Myofibroblast in Kidney Fibrosis: Origin, Activation, and Regulation

Screening of active components in Astragalus mongholicus Bunge and Panax notoginseng formula for anti-fibrosis in CKD: nobiletin inhibits Lgals1/PI3K/AKT signaling to improve renal fibrosis

The Astragalus mongholicus Bunge and Panax notoginseng formula (A&P) has been clinically shown to effectively slow down the progression of chronic kidney disease (CKD) and has demonstrated significant anti-fibrosis effects in experimental CKD model. However, the specific active ingredients and underlying mechanism are still unclear. The active ingredients of A&P were analyzed by Ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-HR-MS). A mouse model of CKD was constructed by 5/6 nephrectomy. Renal function was assessed by creatinine and urea nitrogen. Real-time PCR and Western Blot were performed to detect the mRNA and protein changes in kidney and cells. An in vitro fibrotic cell model was constructed by TGF-β induction in TCMK-1 cells. The results showed that thirteen active ingredients of A&P were identified by UPLC-HR-MS, nine of which were identified by analysis with standards, among which the relative percentage of NOB was high. We found that NOB treatment significantly improved renal function, pathological damage and reduced the expression level of fibrotic factors in CKD mice. The results also demonstrated that Lgals1 was overexpressed in the interstitial kidney of CKD mice, and NOB treatment significantly reduced its expression level, while inhibiting PI3K and AKT phosphorylation. Interestingly, overexpression of Lgals1 significantly increased fibrosis in TCMK1 cells and upregulated the activity of PI3K and AKT, which were strongly inhibited by NOB treatment. NOB is one of the main active components of A&P. The molecular mechanism by which NOB ameliorates renal fibrosis in CKD may be through the inhibition of Lgals1/PI3K/AKT signaling pathway.

WWP2 Regulates Renal Fibrosis and the Metabolic Reprogramming of Profibrotic Myofibroblasts

Key Points

WWP2 expression is elevated in the tubulointerstitium of fibrotic kidneys and contributes to CKD pathogenesis and progression. WWP2 uncouples the profibrotic activation and cell proliferation in renal myofibroblasts. WWP2 controls mitochondrial respiration in renal myofibroblasts through the metabolic regulator peroxisome proliferator-activated receptor gamma coactivator 1-alpha.

Background

Renal fibrosis is a common pathologic end point in CKD that is challenging to reverse, and myofibroblasts are responsible for the accumulation of a fibrillar collagen–rich extracellular matrix. Recent studies have unveiled myofibroblasts' diversity in proliferative and fibrotic characteristics, which are linked to different metabolic states. We previously demonstrated the regulation of extracellular matrix genes and tissue fibrosis by WWP2, a multifunctional E3 ubiquitin–protein ligase. Here, we investigate WWP2 in renal fibrosis and in the metabolic reprograming of myofibroblasts in CKD.

Methods

We used kidney samples from patients with CKD and WWP2 -null kidney disease mice models and leveraged single-cell RNA sequencing analysis to detail the cell-specific regulation of WWP2 in fibrotic kidneys. Experiments in primary cultured myofibroblasts by bulk-RNA sequencing, chromatin immunoprecipitation sequencing, metabolomics, and cellular metabolism assays were used to study the metabolic regulation of WWP2 and its downstream signaling.

Results

The tubulointerstitial expression of WWP2 was associated with fibrotic progression in patients with CKD and in murine kidney disease models. WWP2 deficiency promoted myofibroblast proliferation and halted profibrotic activation, reducing the severity of renal fibrosis in vivo . In renal myofibroblasts, WWP2 deficiency increased fatty acid oxidation and activated the pentose phosphate pathway, boosting mitochondrial respiration at the expense of glycolysis. WWP2 suppressed the transcription of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), a metabolic mediator of fibrotic response, and pharmacologic inhibition of PGC-1α partially abrogated the protective effects of WWP2 deficiency on myofibroblasts.

Conclusions

WWP2 regulates the metabolic reprogramming of profibrotic myofibroblasts by a WWP2-PGC-1α axis, and WWP2 deficiency protects against renal fibrosis in CKD.

Role of mitochondria in pathogenesis and therapy of renal fibrosis

Renal fibrosis, specifically tubulointerstitial fibrosis, represents the predominant pathological consequence observed in the context of progressive chronic kidney conditions. The pathogenesis of renal fibrosis encompasses a multifaceted interplay of mechanisms, including but not limited to interstitial fibroblast proliferation, activation, augmented production of extracellular matrix (ECM) components, and impaired ECM degradation. Notably, mitochondria, the intracellular organelles responsible for orchestrating biological oxidation processes in mammalian cells, assume a pivotal role within this intricate milieu. Mitochondrial dysfunction, when manifest, can incite a cascade of events, including inflammatory responses, perturbed mitochondrial autophagy, and associated processes, ultimately culminating in the genesis of renal fibrosis. This comprehensive review endeavors to furnish an exegesis of mitochondrial pathophysiology and biogenesis, elucidating the precise mechanisms through which mitochondrial aberrations contribute to the onset and progression of renal fibrosis. We explored how mitochondrial dysfunction, mitochondrial cytopathy and mitochondrial autophagy mediate ECM deposition and renal fibrosis from a multicellular perspective of mesangial cells, endothelial cells, podocytes, macrophages and fibroblasts. Furthermore, it succinctly encapsulates the most recent advancements in the realm of mitochondrial-targeted therapeutic strategies aimed at mitigating renal fibrosis.

Scopoletin alleviates high glucose-induced toxicity in human renal proximal tubular cells via inhibition of oxidative damage, epithelial-mesenchymal transition, and fibrogenesis

BACKGROUND

Recent years of evidence suggest the crucial role of renal tubular cells in developing diabetic kidney disease. Scopoletin (SCOP) is a plant-based coumarin with numerous biological activities. This study aimed to determine the effect of SCOP on renal tubular cells in developing diabetic kidney disease and to elucidate mechanisms.

METHODS AND RESULTS

In this study, SCOP was evaluated in vitro using renal proximal tubular (HK-2) cells under hyperglycemic conditions to understand its mechanism of action. In HK-2 cells, SCOP alleviated the high glucose-generated reactive oxygen species (ROS), restored the levels of reduced glutathione, and decreased lipid peroxidation. High glucose-induced alteration in the mitochondrial membrane potential was markedly restored in the SCOP-treated cells. Moreover, SCOP significantly reduced the high glucose-induced apoptotic cell population in the Annexin V-FITC flow cytometry study. Furthermore, high glucose markedly elevated the mRNA expression of fibrotic and extracellular matrix (ECM) components, namely, transforming growth factor (TGF)-β, alfa-smooth muscle actin (α-SMA), collagen I, and collagen III, in HK-2 cells compared to the untreated cells. SCOP treatment reduced these mRNA expressions compared to the high glucose-treated cells. Collagen I and TGF-β protein levels were also significantly reduced in the SCOP-treated cells. Further findings in HK-2 cells revealed that SCOP interfered with the epithelial-mesenchymal transition (EMT) in the high glucose-treated HK-2 cells by normalizing E-cadherin and downregulating the vimentin and α-SMA proteins.

CONCLUSIONS

In conclusion, SCOP modulates the high glucose-generated renal tubular cell oxidative damage and accumulation of ECM components and may be a promising molecule against diabetic nephropathy.

Modified EBP-bFGF targeting endogenous renal extracellular matrix protects against renal ischemia-reperfusion injury in rats

Acute kidney injury (AKI) is a life-threatening disease primarily caused by renal ischemia-reperfusion (I/R) injury, which can result in renal failure. Currently, growth factor therapy is considered a promising and effective approach for AKI treatment. Basic fibroblast growth factor (bFGF), an angiogenic factor with potent activity, efficiently stimulates angiogenesis and facilitates regeneration of renal tissue. However, the unrestricted diffusion of bFGF restricts its clinical application in AKI treatment. Therefore, developing a novel sustained released system for bFGF could enhance its potential in treating AKI. In this study, we genetically engineered a multifunctional recombinant protein by fusing bFGF with a specific peptide (EBP). EBP-bFGF effectively binds to the extracellular matrix in the injured kidney, enabling slow release of bFGF in AKI. Furthermore, following orthotopic injection into I/R rats' ischemic kidneys, EBP-bFGF exhibited stable retention within the tissue. Additionally, EBP-bFGF suppressed apoptosis of renal cells, reduced renal fibrosis, and facilitated recovery of renal function. These findings suggest that EBP-bFGF delivery system represents a promising strategy for treating AKI.

Novel Potential Therapeutic Targets in Autosomal Dominant Polycystic Kidney Disease from the Perspective of Cell Polarity and Fibrosis

Autosomal dominant polycystic kidney disease (ADPKD), a congenital genetic disorder, is a notable contributor to the prevalence of chronic kidney disease worldwide. Despite the absence of a complete cure, ongoing research aims for early diagnosis and treatment. Although agents such as tolvaptan and mTOR inhibitors have been utilized, their effectiveness in managing the disease during its initial phase has certain limitations. This review aimed to explore new targets for the early diagnosis and treatment of ADPKD, considering ongoing developments. We particularly focus on cell polarity, which is a key factor that influences the process and pace of cyst formation. In addition, we aimed to identify agents or treatments that can prevent or impede the progression of renal fibrosis, ultimately slowing its trajectory toward end-stage renal disease. Recent advances in slowing ADPKD progression have been examined, and potential therapeutic approaches targeting multiple pathways have been introduced. This comprehensive review discusses innovative strategies to address the challenges of ADPKD and provides valuable insights into potential avenues for its prevention and treatment.

