Nicotinamide reduces renal interstitial fibrosis by suppressing tubular injury and inflammation

Renal interstitial fibrosis is a common pathological feature in progressive kidney diseases currently lacking effective treatment. Nicotinamide (NAM), a member of water‐soluble vitamin B family, was recently suggested to have a therapeutic potential for acute kidney injury (AKI) in mice and humans. The effect of NAM on chronic kidney pathologies, including renal fibrosis, is unknown. Here we have tested the effects of NAM on renal interstitial fibrosis using in vivo and in vitro models. In vivo, unilateral urethral obstruction (UUO) induced renal interstitial fibrosis as indicated Masson trichrome staining and expression of pro‐fibrotic proteins, which was inhibited by NAM. In UUO, NAM suppressed tubular atrophy and apoptosis. In addition, NAM suppressed UUO‐associated T cell and macrophage infiltration and induction of pro‐inflammatory cytokines, such as TNF‐α and IL‐1β. In cultured mouse proximal tubule cells, NAM blocked TGF–β‐induced expression of fibrotic proteins, while it marginally suppressed the morphological changes induced by TGF‐β. NAM also suppressed the expression of pro‐inflammatory cytokines (eg MCP‐1 and IL‐1β) during TGF‐β treatment of these cells. Collectively, the results demonstrate an anti‐fibrotic effect of NAM in kidneys, which may involve the suppression of tubular injury and inflammation.     

Withaferin A protects against endoplasmic reticulum stress-associated apoptosis,inflammation, and fibrosis in the kidney of a mouse model of unilateral ureteral obstruction

BackgroundWithaferin A is a functional ingredient of a traditional medicinal plant, Withania somnifera, which has been broadly used in India for protecting against chronic diseases. This bioactive steroidal lactone possesses multiple functions such as anti-oxidation, anti-inflammation, and immunomodulation. Chronic kidney disease (CKD) is one of the major health problems worldwide with the high complication, morbidity, and mortality rates. The detailed effects and underlying mechanisms of withaferin A on CKD progression still remain to be clarified.PurposeWe aimed to investigate whether withaferin A treatment ameliorates the development of renal fibrosis and its related mechanisms in a CKD mouse model.MethodsA mouse model of unilateral ureteral obstruction (UUO) was used to mimic the progression of CKD. Male adult C57BL/6J mice were orally administered with 3 mg/kg/day withaferin A for 14 consecutive days after UUO surgery. Candesartan (5 mg/kg/day) was used as a positive control.ResultsBoth Withaferin A and candesartan treatments significantly ameliorated the histopathological changes and collagen deposition in the UUO kidneys. Withaferin A could significantly reverse the increases in the protein levels of pro-fibrotic factors (fibronectin, transforming growth factor-β, and α-smooth muscle actin), inflammatory signaling molecules (phosphorylated nuclear factor-κB-p65, interleukin-1β, and cyclooxygenase-2), and cleaved caspase-3, apoptosis, and infiltration of neutrophils in the UUO kidneys. The protein levels of endoplasmic reticulum (ER) stress-associated molecules (GRP78, GRP94, ATF4, CHOP, phosphorylated eIF2α, and cleaved caspase 12) were increased in the kidneys of UUO mice, which could be significantly reversed by withaferin A treatment.ConclusionWithaferin A protects against the CKD progression that is, at least in part, associated with the moderation of ER stress-related apoptosis, inflammation, and fibrosis in the kidneys of CKD. Withaferin A may serve as a potential therapeutic agent for the development of CKD.     

Loss of poly(ADP-ribose) polymerase 1 attenuates renal fibrosis and inflammation during unilateral ureteral obstruction

