The TGFβ-ERK pathway contributes to Notch3 upregulation in the renal tubular epithelial cells of patients with obstructive nephropathy

Renal interstitial fibrosis is a common renal injury resulted from a variety of chronic kidney conditions and an array of factors. We report here that Notch3 is a potential contributor. In comparison to 6 healthy individuals, a robust elevation of Notch3 expression was observed in the renal tubular epithelial cells of 18 patients with obstructive nephropathy. In a rat unilateral ureteral obstruction (UUO) model which mimics the human disease, Notch3 upregulation closely followed the course of renal injury, renal fibrosis, TGFβ expression, and alpha-smooth muscle actin (α-SMA) expression, suggesting a role of Notch3 in promoting tubulointerstitial fibrosis. This possibility was supported by the observation that TGFβ, the major renal fibrogenic cytokine, stimulated Notch3 expression in human proximal tubule epithelial HK-2 cells. TGFβ enhanced the activation of ERK, p38, but not JNK MAP kinases in HK-2 cells. While inhibition of p38 activation using SB203580 did not affect TGFβ-induced Notch3 expression, inhibition of ERK activation with a MEK1 inhibitor PD98059 dramatically reduced the event. Furthermore, enforced ERK activation through overexpression of the constitutively active MEK1 mutant MEK1Q56P upregulated Notch3 expression in HK-2 cells, and PD98059 reduced ERK activation and Notch3 expression in HK-2 cells expressing MEK1Q56P. Collectively, we provide the first clinical evidence for Notch3 upregulation in patients with obstructive nephropathy; the upregulation is likely mediated through the TGFβ-ERK pathway. This study suggests that Notch3 upregulation contributes to renal injury caused by obstructive nephropathy, which could be prevented or delayed through ERK inhibition.     

Role of Complement 3 in TNF-α-Induced Mesenchymal Transition of Renal Tubular Epithelial Cells In Vitro

Injured renal tubular epithelial cells (RTECs) have been recently thought to directly contribute to the accumulation of myofibroblasts in renal tubulointerstitial fibrosis through a process of epithelial to mesenchymal transition (EMT). However, the factors inducing RTECs to undergo EMT and the underlying mechanisms need to be further elucidated. This study aimed to determine the EMT-inducing activity of proinflammatory cytokine TNF-α and the role for complement 3 (C3) in this activity in an in vitro model of human RTECs (HK-2 cells). Wild type HK-2 cells were treated with TNF-α, IFN-γ or C3a; C3 siRNA- or control siRNA-carrying HK-2 cells were treated with TNF-α. Changes in the cell morphology and phenotype were assessed by microscopy, RT-PCR, western blotting, and immunostaining. TNF-α effectively induced HK-2 cells to express C3 and to transform into morphologically myofibroblast-like cells that lost E-cadherin (a classical epithelial cell marker) expression but acquired alpha-smooth muscle actin (α-SMA, a classical myofibroblast differentiation marker) expression. C3 siRNA robustly attenuated all the morphologic and phenotypic changes induced by TNF-α but the control siRNA showed no effect. Our preliminary observations suggest that TNF-α may induce EMT in RTECs through inducing C3 expression.     

Urinary Uromodulin Excretion Predicts Progression of Chronic Kidney Disease Resulting from IgA Nephropathy

Background

Uromodulin, or Tamm-Horsfall protein, is the most abundant urinary protein in healthy individuals. Recent studies have suggested that uromodulin may play a role in chronic kidney diseases. We examined an IgA nephropathy cohort to determine whether uromodulin plays a role in the progression of IgA nephropathy.

Methods

A total of 344 IgA nephropathy patients were involved in this study. Morphological changes were evaluated with the Oxford classification of IgA nephropathy. Enzyme Linked Immunosorbent Assay (ELISA) measured the urinary uromodulin level on the renal biopsy day. Follow up was done regularly on 185 patients. Time-average blood pressure, time-average proteinuria, estimated glomerular filtration rate (eGFR) and eGFR decline rate were caculated. Association between the urinary uromodulin level and the eGFR decline rate was analyzed with SPSS 13.0.