Epigallocatechin-3-gallate attenuates arsenic-induced fibrogenic changes in human kidney epithelial cells through reversal of epigenetic aberrations and antioxidant activities

Renal fibrosis is a pathogenic intermediate stage of chronic kidney disease (CKD). Nephrotoxicants including arsenic can cause kidney fibrosis through induction of oxidative stress and epigenetic aberrations. Epigallocatechin-3-gallate (EGCG), a green tea polyphenol, is known to have antioxidant and epigenetic modulation properties. Whether EGCG, through its antioxidant and epigenetic modulating activities, can attenuate fibrogenesis is not known. Therefore, the objective of this study was to determine whether EGCG can attenuate arsenic-induced acute injury and long-term exposure associated fibrogenicity in kidney epithelial cells. To address this question, two human kidney epithelial cell lines Caki-1 and HK-2 exposed to arsenic for both acute and long-term durations were treated with EGCG. The protective effect of EGCG on arsenic-induced cytotoxicity and fibrogenicity were evaluated by measuring the cell growth, reactive oxygen species (ROS) production, genes expression, and epigenetic changes in histone marks. Results revealed that EGCG has a protective effect in arsenic-induced acute cytotoxicity in these cells. EGCG scavenges the increased levels of ROS in arsenic exposed cells. Aberrant expression of fibrogenic genes in arsenic exposed cells were restored by EGCG. Abrogation of arsenic-induced fibrogenic changes was also associated with EGCG-mediated restoration of arsenic-induced aberrant expression of epigenetic regulatory proteins and histone marks. Novel findings of this study suggest that EGCG, through its antioxidant and epigenetic modulation capacities, has protective effects against arsenic-induced cytotoxicity and fibrogenic changes in kidney epithelial cells.

Shen-Shuai-II-Recipe inhibits tubular inflammation by PPARα-mediated fatty acid oxidation to attenuate fibroblast activation in fibrotic kidneys

BACKGROUND

Shen Shuai Ⅱ Recipe (SSR) is clinically used to treat chronic kidney diseases (CKDs) with remarkable efficacy and safety. In earlier research, we found the anti-inflammatory, antioxidant, and mitochondrial protective properties of SSR in hypoxic kidney injury model, which is closely related to its renal protection. Further work is needed to understand the underlying molecular mechanisms.

PURPOSE

Further investigation of the mechanisms of action of SSR against renal interstitial fibrosis (RIF) building on previous research leads.

METHODS

Rats receiving CKD model surgery were given with Fenofibrate or SSR once a day for eight weeks. In vitro, the NRK-52E cells were treated with SSR in the presence or absence of 10 μM Sc75741, 0.5 μM PMA, or 1 μM fenofibrate under 1% O2. The effects of SSR on NF-κB/NLRP3 inflammatory cascade, secretion of pro-inflammatory cytokines, fatty acid oxidation (FAO), and renal tubular injury were determined by immunoblotting, luminex liquid suspension chip assay, transmission electron microscopy, and Oil red O staining. Next, we delivered PPARα-interfering sequences to kidney tissue and NRK-52E cells by adeno-associated virus (AAV) injection and siRNA transfection methods. Finally, we evaluated the effect of renal tubular cells on fibroblast activation by co-culture method.

RESULTS

SSR attenuated the release of IL-18, VEGF, and MCP1 cytokines, inhibited the activation of NF-κB/NLRP3 cascade, increased the PPARα, CPT-1α, CPT-2, ACADL, and MCAD protein expression, and improved the lipid accumulation. Further studies have demonstrated that one of the ways in which SSR suppresses the inflammatory response to protect renal tubular cells is through the restoration of PPARα-mediated FAO. In addition, by means of co-culture ways, the results demonstrated that SSR attenuated secretion of inflammatory mediators in NRK-52E cells by PPARα/NF-κB/NLRP3 pathway, thereby inhibiting renal fibroblast activation.

CONCLUSION

SSR inhibits RIF by suppressing inflammatory response of hypoxia-exposed RTECs through PPARα-mediated FAO.

Continuous genetic monitoring of transient mesenchymal gene activities in distal tubule and collecting duct epithelial cells during renal fibrosis

Epithelial cells (ECs) have been proposed to contribute to myofibroblasts or fibroblasts through epithelial-mesenchymal transition (EMT) during renal fibrosis. However, since EMT may occur dynamically, transiently, and reversibly during kidney fibrosis, conventional lineage tracing based on Cre-loxP recombination in renal ECs could hardly capture the transient EMT activity, yielding inconsistent results. Moreover, previous EMT research has primarily focused on renal proximal tubule ECs, with few reports of distal tubules and collecting ducts. Here, we generated dual recombinases-mediated genetic lineage tracing systems for continuous monitoring of transient mesenchymal gene expression in E-cadherin+ and EpCAM+ ECs of distal tubules and collecting ducts during renal fibrosis. Activation of key EMT-inducing transcription factor (EMT-TF) Zeb1 and mesenchymal markers αSMA, vimentin, and N-cadherin, were investigated following unilateral ureteral obstruction (UUO). Our data revealed that E-cadherin+ and EpCAM+ ECs did not transdifferentiate into myofibroblasts, nor transiently expressed these mesenchymal genes during renal fibrosis. In contrast, in vitro a large amount of cultured renal ECs upregulated mesenchymal genes in response to TGF-β, a major inducer of EMT.

Nicotinamide protects against diabetic kidney disease through regulation of Sirt1

PURPOSE

To investigate the effect of nicotinamide (Nam) on diabetic kidney disease (DKD) in mice and explore its mechanism.

METHODS

Thirty DBA/2 J mice were randomly assigned to three groups. After 8 weeks of hyperglycemia induced by streptozocin (STZ), Nam and saline were administrated to STZ + Nam and STZ + NS mice, respectively, for 8 weeks. Non-diabetic mice (NDM) were used as control group. Twenty In2-/- Akita mice were randomly divided into two groups. After 8 weeks of hyperglycemia, Nam and saline were administered to Akita + Nam and Akita + NS mice, respectively, for 6 weeks. Wild-type littermates were used as control group. Markers of renal injury were analyzed, and the molecular mechanisms were explored in human proximal tubular HK2 cells.

RESULTS

Urinary albumin-to-creatinine ratio (UACR) and kidney injury molecule 1 (KIM-1) decreased in the STZ + Nam and Akita + Nam groups. Pathological analysis showed that Nam improved the structure of glomerular basement membrane, ameliorated glomerular sclerosis, and decreased the accumulation of extracellular matrix and collagen. Compared to the diabetic control group, renal fibrosis, inflammation, and oxidative stress were reduced in the Nam-treated mice. The expression of sirtuin 1 (Sirt1) in human proximal tubular HK2 cells was inhibited by high glucose and Nam treatment enhanced its expression. However, in HK2 cells with Sirt1 knockdown, the protective effect of Nam was abolished, indicating that the beneficial effect of Nam was partially dependent on Sirt1.

CONCLUSIONS

Nam has a renoprotective effect against renal injury caused by hyperglycemia and may be a potential target for the treatment of DKD.

Using intravoxel incoherent motion imaging to evaluate uric acid-induced renal injury and efficacy after treatment

OBJECTIVES

To validate the feasibility of intravoxel incoherent motion imaging (IVIM) for monitoring renal injury and uric acid-lowering efficacy in a rat model of hyperuricaemia.

METHODS

A total of 92 rats were analysed and categorized into 4 groups: control (CON), hyperuricaemia (HUA), allopurinol intervention (ALL), and combined intervention (COM). Eight rats were randomly selected from each group and underwent IVIM scanning on days 0, 1, 3, 5, 7, and 9. Quantitative magnetic resonance values (D, D*, and f values) measured from the different renal anatomical regions. Quantitative histopathological analysis was performed to assess renal tubular injury using neutrophil gelatinase-associated lipocalin (NGAL), and renal fibrosis using alpha-smooth-muscle-actin (α-SMA). Pearson's correlation analysis was used to determine the correlation between IVIM-derived parameters and the expression of NGAL and α-SMA.

RESULTS

The D values of the HUA, ALL, and COM groups generally showed a downward trend over time, and this fluctuation was most significant in the HUA group. The D values showed significant intergroup differences at each point, whereas only a few discrepancies were found in the D* and f values. In addition, the renal D value was negatively correlated with the positive staining rates for NGAL and α-SMA (P < .05), except for the lack of correlation between Dos and α-SMA (P > .05).

CONCLUSION

IVIM could be a noninvasive and potential assessment modality for the evaluation of renal injury induced by hyperuricaemia and its prognostic efficacy.

ADVANCES IN KNOWLEDGE

IVIM could be a surrogate manner in monitoring renal damage induced by hyperuricaemia and its treatment evaluation.

Fibroblasts inhibit osteogenesis by regulating nuclear-cytoplasmic shuttling of YAP in mesenchymal stem cells and secreting DKK1

BACKGROUND

Fibrous scars frequently form at the sites of bone nonunion when attempts to repair bone fractures have failed. However, the detailed mechanism by which fibroblasts, which are the main components of fibrous scars, impede osteogenesis remains largely unknown.

RESULTS

In this study, we found that fibroblasts compete with osteogenesis in both human bone nonunion tissues and BMP2-induced ectopic osteogenesis in a mouse model. Fibroblasts could inhibit the osteoblastic differentiation of mesenchymal stem cells (MSCs) via direct and indirect cell competition. During this process, fibroblasts modulated the nuclear-cytoplasmic shuttling of YAP in MSCs. Knocking down YAP could inhibit osteoblast differentiation of MSCs, while overexpression of nuclear-localized YAP-5SA could reverse the inhibition of osteoblast differentiation of MSCs caused by fibroblasts. Furthermore, fibroblasts secreted DKK1, which further inhibited the formation of calcium nodules during the late stage of osteogenesis but did not affect the early stage of osteogenesis. Thus, fibroblasts could inhibit osteogenesis by regulating YAP localization in MSCs and secreting DKK1.

