Cellular and molecular mechanisms of kidney fibrosis

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.

An extra honey polyphenols-rich diet ameliorates the high-fat diet induced chronic kidney disease via modulating gut microbiota in C57BL/6 mice

Honey is not equivalent to sugar and possess a worldwide health promoting effects such as antioxidant, antibacterial, anti-inflammatory, and hepatoprotective activities. Nevertheless, the potential impacts of honey on high-fat diet induced chronic kidney disease (CKD) and gut microbiota remain to be explored. Herein a high-fat diet was used to induce a mouse CKD model, and analysis was conducted on liver, kidney, spleen indices, tissue morphology, biochemical parameters, CKD related genes, and gut microbial diversity. The results indicated that significant inhibitory effects on renal damage caused by a high-fat diet in mice and improvement in disease symptoms were observed upon honey treatment. Significant changes were also found in serum TC, TG, UA, and BUN as well as the inflammation-related protein TNF-α and IL-6 levels in renal tissues. Gene expression analysis revealed that honey intake closely relates to gut microbiota diversity, which can regulate the composition of gut microbiota, increase microbial diversity, especially Bifidobacteriales and S24_7 and promote the synthesis of short chain fatty acids (SCFAs). In summary, this study suggests that honey has both preventive and therapeutic effects on CKD, which may be associated with its ability to improve microbial composition, increase microbial diversity, and regulate SCFAs levels.

Early growth response protein 2 promotes partial epithelial-mesenchymal transition by phosphorylating Smad3 during renal fibrosis

Chronic kidney disease (CKD) is a serious health problem worldwide, which ultimately leads to end-stage renal disease (ESRD). Renal fibrosis is the common pathway and major pathological manifestation for various CKD proceeding to ESRD. However, the underlying mechanisms and effective therapies are still ambiguous. Early growth response 2 (EGR2) is reportedly involved in organ formation and cell differentiation. To determine the role of EGR2 in renal fibrosis, we respectively confirmed the increased expression of EGR2 in kidney specimens from both CKD patients and mice with location in proximal tubules. Genetic deletion of EGR2 attenuated obstructive nephropathy while EGR2 overexpression further promoted renal fibrosis in mice subjected to unilateral ureteral obstruction (UUO) due to extracellular matrix (ECM) deposition mediating by partial epithelial-mesenchymal transition (EMT) as well as imbalance between matrix metalloproteinases (MMPs) and tissue inhibitor of MMPs (TIMPs). We found that EGR2 played a critical role in Smad3 phosphorylation, and inhibition of EGR2 reduced partial EMT leading to blockade of ECM accumulation in cultured human kidney 2 cells (HK2) treated with transforming growth factor β1 (TGF-β1). In addition, the transcription co-stimulator signal transducer and activator of transcription 3 (STAT3) phosphorylation was confirmed to regulate the transcription level of EGR2 in TGF-β1-induced HK2 cells. In conclusion, this study demonstrated that EGR2 played a pathogenic role in renal fibrosis by a p-STAT3-EGR2-p-Smad3 axis. Thus, targeting EGR2 could be a promising strategy for CKD treatment.

Emerging concepts of migrasome: An up-and-coming organelle from biology to the clinic

Since the migrasome concept was first proposed in 2015, extensive research has been conducted on these novel organelles, which grow on retracted fibers at the posterior end of migrating cells. Recently, molecular markers, biological functions, and clinical values based on the initial formation mechanism of migrasomes have emerged. Additionally, researchers are recognizing the significant role that migrasomes play in the pathological and diagnostic processes of clinical diseases. In this review, we summarize recent advances in the biology and clinical application of migrasomes and provide a comprehensive view of the prospective challenges surrounding their clinical application.

Natural polysaccharides as promising reno-protective agents for the treatment of various kidney injury

Renal injury, a prevalent clinical outcome with multifactorial etiology, imposes a substantial burden on society. Currently, there remains a lack of effective management and treatments. Extensive research has emphasized the diverse biological effects of natural polysaccharides, which exhibit promising potential for mitigating renal damage. This review commences with the pathogenesis of four common renal diseases and the shared mechanisms underlying renal injury. The renoprotective roles of polysaccharides in vivo and in vitro are summarized in the following five aspects: anti-oxidative stress effects, anti-apoptotic effects, anti-inflammatory effects, anti-fibrotic effects, and gut modulatory effects. Furthermore, we explore the structure-activity relationship and bioavailability of polysaccharides in relation to renal injury, as well as investigate their utility as biomaterials for alleviating renal injury. The clinical experiments of polysaccharides applied to patients with chronic kidney disease are also reviewed. Broadly, this review provides a comprehensive perspective on the research direction of natural polysaccharides in the context of renal injury, with the primary aim to serve as a reference for the clinical development of polysaccharides as pharmaceuticals and prebiotics for the treatment of kidney diseases.

Inhibition of PKC-δ retards kidney fibrosis via inhibiting cGAS-STING signaling pathway in mice

Kidney fibrosis is considered to be the ultimate aggregation pathway of chronic kidney disease (CKD), but its underlying mechanism remains elusive. Protein kinase C-delta (PKC-δ) plays critical roles in the control of growth, differentiation, and apoptosis. In this study, we found that PKC-δ was highly upregulated in human biopsy samples and mouse kidneys with fibrosis. Rottlerin, a PKC-δ inhibitor, alleviated unilateral ureteral ligation (UUO)-induced kidney fibrosis, inflammation, VDAC1 expression, and cGAS-STING signaling pathway activation. Adeno-associated virus 9 (AAV9)-mediated VDAC1 silencing or VBIT-12, a VDAC1 inhibitor, attenuated renal injury, inflammation, and activation of cGAS-STING signaling pathway in UUO mouse model. Genetic and pharmacologic inhibition of STING relieved renal fibrosis and inflammation in UUO mice. In vitro, hypoxia resulted in PKC-δ phosphorylation, VDAC1 oligomerization, and activation of cGAS-STING signaling pathway in HK-2 cells. Inhibition of PKC-δ, VDAC1 or STING alleviated hypoxia-induced fibrotic and inflammatory responses in HK-2 cells, respectively. Mechanistically, PKC-δ activation induced mitochondrial membrane VDAC1 oligomerization via direct binding VDAC1, followed by the mitochondrial DNA (mtDNA) release into the cytoplasm, and subsequent activated cGAS-STING signaling pathway, which contributed to the inflammation leading to fibrosis. In conclusion, this study has indicated for the first time that PKC-δ is an important regulator in kidney fibrosis by promoting cGAS-STING signaling pathway which mediated by VDAC1. PKC-δ may be useful for treating renal fibrosis and subsequent CKD.

