Renal Fibrogenesis Research Articles

518-P: Involvement of Low-Density Lipoprotein Receptor-Related Protein 5 in Chronic Kidney Diseases via Modulation of TGF-β-Smad2/3 Signaling

Aims: Low-density lipoprotein receptor-related protein 5 (LRP5) is known as a co-receptor of canonical Wnt signaling. This study aimed to investigate LRP5’s role in chronic kidney diseases including diabetic and obstructive nephropathies, and its new role in regulating TGF-β-Smad2/3 signaling in renal fibrogenesis. Methods: The expression of LRP5 was examined in the kidneys of Akita mice, db/db mice and mice with obstructive nephropathy. The regulation of TGF-β signaling by LRP5 was determined in both obstructed kidneys and in human proximal tubule epithelial cells exposed to TGF-β1. Interaction of LRP5 with TGF-β receptors was evaluated by Co-IP assays, immunostainings and cell fractionation. Results: We found that LRP5 levels were substantially up-regulated in the renal tubules of diabetic mice and mice with obstructive nephropathy. In the obstructed kidneys, Lrp5 knockout significantly ameliorated tubulointerstitial fibrosis and attenuated the increases of TGF-β1 and TGF-β receptors (TβRI and TβRII), without affecting canonical Wnt signaling. Utilizing SBE-Luc reporter mice and immunostaining assays, LRP5 depletion was demonstrated to attenuate the activation and nuclear translocation of Smad2/3, whereas LRP5 overexpression enhanced TGF-β-Smad2/3 signaling in tubule epithelial cells. Obstruction-induced LRP5 and TβRI were co-localized in the injured tubules, and furthermore, LRP5 was co-precipitated with TβRI and TβRII. The extracellular domain of LRP5 was essential for its association with TGF-β receptors and profibrotic activity. In addition, LRP5 stabilized TGF-β receptors, increased their membrane presentation in the absence of TGF-β1, and promoted the TGF-β1-induced formation of TβRI/TβRII heterodimers and internalization of these receptors. Conclusion: These findings reveal a novel profibrotic activity of LRP5 by interacting with TGF-β receptors, independent of canonical Wnt signaling. Disclosure X. He: None. R. Cheng: None. C. Huang: None. Y. Chen: None. J. Ma: None.

ATP-citrate lyase is an epigenetic regulator to promote obesity-related kidney injury.

Obesity is a leading cause of chronic kidney disease (CKD), but how obesity promotes renal injury remains poorly understood. Here we showed that ATP-citrate lyase (ACL), an enzyme converting citrate to acetyl-CoA, is highly induced in the kidney of overweight or obese patients with CKD and ob/ob BTBR mice. ACL induction is associated with increased ectopic lipid accumulation (ELA), glomerulosclerosis, and albuminuria. Acetyl-CoA is the substrate for de novo lipogenesis as well as for histone acetylation. By raising acetyl-CoA concentration ACL promotes H3K9/14 and H3K27 hyperacetylation leading to up-regulation of several rate-limiting lipogenic enzymes and fibrogenic factors. On the other hand, the excess acetyl-CoA generated as a result of ACL induction provides the substrate for these lipogenic enzymes to drive de novo lipogenesis leading to ELA, a detrimental event toward renal injury. In mesangial cells, ACL is synergistically induced by high glucose, palmitate, and TNF-α via NF-κB and PKA pathways. Under these conditions, H3K9/14 and H3K27 hyperacetylation, as well as the induction of the lipogenic and fibrogenic proteins, are completely blocked in the presence of an ACL inhibitor. Collectively, these data suggest that ACL is an epigenetic regulator that promotes renal ELA and fibrogenesis leading to renal injury in obesity.-Chen, Y., Deb, D. K., Fu, X., Yi, B., Liang, Y., Du, J., He, L., Li, Y. C. ATP-citrate lyase is an epigenetic regulator to promote obesity-related kidney injury.

Thrombospondin 1 and Its Diverse Roles as a Regulator of Extracellular Matrix in Fibrotic Disease.