CONCLUSIONS

Our research revealed that fibroblasts could modulate the nuclear-cytoplasmic shuttling of YAP in MSCs, thereby inhibiting their osteoblast differentiation. Fibroblasts could also secrete DKK1, which inhibited calcium nodule formation at the late stage of osteogenesis.

Claudin-2 Mediates the Proximal Tubular Epithelial Cell-Fibroblast Crosstalk via Paracrine CTGF

Purpose

Proximal tubular epithelial cell (PTEC) is vulnerable to injury in diabetic kidney disease (DKD) due to high energy expenditure. The injured PTECs-derived profibrotic factors are thought to be driving forces in tubulointerstitial fibrosis (TIF) as they activate surrounding fibroblasts. However, the mechanisms remain unclear.

Methods

The diabetes with uninephrectomy (DKD) rats were used to evaluated renal histological changes and the expression of Claudin-2 by immunofluorescence staining. Then, Claudin-2 expression in PTECs were modulated and subsequently determined the proliferation and activation of fibroblasts by building a transwell co-culture system in normal glucose (NG)or high glucose (HG) condition.

Results

Decreased expression of Claudin-2 in PTECs accompanied by tight junction disruption and increased interstitial fibrosis, were detected in DKD rats. In vitro, downregulated Claudin-2 in PTECs promoted proliferation and activation of fibroblasts, which coincided with elevated expression of profibrotic connective tissue growth factor (CTGF) in PTECs. Silenced CTGF inhibited the profibrotic of PTECs via Claudin-2 inhibition. Fibroblasts co-cultured with PTECs transitioned more to myofibroblasts and generated extracellular matrix (ECM) significantly in response to high glucose (HG) stimulation whereas overexpression of Claudin-2 in PTECs reversed the above results. Upregulating CTGF disrupted the beneficial anti-fibrosis effects obtained by overexpression of Claudin-2 in HG condition.

Conclusion

Our study suggested that Claudin-2 in PTECs, a key mediator of paracellular cation and water transport, promotes the activation and proliferation of surrounding fibroblasts significantly via CTGF in a paracrine manner.

Evidential support for garlic supplements against diabetic kidney disease: a preclinical meta-analysis and systematic review

Garlic (Allium sativum L.) is a popular spice that is widely used for food and medicinal purposes and has shown potential effects on diabetic kidney disease (DKD). Nevertheless, systematic preclinical studies are still lacking. In this meta-analysis and systematic review, we evaluated the role and potential mechanisms of action of garlic and its derived components in animal models of DKD. We searched eight databases for relevant studies from the establishment of the databases to December 2022 and updated in April 2023 before the completion of this review. A total of 24 trials were included in the meta-analysis. It provided preliminary evidence that supplementing with garlic could improve the indicators of renal function (BUN, Scr, 24 h urine volume, proteinuria, and KI) and metabolic disorders (BG, insulin, and body weight). Meanwhile, the beneficial effects of garlic and its components in DKD could be related to alleviating oxidative stress, suppressing inflammatory reactions, delaying renal fibrosis, and improving glucose metabolism. Furthermore, time-dose interval analysis exhibited relatively greater effectiveness when garlic products were supplied at doses of 500 mg kg-1 with interventions lasting 8-10 weeks, and garlic components were administered at doses of 45-150 mg kg-1 with interventions lasting 4-10 weeks. This meta-analysis and systematic review highlights for the first time the therapeutic potential of garlic supplementation in animal models of DKD and offers a more thorough evaluation of its effects and mechanisms to establish an evidence-based basis for designing future clinical trials.

Natural products in traditional Chinese medicine: molecular mechanisms and therapeutic targets of renal fibrosis and state-of-the-art drug delivery systems

Renal fibrosis (RF) is the end stage of several chronic kidney diseases. Its series of changes include excessive accumulation of extracellular matrix, epithelial-mesenchymal transition (EMT) of renal tubular cells, fibroblast activation, immune cell infiltration, and renal cell apoptosis. RF can eventually lead to renal dysfunction or even renal failure. A large body of evidence suggests that natural products in traditional Chinese medicine (TCM) have great potential for treating RF. In this article, we first describe the recent advances in RF treatment by several natural products and clarify their mechanisms of action. They can ameliorate the RF disease phenotype, which includes apoptosis, endoplasmic reticulum stress, and EMT, by affecting relevant signaling pathways and molecular targets, thereby delaying or reversing fibrosis. We also present the roles of nanodrug delivery systems, which have been explored to address the drawback of low oral bioavailability of natural products. This may provide new ideas for using natural products for RF treatment. Finally, we provide new insights into the clinical prospects of herbal natural products.

Defining the molecular fingerprint of bladder and kidney fibroblasts

Fibroblasts are integral to the organization and function of all organs and play critical roles in pathologies such as fibrosis; however, we have limited understanding of the fibroblasts that populate the bladder and kidney. In this review, I describe how transcriptomics is leading to a revolution in our understanding of fibroblast biology by defining the molecular fingerprint (i.e., transcriptome) of universal and specialized fibroblast types, revealing gene signatures that allows one to resolve fibroblasts from other mesenchymal cell types, and providing a new comprehension of the fibroblast lineage. In the kidney, transcriptomics is giving us new insights into the molecular fingerprint of kidney fibroblasts, including those for cortical fibroblasts, medullary fibroblasts, and erythropoietin (EPO)-producing Norn fibroblasts, as well as new information about the gene signatures of kidney myofibroblasts and the transition of kidney fibroblasts into myofibroblasts. Transcriptomics has also revealed that the major cell type in the bladder interstitium is the fibroblast, and that multiple fibroblast types, each with their own molecular fingerprint, are found in the bladder wall. Interleaved throughout is a discussion of how transcriptomics can drive our future understanding of fibroblast identification, diversity, function, and their roles in bladder and kidney biology and physiology in health and in disease states.

High-Salt Diet Aggravates Endothelial-to-Mesenchymal Transition in Glomerular Fibrosis in Dahl Salt-Sensitive Rats

BACKGROUND

Both diabetic and hypertensive nephropathy eventually progress to glomerulosclerosis. Previous studies revealed a potential role of endothelial-to-mesenchymal transition (EndMT) in the pathophysiology of glomerulosclerosis in diabetic rats. Therefore, we hypothesized that EndMT was also involved in the development of glomerulosclerosis in salt-sensitive hypertension. We aimed to explore the effects of high-salt diet on endothelial-to-mesenchymal transition (EndMT) in glomerulosclerosis in Dahl salt-sensitive (Dahl-SS) rats.

METHODS

Eight-week-old male rats were fed high-salt (8%NaCl; DSH group) or normal salt (0.3%NaCl; DSN group) for eight weeks, with systolic blood pressure (SBP), serum creatinine, urea, 24-hour urinary protein/sodium, renal interlobar artery blood flow, and pathological examination measured. We also examined endothelial-(CD31) and fibrosis-related protein(α-SMA) expressions in glomeruli.

RESULTS

High-salt diet increased SBP (DSH vs. DSN, 205.2 ± 8.9 vs. 135.4 ± 7.9 mm Hg, P < 0.01), 24-hour urinary protein (132.55 ± 11.75 vs. 23.52 ± 5.94 mg/day, P < 0.05), urine sodium excretions (14.09 ± 1.49 vs. 0.47 ± 0.06 mmol/day, P < 0.05), and renal interlobar artery resistance. Glomerulosclerosis increased (26.1 ± 4.6 vs. 7.3 ± 1.6%, P < 0.05), glomerular CD31 expressions decreased while α-SMA expression increased in DSH group. Immunofluorescence staining showed that CD31 and α-SMA co-expressed in glomeruli of the DSH group. The degree of glomerulosclerosis negatively correlated with CD31 expressions (r = -0.823, P < 0.01) but positively correlated with α-SMA expressions (r = 0.936, P < 0.01).

CONCLUSIONS

We demonstrated that a high-salt diet led to glomerulosclerosis involving the EndMT process, which played an essential role in glomerulosclerosis in hypertensive Dahl-SS rats.

Mannan-binding lectin ameliorates renal fibrosis by suppressing macrophage-to-myofibroblast transition

Mannan-binding lectin (MBL) is a pattern-recognition molecule that plays a crucial role in innate immunity. MBL deficiency correlates with an increased risk of chronic kidney disease (CKD). However, the molecular mechanisms are not fully defined. Here, we established a CKD model in wild-type (WT) and MBL-deficient (MBL-/-) mice via unilateral ureteral obstruction (UUO). The result showed that MBL deficiency aggravated the pathogenesis of renal fibrosis in CKD mice. Strikingly, the in vivo macrophage depletion investigation revealed that macrophages play an essential role in the MBL-mediated suppression of renal fibrosis. We found that MBL limited the progression of macrophage-to-myofibroblast transition (MMT) in kidney tissues of UUO mice. Further in vitro study showed that MBL-/- macrophages exhibited significantly increased levels of fibrotic-related molecules compared with WT cells upon transforming growth factor beta (TGF-β) stimulation. We demonstrated that MBL inhibited the MMT process by suppressing the production of matrix metalloproteinase 9 (MMP-9) and activation of Akt signaling. In summary, our study revealed an expected role of MBL on macrophage transition during renal fibrosis, thus offering new insight into the potential of MBL as a therapeutic target for CKD.