Poly(ADP-ribose) polymerase 1 (PARP1) contributes to necrotic cell death and inflammation in several disease models; however, the role of PARP1 in fibrogenesis remains to be defined. Here, we tested whether PARP1 was involved in the pathogenesis of renal fibrosis using the unilateral ureteral obstruction (UUO) mouse model. UUO was performed by ligation of the left ureter near the renal pelvis in Parp1-knockout (KO) and wild-type (WT) male mice. After 10 days of UUO, renal PARP1 expression and activation were strongly increased by 6- and 13-fold, respectively. Interstitial fibrosis induced by UUO was significantly attenuated in Parp1-KO kidneys compared with that in WT kidneys at 10 days, but not at 3 days, based on collagen deposition, α-smooth muscle actin (α-SMA), and fibronectin expression. Intriguingly, the UUO kidneys in Parp1-KO mice showed a dramatic decrease in infiltration of neutrophil and reduction in expression of proinflammatory proteins including intercellular adhesion molecule-1, tumor necrosis factor-α, inducible nitric oxide synthase, and toll-like receptor 4 as well as phosphorylation of nuclear factor-κB p65, but not transforming growth factor-β1 (TGF-β1) at both 3 and 10 days. Pharmacological inhibition of PARP1 in rat renal interstitial fibroblast (NRK-49F) cell line or genetic ablation in primary mouse embryonic fibroblast cells did not affect TGF-β1-induced de novo α-SMA expression. Parp1 deficiency significantly attenuated UUO-induced histological damage in the kidney tubular cells, but not apoptosis. These data suggest that PARP1 induces necrotic cell death and contributes to inflammatory signaling pathways that trigger fibrogenesis in obstructive nephropathy.     

Overexpression of Heme Oxygenase-1 Prevents Renal Interstitial Inflammation and Fibrosis Induced by Unilateral Ureter Obstruction

Renal fibrosis plays an important role in the onset and progression of chronic kidney diseases. Many studies have demonstrated that heme oxygenase-1 (HO-1) is involved in diverse biological processes as a cytoprotective molecule, including anti-inflammatory, anti-oxidant, anti-apoptotic, antiproliferative, and immunomodulatory effects. However, the mechanisms of HO-1 prevention in renal interstitial fibrosis remain unknown. In this study, HO-1 transgenic (TG) mice were employed to investigate the effect of HO-1 on renal fibrosis using a unilateral ureter obstruction (UUO) model and to explore the potential mechanisms. We found that HO-1 was adaptively upregulated in kidneys of both TG and wild type (WT) mice after UUO. The levels of HO-1 mRNA and protein were increased in TG mice compared with WT mice under normal conditions. HO-1 expression was further enhanced after UUO and remained high during the entire experimental process. Renal interstitial fibrosis in the TG group was significantly attenuated compared with that in the WT group after UUO. Moreover, overexpression of HO-1 inhibited the loss of peritubular capillaries. In addition, UUO-induced activation and proliferation of myofibroblasts were suppressed by HO-1 overexpression. Furthermore, HO-1 restrained tubulointerstitial infiltration of macrophages and regulated the secretion of inflammatory cytokines in UUO mice. We also found that high expression of HO-1 inhibited reactivation of Wnt/β-catenin signaling, which could play a crucial role in attenuating renal fibrosis. In conclusion, these data suggest that HO-1 prevents renal tubulointerstitial fibrosis possibly by regulating the inflammatory response and Wnt/β-catenin signaling. This study provides evidence that augmentation of HO-1 levels may be a therapeutic strategy against renal interstitial fibrosis.     

Role of TREM1-DAP12 in Renal Inflammation during Obstructive Nephropathy

Tubulo-interstitial damage is a common finding in the chronically diseased kidney and is characterized by ongoing inflammation and fibrosis leading to renal dysfunction and end-stage renal disease. Upon kidney injury, endogenous ligands can be released which are recognized by innate immune sensors to alarm innate immune system. A new family of innate sensors is the family of TREM (triggering receptor expressed on myeloid cell). TREM1 is an activating receptor and requires association with transmembrane adapter molecule DAP12 (DNAX-associated protein 12) for cell signaling. TREM1-DAP12 pathway has a cross-talk with intracellular signaling pathways of several Toll-like receptors (TLRs) and is able to amplify TLR signaling and thereby contributes to the magnitude of inflammation. So far, several studies have shown that TLRs play a role in obstructive nephropathy but the contribution of TREM1-DAP12 herein is unknown. Therefore, we studied TREM1 expression in human and murine progressive renal diseases and further investigated the role for TREM1-DAP12 by subjecting wild-type (WT), TREM1/3 double KO and DAP12 KO mice to murine unilateral ureter obstruction (UUO) model. In patients with hydronephrosis, TREM1 positive cells were observed in renal tissue. We showed that in kidneys from WT mice, DAP12 mRNA and TREM1 mRNA and protein levels were elevated upon UUO. Compared to WT mice, DAP12 KO mice displayed less renal MCP-1, KC and TGF-β1 levels and less influx of macrophages during progression of UUO, whereas TREM1/3 double KO mice displayed less renal MCP-1 level. Renal fibrosis was comparable in WT, TREM1/3 double KO and DAP12 KO mice. We conclude that DAP12, partly through TREM1/3, is involved in renal inflammation during progression of UUO.     