Results

We found that lower baseline urinary uromodulin levels (P = 0.03) and higher time-average proteinuria (P = 0.04) were risk factors for rapid eGFR decline in a follow-up subgroup of the IgA nephropathy cohort. Urinary uromodulin level was correlated with tubulointerstitial lesions (P = 0.016). Patients that had more tubular atrophy/interstitial fibrosis on the surface had lower urinary uromodulin levels (P = 0.02).

Conclusions

Urinary uromodulin level is associated with interstitial fibrosis/tubular atrophy and contributes to eGFR decline in IgA nephropathy.     

Wnt5a promotes renal tubular inflammation in diabetic nephropathy by binding to CD146 through noncanonical Wnt signaling

Immune and inflammatory factors have emerged as key pathophysiological mechanisms in the progression of diabetic renal injury. Noncanonical Wnt5a signaling plays an essential role in obesity- or diabetes-induced metabolic dysfunction and inflammation, but its explicit molecular mechanisms and biological function in diabetic nephropathy (DN) remain unknown. In this study, we found that the expression of Wnt5a and CD146 in the kidney and the level of soluble form of CD146 (sCD146) in serum and urine samples were upregulated in DN patients compared to controls, and this alteration was correlated with the inflammatory process and progression of renal impairment. Blocking the activation of Wnt5a signaling with the Wnt5a antagonist Box5 prevented JNK phosphorylation and high glucose-induced inflammatory responses in db/db mice and high glucose-treated HK-2 cells. Similar effects were observed by silencing Wnt5a with small-interfering RNA (siRNA) in cultured HK-2 cells. Knockdown of CD146 blocked Wnt5a-induced expression of proinflammatory cytokines and activation of JNK, which suggests that CD146 is essential for the activation of the Wnt5a pathway. Finally, we confirmed that Wnt5a directly interacted with CD146 to activate noncanonical Wnt signaling in HK-2 cells. Taken together, our findings suggest that by directly binding to CD146, Wnt5a-induced noncanonical signaling is a contributing mechanism for renal tubular inflammation in diabetic nephropathy. The concentration of sCD146 in serum and urine could be a potential biomarker to predict renal outcomes in DN patients.Subject terms: Kidney diseases, Inflammation     

Renal tubular fluid shear stress promotes endothelial cell activation

Modified urinary fluid shear stress (FSS) induced by variations of urinary fluid flow and composition is observed in early phases of most kidney diseases. In this study, we hypothesized that changes in urinary FSS represent a tubular aggression that contributes to the development of inflammation, a key event in progression of nephropathies. Human renal tubular cells (HK-2) were exposed to FSS for 30 min at 0.01 Pa. Treatment of human endothelial cells (HMEC-1) with the resulting conditioned medium (FSS-CM) increased C-C chemokine ligand 2 (CCL2) and tumor necrosis factor (TNF)-α protein secretion, increased endothelial vascular adhesion molecule-1 (VCAM-1) mRNA expression and stimulated adhesion of human (THP-1) monocytes to the endothelial monolayer. These effects were TNF-α dependent as they were abolished by neutralization of TNF-α. Interestingly, the origin of TNF-α was not epithelial, but resulted from autocrine endothelial production. However, in contrast to short term FSS, long term FSS (5 h) induced the release of the key inflammatory proteins CCL2 and TNF-α directly from tubular cells. In conclusion, these results suggest for the first time that urinary FSS can contribute to the inflammatory state involved in initiation/perpetuation of renal diseases.     

Indoxyl sulfate upregulates renal expression of MCP-1 via production of ROS and activation of NF-κB, p53, ERK, and JNK in proximal tubular cells