Oxidatively stressed extracellular microenvironment drives fibroblast activation and kidney fibrosis

Kidney fibrosis is associated with tubular injury, oxidative stress and activation of interstitial fibroblasts. However, whether these events are somehow connected is poorly understood. In this study, we show that glutathione peroxidase-3 (GPX3) depletion in renal tubular epithelium after kidney injury plays a central role in orchestrating an oxidatively stressed extracellular microenvironment, which drives interstitial fibroblast activation and proliferation. Through transcriptional profiling by RNA-sequencing, we found that the expression of GPX3 was down-regulated in various models of chronic kidney disease (CKD), which was correlated with induction of nicotinamide adenine dinucleotide phosphate (NAPDH) oxidase-4 (NOX4). By using decellularized extracellular matrix (ECM) scaffold, we demonstrated that GPX3-depleted extracellular microenvironment spontaneously induced NOX4 expression and reactive oxygen species (ROS) production in renal fibroblasts and triggered their activation and proliferation. Activation of NOX4 by advanced oxidation protein products (AOPPs) mimicked the loss of GPX3, increased the production of ROS, stimulated fibroblast activation and proliferation, and activated protein kinase C-α (PKCα)/mitogen-activated protein kinase (MAPK)/signal transducer and activator of transcription 3 (STAT3) signaling. Silencing NOX4 or inhibition of MAPK with small molecule inhibitors hampered fibroblast activation and proliferation. In mouse model of CKD, knockdown of NOX4 repressed renal fibroblast activation and proliferation and alleviated kidney fibrosis. These results indicate that loss of GPX3 orchestrates an oxidatively stressed extracellular microenvironment, which promotes fibroblast activation and proliferation through a cascade of signal transduction. Our studies underscore the crucial role of extracellular microenvironment in driving fibroblast activation and kidney fibrosis.

Kidney tubular epithelial cells control interstitial fibroblast fate by releasing TNFAIP8-encapsulated exosomes

Kidney fibrosis, characterized by the activation and expansion of the matrix-producing fibroblasts, is the common outcome of chronic kidney disease (CKD). While fibroblast proliferation is well studied in CKD, little is known about the regulation and mechanism of fibroblast depletion. Here, we show that exosomes derived from stressed/injured tubules play a pivotal role in dictating fibroblast apoptosis and fate. When human kidney tubular cells (HK-2) were stimulated with TGF-β1, they produced and released increased amounts of exosomes (TGFβ-Exo), which prevented renal interstitial fibroblasts from apoptosis. In vivo, injections of TGFβ-Exo promoted renal fibroblast survival, whereas blockade of exosome secretion accelerated fibroblast apoptosis in obstructive nephropathy. Proteomics profiling identified the tumor necrosis factor-α-induced protein 8 (TNFAIP8) as a key component enriched in TGFβ-Exo. TNFAIP8 was induced in renal tubular epithelium and enriched in the exosomes from fibrotic kidneys. Knockdown of TNFAIP8 in tubular cells abolished the ability of TGFβ-Exo to prevent fibroblast apoptosis. In vivo, gain- or loss- of TNFAIP8 prevented or aggravated renal fibroblast apoptosis after obstructive injury. Mechanistically, exosomal-TNFAIP8 promoted p53 ubiquitination leading to its degradation, thereby inhibiting fibroblasts apoptosis and inducing their proliferation. Collectively, these results indicate that tubule-derived exosomes play a critical role in controlling the size of fibroblast population during renal fibrogenesis through shuttling TNFAIP8 to block p53 signaling. Strategies to target exosomes may be effective strategies for the therapy of fibrotic CKD.

Isolation and characterization of dihydropyran-ring containing meroterpenoids from Ganoderma lucidum and their inhibitory activity against renal fibrosis-related protein expression

The Ganoderma lucidum mushroom, which has been used as a traditional medicine in China for more than 2000 years, is a source of many interesting natural product. In this study, the five undescribed minor meroterpenoids baoslingzhines F-J (1-5), containing a dihydropyran moiety, were isolated as racemic mixtures from the fruiting bodies of G. lucidum. These substances were structurally and stereochemically characterized by using spectroscopic and computational methods. Chiral HPLC was employed to separate the (+)- and (-)-antipodes. A survey of the activities against kidney fibrosis showed that both enantiomers of baoslingzhines F-J inhibit expression of renal fibrosis-related proteins, including fibronectin, collagen I and ɑ-SMA in TGF-β1-induced rat kidney proximal tubular cells.

Mechanism of transforming growth factor-1 induce renal fibrosis based on transcriptome sequencing analysis

OBJECTIVES

To explore the mechanism of transforming growth factor-β1 (TGF-β1) induce renal fibrosis.

METHODS

Renal fibroblast NRK-49F cells treated with and without TGF-β1 were subjected to RNA-seq analysis. DESeq2 was used for analysis. Differentially expressed genes were screened with the criteria of false discovery rate<0.05 and l o g 2 F C >1. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed for differentially expressed genes. Genes encoding transcription factors were further screened for differential expression genes. Then, the expression of these genes during renal fibrosis was verified using unilateral ureteral obstruction (UUO)-induced mouse renal fibrosis model and a public gene expression dataset (GSE104954).

RESULTS

After TGF-β1 treatment for 6, 12 and 24 h, 552, 1209 and 1028 differentially expressed genes were identified, respectively. GO analysis indicated that these genes were significantly enriched in development, cell death, and cell migration. KEGG pathway analysis showed that in the early stage of TGF-β1 induction (TGF-β1 treatment for 6 h), the changes in Hippo, TGF-β and Wnt signaling pathways were observed, while in the late stage of TGF-β1 induction (TGF-β1 treatment for 24 h), the changes of extracellular matrix-receptor interaction, focal adhesion and adherens junction were mainly enriched. Among the 291 up-regulated differentially expressed genes treated with TGF-β1 for 6 h, 13 genes (Snai1, Irf8, Bhlhe40, Junb, Arid5a, Vdr, Lef1, Ahr, Foxo1, Myc, Tcf7, Foxc2, Glis1) encoded transcription factors. Validation in a cell model showed that TGF-β1 induced expression of 9 transcription factors (encoded by Snai1, Irf8, Bhlhe40, Junb, Arid5a, Vdr, Lef1, Myc, Tcf7), while the expression levels of the other 4 genes did not significantly change after TGF-β1 treatment. Validation results in UUO-induced mouse renal fibrosis model showed that Snai1, Irf8, Bhlhe40, Junb, Arid5a, Myc and Tcf7 were up-regulated after UUO, Vdr was down-regulated and there was no significant change in Lef1. Validation based on the GSE104954 dataset showed that IRF8 was significantly overexpressed in the renal tubulointerstitium of patients with diabetic nephropathy or IgA nephropathy, MYC was highly expressed in diabetic nephropathy, and the expressions of the other 7 genes were not significantly different compared with the control group.

CONCLUSIONS

TGF-β1 induces differentially expressed genes in renal fibroblasts, among which Irf8 and Myc were identified as potential targets of chronic kidney disease and renal fibrosis.

Pharmacological inhibition of SMYD2 protects against cisplatin-induced renal fibrosis and inflammation

SET and MYND domain protein 2 (SMYD2) can methylate histone H3 at lysine36 (H3K36) and some non-histone substrates to play a role in tumorigenesis. However, It is unclear how SMYD2 contributes to chronic kidney disease (CKD). Here, AZ505 or LLY507, which could inhibit SMYD2, were used in cisplatin-induced CKD to investigate the effects and possible mechanisms by which they might act. We found that high expression of SMYD2 in cisplatin-induced CKD. However, AZ505 or LLY507 can significantly inhibit its expression, improve renal function injury and fibrosis induced by cisplatin, inhibit the transition of epithelial cells to a fibrogenic phenotype and fibrosis-related proteins, inhibit the expression of Inflammatory Cytokines (such as IL-6 and TNF-α), And inhibit the phosphorylation of pro-fibrosis molecule Smad3 and signal transduction and transcription activator-3 (STAT3) and up-regulated the expression of renal protective factor Smad7. In cultured tubular epithelial cells, AZ505 also can inhibit the expression of EMT, fibrosis-related proteins, and inflammatory cytokines in cisplatin-induced tubular epithelial cells. Based on these findings, SMYD2 may be a critical regulator of cisplatin-induced CKD and targeted pharmacological inhibition of SMYD2 may prevent cisplatin-induced CKD through Smad3 or STAT3-related signaling pathways.

YAP/TAZ: Molecular pathway and disease therapy

The Yes-associated protein and its transcriptional coactivator with PDZ-binding motif (YAP/TAZ) are two homologous transcriptional coactivators that lie at the center of a key regulatory network of Hippo, Wnt, GPCR, estrogen, mechanical, and metabolism signaling. YAP/TAZ influences the expressions of downstream genes and proteins as well as enzyme activity in metabolic cycles, cell proliferation, inflammatory factor expression, and the transdifferentiation of fibroblasts into myofibroblasts. YAP/TAZ can also be regulated through epigenetic regulation and posttranslational modifications. Consequently, the regulatory function of these mechanisms implicates YAP/TAZ in the pathogenesis of metabolism-related diseases, atherosclerosis, fibrosis, and the delicate equilibrium between cancer progression and organ regeneration. As such, there arises a pressing need for thorough investigation of YAP/TAZ in clinical settings. In this paper, we aim to elucidate the signaling pathways that regulate YAP/TAZ and explore the mechanisms of YAP/TAZ-induce diseases and their potential therapeutic interventions. Furthermore, we summarize the current clinical studies investigating treatments targeting YAP/TAZ. We also address the limitations of existing research on YAP/TAZ and propose future directions for research. In conclusion, this review aims to provide fresh insights into the signaling mediated by YAP/TAZ and identify potential therapeutic targets to present innovative solutions to overcome the challenges associated with YAP/TAZ.