Radiology of fibrosis part III: genitourinary system

Fibrosis is a pathological process involving the abnormal deposition of connective tissue, resulting from improper tissue repair in response to sustained injury caused by hypoxia, infection, or physical damage. It can impact any organ, leading to their dysfunction and eventual failure. Additionally, tissue fibrosis plays an important role in carcinogenesis and the progression of cancer.Early and accurate diagnosis of organ fibrosis, coupled with regular surveillance, is essential for timely disease-modifying interventions, ultimately reducing mortality and enhancing quality of life. While extensive research has already been carried out on the topics of aberrant wound healing and fibrogenesis, we lack a thorough understanding of how their relationship reveals itself through modern imaging techniques.This paper focuses on fibrosis of the genito-urinary system, detailing relevant imaging technologies used for its detection and exploring future directions.

Renal antiporter ClC-5 regulates collagen I/IV through the β-catenin pathway and lysosomal degradation

Mutations in Cl-/H+ antiporter ClC-5 cause Dent's disease type 1 (DD1), a rare tubulopathy that progresses to renal fibrosis and kidney failure. Here, we have used DD1 human cellular models and renal tissue from DD1 mice to unravel the role of ClC-5 in renal fibrosis. Our results in cell systems have shown that ClC-5 deletion causes an increase in collagen I (Col I) and IV (Col IV) intracellular levels by promoting their transcription through the β-catenin pathway and impairing their lysosomal-mediated degradation. Increased production of Col I/IV in ClC-5-depleted cells ends up in higher release to the extracellular medium, which may lead to renal fibrosis. Furthermore, our data have revealed that 3-mo-old mice lacking ClC-5 (Clcn5 +/- and Clcn5 -/- ) present higher renal collagen deposition and fibrosis than WT mice. Altogether, we describe a new regulatory mechanism for collagens' production and release by ClC-5, which is altered in DD1 and provides a better understanding of disease progression to renal fibrosis.

The current landscape of antifibrotic therapy across different organs: A systematic approach

Fibrosis is a common pathological process that can affect virtually all the organs, but there are hardly any effective therapeutic options. This has led to an intense search for antifibrotic therapies over the last decades, with a great number of clinical assays currently underway. We have systematically reviewed all current and recently finished clinical trials involved in the development of new antifibrotic drugs, and the preclinical studies analyzing the relevance of each of these pharmacological strategies in fibrotic processes affecting tissues beyond those being clinically studied. We analyze and discuss this information with the aim of determining the most promising options and the feasibility of extending their therapeutic value as antifibrotic agents to other fibrotic conditions.

Stem cell-based therapy for fibrotic diseases: mechanisms and pathways

Fibrosis is a pathological process, that could result in permanent scarring and impairment of the physiological function of the affected organ; this condition which is categorized under the term organ failure could affect various organs in different situations. The involvement of the major organs, such as the lungs, liver, kidney, heart, and skin, is associated with a high rate of morbidity and mortality across the world. Fibrotic disorders encompass a broad range of complications and could be traced to various illnesses and impairments; these could range from simple skin scars with beauty issues to severe rheumatologic or inflammatory disorders such as systemic sclerosis as well as idiopathic pulmonary fibrosis. Besides, the overactivation of immune responses during any inflammatory condition causing tissue damage could contribute to the pathogenic fibrotic events accompanying the healing response; for instance, the inflammation resulting from tissue engraftment could cause the formation of fibrotic scars in the grafted tissue, even in cases where the immune system deals with hard to clear infections, fibrotic scars could follow and cause severe adverse effects. A good example of such a complication is post-Covid19 lung fibrosis which could impair the life of the affected individuals with extensive lung involvement. However, effective therapies that halt or slow down the progression of fibrosis are missing in the current clinical settings. Considering the immunomodulatory and regenerative potential of distinct stem cell types, their application as an anti-fibrotic agent, capable of attenuating tissue fibrosis has been investigated by many researchers. Although the majority of the studies addressing the anti-fibrotic effects of stem cells indicated their potent capabilities, the underlying mechanisms, and pathways by which these cells could impact fibrotic processes remain poorly understood. Here, we first, review the properties of various stem cell types utilized so far as anti-fibrotic treatments and discuss the challenges and limitations associated with their applications in clinical settings; then, we will summarize the general and organ-specific mechanisms and pathways contributing to tissue fibrosis; finally, we will describe the mechanisms and pathways considered to be employed by distinct stem cell types for exerting anti-fibrotic events.

The main molecular mechanisms of ferroptosis and its role in chronic kidney disease

The term ferroptosis, coined in 2012, has been widely applied in various disease research fields. Ferroptosis is a newly regulated form of cell death distinct from apoptosis, necrosis, and autophagy, the mechanisms of which have been extensively studied. Chronic kidney disease, characterized by renal dysfunction, is a common disease severely affecting human health, with its occurrence and development influenced by multiple factors and leading to dysfunction in multiple systems. It often lacks obvious clinical symptoms in the early stages, and thus, diagnosis is typically made in the later stages, complicating treatment. While research on ferroptosis and acute kidney injury has made continuous progress, studies on the association between ferroptosis and chronic kidney disease remain limited. This review aims to summarize chronic kidney disease, investigate the mechanism and regulation of ferroptosis, and attempt to elucidate the role of ferroptosis in the occurrence and development of chronic kidney disease.