Blockade of myeloid differentiation protein 2 prevents obesity‐induced inflammation and nephropathy

Obesity is a major and independent risk factor of kidney diseases. The pathogenic mechanisms of obesity‐associated renal injury are recognized to at least involve a lipid‐rich and pro‐inflammatory state of the renal tissues, but specific mechanisms establishing causal relation remain unknown. Saturated fatty acids are elevated in obesity, and known to induce chronic inflammation in kidneys. Myeloid differentiation protein 2 (MD2) is an important protein in lipopolysaccharide‐induced innate immunity response and inflammation. We suggested that obesity‐associated renal injury is regulated by MD2 thereby driving an inflammatory renal injury. The used three mouse models for in vivo study: MD2 knockout mice (KO) maintained on high fat diet (HFD), wild‐type mice on HFD plus L6H21, a specific MD2 inhibitor and KO mice given palmitic acid (PA) by IV injection. The in vitro studies were carried out in cultured renal tubular epithelial cells, mouse mesangial cells and primary macrophages, respectively. The HFD mice presented with increased hyperlipidemia, serum creatinine and proteinuria. Renal tissue from HFD mice had increased fibrosis, inflammatory cytokines, macrophage infiltration, and activation of NF‐κB and MAPKs. This HFD‐induced renal injury profile was not observed in KO mice or L6H21‐treated mice. Mice given PA mimmicked the HFD‐induced renal injury profiles, which were prevented by MD2 knockout. The in vitro data further confirmed MD2 mediates PA‐induced inflammation. MD2 is causally related with obesity‐associated renal inflammatory injury. We believe that MD2 is an attractive target for future therapeutic strategies in obesity‐associated kidney diseases.     

Deletion of Smad3 protects against C-reactive protein-induced renal fibrosis and inflammation in obstructive nephropathy

Introduction and Aims: Elevated plasma levels of C-reactive protein (CRP) are closely associated with progressive renal injury in patients with chronic kidney disease (CKD). Here, we tested a hypothesis that CRP may promote renal fibrosis and inflammation via a TGF-β/Smad3-dependent mechanism.Methods: Role and mechanisms of TGF-β/Smad3 in CRP-induced renal fibrosis and inflammation were examined in a mouse model of unilateral ureteral obstruction (UUO) induced in CRP Tg/Smad3 KO mice and in a rat tubular epithelial cell line in which Smad3 gene is stably knocked down (S3KD-NRK52E).Results: We found that mice overexpressing the human CRP gene were largely promoted renal inflammation and fibrosis as evidenced by increasing IL-1β, TNF-α, MCP-1 expression, F4/80⁺ macrophages infiltration, and marked accumulation of α-smooth muscle actin (α-SMA), collagen I and fibronectin in the UUO kidney, which were blunted when Smad3 gene was deleted in CRPtg-Smad3KO. Mechanistically, we found that the protection of renal inflammation and fibrosis in the UUO kidney of CRPtg-Smad3KO mice was associated with the inactivation of CD32-NF-κB and TGF-β/Smad3 signaling.Conclusion: In conclusion, Smad3 deficiency protects against CRP-mediated renal inflammation and fibrosis in the UUO kidney by inactivating CD32-NF-κB and TGF-β/Smad3 signaling.     