Thrombospondin 1 (TSP1) is a matricellular extracellular matrix protein that has diverse roles in regulating cellular processes important for the pathogenesis of fibrotic diseases. We will present evidence for the importance of TSP1 control of latent transforming growth factor beta activation in renal fibrosis with an emphasis on diabetic nephropathy. Other functions of TSP1 that affect renal fibrosis, including regulation of inflammation and capillary density, will be addressed. Emerging roles for TSP1 N-terminal domain regulation of collagen matrix assembly, direct effects of TSP1-collagen binding, and intracellular functions of TSP1 in mediating endoplasmic reticulum stress responses in extracellular matrix remodeling and fibrosis, which could potentially affect renal fibrogenesis, will also be discussed. Finally, we will address possible strategies for targeting TSP1 functions to treat fibrotic renal disease.

Activation of the prostaglandin E2 EP2 receptor attenuates renal fibrosis in unilateral ureteral obstructed mice and human kidney slices.

AimRenal fibrosis plays a pivotal role in the development and progression of chronic kidney disease, which affects 10% of the adult population. Previously, it has been demonstrated that the cyclooxygenase‐2 (COX‐2)/prostaglandin (PG) system influences the progression of renal injury. Here, we evaluated the impact of butaprost, a selective EP2 receptor agonist, on renal fibrosis in several models of kidney injury, including human tissue slices.MethodsWe studied the anti‐fibrotic efficacy of butaprost using Madin‐Darby Canine Kidney (MDCK) cells, mice that underwent unilateral ureteral obstruction and human precision‐cut kidney slices. Fibrogenesis was evaluated on a gene and protein level by qPCR and Western blotting.ResultsButaprost (50 μM) reduced TGF‐β‐induced fibronectin (FN) expression, Smad2 phosphorylation and epithelial‐mesenchymal transition in MDCK cells. In addition, treatment with 4 mg/kg/day butaprost attenuated the development of fibrosis in mice that underwent unilateral ureteral obstruction surgery, as illustrated by a reduction in the gene and protein expression of α‐smooth muscle actin, FN and collagen 1A1. More importantly, a similar anti‐fibrotic effect of butaprost was observed in human precision‐cut kidney slices exposed to TGF‐β. The mechanism of action of butaprost appeared to be a direct effect on TGF‐β/Smad signalling, which was independent of the cAMP/PKA pathway.ConclusionIn conclusion, this study demonstrates that stimulation of the EP2 receptor effectively mitigates renal fibrogenesis in various fibrosis models. These findings warrant further research into the clinical application of butaprost, or other EP2 agonists, for the inhibition of renal fibrosis.

Rac-GTPase promotes fibrotic TGF-β1 signaling and chronic kidney disease via EGFR, p53, and Hippo/YAP/TAZ pathways.

Rac-GTPases are major regulators of cytoskeletal remodeling and their deregulation contributes to numerous pathologies. Whether or how Rac promotes tubulointerstitial fibrosis and chronic kidney disease (CKD) is currently unknown. We showed that the major profibrotic cytokine, TGF-β1 promoted rapid Rac1-GTP loading in human kidney 2 (HK-2) human renal epithelial cells. A Rac-specific chemical inhibitor, EHT 1864, blocked TGF-β1-induced fibrotic reprogramming in kidney epithelial cells and fibroblasts. Stable Rac1 depletion in HK-2 cells, moreover, eliminated TGF-β1-mediated non-SMAD pathway activation [e.g., Src, epidermal growth factor receptor (EGFR), p53] and subsequent plasminogen activator inhibitor-1 (PAI-1), connective tissue growth factor, fibronectin, and p21 induction. Rac1 and p22phox knockdown abrogated free radical generation by TGF-β1 in HK-2 cells, consistent with the role of Rac1 in NAPD(H). TGF-β1-induced renal epithelial cytostasis was also completely bypassed by Rac1, p22phox, p47phox, and PAI-1 silencing. Rac1b isoform expression was robustly induced in the fibrotic kidneys of mice and humans. Intraperitoneal administration of EHT 1864 in mice dramatically attenuated ureteral unilateral obstruction-driven EGFR, p53, Rac1b, yes-associated protein/transcriptional coactivator with PDZ-binding motif activation/expression, dedifferentiation, cell cycle arrest, and renal fibrogenesis evident in vehicle-treated obstructed kidneys. Thus, the Rac1-directed redox response is critical for TGF-β1-driven epithelial dysfunction orchestrated, in part, via PAI-1 up-regulation. Rac pathway inhibition suppressed renal oxidative stress and maladaptive repair, identifying Rac as a novel therapeutic target against progressive CKD.-Patel, S., Tang, J., Overstreet, J. M., Anorga, S., Lian, F., Arnouk, A., Goldschmeding, R., Higgins, P. J., Samarakoon, R. Rac-GTPase promotes fibrotic TGF-β1 signaling and chronic kidney disease via EGFR, p53, and Hippo/YAP/TAZ pathways.