Cellular mechanotransduction in health and diseases: from molecular mechanism to therapeutic targets

Cellular mechanotransduction, a critical regulator of numerous biological processes, is the conversion from mechanical signals to biochemical signals regarding cell activities and metabolism. Typical mechanical cues in organisms include hydrostatic pressure, fluid shear stress, tensile force, extracellular matrix stiffness or tissue elasticity, and extracellular fluid viscosity. Mechanotransduction has been expected to trigger multiple biological processes, such as embryonic development, tissue repair and regeneration. However, prolonged excessive mechanical stimulation can result in pathological processes, such as multi-organ fibrosis, tumorigenesis, and cancer immunotherapy resistance. Although the associations between mechanical cues and normal tissue homeostasis or diseases have been identified, the regulatory mechanisms among different mechanical cues are not yet comprehensively illustrated, and no effective therapies are currently available targeting mechanical cue-related signaling. This review systematically summarizes the characteristics and regulatory mechanisms of typical mechanical cues in normal conditions and diseases with the updated evidence. The key effectors responding to mechanical stimulations are listed, such as Piezo channels, integrins, Yes-associated protein (YAP) /transcriptional coactivator with PDZ-binding motif (TAZ), and transient receptor potential vanilloid 4 (TRPV4). We also reviewed the key signaling pathways, therapeutic targets and cutting-edge clinical applications of diseases related to mechanical cues.

A2BAR Antagonism Decreases the Glomerular Expression and Secretion of Chemoattractants for Monocytes and the Pro-Fibrotic M2 Macrophages Polarization during Diabetic Nephropathy

Some chemoattractants and leukocytes such as M1 and M2 macrophages are known to be involved in the development of glomerulosclerosis during diabetic nephropathy (DN). In the course of diabetes, an altered and defective cellular metabolism leads to the increase in adenosine levels, and thus to changes in the polarity (M1/M2) of macrophages. MRS1754, a selective antagonist of the A2B adenosine receptor (A2BAR), attenuated glomerulosclerosis and decreased macrophage-myofibroblast transition in DN rats. Therefore, we aimed to investigate the effect of MRS1754 on the glomerular expression/secretion of chemoattractants, the intraglomerular infiltration of leukocytes, and macrophage polarity in DN rats. Kidneys/glomeruli of non-diabetic, DN, and MRS1754-treated DN rats were processed for transcriptomic analysis, immunohistopathology, ELISA, and in vitro macrophage migration assays. The transcriptomic analysis identified an upregulation of transcripts and pathways related to the immune system in the glomeruli of DN rats, which was attenuated using MRS1754. The antagonism of the A2BAR decreased glomerular expression/secretion of chemoattractants (CCL2, CCL3, CCL6, and CCL21), the infiltration of macrophages, and their polarization to M2 in DN rats. The in vitro macrophages migration induced by conditioned-medium of DN glomeruli was significantly decreased using neutralizing antibodies against CCL2, CCL3, and CCL21. We concluded that the pharmacological blockade of the A2BAR decreases the transcriptional expression of genes/pathways related to the immune response, protein expression/secretion of chemoattractants, as well as the infiltration of macrophages and their polarization toward the M2 phenotype in the glomeruli of DN rats, suggesting a new mechanism implicated in the antifibrotic effect of MRS1754.

The PI3K-Akt-mTOR pathway mediates renal pericyte-myofibroblast transition by enhancing glycolysis through HKII

BACKGROUND

Pericyte-myofibroblast transition (PMT) has been confirmed to contribute to renal fibrosis in several kidney diseases, and transforming growth factor-β1 (TGF-β1) is a well-known cytokine that drives PMT. However, the underlying mechanism has not been fully established, and little is known about the associated metabolic changes.

METHODS

Bioinformatics analysis was used to identify transcriptomic changes during PMT. PDGFRβ + pericytes were isolated using MACS, and an in vitro model of PMT was induced by 5 ng/ml TGF-β1. Metabolites were analyzed by ultraperformance liquid chromatography (UPLC) and tandem mass spectrometry (MS). 2-Deoxyglucose (2-DG) was used to inhibit glycolysis via its actions on hexokinase (HK). The hexokinase II (HKII) plasmid was transfected into pericytes for HKII overexpression. LY294002 or rapamycin was used to inhibit the PI3K-Akt-mTOR pathway for mechanistic exploration.

RESULTS

An increase in carbon metabolism during PMT was detected through bioinformatics and metabolomics analysis. We first detected increased levels of glycolysis and HKII expression in pericytes after stimulation with TGF-β1 for 48 h, accompanied by increased expression of α-SMA, vimentin and desmin. Transdifferentiation was blunted when pericytes were pretreated with 2-DG, an inhibitor of glycolysis. The phosphorylation levels of PI3K, Akt and mTOR were elevated during PMT, and after inhibition of the PI3K-Akt-mTOR pathway with LY294002 or rapamycin, glycolysis in the TGF-β1-treated pericytes was decreased. Moreover, PMT and HKII transcription and activity were blunted, but the plasmid-mediated overexpression of HKII rescued PMT inhibition.

CONCLUSIONS

The expression and activity of HKII as well as the level of glycolysis were increased during PMT. Moreover, the PI3K-Akt-mTOR pathway regulates PMT by increasing glycolysis through HKII regulation.

Calcium oxalate crystal-induced secretome derived from proximal tubular cells, not that from distal tubular cells, induces renal fibroblast activation

BACKGROUND

Kidney stone disease (KSD) is commonly accompanied with renal fibrosis, characterized by accumulation and reorganization of extracellular matrix (ECM). During fibrogenesis, resident renal fibroblasts are activated to become myofibroblasts that actively produce ECM. However, such fibroblast-myofibroblast differentiation in KSD remained unclear. Our present study thus examined effects of secreted products (secretome) derived from proximal (HK-2) vs. distal (MDCK) renal tubular cells exposed to calcium oxalate monohydrate (COM) crystals on activation of renal fibroblasts (BHK-21).

METHODS

HK-2 and MDCK cells were treated with 100 µg/ml COM crystals under serum-free condition for 16 h. In parallel, the cells maintained in serum-free medium without COM treatment served as the control. Secretome derived from culture supernatant of each sample was mixed (1:1) with fresh serum-free medium and then used for BHK-21 culture for another 24 h.

RESULTS

Analyses revealed that COM-treated-HK-2 secretome significantly induced proliferation, caused morphological changes, increased spindle index, and upregulated fibroblast-activation markers (F-actin, α-SMA and fibronectin) in BHK-21 cells. However, COM-treated-MDCK secretome had no significant effects on these BHK-21 parameters. Moreover, level of transforming growth factor-β1 (TGF-β1), a profibrotic factor, significantly increased in the COM-treated-HK-2 secretome but not in the COM-treated-MDCK secretome.

CONCLUSIONS

These data indicate, for the first time, that proximal and distal tubular epithelial cells exposed to COM crystals send different messages to resident renal fibroblasts. Only the secretome derived from proximal tubular cells, not that from the distal cells, induces renal fibroblast activation after their exposure to COM crystals. Such differential effects are partly due to TGF-β1 secretion, which is induced by COM crystals only in proximal tubular cells.

Ginkgo biloba extract attenuates cisplatin-induced renal interstitial fibrosis by inhibiting the activation of renal fibroblasts through down-regulating the HIF-1α/STAT3/IL-6 pathway in renal tubular epithelial cells

BACKGROUND

Activation of renal fibroblasts into myofibroblasts plays an important role in promoting renal interstitial fibrosis (RIF). Ginkgo biloba extract (EGb) can alleviate RIF induced by cisplatin (CDDP).

PURPOSE

To elucidate the effect of EGb treatment on cisplatin-induced RIF and reveal its potential mechanism.

METHODS

The two main active components in EGb were determined by high-performance liquid chromatography (HPLC) analysis. Rats were induced by CDDP and then treated with EGb, 2ME2 (HIF-1α inhibitor) or amifostine. After HK-2 cells and HIF-1α siRNA HK-2 cells were treated with CDDP, EGb or amifostine, the conditioned medium from each group was cultured with NRK-49F cells. The renal function of rats was detected. The renal damage and fibrosis were evaluated by H&E and Masson trichrome staining. The IL-6 content in the cell medium was detected by ELISA. The expression levels of indicators related to renal fibrosis and signaling pathway were examined by western blotting and qRT-PCR.

RESULTS

HPLC analysis showed that the contents of quercetin and kaempferol in EGb were 36.0 μg/ml and 45.7 μg/ml, respectively. In vivo, EGb and 2ME2 alleviated renal damage and fibrosis, as well as significantly decreased the levels of α-SMA, HIF-1α, STAT3 and IL-6 in rat tissues induced by CDDP. In vitro, the levels of HIF-1α, STAT3 and IL-6 were significantly increased in HK-2 cells and HIF-1α siRNA HK-2 cells induced by CDDP. Notably, HIF-1α siRNA significantly decreased the levels of HIF-1α, STAT3 and IL-6 in HK-2 cells, as well as the IL-6 level in medium from HK-2 cells. Additionally, the α-SMA level in NRK-49F cells was significantly increased after being cultured with conditioned medium from HK-2 cells or HIF-1α siRNA HK-2 cells exposed to CDDP. Furthermore, exogenous IL-6 increased the α-SMA level in NRK-49F cells. Importantly, the expression levels of the above-mentioned indicators were significantly decreased after the HK-2 cells and HIF-1α siRNA HK-2 cells were treated with EGb.

CONCLUSION

This study revealed that EGb improves CDDP-induced RIF, and the mechanism may be related to its inhibition of the renal fibroblast activation by down-regulating the HIF-1α/STAT3/IL-6 pathway in renal tubular epithelial cells.