AimsMonocyte chemotactic protein-1 (MCP-1) plays an important role in recruiting monocytes/macrophages to injured tubulointerstitial tissue. The present study examined whether indoxyl sulfate, a uremic toxin, regulates renal expression of MCP-1.Main methodsThe effect of indoxyl sulfate on the expression of MCP-1 was determined using human proximal tubular cells (HK-2 cells) and following animals: (1) Dahl salt-resistant normotensive rats (DN), (2) Dahl salt-resistant normotensive indoxyl sulfate-administered rats (DN + IS), (3) Dahl salt-sensitive hypertensive rats (DH), and (4) Dahl salt-sensitive hypertensive indoxyl sulfate-administered rats (DH + IS).Key findingsDN + IS, DH, and DH + IS rats showed significantly increased mRNA expression of MCP-1 in the kidneys compared with DN rats. DH + IS rats tended to show increased mRNA expression of MCP-1 in the kidneys compared with DH rats. Immunohistochemistry demonstrated the stimulatory effects of indoxyl sulfate on MCP-1 expression and monocyte/macrophage infiltration in the kidneys. Indoxyl sulfate upregulated mRNA and protein expression of MCP-1 in HK-2 cells. Indoxyl sulfate induced activation of ERK, p38, and JNK as well as of NF-κB and p53 in HK-2 cells. An antioxidant, and inhibitors of NF-κB, p53, ERK pathway (MEK1/2), and JNK suppressed indoxyl sulfate-induced mRNA expression of MCP-1 in HK-2 cells.SignificanceIndoxyl sulfate upregulates renal expression of MCP-1 through production of reactive oxygen species (ROS), and activation of NF-κB, p53, ERK, and JNK in proximal tubular cells. Thus, accumulation of indoxyl sulfate in chronic kidney disease might be involved in the pathogenesis of tubulointerstitial injury through induction of MCP-1 in the kidneys.     

Fusion of bone marrow-derived cells with renal tubules contributes to renal dysfunction in diabetic nephropathy

Although diabetic nephropathy (DN) is a major cause of end-stage renal disease, the mechanism of dysfunction has not yet been clarified. We previously reported that in diabetes proinsulin-producing bone marrow-derived cells (BMDCs) fuse with hepatocytes and neurons. Fusion cells are polyploidy and produce tumor necrosis factor (TNF)-α, ultimately causing diabetic complications. In this study, we assessed whether the same mechanism is involved in DN. We performed bone marrow transplantation from male GFP-Tg mice to female C57BL/6J mice and produced diabetes by streptozotocin (STZ) or a high-fat diet. In diabetic kidneys, massive infiltration of BMDCs and tubulointerstitial injury were prominent. BMDCs and damaged tubular epithelial cells were positively stained with proinsulin and TNF-α. Cell fusion between BMDCs and renal tubules was confirmed by the presence of Y chromosome. Of tubular epithelial cells, 15.4% contain Y chromosomes in STZ-diabetic mice, 8.6% in HFD-diabetic mice, but only 1.5% in nondiabetic mice. Fusion cells primarily expressed TNF-α and caspase-3 in diabetic kidney. These in vivo findings were confirmed by in vitro coculture experiments between isolated renal tubular cells and BMDCs. It was concluded that cell fusion between BMDCs and renal tubular epithelial cells plays a crucial role in DN.     

Connective tissue growth factor and fibronectin secretion in renal tubular epithelial cells induced by TGF-beta1: suppressive effects of troglitazone

Although some studies have suggested that troglitazone could retard the progression of glomerulosclerosis, its effects on renal tubulointerstitial fibrosis have not been completely clarified. The aim of this study was to investigate the effects of troglitazone on the secretion of connective tissue growth factor (CTGF) and fibronectin (FN) in human renal proximal tubular epithelial (HK-2) cells induced by transforming growth factor-beta1 (TGF-beta1). The mRNA of CTGF and FN were measured by semi-quantitative RT-PCR. CTGF and FN protein were detected by Western blot and ELISA, respectively. Our results revealed that troglitazone could inhibit CTGF and FN expression in a dose-dependent manner in human renal proximal tubular epithelial cells induced by TGF-beta1, which may be one of the mechanisms of troglitazone contributing to retard the progression of renal tubulointerstitial fibrosis.     