Tauroursodeoxycholic acid attenuates cyclosporine-induced renal fibrogenesis in the mouse model

Chronic exposure to cyclosporine causes nephrotoxicity and organ damage. Here we show that cyclosporine nephrotoxicity in vivo is associated with the activation of the unfolded protein response (UPR) pathway to initiate tissue fibrosis. We demonstrate that cyclosporine therapy activated the IRE1α branch of the unfolded protein response (UPR) and stimulated the TGFβ1 signaling pathway in the kidneys of male mice. Co-administration of the proteostasis promoter tauroursodeoxycholic acid (TUDCA) with cyclosporine inhibited the UPR pathway in the kidneys of treated male mice as well as decreased the development of renal fibrogenesis.

Stimulating Type 1 Angiotensin Receptors on T Lymphocytes Attenuates Renal Fibrosis

Most forms of chronic kidney disease culminate in renal fibrosis that heralds organ failure. In contrast to the protective effects of globally blocking type 1 angiotensin (AT1) receptors throughout the body, activating AT1 receptors directly on immune cells may serve protective functions. However, the effects of stimulating the T-cell AT1 receptor on the progression of renal fibrosis remain unknown. In this study, mice with T-cell-specific deletion of the dominant murine AT1 receptor isoform Lck-Cre Agtraflox/flox [total knockout (TKO)] and wild-type (WT) controls were subjected to the unilateral ureteral obstruction model of kidney fibrosis. Compared with WT controls, obstructed kidneys from TKO mice at day 14 had increased collagen 1 deposition. CD4+ T cells, CD11b+Ly6Chi myeloid cells, and mRNA levels of Th1 inflammatory cytokines are elevated in obstructed TKO kidneys, suggesting that augmented Th1 responses in the TKO mice may exaggerate renal fibrosis by driving proinflammatory macrophage differentiation. In turn, T-bet deficient (T-bet knockout) mice lacking Th1 responses have attenuated collagen deposition after unilateral ureteral obstruction. We conclude that activating the AT1 receptoron T cells mitigates renal fibrogenesis by inhibiting Th1 differentiation and renal accumulation of profibrotic macrophages.

Administration of a selective prostaglandin E2 receptor agonist attenuates renal fibrosis in vitro and in vivo

Renal fibrosis plays a pivotal role in the development and progression of chronic kidney disease (CKD), which affects 10% of the adult population. Previously, it has been demonstrated that the cyclooxygenase‐2 (COX‐2)/prostaglandin (PG) system influences the progression of renal injury. PGE2 interacts with four different G‐protein‐coupled PGE2 EP receptors, known as EP1–EP4, and plays a role in several biological functions. Previous studies show that the EP2 receptor is involved in progression of lung fibrosis. In this study, we investigated the effect of an EP2 agonist (butaprost) on renal fibrogenesis on a cellular, renal tissue and organismal level using well‐established in vivo and in vitro models as well as a recently developed human model of renal fibrosis. This model is ideal to study multicellular pathological processes, e.g. fibrosis, directly in human tissue since cellular diversity and organ architecture is maintained in the slices. Butaprost (50 μM) reduced TGF‐β‐induced fibronectin (FN) expression, Smad2/3 phosphorylation and epithelial‐mesenchymal transition in MDCK cells. In addition, treatment with 4 mg/kg butaprost attenuated the development of fibrosis in mice that underwent unilateral ureteral obstruction (UUO) surgery, as illustrated by a significant reduction in the gene and protein expression of α‐smooth muscle actin, FN and collagen 1A1. More importantly, a similar anti‐fibrotic effect of butaprost was observed in human precision‐cut kidney slices exposed to TGF‐β. The mechanism of action of butaprost appeared to be a direct effect on TGF‐β/Smad signaling, which was independent of the cAMP/PKA pathway. In conclusion, this study demonstrates that stimulation of the EP2 receptor effectively mitigates renal fibrogenesis in various fibrosis models. These findings warrant further research into the clinical application of butaprost, or other EP2 agonists, for the inhibition of renal fibrosis.Support or Funding Information Sources of support: This work was kindly supported by Lundbeckfonden, grant number R231‐2016‐2344 as well as the Danish Council for Independent Research, grant number 6110‐00231B, Aarhus University Research Foundation, grant number AUFF‐E‐2015‐FLS‐8‐69 and Hildur and Dagny Jacobsens Foundation grant number 1295716‐1.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