CDC20 inhibition alleviates fibrotic response of renal tubular epithelial cells and fibroblasts by regulating nuclear translocation of β-catenin

Fibrosis is a common pathological phenomenon in progressive kidney disease leading to eventual loss of kidney function. Previous studies demonstrated that CDC20 plays a role in cancers by regulating epithelial-mesenchymal transition (EMT) and the infiltration of fibroblasts, suggesting the potential of CDC20 in regulating fibrotic response. However, the role of CDC20 in renal fibrosis is yet unclear. Herein, we reported that renal CDC20 was remarkably upregulated in renal tubular epithelial cells and fibroblasts in chronic kidney disease (CKD) patients, which was in line with a positive correlation with the severity of kidney fibrosis. In mice with unilateral urinary obstruction, CDC20 was also strikingly enhanced, and treatment with Apcin, an inhibitor of CDC20, ameliorated kidney fibrosis. Consistently, the pharmacological inhibition of CDC20 in mouse proximal tubular epithelial cells and rat fibroblasts attenuated TGF-β1-induced fibrotic responses, while overexpression of CDC20 aggravated such responses. Additional studies revealed that CDC20 induces nuclear translocation of β-catenin, which in turn initiates and promotes the pathological process of fibrosis in CKD. Thus, enhanced CDC20 in renal tubular cells and fibroblasts promotes renal fibrosis by activating β-catenin, and CDC20 inhibition may serve as a promising strategy for the prevention and treatment of renal fibrosis.

Kidney fibrosis: from mechanisms to therapeutic medicines

Chronic kidney disease (CKD) is estimated to affect 10-14% of global population. Kidney fibrosis, characterized by excessive extracellular matrix deposition leading to scarring, is a hallmark manifestation in different progressive CKD; However, at present no antifibrotic therapies against CKD exist. Kidney fibrosis is identified by tubule atrophy, interstitial chronic inflammation and fibrogenesis, glomerulosclerosis, and vascular rarefaction. Fibrotic niche, where organ fibrosis initiates, is a complex interplay between injured parenchyma (like tubular cells) and multiple non-parenchymal cell lineages (immune and mesenchymal cells) located spatially within scarring areas. Although the mechanisms of kidney fibrosis are complicated due to the kinds of cells involved, with the help of single-cell technology, many key questions have been explored, such as what kind of renal tubules are profibrotic, where myofibroblasts originate, which immune cells are involved, and how cells communicate with each other. In addition, genetics and epigenetics are deeper mechanisms that regulate kidney fibrosis. And the reversible nature of epigenetic changes including DNA methylation, RNA interference, and chromatin remodeling, gives an opportunity to stop or reverse kidney fibrosis by therapeutic strategies. More marketed (e.g., RAS blockage, SGLT2 inhibitors) have been developed to delay CKD progression in recent years. Furthermore, a better understanding of renal fibrosis is also favored to discover biomarkers of fibrotic injury. In the review, we update recent advances in the mechanism of renal fibrosis and summarize novel biomarkers and antifibrotic treatment for CKD.

The heterogeneity of fibrosis and angiogenesis in endometriosis revealed by single-cell RNA-sequencing

Fibrosis, angiogenesis and chronic inflammation are the inherent characteristics of endometriosis (EMS). The cellular heterogeneity of ectopic and non-ectopic endometrium by single-cell RNA-sequencing (scRNA-seq)at secretory phase without the disturbance of hormone drugs hasn't been explored so far. In this study, scRNA-seq was adopted to explore the properties of ectopic endometrium (ECE), eutopic endometrium (EUE) and normal endometrium (NOE) at secretory phase. We found that (i) The proportion of myofibroblasts, pericytes, endothelial cells and macrophages in ECE overwhelms that of non-ectopic tissues (EUE and NOE), and Myofibro.C2 was the predominant myofibroblast sub-cluster in ECE. (ii) Myofibroblasts were mainly fibroblast-to-myofibroblast transdifferentiation (FMT) and pericytes were endothelial cell-dependent differentiation in ECE. (iii) Both myofibroblasts and pericytes had a low differentiation potential. (iv) The increased inflammation score, deceased NK cells, T cell exhaustion score and antigen-presenting capacity in ECE confirmed the inflammatory properties and immunodeficiency of ECE. These findings suggested that myofibroblasts, pericytes and macrophages may be the potential targets for anti-fibrotic, anti-angiogenic and anti-inflammatory therapy of EMS.

Gastrodin attenuates renal injury and collagen deposition via suppression of the TGF-β1/Smad2/3 signaling pathway based on network pharmacology analysis

Background: Gastrodin has been widely used clinically in China as an antihypertensive drug. However, its effect on hypertensive renal injury is yet to be elucidated. The current study aimed to investigate the effects of gastrodin on hypertensive renal injury and its underlying mechanisms by network pharmacology analysis and validation in vivo and in vitro. Methods: A total of 10 spontaneously hypertensive rats (SHRs) were randomly categorized into the following two groups: SHR and SHR + Gastrodin groups. Wistar Kyoto (WKY) rats were used as the control group (n = 5). The SHR + Gastrodin group was intragastrically administered gastrodin (3.5 mg/kg/day), and the rats in both WKY and SHR groups were intragastrically administered an equal amount of double-distilled water for 10 weeks. Hematoxylin-eosin, Masson's trichrome, and Sirius red staining were used to detect the pathological changes and collagen content in the renal tissues. Network pharmacology analysis was performed to explore its potential targets and related pathways. In vitro, the CCK-8 assay was used to determine the cell viability. Immunohistochemistry and western-blotting analyses were employed to assess the protein expression associated with renal fibrosis and transforming growth factor-β1 (TGF-β1) pathway-related proteins in the renal tissues or in TGF-β1-stimulated rat kidney fibroblast cell lines (NRK-49F). Results: Gastrodin treatment attenuates renal injury and pathological alterations in SHRs, including glomerular sclerosis and atrophy, epithelial cell atrophy, and tubular dilation. Gastrodin also reduced the accumulation of collagen in the renal tissues of SHRs, which were confirmed by downregulation of α-SMA, collagen I, collagen III protein expression. Network pharmacology analysis identified TGFB1 and SMAD2 as two of lead candidate targets of gastrodin on against hypertensive renal injury. Consistently, gastrodin treatment downregulated the increase of the protein expression of TGF-β1, and ratios of both p-Smad2/Smad2 and p-Samd3/Smad3 in renal tissues of SHRs. In vitro, gastrodin (25-100 μM) treatment significantly reversed the upregulation of α-SMA, fibronectin, collagen I, as well as p-Smad2 and p-Smad3 protein expressions without affecting the cell viability of TGF-β1 stimulated NRK-49F cells. Conclusion: Gastrodin treatment significantly attenuates hypertensive renal injury and renal fibrosis and suppresses TGF-β1/Smad2/3 signaling in vivo and in vitro.

Kaempferol inhibits renal fibrosis by suppression of the sonic hedgehog signaling pathway

BACKGROUND

Most chronic kidney diseases (CKDs) develop to end-stage renal disease (ESRD), which is characterized by fibrosis and permanent tissue and function loss. As a result, better and more effective remedies are essential. Kaempferol (KAE) is a common flavonoid extracted from plants. It can control the progression of kidney fibrosis and the epithelial-to-mesenchymal transition (EMT) of the renal tubular system.

PURPOSE

We aim to investigate the effect of KAE therapy on extracellular matrix deposition and stimulation of EMT in vitro and in vivo to elucidate the treatment mechanisms regulating these effects.

STUDY DESIGN

Chronic hypertension-induced kidney fibrosis was studied in spontaneously hypertensive rats with chronic kidney disease. Biochemical analysis, histological staining, and the expression level of relative proteins were used to assess the effect of KAE on renal function and fibrosis. The direct impact of KAE on proliferation and migration was evaluated using human renal tubular epithelial cells (HK-2) induced by transforming growth factor-β1 (TGF-β1), which can then induce EMT. The molecular mechanism of KAE was verified using co-IP assay and immunofluorescence.

RESULTS

KAE could reduce blood pressure and decrease the extracellular matrix (ECM) components (including collagen I and collagen Ш), TGF-β1, and α-SMA in the kidneys of hypertension-induced rats with chronic kidney disease. Moreover, in HK-2 cell treated with TGF-β1, KAE administration significantly suppressed proliferation, migration, and EMT via increasing the expression of E-cadherin, while reducing the N-cadherin and α-SMA. Sufu was exceedingly repressed in HK-2 cells treated with TGF-β1. KAE inhibited the activation of Shh and Gli through increasing the expression of Sufu, thereby blocking the nuclear translocation of Gli1 in vitro.

CONCLUSION

KAE ameliorated kidney fibrosis and EMT by inhibiting the sonic hedgehog signaling pathway, thereby to attenuate the pathological progression of hypertensive kidney fibrosis.

Antioxidant, Anti-Apoptotic, and Anti-Inflammatory Effects of Farrerol in a Mouse Model of Obstructive Uropathy

Obstructive uropathy is a clinical condition that can lead to chronic kidney disease. However, treatments that can prevent the progression of renal injury and fibrosis are limited. Farrerol (FA) is a natural flavone with potent antioxidant and anti-inflammatory properties. Here, we investigated the effect of FA on renal injury and fibrosis in a mouse model of unilateral ureteral obstruction (UUO). Mice underwent a sham or UUO operation and received intraperitoneal injections of FA (20 mg/kg) daily for 8 consecutive days. Histochemistry, immunohistochemistry and immunofluorescence staining, TdT-mediated dUTP nick end labeling assay, Western blotting, gene expression analysis, and biochemical tests were performed. FA attenuated renal dysfunction (p < 0.05) and ameliorated renal tubular injury (p < 0.01) and interstitial fibrosis (p < 0.001) in UUO mice. FA alleviated 4-hydroxynonenal expression (p < 0.001) and malondialdehyde levels (p < 0.01) by regulating pro-oxidant and antioxidant enzymes. Apoptosis in the kidneys of UUO mice was inhibited by FA (p < 0.001), and this action was accompanied by decreased expression of cleaved caspase-3 (p < 0.01). Moreover, FA alleviated pro-inflammatory cytokine production (p < 0.001) and macrophage infiltration (p < 0.01) in the kidneys of UUO mice. These results suggest that FA ameliorates renal injury and fibrosis in the UUO model by inhibiting oxidative stress, apoptosis, and inflammation.