Persistent activation of autophagy in kidney tubular cells promotes renal interstitial fibrosis during unilateral ureteral obstruction

Renal fibrosis is the final, common pathway of end-stage renal disease. Whether and how autophagy contributes to renal fibrosis remains unclear. Here we first detected persistent autophagy in kidney proximal tubules in the renal fibrosis model of unilateral ureteral obstruction (UUO) in mice. UUO-associated fibrosis was suppressed by pharmacological inhibitors of autophagy and also by kidney proximal tubule-specific knockout of autophagy-related 7 (PT-Atg7 KO). Consistently, proliferation and activation of fibroblasts, as indicated by the expression of ACTA2/α-smooth muscle actin and VIM (vimentin), was inhibited in PT-Atg7 KO mice, so was the accumulation of extracellular matrix components including FN1 (fibronectin 1) and collagen fibrils. Tubular atrophy, apoptosis, nephron loss, and interstitial macrophage infiltration were all inhibited in these mice. Moreover, these mice showed a specific suppression of the expression of a profibrotic factor FGF2 (fibroblast growth factor 2). In vitro, TGFB1 (transforming growth factor β 1) induced autophagy, apoptosis, and FN1 accumulation in primary proximal tubular cells. Inhibition of autophagy suppressed FN1 accumulation and apoptosis, while enhancement of autophagy increased TGFB1-induced-cell death. These results suggest that persistent activation of autophagy in kidney proximal tubules promotes renal interstitial fibrosis during UUO. The profibrotic function of autophagy is related to the regulation on tubular cell death, interstitial inflammation, and the production of profibrotic factors.     

Suppression of LMCD1 ameliorates renal fibrosis by blocking the activation of ERK pathway

Tubulointerstitial fibrosis is a common pathway of chronic kidney disease (CKD) and is closely related to the progression of CKD. LMCD1, acting as an intermediary, has been reported to play a role in cardiac fibrosis. However, its role in renal fibrosis is yet to be deciphered. Based on the GEO database, we found the expression of LMCD1 is increased in kidney tissues of CKD patients and in human proximal tubular epithelial (HK-2) cells treated with transforming growth factor-β1 (TGF-β1), suggesting that LMCD1 may be involved in tubulointerstitial fibrosis. Herein, we investigated the role of LMCD1 in mice with unilateral ureteral obstruction (UUO) and in TGF-β1-stimulated HK-2 cells. In the UUO model, the expression of LMCD1 was upregulated. UUO-induced renal histopathological changes were mitigated by knockdown of LMCD1. LMCD1 silence alleviated renal interstitial fibrosis in UUO mice by decreasing the expression of TGF-β1, fibronectin, collagen I, and collagen III. LMCD1 deficiency suppressed cell apoptosis in kidney to prevent UUO-triggered renal injury. Furthermore, LMCD1 deficiency blocked the activation of ERK signaling in UUO mice. In vitro, LMCD1 was upregulated in HK-2 cells after TGF-β1 stimulation. LMCD1 silence abrogated TGF-β1-mediated upregulation of fibrotic genes. Treatment of HK-2 cells with ERK-specific inhibitor SCH772984 and agonist TPA validated LMCD1 exerted its function via activating ERK signaling. Together, our findings suggest that inhibition of LMCD1 protects against renal interstitial fibrosis by impeding ERK activation.     

Genetic deficiency of Smad3 protects the kidneys from atrophy and interstitial fibrosis in 2K1C hypertension

Although the two-kidney, one-clip (2K1C) model is widely used as a model of human renovascular hypertension, mechanisms leading to the development of fibrosis and atrophy in the cuffed kidney and compensatory hyperplasia in the contralateral kidney have not been defined. Based on the well-established role of the transforming growth factor (TGF)-β signaling pathway in renal fibrosis, we tested the hypothesis that abrogation of TGF-β/Smad3 signaling would prevent fibrosis in the cuffed kidney. Renal artery stenosis (RAS) was established in mice with a targeted disruption of exon 2 of the Smad3 gene (Smad3 KO) and wild-type (WT) controls by placement of a polytetrafluoroethylene cuff on the right renal artery. Serial pulse-wave Doppler ultrasound assessments verified that blood flow through the cuffed renal artery was decreased to a similar extent in Smad3 KO and WT mice. Two weeks after surgery, systolic blood pressure and plasma renin activity were significantly elevated in both the Smad3 KO and WT mice. The cuffed kidney of WT mice developed renal atrophy (50% reduction in weight after 6 wk, P < 0.0001), which was associated with the development of interstitial fibrosis, tubular atrophy, and interstitial inflammation. Remarkably, despite a similar reduction of renal blood flow, the cuffed kidney of the Smad3 KO mice showed minimal atrophy (9% reduction in weight, P = not significant), with no significant histopathological alterations (interstitial fibrosis, tubular atrophy, and interstitial inflammation). We conclude that abrogation of TGF-β/Smad3 signaling confers protection against the development of fibrosis and atrophy in RAS.     