Anti-pulmonary fibrosis activity analysis of methyl rosmarinate obtained from Salvia castanea Diels f. tomentosa Stib. using a scalable process

Pulmonary fibrosis is a progressive, irreversible, chronic interstitial lung disease associated with high morbidity and mortality rates. Current clinical drugs, while effective, do not reverse or cure pulmonary fibrosis and have major side effects, there are urgent needs to develop new anti-pulmonary fibrosis medicine, and corresponding industrially scalable process as well. Salvia castanea Diels f. tomentosa Stib., a unique herb in Nyingchi, Xizang, China, is a variant of S. castanea. and its main active ingredient is rosmarinic acid (RA), which can be used to prepare methyl rosmarinate (MR) with greater drug potential. This study presented an industrially scalable process for the preparation of MR, which includes steps such as polyamide resin chromatography, crystallization and esterification, using S. castanea Diels f. tomentosa Stib. as the starting material and the structure of the product was verified by NMR technology. The anti-pulmonary fibrosis effects of MR were further investigated in vivo and in vitro. Results showed that this process can easily obtain high-purity RA and MR, and MR attenuated bleomycin-induced pulmonary fibrosis in mice. In vitro, MR could effectively inhibit TGF-β1-induced proliferation and migration of mouse fibroblasts L929 cells, promote cell apoptosis, and decrease extracellular matrix accumulation thereby suppressing progressive pulmonary fibrosis. The anti-fibrosis effect of MR was stronger than that of the prodrug RA. Further study confirmed that MR could retard pulmonary fibrosis by down-regulating the phosphorylation of the TGF-β1/Smad and MAPK signaling pathways. These results suggest that MR has potential therapeutic implications for pulmonary fibrosis, and the establishment of this scalable preparation technology ensures the development of MR as a new anti-pulmonary fibrosis medicine.

Metabolism and bioenergetics in the pathophysiology of organ fibrosis

Fibrosis is the tissue scarring characterized by excess deposition of extracellular matrix (ECM) proteins, mainly collagens. A fibrotic response can take place in any tissue of the body and is the result of an imbalanced reaction to inflammation and wound healing. Metabolism has emerged as a major driver of fibrotic diseases. While glycolytic shifts appear to be a key metabolic switch in activated stromal ECM-producing cells, several other cell types such as immune cells, whose functions are intricately connected to their metabolic characteristics, form a complex network of pro-fibrotic cellular crosstalk. This review purports to clarify shared and particular cellular responses and mechanisms across organs and etiologies. We discuss the impact of the cell-type specific metabolic reprogramming in fibrotic diseases in both experimental and human pathology settings, providing a rationale for new therapeutic interventions based on metabolism-targeted antifibrotic agents.

TRPC6 Knockout Alleviates Renal Fibrosis through PI3K/AKT/GSK3B Pathway

OBJECTIVE

Renal fibrosis is the ultimate pathway of various forms of acute and chronic kidney damage. Notably, the knockout of transient receptor potential channel 6 (TRPC6) has shown promise in alleviating renal fibrosis. However, the regulatory impact of TRPC6 on renal fibrosis remains unclear.

METHODS

In vivo, TRPC6 knockout (TRPC6-/-) mice and age-matched 129 SvEv (WT) mice underwent unilateral renal ischemia-reperfusion (uIR) injury surgery on the left renal pedicle or sham operation. Kidneys and serum were collected on days 7, 14, 21, and 28 after euthanasia. In vitro, primary tubular epithelial cells (PTECs) were isolated from TRPC6-/- and WT mice, followed by treatment with transforming growth factor β1 (TGFβ1) for 72 h. The anti-fibrotic effect of TRPC6-/- and the underlying mechanisms were assessed through hematoxylin-eosin staining, Masson staining, immunostaining, qRT-PCR, and Western blotting.

RESULTS

Increased TRPC6 expression was observed in uIR mice and PTECs treated with TGFβ1. TRPC6-/- alleviated renal fibrosis by reducing the expression of fibrotic markers (Col-1, α-SMA, and vimentin), as well as decreasing the apoptosis and inflammation of PTECs during fibrotic progression both in vivo and in vitro. Additionally, we found that the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/glycogen synthase kinase 3 beta (GSK3β) signaling pathway, a pivotal player in renal fibrosis, was down-regulated following TRPC6 deletion.

CONCLUSION

These results suggest that the ablation of TRPC6 may mitigate renal fibrosis by inhibiting the apoptosis and inflammation of PTECs through down-regulation of the PI3K/AKT/GSK3β pathway. Targeting TRPC6 could be a novel therapeutic strategy for preventing chronic kidney disease.

Arsenic exposure induced renal fibrosis via regulation of mitochondrial dynamics and the NLRP3-TGF-β1/SMAD signaling pathway

Environmental arsenic exposure is one of the major global public health problems. Studies have shown that arsenic exposure can cause renal fibrosis, but the underlying mechanism is still unclear. Integrating the in vivo and in vitro models, this study investigated the potential molecular pathways for arsenic-induced renal fibrosis. In this study, SD rats were treated with 0, 5, 25, 50, and 100 mg/L NaAsO2 for 8 weeks via drinking water, and HK2 cells were treated with different doses of NaAsO2 for 48 h. The in vivo results showed that arsenic content in the rats' kidneys increased as the dose increased. Body weight decreased and kidney coefficient increased at 100 mg/L. As a response to the elevated NaAsO2 dose, inflammatory cell infiltration, renal tubular injury, glomerular atrophy, tubulointerstitial hemorrhage, and fibrosis became more obvious indicated by HE and Masson staining. The kidney transcriptome profiles further supported the protein-protein interactions involved in NaAsO2-induced renal fibrosis. The in vivo results, in together with the in vitro experiments, have revealed that exposure to NaAsO2 disturbed mitochondrial dynamics, promoted mitophagy, activated inflammation and the TGF-β1/SMAD signaling pathway, and finally resulted in fibrosis. In summary, arsenic exposure contributed to renal fibrosis via regulating the mitochondrial dynamics and the NLRP3-TGF-β1/SMAD signaling axis. This study presented an adverse outcome pathway for the development of renal fibrosis due to arsenic exposure through drinking water.