Acarbose Protects Glucolipotoxicity-Induced Diabetic Nephropathy by Inhibiting Ras Expression in High-Fat Diet-Fed db/db Mice

Diabetic nephropathy (DN) exacerbates renal tissue damage and is a major cause of end-stage renal disease. Reactive oxygen species play a vital role in hyperglycemia-induced renal injury. This study examined whether the oral hypoglycemic drug acarbose (Ab) could attenuate the progression of DN in type 2 diabetes mellitus mice. In this study, 50 mg/kg body weight of Ab was administered to high-fat diet (HFD)-fed db/db mice. Their body weight was recorded every week, and the serum glucose concentration was monitored every 2 weeks. Following their euthanasia, the kidneys of mice were analyzed through hematoxylin and eosin, periodic acid Schiff, Masson's trichrome, and immunohistochemistry (IHC) staining. The results revealed that Ab stabilized the plasma glucose and indirectly improved the insulin sensitivity and renal functional biomarkers in diabetic mice. In addition, diabetes-induced glomerular hypertrophy, the saccharide accumulation, and formation of collagen fiber were reduced in diabetic mice receiving Ab. Although the dosages of Ab cannot decrease the blood sugar in db/db mice, our results indicate that Ab alleviates glucolipotoxicity-induced DN by inhibiting kidney fibrosis-related proteins through the Ras/ERK pathway.

Ranunculus ternatus Thunb extract attenuates renal fibrosis of diabetic nephropathy via inhibiting SMYD2

CONTEXT

Ranunculus ternatus Thunb (Ranunculaceae), (RTT) is used clinically for the treatment of tuberculosis or as tumour adjuvant therapy, but its potential effect on diabetic nephropathy (DN) has not been studied.

OBJECTIVE

To investigate the effect of RTT extract in renal fibrosis of DN.

MATERIALS AND METHODS

C57BL/6 mice were randomly divided into four groups (n = 12). Diabetes mellitus (DM) mice were induced by streptozotocin (STZ, 55 mg/kg/day) for five consecutive days and treated by RTT extract (2 g/kg). Afterward, blood glucose, HE and Masson staining were assayed. The expression levels of Vimentin, ɑ-SMA, TNF-ɑ, NF-κB p-p65, NF-κB p65, SMYD2, H3K36me3, H3K4me3 were determined by western blots. Firbronectin was respectively assayed by western blot and immunofluorescent staining.

RESULTS

RTT extract significantly ameliorated renal injury and renal fibrosis in the renal tissue of STZ-induced diabetic mice as demonstrated by the decreased expression level of Fibronectin (65%), Vimentin and α-SMA (75% & 53%). In addition, the levels of TNF-α (57%), NF-κB p-p65 and NF-κB p65 (35% & 25%) were elevated in the DN mice. Importantly, these were alleviated after RTT extract treatment. Moreover, we observed that the protein levels of SMYD2 (30%), H3K36me3 and H3K4me3 (53% & 75%) were reduced in DN mice after treatment with RTT extract.

DISCUSSION AND CONCLUSIONS

RTT extract mediates antifibrotic effects and anti-inflammatory responses in STZ-induced DN mainly through suppressing SMYD2 activation and H3K36me3 and H3K4me3 protein expression. RTT extract might have therapeutic potential against high glucose-induced nephropathy.

Protective Effects of Carnosol on Renal Interstitial Fibrosis in a Murine Model of Unilateral Ureteral Obstruction

Renal fibrosis is a common feature of chronic kidney disease and is a promising therapeutic target. However, there is still limited treatment for renal fibrosis, so the development of new anti-fibrotic agents is urgently needed. Accumulating evidence suggest that oxidative stress and endoplasmic reticulum (ER) stress play a critical role in renal fibrosis. Carnosol (CS) is a bioactive diterpene compound present in rosemary plants and has potent antioxidant and anti-inflammatory properties. In this study, we investigated the potential effects of CS on renal injury and fibrosis in a murine model of unilateral ureteral obstruction (UUO). Male C57BL/6J mice underwent sham or UUO surgery and received intraperitoneal injections of CS (50 mg/kg) daily for 8 consecutive days. CS improved renal function and ameliorated renal tubular injury and interstitial fibrosis in UUO mice. It suppressed oxidative injury by inhibiting pro-oxidant enzymes and activating antioxidant enzymes. Activation of ER stress was also attenuated by CS. In addition, CS inhibited apoptotic and necroptotic cell death in kidneys of UUO mice. Furthermore, cytokine production and immune cell infiltration were alleviated by CS. Taken together, these findings indicate that CS can attenuate renal injury and fibrosis in the UUO model.

Astragalus and its formulas as a therapeutic option for fibrotic diseases: Pharmacology and mechanisms

Fibrosis is the abnormal deposition of extracellular matrix, characterized by accumulation of collagen and other extracellular matrix components, which causes organ dysfunction and even death. Despite advances in understanding fibrosis pathology and clinical management, there is no treatment for fibrosis that can prevent or reverse it, existing treatment options may lead to diarrhea, nausea, bleeding, anorexia, and liver toxicity. Thus, effective drugs are needed for fibrotic diseases. Traditional Chinese medicine has played a vital role in fibrotic diseases, accumulating evidence has demonstrated that Astragalus (Astragalus mongholicus Bunge) can attenuate multiple fibrotic diseases, which include liver fibrosis, pulmonary fibrosis, peritoneal fibrosis, renal fibrosis, cardiac fibrosis, and so on, mechanisms may be related to inhibition of epithelial-mesenchymal transition (EMT), reactive oxygen species (ROS), transforming growth factor beta 1 (TGF-β1)/Smads, apoptosis, inflammation pathways. The purpose of this review was to summarize the pharmacology and mechanisms of Astragalus in treating fibrotic diseases, the data reviewed demonstrates that Astragalus is a promising anti-fibrotic drug, its main anti-fibrotic components are Calycosin, Astragaloside IV, Astragalus polysaccharides and formononetin. We also review formulas that contain Astragalus with anti-fibrotic effects, in which Astragalus and Salvia miltiorrhiza Bunge, Astragalus and Angelica sinensis (Oliv.) Diels are the most commonly used combinations. We propose that combining active components into new formulations may be a promising way to develop new drugs for fibrosis. Besides, we expect Astragalus to be accepted as a clinically effective method of treating fibrosis.

Cellular phenotypic transitions in diabetic nephropathy: An update

Diabetic nephropathy (DN) is a major cause of morbidity and mortality in diabetes and is the most common cause of end stage renal disease (ESRD). Renal fibrosis is the final pathological change in DN. It is widely believed that cellular phenotypic switching is the cause of renal fibrosis in diabetic nephropathy. Several types of kidney cells undergo activation and differentiation and become reprogrammed to express markers of mesenchymal cells or podocyte-like cells. However, the development of targeted therapy for DN has not yet been identified. Here, we discussed the pathophysiologic changes of DN and delineated the possible origins that contribute to myofibroblasts and podocytes through phenotypic transitions. We also highlight the molecular signaling pathways involved in the phenotypic transition, which would provide valuable information for the activation of phenotypic switching and designing effective therapies for DN.

Nephropathy 1st inhibits renal fibrosis by activating the PPARγ signaling pathway

Renal fibrosis is a manifestation of kidney injury. Nephropathy 1st is a traditional Chinese herbal medicine that has been used as a therapy for kidney disease, but the underlying mechanisms remain elusive. The aim of this study was to investigate the role and underlying mechanisms of Nephropathy 1st on the progression of kidney disease. In the present study, unilateral ureteral obstruction was performed to establish the renal fibrosis rat model. By hematoxylin–eosin staining and immunohistochemical staining analysis, the severity of renal fibrosis was evaluated in vivo. Serum creatinine (CREA) and urea nitrogen (BUN) were measured by ELISA. The expression levels of Col-I, FN, PPARγ, and Klotho were measured by Western blot in rat NRK-49F cells and in fibrotic rats. GW9662 was used to inhibit PPARγ signaling. Metabonomic analysis showed metabolic differences among groups. Nephropathy 1st administration alleviated the progression of rat renal fibrosis and reduced serum creatinine (Scr) and BUN levels. Mechanistically, Nephropathy 1st promoted the expression of PPARγ and thus activated PPARγ signaling, thereby reducing the pro-fibrotic phenotypes of fibroblasts. The therapeutic effect of Nephropathy 1st was abrogated by the PPARγ inhibitor GW9662. Moreover, Nephropathy 1st normalized the dysregulated lipid metabolism in renal fibrosis rats. In conclusion, Nephropathy 1st alleviates renal fibrosis development in a PPARγ-dependent manner.

Chrysophanol, a main anthraquinone from Rheum palmatum L. (rhubarb), protects against renal fibrosis by suppressing NKD2/NF-κB pathway

PURPOSE

Chronic kidney disease (CKD), characterized as renal dysfunction and multi-system damage, has become a serious public health problem with high prevalence and mortality. Rheum palmatum L. (rhubarb) is one of the most widely used Chinese herb with renal protective activity. However, the active components and underlying mechanisms of rhubarb remain unknown. In this work, we tried to explore the pharmacological mechanism of chrysophanol, a main anthraquinone from rhubarb, against CKD by in vivo and in vitro models.

STUDY DESIGN

The therapeutic effect of chrysophanol and its underlying mechanism were investigated using CKD mouse model induced by unilateral ureteral occlusion (UUO), and human kidney 2 (HK-2) cells stimulated by TGF-β1 in vivo.

METHODS

The impact of chrysophanol on renal function, inflammation, fibrosis of CKD mice were evaluated. Then, the protein expressions of FN1, collagen ɑI, α-SMA, NF-κB and naked keratinocyte homolog 2 (NKD2) were investigated. In vitro studies, the inhibition on inflammation and fibrogenesis by chrysophanol was further validated in TGF-β1-stimulated HK2 cells, and the regulation of chrysophanol on NKD2/NF-κB pathway was analyzed. Moreover, NKD2 was overexpressed in HK-2 cells to confirm the role of NKD2/NF-κB pathway in chrysophanol-mediated efficacy. Finally, the binding mode of chrysophanol with NKD2 was studied using in silico molecular docking and microscale thermophoresis (MST) assay.