AKI to CKD Transition is driven by Alpha 2 Adrenergic Receptors

BackgroundEnhanced tissue level and activity of norepinephrine (NE) have been recognized as risk factors of development and progression of chronic kidney disease (CKD). Our reports showed renal denervation (DNx) can prevent renal fibrosis and inflammation in renal fibrogenesis models. However, the underlying mechanism by which renal DNx prevents the long‐term sequelae of acute kidney injury (AKI) remains to be elucidated.MethodsBased on our published data, we hypothesized that NE mediates its effect through activation of alpha 2 adrenergic receptors (α2‐ARs). In this study, we investigated whether genetic and/or pharmacological inhibition of α2‐ARs prevents ischemia/reperfusion injury (IRI)‐induced inflammation and CKD progression.ResultsRenal bilateral IRI resulted in severe kidney fibrosis in medullary region over 2 weeks with persistent tubular injury and massive macrophage infiltration. Renal DNx suppressed renal inflammation, tubular damage, and fibrosis progression, as well as increase in blood pressure, 2 weeks post‐IRI. Pharmacological inhibition of α2‐AR also inhibited fibrosis progression with reduced downstream targets of NE‐α2‐AR axis, including angiotensinogen and fibrogenic factors. Consistent with results in renal DNx and pharmacological inhibition of α2‐AR, inhibition of α2A‐ and α2C‐AR subtypes by pharmacological or genetic manipulation additively prevented macrophage accumulation with downregulation of M1 and M2 macrophage markers, resulting in suppression of persistent renal tubular injury and fibrosis progression.ConclusionTaken together, blockage of α2‐AR subtypes prevents IRI‐induced AKI to CKD transition through inhibition of macrophage accumulation, persistent renal tubular injury and fibrosis progression, suggesting that targeting α2‐ARs may be a potential therapeutic strategy to prevent long‐term sequelae of ischemic AKI.Support or Funding InformationThis work was supported by NIH DK‐083291 and DK‐090332 and UNMC College of Medicine Bridge fund.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

RETRACTED: Protective effect of DMDD, isolated from the root of Averrhoa carambola L., on high glucose induced EMT in HK-2 cells by inhibiting the TLR4-BAMBI-Smad2/3 signaling pathway