CircInpp5b Ameliorates Renal Interstitial Fibrosis by Promoting the Lysosomal Degradation of DDX1

Renal interstitial fibrosis (RIF) is a classic pathophysiological process of chronic kidney disease (CKD). However, the mechanisms underlying RIF remain unclear. The present study found that a novel circular RNA, cirInpp5b, might be involved in RIF by high-throughput sequencing. Subsequent experiments revealed that circInpp5b was reduced in UUO mouse kidney tissues and TGF-β1-treated proximal tubular cells. The overexpression of circInpp5b inhibited RIF in UUO mice and prevented extracellular matrix (ECM) deposition in TGF-β1-treated proximal tubular cells. Furthermore, overexpression of circInpp5b down-regulated the protein level of DDX1. Mechanistically, circInpp5b bound to the DDX1 protein and promoted its lysosomal degradation. Collectively, the findings of our study demonstrate that circInpp5b ameliorates RIF by binding to the DDX1 protein and promoting its lysosomal degradation.

Transcriptome Analysis of BAFF/BAFF-R System in Murine Nephrotoxic Serum Nephritis

Chronic kidney disease (CKD) is an emerging cause for morbidity and mortality worldwide. Acute kidney injury (AKI) can transition to CKD and finally to end-stage renal disease (ESRD). Targeted treatment is still unavailable. NF-κB signaling is associated with CKD and activated by B cell activating factor (BAFF) via BAFF-R binding. In turn, renal tubular epithelial cells (TECs) are critical for the progression of fibrosis and producing BAFF. Therefore, the direct involvement of the BAFF/BAFF-R system to the pathogenesis of CKD is conceivable. We performed non-accelerated nephrotoxic serum nephritis (NTN) as the CKD model in BAFF KO (B6.129S2-Tnfsf13btm1Msc/J), BAFF-R KO (B6(Cg)-Tnfrsf13ctm1Mass/J) and wildtype (C57BL/6J) mice to analyze the BAFF/BAFF-R system in anti-glomerular basement membrane (GBM) disease using high throughput RNA sequencing. We found that BAFF signaling is directly involved in the upregulation of collagen III as BAFF ko mice showed a reduced expression. However, these effects were not mediated via BAFF-R. We identified several upregulated genes that could explain the effects of BAFF in chronic kidney injury such as Txnip, Gpx3, Igfbp7, Ccn2, Kap, Umod and Ren1. Thus, we conclude that targeted treatment with anti-BAFF drugs such as belimumab may reduce chronic kidney damage. Furthermore, upregulated genes may be useful prognostic CKD biomarkers.

Gucy1α1 specifically marks kidney, heart, lung and liver fibroblasts

Fibrosis is a common outcome of numerous pathologies, including chronic kidney disease (CKD), a progressive renal function deterioration. Current approaches to target activated fibroblasts, key effector contributors to fibrotic tissue remodeling, lack specificity. Here, we report Gucy1α1 as a specific kidney fibroblast marker. Gucy1α1 levels significantly increased over the course of two clinically relevant murine CKD models and directly correlated with established fibrosis markers. Immunofluorescent (IF) imaging showed that Gucy1α1 comprehensively labelled cortical and medullary quiescent and activated fibroblasts in the control kidney and throughout injury progression, respectively. Unlike traditionally used markers platelet derived growth factor receptor beta (Pdgfrβ) and vimentin (Vim), Gucy1α1 did not overlap with off-target populations such as podocytes. Notably, Gucy1α1 labelled kidney fibroblasts in both male and female mice. Furthermore, we observed elevated GUCY1α1 expression in the human fibrotic kidney and lung. Studies in the murine models of cardiac and liver fibrosis revealed Gucy1α1 elevation in activated Pdgfrβ-, Vim- and alpha smooth muscle actin (αSma)-expressing fibroblasts paralleling injury progression and resolution. Overall, we demonstrate Gucy1α1 as an exclusive fibroblast marker in both sexes. Due to its multiorgan translational potential, GUCY1α1 might provide a novel promising strategy to specifically target and mechanistically examine fibroblasts.

Targeting tumor suppressor p53 for organ fibrosis therapy

Fibrosis is a reparative and progressive process characterized by abnormal extracellular matrix deposition, contributing to organ dysfunction in chronic diseases. The tumor suppressor p53 (p53), known for its regulatory roles in cell proliferation, apoptosis, aging, and metabolism across diverse tissues, appears to play a pivotal role in aggravating biological processes such as epithelial-mesenchymal transition (EMT), cell apoptosis, and cell senescence. These processes are closely intertwined with the pathogenesis of fibrotic disease. In this review, we briefly introduce the background and specific mechanism of p53, investigate the pathogenesis of fibrosis, and further discuss p53's relationship and role in fibrosis affecting the kidney, liver, lung, and heart. In summary, targeting p53 represents a promising and innovative therapeutic approach for the prevention and treatment of organ fibrosis.

Strategies to Counteract Oxidative Stress and Inflammation in Chronic-Degenerative Diseases 2.0

Oxidative stress and inflammation are recognized as pivotal contributors and common features of several chronic degenerative diseases, including cancer, metabolic syndrome, type 2 diabetes, cardiovascular diseases and neurodegenerative disorders, affecting a high percentage of the population [...].