Up-regulation of the human-specific CHRFAM7A gene protects against renal fibrosis in mice with obstructive nephropathy

Renal fibrosis is a major factor in the progression of chronic kidney diseases. Obstructive nephropathy is a common cause of renal fibrosis, which is also accompanied by inflammation. To explore the effect of human-specific CHRFAM7A expression, an inflammation-related gene, on renal fibrosis during obstructive nephropathy, we studied CHRFAM7A transgenic mice and wild type mice that underwent unilateral ureteral obstruction (UUO) injury. Transgenic overexpression of CHRFAM7A gene inhibited UUO-induced renal fibrosis, which was demonstrated by decreased fibrotic gene expression and collagen deposition. Furthermore, kidneys from transgenic mice had reduced TGF-β1 and Smad2/3 expression following UUO compared with those from wild type mice with UUO. In addition, the overexpression of CHRFAM7A decreased release of inflammatory cytokines in the kidneys of UUO-injured mice. In vitro, the overexpression of CHRFAM7A inhibited TGF-β1-induced increase in expression of fibrosis-related genes in human renal tubular epithelial cells (HK-2 cells). Additionally, up-regulated expression of CHRFAM7A in HK-2 cells decreased TGF-β1-induced epithelial-mesenchymal transition (EMT) and inhibited activation f TGF-β1/Smad2/3 signalling pathways. Collectively, our findings demonstrate that overexpression of the human-specific CHRFAM7A gene can reduce UUO-induced renal fibrosis by inhibiting TGF-β1/Smad2/3 signalling pathway to reduce inflammatory reactions and EMT of renal tubular epithelial cells.     

Reduced NOV/CCN3 Expression Limits Inflammation and Interstitial Renal Fibrosis after Obstructive Nephropathy in Mice

The main hallmark of chronic kidney disease (CKD) is excessive inflammation leading to interstitial tissue fibrosis. It has been recently reported that NOV/CCN3 could be involved in kidney damage but its role in the progression of nephropathies is poorly known. NOV/CCN3 is a secreted multifunctional protein belonging to the CCN family involved in different physiological and pathological processes such as angiogenesis, inflammation and cancers. The purpose of our study was to determine the role of NOV/CCN3 in renal inflammation and fibrosis related to primitive tubulointerstitial injury. After unilateral ureteral obstruction (UUO), renal histology and real-time PCR were performed in NOV/CCN3-/- and wild type mice. NOV/CCN3 mRNA expression was increased in the obstructed kidneys in the early stages of the obstructive nephropathy. Interestingly, plasmatic levels of NOV/CCN3 were strongly induced after 7 days of UUO and the injection of recombinant NOV/CCN3 protein in healthy mice significantly increased CCL2 mRNA levels. Furthermore, after 7 days of UUO NOV/CCN3-/- mice displayed reduced proinflammatory cytokines and adhesion markers expression leading to restricted accumulation of interstitial monocytes, in comparison with their wild type littermates. Consequently, in NOV/CCN3-/- mice interstitial renal fibrosis was blunted after 15 days of UUO. In agreement with our experimental data, NOV/CCN3 expression was highly increased in biopsies of patients with tubulointerstitial nephritis. Thus, the inhibition of NOV/CCN3 may represent a novel target for the progression of renal diseases.     