Circulating TNF Receptors 1 and 2 Are Associated with the Severity of Renal Interstitial Fibrosis in IgA Nephropathy

The current study aimed to examine whether the levels of TNF receptors 1 and 2 (TNFR1 and TNFR2) in serum and urine were associated with other markers of kidney injury and renal histological findings, including TNFR expression, in IgA nephropathy (IgAN). The levels of the parameters of interest were measured by immunoassay in 106 biopsy-proven IgAN patients using samples obtained immediately before renal biopsy and in 34 healthy subjects. Renal histological findings were evaluated using immunohistochemistry. The levels of serum TNFRs were higher in IgAN patients than in healthy subjects. The levels of both TNFRs in serum or urine were strongly correlated with each other (r > 0.9). Serum TNFR levels were positively correlated with the urinary protein to creatinine ratio (UPCR) and four markers of tubular damage of interest (N-acetyl-β-D-glucosaminidase [NAG], β2 microglobulin [β2m], liver-type fatty acid-binding protein [L-FABP], and kidney injury molecule-1 [KIM-1]) and negatively correlated with estimated glomerular filtration rate (eGFR). Patients in the highest tertile of serum TNFR levels showed more severe renal interstitial fibrosis than did those in the lowest or second tertiles. The tubulointerstitial TNFR2-, but not TNFR1-, positive area was significantly correlated with the serum levels of TNFRs and eGFR. Stepwise multiple regression analysis revealed that elevated serum TNFR1 or TNFR2 levels were a significant determinant of renal interstitial fibrosis after adjusting for eGFR, UPCR, and other markers of tubular damage. In conclusion, elevated serum TNFR levels were significantly associated with the severity of renal interstitial fibrosis in IgAN patients. However, the source of TNFRs in serum and urine remains unclear.     

CD36 promotes NLRP3 inflammasome activation via the mtROS pathway in renal tubular epithelial cells of diabetic kidneys

Tubulointerstitial inflammation plays a key role in the pathogenesis of diabetic nephropathy (DN). Interleukin-1β (IL-1β) is the key proinflammatory cytokine associated with tubulointerstitial inflammation. The NLRP3 inflammasome regulates IL-1β activation and secretion. Reactive oxygen species (ROS) represents the main mediator of NLRP3 inflammasome activation. We previously reported that CD36, a class B scavenger receptor, mediates ROS production in DN. Here, we determined whether CD36 is involved in NLRP3 inflammasome activation and explored the underlying mechanisms. We observed that high glucose induced-NLRP3 inflammasome activation mediate IL-1β secretion, caspase-1 activation, and apoptosis in HK-2 cells. In addition, the levels of CD36, NLRP3, and IL-1β expression (protein and mRNA) were all significantly increased under high glucose conditions. CD36 knockdown resulted in decreased NLRP3 activation and IL-1β secretion. CD36 knockdown or the addition of MitoTempo significantly inhibited ROS production in HK-2 cells. CD36 overexpression enhanced NLRP3 activation, which was reduced by MitoTempo. High glucose levels induced a change in the metabolism of HK-2 cells from fatty acid oxidation (FAO) to glycolysis, which promoted mitochondrial ROS (mtROS) production after 72 h. CD36 knockdown increased the level of AMP-activated protein kinase (AMPK) activity and mitochondrial FAO, which was accompanied by the inhibition of NLRP3 and IL-1β. The in vivo experimental results indicate that an inhibition of CD36 could protect diabetic db/db mice from tubulointerstitial inflammation and tubular epithelial cell apoptosis. CD36 mediates mtROS production and NLRP3 inflammasome activation in db/db mice. CD36 inhibition upregulated the level of FAO-related enzymes and AMPK activity in db/db mice. These results suggest that NLRP3 inflammasome activation is mediated by CD36 in renal tubular epithelial cells in DN, which suppresses mitochondrial FAO and stimulates mtROS production.Subject terms: Biochemistry, Cell biology     

Tacrolimus ameliorates tubulointerstitial inflammation in diabetic nephropathy via inhibiting the NFATc1/TRPC6 pathway