Curcumin prevents high glucose-induced stimulatory effects of renal cell secretome on fibroblast activation via mitigating intracellular free radicals and TGF-β secretion

Diabetic kidney disease (DKD) is a leading cause of kidney failure. However, the involvement of renal fibroblasts and their communications with renal epithelial cells during DKD remain poorly understood. We investigated the potential role of renal proximal tubular epithelial cells (PTECs) in renal fibroblast activation that might lead to DKD. Additionally, the protective effects of curcumin, a known antioxidant, against renal fibroblast activation induced by high glucose-treated PTECs were investigated. Secretome was collected from HK-2 PTECs under normal glucose, high glucose, high glucose pretreated/cotreated with curcumin, or osmotic control condition for 24 h. Such secretome was then used to treat BHK-21 renal fibroblasts for 24 h. BHK-21 cells treated with high glucose-induced secretome had increased levels of fibroblast activation markers, including spindle index, F-actin, α-smooth muscle actin (α-SMA), fibronectin, collagen I, matrix metalloproteinase-2 (MMP-2) and MMP-9, as compared with normal glucose and osmotic control conditions. However, all these increases were successfully mitigated by curcumin. In addition, high glucose markedly increased intracellular reactive oxygen species (ROS) and transforming growth factor-β (TGF-β) secretion, but did not affect the secretion of platelet-derived growth factor A (PDGFA) and interleukin-1β (IL-1β), in HK-2 renal cells as compared with normal glucose and osmotic control conditions. Both intracellular ROS and secreted TGF-β levels were successfully mitigated by curcumin. Therefore, curcumin prevents the high glucose-induced stimulatory effects of renal cell secretome on fibroblast activation, at least in part, via mitigating intracellular ROS and TGF-β secretion.

3D Printed Tubulointerstitium Chip as an In Vitro Testing Platform

Chronic kidney disease (CKD) ranks as the twelfth leading cause of death worldwide with limited treatment options. The development of in vitro models replicating defined segments of the kidney functional units, the nephrons, in a physiologically relevant and reproducible manner can facilitate drug testing. The aim of this study was to produce an in vitro organ-on-a-chip platform with extrusion-based three-dimensional (3D) printing. The manufacturing of the tubular platform was produced by printing sacrificial fibers with varying diameters, providing a suitable structure for cell adhesion and proliferation. The chip platform was seeded with primary murine tubular epithelial cells and human umbilical vein endothelial cells. The effect of channel geometry, its reproducibility, coatings for cell adhesion, and specific cell markers were investigated. The developed chip presents single and dual channels, mimicking segments of a renal tubule and the capillary network, together with an extracellular matrix gel analogue placed in the middle of the two channels, envisioning the renal tubulointerstitium in vitro. The 3D printed platform enables perfusable circular cross-section channels with fully automated, rapid, and reproducible manufacturing processes at low costs. This kidney tubulointerstitium on-a-chip provides the first step toward the production of more complex in vitro models for drug testing.

Bile Acid Receptor Agonist Reverses Transforming Growth Factor-β1-Mediated Fibrogenesis in Human Induced Pluripotent Stem Cells-Derived Kidney Organoids

Chronic kidney disease progresses through the replacement of functional tissue compartments with fibrosis, a maladaptive repair process. Shifting kidney repair toward a physiologically intact architecture, rather than fibrosis, is key to blocking chronic kidney disease progression. Much research into the mechanisms of fibrosis is performed in rodent models with less attention to the human genetic context. Recently, human induced pluripotent stem cell (iPSC)-derived organoids have shown promise in overcoming the limitation. In this study, we developed a fibrosis model that uses human iPSC-based 3-dimensional renal organoids, in which exogenous transforming growth factor-β1 (TGF-β1) induced the production of extracellular matrix. TGF-β1-treated organoids showed tubulocentric collagen 1α1 production by regulating downstream transcriptional regulators, Farnesoid X receptor, phosphorylated mothers against decapentaplegic homolog 3 (p-SMAD3), and transcriptional coactivator with PDZ-binding motif (TAZ). Increased nuclear TAZ expression was confirmed in the tubular epithelium in human kidney biopsies with tubular injury and early fibrosis. A dual bile acid receptor agonist (INT-767) increased Farnesoid X receptor and reduced p-SMAD3 and TAZ, attenuating TGF-β1-induced fibrosis in kidney organoids. Finally, we show that TAZ interacted with TEA-domain transcription factors and p-SMAD3 with TAZ and TEA-domain transcription factor 4 coregulating collagen 1α1 gene transcription. In summary, we establish a novel, readily manipulable fibrogenesis model and posit a role for bile acid receptor agonism early in renal parenchymal fibrosis.

Investigational new drugs for the treatment of chronic renal failure: an overview of the literature

INTRODUCTION

Chronic kidney disease (CKD) is widespread throughout the world, with a high social and health impact. It is considered a 'silent killer' for its sudden onset without symptoms in the early stages of the disease. The main goal of nephrologists is to slow the progression of kidney disease and treat the associated symptoms with a range of new medications.

AREAS COVERED

The aim of this systematic review is to analyze the new investigational drugs for the treatment of chronic renal failure. Data were obtained from the available scientific literature and from the ClinicalTrials.gov website.

EXPERT OPINION

Among the drugs currently being researched, SGLT2 inhibitors appear to be the most promising drugs for the treatment of CKD, has they have slower progression of CKD and protection of cardiorenal function. An important role in the future of CKD treatment is played by autologous cell-therapy, which appears to be a new frontier in the treatment of CKD. Other therapeutic strategies are currently being investigated and have been shown to slow the progression of CKD. However, further studies are needed to determine whether these approaches may offer benefits in slowing the progression of CKD in the near future.