Continuous AMD3100 Treatment Worsens Renal Fibrosis through Regulation of Bone Marrow Derived Pro-Angiogenic Cells Homing and T-Cell-Related Inflammation

AMD3100 is a small molecule inhibitor of chemokine receptor type 4 (CXCR4), which is located in the cell membranes of CD34+ cells and a variety of inflammatory cells and has been reported to reduce organ fibrosis in the lung, liver and myocardium. However, the effect of AMD3100 on renal fibrosis is unknown. This study investigated the impact of AMD3100 on renal fibrosis. C57bl/6 mice were subjected to unilateral ureteral obstruction (UUO) surgery with or without AMD3100 administration. Tubular injury, collagen deposition and fibrosis were detected and analyzed by histological staining, immunocytochemistry and Western Blot. Bone marrow derived pro-angiogenic cells (CD45+, CD34+ and CD309+ cells) and capillary density (CD31+) were measured by flow cytometry (FACS) and immunofluorescence (IF). Inflammatory cells, chemotactic factors and T cell proliferation were characterized. We found that AMD3100 treatment did not alleviate renal fibrosis but, rather, increased tissue damage and renal fibrosis. Continuous AMD3100 administration did not improve bone marrow derived pro-angiogenic cells mobilization but, rather, inhibited the migration of bone marrow derived pro-angiogenic cells into the fibrotic kidney. Additionally, T cell infiltration was significantly increased in AMD3100-treated kidneys compared to un-treated kidneys. Thus, treatment of UUO mice with AMD3100 led to an increase in T cell infiltration, suggesting that AMD3100 aggravated renal fibrosis.     

Reduced Klotho expression level in kidney aggravates renal interstitial fibrosis

Renal expression of the klotho gene is markedly suppressed in chronic kidney disease (CKD). Since renal fibrosis is the final common pathology of CKD, we tested whether decreased Klotho expression is a cause and/or a result of renal fibrosis in mice and cultured renal cell lines. We induced renal fibrosis by unilateral ureteral obstruction (UUO) in mice with reduced Klotho expression (kl/+ mice) and compared them with wild-type mice. The UUO kidneys from kl/+ mice expressed significantly higher levels of fibrosis markers such as α-smooth muscle actin (α-SMA), fibronectin, and transforming growth factor-β(1) (TGF-β(1)) than those from wild-type mice. In addition, in cultured renal fibroblast cells (NRK49F), the levels of α-SMA and PAI1 expression were significantly suppressed by addition of recombinant Klotho protein to the medium. The similar effects were observed by a TGF-β(1) receptor inhibitor (ALK5 inhibitor). These observations suggest that low renal Klotho expression enhances TGF-β(1) activity and is a cause of renal fibrosis. On the other hand, TGF-β(1) reduced Klotho expression in renal cultured epithelial cells (inner medullary collecting duct and human renal proximal tubular epithelium), suggesting that low renal Klotho expression is a result of renal fibrosis. Taken together, renal fibrosis can trigger a deterioration spiral of Klotho expression, which may be involved in the pathophysiology of CKD progression.     

Autophagy in FOXD1 stroma-derived cells regulates renal fibrosis through TGF-β and NLRP3 inflammasome pathway

Renal fibrosis is the final common pathway of various renal injuries and it leads to chronic kidney disease. Recent studies reported that FOXD1-lineage pericyte plays a critical role in tubulointerstitial fibrosis (TIF). However the regulatory mechanisms remain unclear. Autophagy is a cellular process of degradation of damaged cytoplasmic components that regulates cell death and proliferation. To investigate the role of autophagy in FOXD1-lineage pericytes on renal TIF, we generated the FOXD1-lineage stromal cell-specific Atg7 deletion (Atg7^△FOXD1) mice. FOXD1-lineage stromal cell-specific Atg7 deletion enhanced renal TIF through Smad-dependent transforming growth factor (TGF)-β signaling after unilateral ureteral obstruction (UUO). FOXD1-lineage stromal cell-specific Atg7 deletion increased the accumulation of interstitial myofibroblasts and enhanced the differentiation of pericytes into myofibroblasts after UUO. Peritubular capillary rarefaction was accelerated in Atg7^△FOXD1 mice after UUO. Atg7^△FOXD1 mice increased the accumulation of SQSTM1/p62-positive aggregates in the obstructed kidney and resulted in increased expression of NLRP3 inflammasome, interleukin (IL) 1-β and caspase-1 signaling pathway, which enhanced apoptosis of interstitial cells after UUO. In summary, our data showed that autophagy in FOXD1-lineage stromal cells plays a protective role in renal TIF through regulating the Smad4 dependent TGF-β an NLRP3 inflammasome signaling pathway.     