Hyperglycemia stimulated epithelial-mesenchymal transition (EMT) plays a critical role in initiating and progressing renal fibrosis in diabetic kidney disease (DKD). It is crucial to explore novel renal protective drugs for the treatment of DKD. The present study is to confirm our hypothesis and to accumulate the information for the application of DMDD (2-Dodecyl-6-methoxycyclohexa-2,5-diene-1,4-dione) as a novel therapeutic agent to potentially inhibit renal fibrogenesis and EMT in the DKD. High glucose induced renal proximal tubular epithelial cell line (HK-2 cells) was cultured and treated with DMDD. The cell viability and DMDD cytotoxicity were assessed by CCK8. Immunofluorescence was used for detection of TLR4 and downstream protein in normal and high glucose induced HK-2 cells. HK-2 cells were transfected with lentivirus codifying for BAMBI (BMP and activin membrane bound inhibitor) and interfering RNA for determination of the effect of BAMBI over-expression and silencing, respectively. TLR4-BAMBI-Smad2/3 pathway was analyzed by means of RT-PCR and western blot. A high concentration (60mM) of glucose induced significant EMT process and TLR4 expression was increased obviously in this circumstance. DMDD inhibited high expressions of TLR4 and Smad2/3 in HG induced cells and decreased the expression of BAMBI. In addition, the effects of decreased BAMBI expression and increased Smad2/3 expression in HG cultured cells were reversed in the cells of TAK-242 (TLR4 signaling inhibitor) intervention. BAMBI gene silencing dramatically increased EMT process and the over-expression of BAMBI was opposite in HK-2 cells with HG condition. These observations of EMT were ameliorated when the HK-2 cells were pre-treated with DMDD. Our study demonstrates that DMDD treatment improves EMT in the HG induced HK-2 cells. In addition, DMDD significantly inhibits EMT by TLR4-BAMBI-Smad2/3 pathway, which hints that DMDD may be an alternative approach in diabetic renal injury.

Potential Role of the Resident Mesenchymal Stem-Like Cells in Renal Fibrogenesis after Ureteral Obstruction.

The mechanisms of renal fibrogenesis after ureteral obstruction remain unclear. We tried to primarily expand mesenchymal stem cells from renal tissues and then investigated their role in fibrogenesis after ureteral obstruction. Unilateral ureteral obstruction was induced by ligating the left ureteral duct of adult C57BL/6 mice. We collected the kidneys for experiments at 2, 7, and 14 days after operation. Histological analysis showed obviously fibrotic changes in the left kidney at 7 days and further increased at 14 days after ureteral obstruction. To expand mesenchymal stem cells, we minced the renal tissues into small explants (about 1 mm3) and cultured onto 10 cm dishes. Interestingly, the outgrowth of cells was observed significantly earlier from the explants of the obstructed left kidney than that of the unobstructed right kidney. These expanded cells showed the potency of adipogenic, osteogenic, and chondrogenic differentiations and positively expressed with CD44 and partly expressed with CD90, CD105, and CD106, but negatively expressed with CD34, CD45, and FSP1, suggesting the phenotype of mesenchymal stem-like cells (MSLCs). The mouse fibrosis RT2 profiler PCR array showed that many genes were changed over 2-fold in the MSLCs expanded from both kidneys at 2, 7, and 14 days after operation. Interestingly, profibrotic genes were prevalently enhanced in the left kidney with ureteral obstruction. Histological analysis also showed obviously infiltration of inflammatory cells in the left kidney at 14 days after operation. Our data indicate the potential role of resident MSLCs in renal fibrogenesis after ureteral obstruction, but further experiments are required to understand the relevant mechanisms.

TGF-β/Smad and Renal Fibrosis.

Renal fibrosis is characterized by excessive deposition of extracellular matrix (ECM) that disrupts and replaces functional parenchyma, which leads to organ failure. It is known as the major pathological mechanism of chronic kidney disease (CKD). Although CKD has an impact on no less than 10% of the world population, therapeutic options are still limited. Regardless of etiology, elevated TGF-β levels are highly correlated with the activated pro-fibrotic pathways and disease progression. TGF-β, the key driver of renal fibrosis, is involved in a dynamic pathophysiological process that leads to CKD and end-stage renal disease (ESRD). It is becoming clear that epigenetics regulates renal programming, and therefore, the development and progression of renal disease. Indeed, recent evidence shows TGF-β1/Smad signaling regulates renal fibrosis via epigenetic-correlated mechanisms. This review focuses on the function of TGF-β/Smads in renal fibrogenesis, and the role of epigenetics as a regulator of pro-fibrotic gene expression.