Empagliflozin and pirfenidone confer renoprotection through suppression of glycogen synthase kinase-3β and promotion of tubular regeneration in rats with induced metabolic syndrome

Metabolic syndrome (MetS) is largely coupled with chronic kidney disease (CKD). Glycogen synthase kinase-3β (GSK-3β) pathway drives tubular injury in animal models of acute kidney injury; but its contribution in CKD is still elusive. This study investigated the effect empagliflozin and/or pirfenidone against MetS-induced kidney dysfunction, and to clarify additional underpinning mechanisms particularly the GSK-3β signaling pathway. Adult male rats received 10%w/v fructose in drinking water for 20 weeks to develop MetS, then treated with either drug vehicle, empagliflozin (30 mg/kg/day) and/or pirfenidone (100 mg/kg/day) via oral gavage for subsequent 4 weeks, concurrently with the high dietary fructose. Age-matched rats receiving normal drinking water were used as controls. After 24 weeks, blood and kidneys were harvested for subsequent analyses. Rats with MetS showed signs of kidney dysfunction, structural changes and interstitial fibrosis. Activation of GSK-3β, decreased cyclinD1 expression and enhanced apoptotic signaling were found in kidneys of MetS rats. There was abundant alpha-smooth muscle actin (α-SMA) expression along with up-regulation of TGF-β1/Smad3 in kidneys of MetS rats. These derangements were almost alleviated by empagliflozin or pirfenidone, with evidence that the combined therapy was more effective than either individual drug. This study emphasizes a novel mechanism underpinning the beneficial effects of empagliflozin and pirfenidone on kidney dysfunction associated with MetS through targeting GSK-3β signaling which can mediate the regenerative capacity, anti-apoptotic effects and anti-fibrotic properties of such drugs. These findings recommend the possibility of using empagliflozin and pirfenidone as promising therapies for management of CKD in patients with MetS.

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.

Secreted frizzled-related protein 5 protects against renal fibrosis by inhibiting Wnt/β-catenin pathway

Renal fibrosis (RF) is an important pathogenesis for renal function deterioration in chronic kidney disease. Secreted frizzled-related protein 5 (SFRP5) is an anti-fibrotic adipokine but its direct role on RF remains unknown. It was aimed to study the protective effect of SFRP5 against RF and interference with Wnt/β-catenin signaling pathway for the first time. First, the therapeutic efficacy of SFRP5 was evaluated by adenovirus overexpression in rats with unilateral ureteral obstruction (UUO) in vivo. Thirty-six rats were randomly divided into the sham, UUO, and SFRP5 (UUO + Ad-SFRP5) groups. Half rats in each group were selected at random for euthanasia at 7 days and the others until 14 days. Then, the transforming growth factor (TGF)-β1-induced epithelial-mesenchymal transition (EMT) was established in HK-2 cells in vitro. The cells were divided into four groups: the control group, the TGF-β1 group, the TGF-β1 + SFRP5 group, and the TGF-β1 + SFRP5 + anti-SFRP5 group. The makers of EMT and Wnt/β-catenin pathway proteins were investigated. In the UUO model, expression of SFRP5 showed compensatory upregulation, and adenoviral-mediated SFRP5 over-expression remarkably attenuated RF, as demonstrated by maintenance of E-cadherin and suppression of α-smooth muscle actin (SMA). In vitro, SFRP5 was shown to inhibit TGF-β1-mediated positive regulation of α-SMA, fibronectin, collagen I but negative regulation of E-cadherin. Furthermore, SFRP5 abrogated activation of Wnt/β-catenin, which was the essential pathway in EMT and RF pathogenesis. The changes after a neutralizing antibody to SFRP5 confirmed the specificity of SFRP5 for inhibition. These findings suggest that SFRP5 can directly ameliorate EMT and protect against RF by inhibiting Wnt/β-catenin pathway.

Hirudin in the Treatment of Chronic Kidney Disease

Chronic kidney disease (CKD) is a common public health concern. The global burden of CKD is increasing due to the high morbidity and mortality associated with it, indicating the shortcomings of therapeutic drugs at present. Renal fibrosis is the common pathology of CKD, which is characterized by glomerulosclerosis, renal tubular atrophy, and renal interstitial fibrosis. Natural hirudin is an active ingredient extracted from Hirudo medicinalis, which has been found to be the strongest natural specific inhibitor of thrombin. Evidence based on pharmacological data has shown that hirudin has important protective effects in CKD against diabetic nephrology, nephrotic syndrome, and renal interstitial fibrosis. The mechanisms of hirudin in treating CKD are mainly related to inhibiting the inflammatory response, preventing apoptosis of intrinsic renal cells, and inhibiting the interactions between thrombin and protease-activated receptors. In this review, we summarize the function and beneficial properties of hirudin for the treatment of CKD, and its underlying mechanisms.

Comparative Analysis of Acute Kidney Injury Models and Related Fibrogenic Responses: Convergence on Methylation Patterns Regulated by Cold Shock Protein

BACKGROUND

Fibrosis is characterized by excessive extracellular matrix formation in solid organs, disrupting tissue architecture and function. The Y-box binding protein-1 (YB-1) regulates fibrosis-related genes (e.g., Col1a1, Mmp2, and Tgfβ1) and contributes significantly to disease progression. This study aims to identify fibrogenic signatures and the underlying signaling pathways modulated by YB-1.

METHODS

Transcriptomic changes associated with matrix gene patterns in human chronic kidney diseases and murine acute injury models were analyzed with a focus on known YB-1 targets. Ybx1-knockout mouse strains (Ybx1ΔRosaERT+TX and Ybx1ΔLysM) were subjected to various kidney injury models. Fibrosis patterns were characterized by histopathological staining, transcriptome analysis, qRT-PCR, methylation analysis, zymography, and Western blotting.

RESULTS

Integrative transcriptomic analyses revealed that YB-1 is involved in several fibrogenic signatures related to the matrisome, the WNT, YAP/TAZ, and TGFß pathways, and regulates Klotho expression. Changes in the methylation status of the Klotho promoter by specific methyltransferases (DNMT) are linked to YB-1 expression, extending to other fibrogenic genes. Notably, kidney-resident cells play a significant role in YB-1-modulated fibrogenic signaling, whereas infiltrating myeloid immune cells have a minimal impact.