Petchiether A attenuates obstructive nephropathy by suppressing TGF‐β/Smad3 and NF‐κB signalling

Obstructive nephropathy is the end result of a variety of diseases that block drainage from the kidney(s). Transforming growth factor‐β1 (TGF‐β1)/Smad3‐driven renal fibrosis is the common pathogenesis of obstructive nephropathy. In this study, we identified petchiether A (petA), a novel small‐molecule meroterpenoid from Ganoderma, as a potential inhibitor of TGF‐β1‐induced Smad3 phosphorylation. The obstructive nephropathy was induced by unilateral ureteral obstruction (UUO) in mice. Mice received an intraperitoneal injection of petA/vehicle before and after UUO or sham operation. An in vivo study revealed that petA protected against renal inflammation and fibrosis by reducing the infiltration of macrophages, inhibiting the expression of proinflammatory cytokines (interleukin‐1β and tumour necrosis factor‐α) and reducing extracellular matrix deposition (α‐smooth muscle actin, collagen I and fibronectin) in the obstructed kidney of UUO mice; these changes were associated with suppression of Smad3 and NF‐κB p65 phosphorylation. Petchiether A inhibited Smad3 phosphorylation in vitro and down‐regulated the expression of the fibrotic marker collagen I in TGF‐β1‐treated renal epithelial cells. Further, we found that petA dose‐dependently suppressed Smad3‐responsive promoter activity, indicating that petA inhibits gene expression downstream of the TGF‐β/Smad3 signalling pathway. In conclusion, our findings suggest that petA protects against renal inflammation and fibrosis by selectively inhibiting TGF‐β/Smad3 signalling.     

Bone marrow–derived mesenchymal stem cells attenuate tubulointerstitial injury through multiple mechanisms in UUO model

Current evidence supports the use of bone marrow–derived mesenchymal stem cells (MSCs) for a diverse range of clinical applications, and many studies have shown that MSCs have renal-protective effects, but the mechanism is not well understood. Therefore, in this study, we aim to further identify whether MSCs can attenuate renal fibrosis by decreasing tubulointerstitial injury in a unilateral ureteral obstruction (UUO) model. In this study, we cultured MSCs and then transplanted them into a UUO model through the tail vein. Histology, cell proliferation, peritubular capillary (PTC) loss and myofibroblast markers were examined on days 3, 7 and 14 after surgery. We demonstrated that renal interstitial fibrosis in the MSC group was significantly attenuated compared with the UUO and DMEM groups. Moreover, MSC treatment inhibited the loss of PTCs and increased parenchymal cell proliferation. In addition, UUO-induced activation and proliferation of myofibroblasts were suppressed by MSC infusion. Furthermore, MSCs attenuated tubulointerstitial infiltration of macrophages in UUO mice. Tubulointerstitial damage plays a very important role in the progression of chronic kidney disease (CKD). PTC loss, macrophage recruitment, and myofibroblast activation are directly correlated with the development of renal tubulointerstitial fibrosis. Our results suggest that MSC infusion in the UUO model is a promising therapeutic strategy for promoting kidney repair.     

Identification of a microRNA signature in renal fibrosis: role of miR-21

Renal fibrosis is a final stage of many forms of kidney disease and leads to impairment of kidney function. The molecular pathogenesis of renal fibrosis is currently not well-understood. microRNAs (miRNAs) are important players in initiation and progression of many pathologic processes including diabetes, cancer, and cardiovascular disease. However, the role of miRNAs in kidney injury and repair is not well-characterized. In the present study, we found a unique miRNA signature associated with unilateral ureteral obstruction (UUO)-induced renal fibrosis. We found altered expression in UUO kidneys of miRNAs that have been shown to be responsive to stimulation by transforming growth factor (TGF)-β1 or TNF-α. Among these miRNAs, miR-21 demonstrated the greatest increase in UUO kidneys. The enhanced expression of miR-21 was located mainly in distal tubular epithelial cells. miR-21 expression was upregulated in response to treatment with TGF-β1 or TNF-α in human renal tubular epithelial cells in vitro. Furthermore, we found that blocking miR-21 in vivo attenuated UUO-induced renal fibrosis, presumably through diminishing the expression of profibrotic proteins and reducing infiltration of inflammatory macrophages in UUO kidneys. Our data suggest that targeting specific miRNAs could be a novel therapeutic approach to treat renal fibrosis.