Tubulointerstitial inflammation is crucial for the progression of diabetic nephropathy (DN), and tubular cells act as a driving force in the inflammatory cascade. Emerging data suggested that tacrolimus (TAC) ameliorates podocyte injury and macrophage infiltration in streptozotocin (STZ) mice. However, the effect of TAC on tubulointerstitial inflammation remains unknown. We found that albuminuria and tubulointerstitial damage improved in db/db mice treated with TAC. Macrophage infiltration and expression of IL‐6, TNF‐α, fibronectin, collagen 1 and cleaved caspase 3 were inhibited as well. In addition, the expression of nuclear factor of activated T cell 1 (NFATc1) and transient receptor potential channel 6 (TRPC6) was up‐regulated in the kidneys of DN patients and correlated with tubular injury and inflammation. The expression of NFATc1 and TRPC6 also increased in the kidneys of db/db mice and HK‐2 cells with high glucose (HG), while TAC inhibited these effects. HG‐induced inflammatory markers and apoptosis were reversed by TAC and NFATc1 siRNA in HK‐2 cells, which was abolished by TRPC6 plasmid. Furthermore, HG‐induced TRPC6 expression was inhibited by NFATc1 siRNA, while NFATc1 nuclear translocation was inhibited by TAC, but was restored by TRPC6 plasmid in HK‐2 cells under HG conditions. These findings suggest that TAC ameliorates tubulointerstitial inflammation in DN through NFATc1/TRPC6 feedback loop.     

AMPK agonist alleviate renal tubulointerstitial fibrosis via activating mitophagy in high fat and streptozotocin induced diabetic mice

Renal tubulointerstitial fibrosis was a crucial pathological feature of diabetic nephropathy (DN), and renal tubular injury might associate with abnormal mitophagy. In this study, we investigated the effects and molecular mechanisms of AMPK agonist metformin on mitophagy and cellular injury in renal tubular cell under diabetic condition. The high fat diet (HFD) and streptozotocin (STZ)-induced type 2 diabetic mice model and HK-2 cells were used in this study. Metformin was administered in the drinking water (200 mg/kg/d) for 24 weeks. Renal tubulointerstitial lesions, oxidative stress and some indicators of mitophagy (e.g., LC3II, Pink1, and Parkin) were examined both in renal tissue and HK-2 cells. Additionally, compound C (an AMPK inhibitor) and Pink1 siRNA were applied to explore the molecular regulation mechanism of metformin on mitophagy. We found that the expression of p-AMPK, Pink1, Parkin, LC3II, and Atg5 in renal tissue of diabetic mice was decreased obviously. Metformin reduced the levels of serum creatinine, urine protein, and attenuated renal oxidative injury and fibrosis in HFD/STZ induced diabetic mice. In addition, Metformin reversed mitophagy dysfunction and the over-expression of NLRP3. In vitro pretreatment of HK-2 cells with AMPK inhibitor compound C or Pink1 siRNA negated the beneficial effects of metformin. Furthermore, we noted that metformin activated p-AMPK and promoted the translocation of Pink1 from the cytoplasm to mitochondria, then promoted the occurrence of mitophagy in HK-2 cells under HG/HFA ambience. Our results suggested for the first time that AMPK agonist metformin ameliorated renal oxidative stress and tubulointerstitial fibrosis in HFD/STZ-induced diabetic mice via activating mitophagy through a p-AMPK-Pink1-Parkin pathway.Subject terms: Diabetes complications, End-stage renal disease, Experimental models of disease     

c‐Jun N‐terminal kinase is largely involved in the regulation of tricellular tight junctions via tricellulin in human pancreatic duct epithelial cells

Tricellulin (TRIC) is a tight junction protein at tricellular contacts where three epithelial cells meet, and it is required for the maintenance of the epithelial barrier. To investigate whether TRIC is regulated via a c‐Jun N‐terminal kinase (JNK) pathway, human pancreatic HPAC cells, highly expressed at tricellular contacts, were exposed to various stimuli such as the JNK activators anisomycin and 12‐O‐tetradecanoylphorbol 13‐acetate (TPA), and the proinflammatory cytokines IL‐1β, TNFα, and IL‐1α. TRIC expression and the barrier function were moderated by treatment with the JNK activator anisomycin, and suppressed not only by inhibitors of JNK and PKC but also by siRNAs of TRIC. TRIC expression was induced by treatment with the PKC activator TPA and proinflammatory cytokines IL‐1β, TNFα, and IL‐1α, whereas the changes were inhibited by a JNK inhibitor. Furthermore, in normal human pancreatic duct epithelial cells using hTERT‐transfected primary cultured cells, the responses of TRIC expression to the various stimuli were similar to those in HPAC cells. TRIC expression in tricellular tight junctions is strongly regulated together with the barrier function via the JNK transduction pathway. These findings suggest that JNK may be involved in the regulation of tricellular tight junctions including TRIC expression and the barrier function during normal remodeling of epithelial cells, and prevent disruption of the epithelial barrier in inflammation and other disorders in pancreatic duct epithelial cells. J. Cell. Physiol. 225: 720–733, 2010. © 2010 Wiley‐Liss, Inc.     