Canonical BMP signaling in tubular cells mediates recovery after acute kidney injury

Bone morphogenetic protein (BMP) signaling has been shown to modulate the development of renal fibrosis in animal models of kidney injury, but the downstream mediators are incompletely understood. In wild-type mice, canonical BMP signaling mediated by SMAD1/5/8 transcription factors was constitutively active in healthy renal tubules, transiently down-regulated after ischemia reperfusion injury (IRI), and reactivated during successful tubular regeneration. We then induced IRI in mice with a tubular-specific BMP receptor 1A (BMPR1A) deletion. These mice failed to reactivate SMAD1/5/8 signaling in the post-ischemic phase and developed renal fibrosis after injury. Using unbiased genomic analyses, we identified three genes encoding inhibitor of DNA-binding (ID) proteins (Id1, Id2, and Id4) as key targets of BMPR1A-SMAD1/5/8 signaling. BMPR1A-deficient mice failed to re-induce these targets following IRI. Instead, BMPR1A-deficiency resulted in activation of pro-fibrotic signaling proteins that are normally repressed by ID proteins, namely, p38 mitogen-activated protein kinase and cell cycle inhibitor p27. These data indicate that the post-ischemic activation of canonical BMP signaling acts endogenously to repress pro-fibrotic signaling in tubular cells and may help to prevent the progression of acute kidney injury to chronic kidney disease.

Pharmacological inhibition of autophagy by 3-MA attenuates hyperuricemic nephropathy.

Autophagy has been identified as a cellular process of bulk degradation of cytoplasmic components and its persistent activation is critically involved in the renal damage induced by ureteral obstruction. However, the role and underlying mechanisms of autophagy in hyperuricemic nephropathy (HN) remain unknown. In the present study, we observed that inhibition of autophagy by 3-methyladenine (3-MA) abolished uric acid-induced differentiation of renal fibroblasts to myofibroblasts and activation of transforming growth factor-β1 (TGF-β1), epidermal growth factor receptor (EGFR), and Wnt signaling pathways in cultured renal interstitial fibroblasts. Treatment with 3-MA also abrogated the development of HN in vivo as evidenced by improving renal function, preserving renal tissue architecture, reducing the number of autophagic vacuoles, and decreasing microalbuminuria. Moreover, 3-MA was effective in attenuating renal deposition of extracellular matrix (ECM) proteins and expression of α-smooth muscle actin (α-SMA) and reducing renal epithelial cells arrested at the G2/M phase of cell cycle. Injury to the kidney resulted in increased expression of TGF-β1 and TGFβ receptor I, phosphorylation of Smad3 and TGF-β-activated kinase 1 (TAK1), and activation of multiple cell signaling pathways associated with renal fibrogenesis, including Wnt, Notch, EGFR, and nuclear factor-κB (NF-κB). 3-MA treatment remarkably inhibited all these responses. In addition, 3-MA effectively suppressed infiltration of macrophages and lymphocytes as well as release of multiple profibrogenic cytokines/chemokines in the injured kidney. Collectively, these findings indicate that hyperuricemia-induced autophagy is critically involved in the activation of renal fibroblasts and development of renal fibrosis and suggest that inhibition of autophagy may represent a potential therapeutic strategy for HN.

Profibrotic effects of angiotensin II and transforming growth factor beta on feline kidney epithelial cells.

ObjectivesThe aim of this study was to evaluate the role of angiotensin II (AT-II) and its main mediator, transforming growth factor beta 1 (TGF-β1), in the development of feline renal fibrosis.MethodsExpression of marker genes indicating epithelial-to-mesenchymal transition (EMT), profibrotic mediators and matricellular proteins was measured in feline kidney epithelial cells (Crandell Rees feline kidney [CRFK] cells) after incubation with AT-II and/or TGF-β1.ResultsCells incubated with TGF-β1 or the combination of TGF-β1 with AT-II showed clear EMT with more stretched fibroblastic cells, whereas the cells incubated without TGF-β1 and AT-II (control) showed more epithelial cells. Gene expression of collagen type I (COL1), tenascin-C (TNC), trombospondin-1 (TSP-1), connective tissue growth factor (CTGF) and alpha-smooth muscle actin (α-SMA) increased significantly after incubation of the CRFK cells with TGF-β1 or TGF-β1 in combination with AT-II for 12 h. As incubation of the CRFK cells with only AT-II did not show any significant rise in gene expression of the above-mentioned genes, this was further investigated. In contrast to healthy feline kidney tissue, CRFK cells showed almost no expression of the AT-II type 1 (AT1) receptor.Conclusions and relevanceTGF-β1 significantly induced expression of the EMT marker gene α-SMA, profibrotic mediator CTGF, and fibrogenic proteins COL1, TNC and TSP-1 in CRFK cells. The effect of TGF-β1 on myofibroblast formation was also observed by the stretched appearance of the CRFK cells. As CRFK cells expressed almost no AT1 receptors, this cell line proved not suitable for testing the efficacy of drugs that interact with the AT1 receptor. As AT-II stimulates the effects of TGF-β1 in mammals, the results of this study suggest an indirect profibrotic effect of AT-II besides the demonstrated profibrotic effect of TGF-β1 and thus the development of feline renal fibrosis. Modulation of EMT or proliferation of myofibroblasts could serve as a diagnostic tool and a novel therapeutic target to inhibit renal fibrogenesis, and could possibly serve in the therapy of feline renal fibrosis.