CONCLUSIONS

YB-1 emerges as a master regulator of fibrogenesis, guiding DNMT1 to fibrosis-related genes. This highlights YB-1 as a potential target for epigenetic therapies interfering in this process.

Crosstalk among podocytes, glomerular endothelial cells and mesangial cells in diabetic kidney disease: an updated review

Diabetic kidney disease (DKD) is a long-term and serious complication of diabetes that affects millions of people worldwide. It is characterized by proteinuria, glomerular damage, and renal fibrosis, leading to end-stage renal disease, and the pathogenesis is complex and involves multiple cellular and molecular mechanisms. Among three kinds of intraglomerular cells including podocytes, glomerular endothelial cells (GECs) and mesangial cells (MCs), the alterations in one cell type can produce changes in the others. The cell-to-cell crosstalk plays a crucial role in maintaining the glomerular filtration barrier (GFB) and homeostasis. In this review, we summarized the recent advances in understanding the pathological changes and interactions of these three types of cells in DKD and then focused on the signaling pathways and factors that mediate the crosstalk, such as angiopoietins, vascular endothelial growth factors, transforming growth factor-β, Krüppel-like factors, retinoic acid receptor response protein 1 and exosomes, etc. Furthermore, we also simply introduce the application of the latest technologies in studying cell interactions within glomerular cells and new promising mediators for cell crosstalk in DKD. In conclusion, this review provides a comprehensive and updated overview of the glomerular crosstalk in DKD and highlights its importance for the development of novel intervention approaches.

Shared and Distinct Renal Transcriptome Signatures in 3 Standard Mouse Models of Chronic Kidney Disease

INTRODUCTION

Several mouse models with diverse disease etiologies are used in preclinical research for chronic kidney disease (CKD). Here, we performed a head-to-head comparison of renal transcriptome signatures in standard mouse models of CKD to assess shared and distinct molecular changes in three mouse models commonly employed in preclinical CKD research and drug discovery.

METHODS

All experiments were conducted on male C57BL/6J mice. Mice underwent sham, unilateral ureter obstruction (UUO), or unilateral ischemic-reperfusion injury (uIRI) surgery and were terminated two- and 6-weeks post-surgery, respectively. The adenine-supplemented diet-induced (ADI) model of CKD was established by feeding with adenine diet for 6 weeks and compared to control diet feeding. For all models, endpoints included plasma biochemistry, kidney histology, and RNA sequencing.

RESULTS

All models displayed increased macrophage infiltration (F4/80 IHC) and fibrosis (collagen 1a1 IHC). Compared to corresponding controls, all models were characterized by an extensive number of renal differentially expressed genes (≥11,000), with a notable overlap in transcriptomic signatures across models. Gene expression markers of fibrosis, inflammation, and kidney injury supported histological findings. Interestingly, model-specific transcriptome signatures included several genes representing current drug targets for CKD, emphasizing advantages and limitations of the three CKD models in preclinical target and drug discovery.

CONCLUSION

The UUO, uIRI, and ADI mouse models of CKD have significant commonalities in their renal global transcriptome profile. Model-specific renal transcriptional signatures should be considered when selecting the specific model in preclinical target and drug discovery.

The protective effect and mechanism of piperazine ferulate in rats with 5/6 nephrectomy-caused chronic kidney disease

Chronic kidney disease (CKD) is a type of chronic disease in which multiple factors are responsible for the structural and functional disorders of the kidney. Piperazine ferulate (PF) has anti-platelet and anti-fibrotic effects, and its mechanism of action remains to be elucidated. This study aimed to investigate the protective effect of PF against CKD in rats and to determine its mechanism of action. Network pharmacology was used to predict potential PF action targets in the treatment of CKD and to further validate them. A rat model of CKD was established; blood was collected, etc., for the assessment of the renal function; renal pathologic damage was examined using hematoxylin and eosin (HE) staining and Masson staining; changes in the levels of TGF-β1 and α-SMA were determined with ELISA; EPOR, FN, and COL I expression were detected utilizing immunohistochemistry; and HIF-1α, HIF-2α, and EPO protein molecules were analyzed deploying western blotting. PF reduces Scr, BUN, and 24 h UP levels; decreases FN and COL I expression; and attenuates renal injury. Additionally, PF inhibited TGF-β1 and stimulated the production of HIF-1α and HIF-2α, which downregulated α-SMA and upregulated EPO. PF attenuated the progression of the CKD pathology, and the mechanism of its action is possibly associated with the promotion of HIF-1α/HIF-2α/EPO production and TGF-β1 reduction.

Fibroblast growth factor 21 alleviates unilateral ureteral obstruction-induced renal fibrosis by inhibiting Wnt/β-catenin signaling pathway

Fibroblast growth factor 21 (FGF21) is a key regulator of energy metabolism. Recent studies suggested that serum FGF21 levels increase with declining renal function. However, the link between FGF21 and kidney diseases and the direct effect of FGF21 in renal fibrosis remains unclear. In this study, FGF21 was upregulated in unilateral ureteral obstruction (UUO)-induced renal fibrosis and cellular fibrosis induced by transforming growth factor-β, and renal expression of FGF21 was positively correlated with fibrosis markers. Additionally, FGF21 was regulated by Wnt/β-catenin signaling pathway. The knockdown and overexpression of FGF21 in mouse tubular epithelial cells demonstrated that FGF21 alleviates renal fibrosis by inhibiting the Wnt/β-catenin signaling pathway. To investigate the effect of FGF21 on renal fibrosis in vivo, we established an overexpression model by injecting the plasmid in mice and found that FGF21 overexpression relieved UUO-induced renal fibrosis and renal inflammatory response. Taken together, FGF21 is upregulated with the activation of Wnt/β-catenin signaling pathway and alleviates renal fibrosis by inhibiting the activation of Wnt/β-catenin signaling pathway in a negative feedback mode. These results provide a new understanding for the source of elevated serum FGF21 in patients with chronic kidney disease and prove that FGF21 is a direct inhibitor of the progression of renal fibrosis, thus providing novel therapeutic intervention insights for renal fibrosis.

