin, and is thus a potential therapeutic target.