Long noncoding RNA lnc-TSI inhibits renal fibrogenesis by negatively regulating the TGF-β/Smad3 pathway.

Transforming growth factor-β (TGF-β) is a well-established central mediator of renal fibrosis, a common outcome of almost all progressive chronic kidney diseases. Here, we identified a poorly conserved and kidney-enriched long noncoding RNA in TGF-β1-stimulated human tubular epithelial cells and fibrotic kidneys, which we termed TGF-β/Smad3-interacting long noncoding RNA (lnc-TSI). Lnc-TSI was transcriptionally regulated by Smad3 and specifically inhibited TGF-β-induced Smad3 phosphorylation and downstream profibrotic gene expression. Lnc-TSI acted by binding with the MH2 domain of Smad3, blocking the interaction of Smad3 with TGF-β receptor I independent of Smad7. Delivery of human lnc-TSI into unilateral ureteral obstruction (UUO) mice, a well-established model of renal fibrosis, inhibited phosphorylation of Smad3 in the kidney and attenuated renal fibrosis. In a cohort of 58 patients with biopsy-confirmed IgA nephropathy (IgAN), lnc-TSI renal expression negatively correlated with the renal fibrosis index (r = -0.56, P < 0.001) after adjusting for cofounders. In a longitudinal study, 32 IgAN patients with low expression of renal lnc-TSI at initial biopsy had more pronounced increases in their renal fibrosis index and experienced stronger declines in renal function at repeat biopsy at a mean of 48 months of follow-up. These data suggest that lnc-TSI reduced renal fibrogenesis through negative regulation of the TGF-β/Smad pathway.

Renal tubules transcriptome reveals metabolic maladaption during the progression of ischemia-induced acute kidney injury

Renal tubular epithelial cells (TECs) play a critical role in driving acute kidney injury (AKI) progression, but the key molecular features in TECs during this process is not clear. To better understand the molecular characteristics in renal TECs during AKI and renal fibrogenesis, an irreversible AKI mouse model induced by ischemia/reperfusion injury (IRI) was used in this study. The renal tubules were isolated and tubule specific transcriptome was detected by RNA-seq at different stages in the progression of AKI in this model. The overall transcriptome indicated injury and repair process of TEC after renal IRI. In addition, metabolism maladaption was observed during AKI progression to chronic fibrosis. Particularly, we found dysregulation of multiple steps of lipid metabolism in tubule transcriptomes. Oil red O staining revealed massive lipid droplets accumulation in TECs at day 10, thus confirming the defect of lipid metabolism. This is the first study to charaterize renal tubule specific transcriptome during AKI progression. The results shed light on the molecular features in TECs for progressive AKI.

Vitamin D Receptor: A Novel Therapeutic Target for Kidney Diseases.