RESULTS

Chrysophanol could significantly improve the kidney dysfunction, alleviate renal pathology, and reverse the elevated levels of renal fibrosis markers such as FN1, collagen ɑI and α-SMA. Furthermore, chrysophanol effectively inhibited TNF-α, IL-6, and IL-1β production, and suppressed NF-κB activation and NKD2 expression. The findings of in vitro study were consistent with those of animal expriment. Using NKD2-overexpressing HK-2 cells, we also demonstrated that overexpression of NKD2 significantly compromised the anti-fibrotic effects of chrysophanol. In addition, molecular docking and MST analysis revealed that NKD2 was a direct target of chrysophanol.

CONCLUSION

Together, our work demonstrated for the first time that chrysophanol could effectively ameliorate renal fibrosis by inhibiting NKD2/NF-κB pathway. Chrysophanol can potentially prevent CKD by suppressing renal NKD2 expression directly.

Role of nuclear factor kappa B, interleukin-19, interleukin-34, and interleukin-37 expression in diabetic nephropathy

Background

The long-term effects of diabetes mellitus (DM) can impair several organs, including the kidney, resulting in serious health problems. Diabetic nephropathy (DN), a primary contributor in end-stage renal failure worldwide, affects 20–30% of patients with type 2 DM (T2DM). This study was designed to assess the contribution of nuclear factor kappa B (NF-κB) and interleukin (IL)-6, IL-19, IL-34, and IL-37 in the development of DN.

Methods

The study included 160 participants, of which 130 were allocated into the patients with diabetes group, patients with chronic kidney disease (CKD), and patients with diabetic chronic kidney disease (DCKD), and 30 were healthy controls.

Results

The obtained data revealed a significant (p < 0.05) increase in IL-19, IL-34, and NF-κB mRNA expression and serum IL-6 levels in patient groups (CKD and DCKD) compared with the healthy control group, whereas IL-19, IL-34, and NF-κB mRNA expression showed a marked elevation in the DCKD group when compared with patients with CKD. Conversely, IL-37 mRNA expression and serum superoxide dismutase (SOD) activity were significantly (p < 0.05) decreased in both groups relative to the healthy controls, whereas the decrease was markedly higher in the DCKD group when compared with the CKD group.

Conclusion

The obtained results could indicate the potential implication of NF-κB, IL-19, IL-34, and IL-6 levels, along with the decrease in IL-37 expression and serum SOD activity, in the pathophysiology of kidney disease in diabetes. Moreover, designing drugs targeting these cytokines and/or their signal pathways may prevent or alleviate the progression of kidney disease.

A Molecular Mechanism Study to Reveal Hirudin's Downregulation to PI3K/AKT Signaling Pathway through Decreasing PDGFRβ in Renal Fibrosis Treatment

Chronic kidney disease (CKD) is identified as a widespread chronic progressive disease jeopardizing public health which characterized by gradually loss of renal function. However, there is no efficient therapy to prevail over this disease. Our study was attempting to reveal hirudin's regulation to renal fibrosis as well as the molecular mechanism. We built renal fibrosis models on both cell and animal levels, which were subsequently given with hirudin disposal; then, we performed the transwell assay to estimate the cells' migration and had our detection to relevant proteins with western blot and immunofluorescence. Finally, we commenced both the identification and the determination to the hirudin targeted proteins and its downstream signaling pathways with the methods of network pharmacology. And the results turned out that when it was compared with the model group, the group with hirudin addition came with the suppression in the migration of renal tubular epithelial cells NRK-52E and with a conspicuous decline in the expressions of fibronectin, N-cadherin, vimentin, TGF-β, and snail. After that, we predicted that there were 17 hirudin target points mainly involving in the PI3K-AKT signaling pathway. Our outcomes of the animal level demonstrated that the conditions of interstitial fibrosis, severe tubular dilatation or atrophy, inflammatory cell infiltration, and massive accumulation of interstitial collagen in the model group were withdrawn after the addition of hirudin. In addition, p-PDGFRβ, p-PI3K, and p-AKT protein expressions were significantly reduced, and the PI3K/AKT pathway was downregulated after hirudin treatment in the model group of NRK-52E cells and animals. Therefore, we had our conclusion that hirudin is capable of suppressing the PI3K-AKT signaling pathway as well as the EMT by decreasing PDGFRβ phosphorylation.

The progress and prospect of natural components in rhubarb (Rheum ribes L.) in the treatment of renal fibrosis

Background: Renal fibrosis is a key pathological change that occurs in the progression of almost all chronic kidney diseases . CKD has the characteristics of high morbidity and mortality. Its prevalence is increasing each year on a global scale, which seriously affects people’s health and quality of life. Natural products have been used for new drug development and disease treatment for many years. The abundant natural products in R. ribes L. can intervene in the process of renal fibrosis in different ways and have considerable therapeutic prospects.

Purpose: The etiology and pathology of renal fibrosis were analyzed, and the different ways in which the natural components of R. ribes L. can intervene and provide curative effects on the process of renal fibrosis were summarized. Methods: Electronic databases, such as PubMed, Life Science, MEDLINE, and Web of Science, were searched using the keywords ‘R. ribes L.’, ‘kidney fibrosis’, ‘emodin’ and ‘rhein’, and the various ways in which the natural ingredients protect against renal fibrosis were collected and sorted out.

Results: We analyzed several factors that play a leading role in the pathogenesis of renal fibrosis, such as the mechanism of the TGF-β/Smad and Wnt/β-catenin signaling pathways. Additionally, we reviewed the progress of the treatment of renal fibrosis with natural components in R. ribes L. and the intervention mechanism of the crucial therapeutic targets.

Conclusion: The natural components of R. ribes L. have a wide range of intervention effects on renal fibrosis targets, which provides new ideas for the development of new anti-kidney fibrosis drugs.

Natural products: potential drugs for the treatment of renal fibrosis

With the increasing prevalence and mortality, chronic kidney disease (CKD) has become a world public health problem. As the primary pathological manifestation in CKD, renal fibrosis is often used as a critical target for the treatment of CKD and inhibits the progression of CKD to end-stage renal disease (ESRD). As a potential drug, natural products have been confirmed to have the potential as a routine or supplementary therapy for chronic kidney disease, which may target renal fibrosis and act through various pharmacological activities such as anti-inflammatory and anti-oxidation of natural products. This article briefly introduces the pathological mechanism of renal fibrosis and systematically summarizes the latest research on the treatment of renal fibrosis with natural products of Chinese herbal medicines.

Tumor necrosis factor-α coordinates with transforming growth factor-β1 to induce epithelial-mesenchymal transition and migration via the NF-κB/NOX4 pathway in bronchial epithelial cells

BACKGROUND

Epithelial-to-mesenchymal transition (EMT) is the process by which epithelial cells transform into mesenchymal cells, which plays a significant role in lung fibrotic disease. Transforming growth factor-β1(TGF-β1) is considered to be the most effective EMT inducer. The purpose of this study was to investigate the effect of the proinflammatory cytokine tumor necrosis factor-α (TNF-α) on TGF-β1-induced EMT and the underlying mechanisms in the human bronchial epithelial cell line BEAS-2B.

METHODS

Human bronchial epithelial BEAS-2B cells were treated with TGF-β1 and TNF-α separately or in combination for 24 h, and qRT-PCR, western blotting, immunofluorescence staining, and migration assays were used to investigate the EMT process. Moreover, to further explore the effect of the NF-κB pathway on the EMT process, inhibitor assays (BAY-117082, NF-κB inhibitor), wound healing assays, and western blotting were performed.

RESULTS

The results showed that both cytokines enhanced the transformation of BEAS-2B cells from epithelial to mesenchymal cells. In addition, combined treatment with TNF-α and TGF-β1 further reduced E-cadherin expression, which conversely elevated α-SMA and vimentin mRNA and protein levels. Correspondingly, the migration rate of BEAS-2B cells was also increased. Furthermore, inhibiting the NF-κB signaling pathway blocked the expression of EMT-related markers and NOX4 induced by TGF-β1 and TNF-α, as well as cell migration.

CONCLUSION

Taken together, TNF-α and TGF-β1 cooperatively promoted EMT and cell migration in BEAS-2B cells through the NF-κB/NOX4 signaling pathway.

BMP3 inhibits TGFβ2-mediated myofibroblast differentiation during wound healing of the embryonic cornea

Often acute damage to the cornea initiates drastic tissue remodeling, resulting in fibrotic scarring that disrupts light transmission and precedes vision impairment. Very little is known about the factors that can mitigate fibrosis and promote scar-free cornea wound healing. We previously described transient myofibroblast differentiation during non-fibrotic repair in an embryonic cornea injury model. Here, we sought to elucidate the mechanistic regulation of myofibroblast differentiation during embryonic cornea wound healing. We found that alpha-smooth muscle actin (αSMA)-positive myofibroblasts are superficial and their presence inversely correlates with wound closure. Expression of TGFβ2 and nuclear localization of pSMAD2 were elevated during myofibroblast induction. BMP3 and BMP7 were localized in the corneal epithelium and corresponded with pSMAD1/5/8 activation and absence of myofibroblasts in the healing stroma. In vitro analyses with corneal fibroblasts revealed that BMP3 inhibits the persistence of TGFβ2-induced myofibroblasts by promoting disassembly of focal adhesions and αSMA fibers. This was confirmed by the expression of vinculin and pFAK. Together, these data highlight a mechanism to inhibit myofibroblast persistence during cornea wound repair.