Expression of Somatostatin and Somatostatin Receptor Subtypes 1�C5 in Human Normal and Diseased Kidney

Somatostatin mediates inhibitory functions through five G protein–coupled somatostatin receptors (sst_1–5). We used immunohistochemistry, immunofluorescence, and RT-PCR to determine the presence of somatostatin receptors sst₁, sst_2A, sst_2B, sst₃, sst₄, and sst₅ in normal and IgA nephropathy human kidney. All somatostatin receptors were detected in the thin tubules (distal convoluted tubules and loops of Henle) and thick tubules (proximal convoluted tubules) in the tissue sections from nephrectomy and biopsy samples. Immunopositive sst₁ and sst₄ staining was more condensed in the cytoplasm of tubular epithelial cells. In normal kidney tissue sections, podocytes and mesangial cells in the glomeruli stained for sst₁, sst_2B, sst₄ and sst₅, and stained weakly for sst₃. In IgA kidney tissue, the expression of somatostatin receptors was significantly increased with particular immmunopositive staining for sst₁, sst_2B, sst₄, and sst₅ within glomeruli. In the epithelial cells, the staining for sst_2B and sst₄ in proximal tubules and sst₁, sst_2B, and sst₅ in distal tubules was increased. The mRNA expression of sst_1–5 was also detected by RT-PCR. Somatostatin and all five receptor subtypes were ubiquitously distributed in normal kidney and IgA nephropathy. The increased expression of somatostatin receptors in IgA nephropathy kidney might be the potential pathogenesis of inflammatory renal disease. (J Histochem Cytochem 56:733–743, 2008)     

Pathophysiological significance of cylindromatosis in the vascular endothelium and macrophages for the initiation of age-related atherogenesis

Cardiovascular disease is one of the leading causes of death in the elderly, and novel therapeutic targets against atherogenesis are urgent. The initiation of atherosclerotic changes of monocyte adhesion on the vascular endothelium and subsequent foam cell formation are noteworthy pathophysiologies when searching for strategies to prevent the progression of age-related atherosclerosis. We report the significance of the deubiquitinating enzyme cylindromatosis (CYLD) in vascular remodeling by interference with inflammatory responses regulated by NF-κB signaling. The purpose of this study was to elucidate the pathological functions of CYLD in the early phase of atherogenesis associated with aging.Treatment with inflammatory cytokines induced endogenous CYLD in aortic endothelial cells (HAECs) and THP-1?cells. siRNA-mediated CYLD silencing led to enhanced monocyte adhesion along with increased adhesion molecules in HAECs treated with TNFα. In siRNA-mediated CYLD silenced RAW 264.7 macrophages treated with oxidized LDL (oxLDL), augmented lipid accumulation was observed, along with increased expression of the class A macrophage scavenger receptor (SR-A), lectin-like oxidized LDL receptor-1 (LOX-1), CD36, fatty acid binding protein 4 (FABP4), the cholesterol ester synthase acyl-CoA cholesterol acyltransferase (ACAT1), MCP-1, and IL-1β and decreased expression of scavenger receptor class B type I (SR-BI). Intriguingly, CYLD gene expression was significantly reduced in bone marrow-derived macrophages of aged mice compared that of young mice, as well as in senescent HAECs compared with young cells.These findings suggest that age-related attenuation of CYLD expression in endothelial cells (ECs) and macrophages triggers the initiation of age-related atherogenesis by exacerbating monocyte adhesion on the endothelium and foam cell formation. CYLD in the vasculature may be a novel therapeutic target, especially in the early preventive intervention against the initiation of age-related atherogenesis.     

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.