Background: Kidney disease is a serious problem that adversely affects human health, but critical knowledge is lacking on how to effectively treat established chronic kidney disease. Mounting evidence from animal and clinical studies has suggested that Vitamin D Re-ceptor (VDR) activation has beneficial effects on various renal diseases.Methods: A structured search of published research literature regarding VDR structure and function, VDR in various renal diseases (e.g., IgA nephropathy, idiopathic nephrotic syndrome, renal cell carcinoma, diabetic nephropathy, lupus nephritis) and therapies targeting VDR was performed for several databases.Result: Included in this study are the results from 177 published research articles. Evidence from these papers indicates that VDR activation is involved in the protection against renal inju-ry in kidney diseases by a variety of mechanisms, including suppression of RAS activation, an-ti-inflammation, inhibiting renal fibrogenesis, restoring mitochondrial function, suppression of autoimmunity and renal cell apoptosis.Conclusion: VDR offers an attractive druggable target for renal diseases. Increasing our under-standing of VDR in the kidney is a fertile area of research and may provide effective weapons in the fight against kidney diseases

Intravoxel incoherent motion MRI-derived parameters and T2* relaxation time for noninvasive assessment of renal fibrosis: An experimental study in a rabbit model of unilateral ureter obstruction

PurposeTo evaluate the association of apparent diffusion coefficient (ADC), intravoxel incoherent motion (IVIM) MRI-derived parameters, and T2* relaxation time with histopathological changes observed during renal fibrogenesis in a rabbit model of unilateral ureter obstruction (UUO). MethodsTwenty New Zealand White rabbits underwent baseline MRI followed by surgery (sham or UUO) and then follow-up MRI at postoperative day (POD) 0, 3, 7, and 14. Hematoxylin and eosin and Masson's trichrome staining was performed to evaluate cell density and area of fibrosis. Spearman rank correlation and Pearson correlation tests and one-way analysis of variance were used for statistical analyses. ResultsThere was a continuous increase in the area of fibrosis and cell density: rho = 0.900 (95% confidence interval [CI] = 0.760, 0.960; p < 0.0001) and 0.904 (95% CI = 0.769, 0.962; p < 0.0001), respectively. There was a tendency for all MRI variables to decrease at POD 3 and partly recover at POD 7. ADC, D, f, and T2* relaxation time showed significant correlation with area of fibrosis and cell density (r = −0.5177 and −0.6962, −0.5395 and −0.7851, −0.7168 and −0.7902, and −0.6808 and −0.7212, respectively; p = 0.0052–0.0481) while D* did not (p = 0.1997 and 0.7853, respectively). ConclusionsADC, IVIM MRI-derived parameters, and T2* relaxation time were significantly associated with the area of fibrosis and cell density during renal fibrogenesis in a rabbit model of UUO. After validation in future studies, MRI may have potential for noninvasive assessment modality of renal fibrosis.

Myeloid-specific targeting of Notch ameliorates murine renal fibrosis via reduced infiltration and activation of bone marrow-derived macrophage

Macrophages play critical roles in renal fibrosis. However, macrophages exhibit ontogenic and functional heterogeneities, and which population of macrophages contributes to renal fibrosis and the underlying mechanisms remain unclear. In this study, we genetically targeted Notch signaling by disrupting the transcription factor recombination signal binding protein-Jκ (RBP-J), to reveal its role in regulation of macrophages during the unilateral ureteral obstruction (UUO)-induced murine renal fibrosis. Myeloid-specific disruption of RBP-J attenuated renal fibrosis with reduced extracellular matrix deposition and myofibroblast activation, as well as attenuated epithelial-mesenchymal transition, likely owing to the reduced expression of TGF-β. Meanwhile, RBP-J deletion significantly hampered macrophage infiltration and activation in fibrotic kidney, although their proliferation appeared unaltered. By using macrophage clearance experiment, we found that kidney resident macrophages made negligible contribution, but bone marrow (BM)-derived macrophages played a major role in renal fibrogenesis. Further mechanistic analyses showed that Notch blockade reduced monocyte emigration from BM by down-regulating CCR2 expression. Finally, we found that myeloid-specific Notch activation aggravated renal fibrosis, which was mediated by CCR2+ macrophages infiltration. In summary, our data have unveiled that myeloid-specific targeting of Notch could ameliorate renal fibrosis by regulating BM-derived macrophages recruitment and activation, providing a novel strategy for intervention of this disease.