Targeted therapy in glomerular diseases

Targeted therapy has emerged as a more precise approach to treat glomerular diseases, focusing on specific molecular or cellular processes that contribute to disease development or progression. This approach complements or replaces traditional immunosuppressive therapy, optimizes supportive care, and provides a more personalized treatment strategy. In this review, we summarize the evolving understanding of pathogenic mechanisms in immune-mediated glomerular diseases and the developing targeted therapies based on these mechanisms. We begin by discussing pan-B-cell depletion, anti-CD20 rituximab, and targeting B-cell survival signaling through the BAFF/APRIL pathway. We also exam specific plasma cell depletion with anti-CD38 antibody. We then shift our focus to complement activation in glomerular diseases, which is involved in antibody-mediated glomerular diseases, such as IgA nephropathy, membranous nephropathy, ANCA-associated vasculitis, and lupus nephritis. Non-antibody-mediated complement activation occurs in glomerular diseases, including C3 glomerulopathy, complement-mediated atypical hemolytic uremic syndrome, and focal segmental glomerulosclerosis. We discuss specific inhibition of terminal, lectin, and alternative pathways in different glomerular diseases. Finally, we summarize current clinical trials targeting the final pathways of various glomerular diseases, including kidney fibrosis. We conclude that targeted therapy based on individualized pathogenesis should be the future of treating glomerular diseases.

Potential therapeutic medicines for renal fibrosis: Small-molecule compounds and natural products

Renal fibrosis is the pathological change process of chronic kidney disease deteriorating continuously. When the renal organ is stimulated by external stimuli, it will trigger the damage and phenotypic changes of some intrinsic cells in the kidney. When the body's autoimmune regulation or external treatment is not prompted enough to restore the organ, the pathological process is gradually aggravating, inducing a large amount of intracellular collagen deposition, which leads to the appearance of fibrosis and scarring. The renal parenchyma (including glomeruli and tubules) begins to harden, making it difficult to repair the kidney lesions. In the process of gradual changes in the kidney tissue, the kidney units are severely damaged and the kidney function shows a progressive decline, eventually resulting in the clinical manifestation of end-stage renal failure, namely uremia. This review provides a brief description of the diagnosis, pathogenesis, and potential therapeutic inhibitors of renal fibrosis. Since renal fibrosis has not yet had a clear therapeutic target and related drugs, some potential targets and relevant inhibitors are discussed, especially pharmacological effects and interactions with targets. Some existing natural products have potential efficacy for renal fibrosis, which is also roughly summarized, hoping that this article would have reference significance for the treatment of renal fibrosis.

GRK5 promoted renal fibrosis via HDAC5/Smad3 signaling pathway

Renal fibrosis is a common pathological feature of chronic kidney diseases (CKD), poses a significant burden in the aging population, and is a major cause of end-stage renal disease (ESRD). In this study, we investigated the role of G protein-coupled receptor kinases (GRKs) 5 in the pathogenesis of renal fibrosis. GRK5 is a serine/threonine kinase that regulates G protein-coupled receptor (GPCR) signaling. GRK5 has been shown to play a role in various diseases including cardiac disorders and cancer. However, the role of GRK5 in renal fibrosis remains largely unknown. Our finding revealed that GRK5 was significantly overexpressed in renal fibrosis. Specifically, GRK5 was transferred into the nucleus via its nuclear localization sequence to regulate histone deacetylases (HDAC) 5 expression under renal fibrosis. GRK5 acted as an upstream regulator of HDAC5/Smad3 signaling pathway. HDAC5 regulated and prevented the transcriptional activity of myocyte enhancer factor 2A (MEF2A) to repress the transcription of Smad7 which leading to the activation of Smad3. These findings first revealed that GRK5 may be a potential therapeutic target for the treatment of renal fibrosis. Inhibition of GRK5 activity may be a promising strategy to attenuate the progression of renal fibrosis.

Integrated analysis reveals crosstalk between pyroptosis and immune regulation in renal fibrosis

Purpose

The pathogenesis of renal fibrosis (RF) involves intricate interactions between profibrotic processes and immune responses. This study aimed to explore the potential involvement of the pyroptosis signaling pathway in immune microenvironment regulation within the context of RF. Through comprehensive bioinformatics analysis and experimental validation, we investigated the influence of pyroptosis on the immune landscape in RF.

Methods

We obtained RNA-seq datasets from Gene Expression Omnibus (GEO) databases and identified Pyroptosis-Associated Regulators (PARs) through literature reviews. Systematic evaluation of alterations in 27 PARs was performed in RF and normal kidney samples, followed by relevant functional analyses. Unsupervised cluster analysis revealed distinct pyroptosis modification patterns. Using single-sample gene set enrichment analysis (ssGSEA), we examined the correlation between pyroptosis and immune infiltration. Hub regulators were identified via weighted gene coexpression network analysis (WGCNA) and further validated in a single-cell RNA-seq dataset. We also established a unilateral ureteral obstruction-induced RF mouse model to verify the expression of key regulators at the mRNA and protein levels.

Results

Our comprehensive analysis revealed altered expression of 19 PARs in RF samples compared to normal samples. Five hub regulators, namely PYCARD, CASP1, AIM2, NOD2, and CASP9, exhibited potential as biomarkers for RF. Based on these regulators, a classifier capable of distinguishing normal samples from RF samples was developed. Furthermore, we identified correlations between immune features and PARs expression, with PYCARD positively associated with regulatory T cells abundance in fibrotic tissues. Unsupervised clustering of RF samples yielded two distinct subtypes (Subtype A and Subtype B), with Subtype B characterized by active immune responses against RF. Subsequent WGCNA analysis identified PYCARD, CASP1, and NOD2 as hub PARs in the pyroptosis modification patterns. Single-cell level validation confirmed PYCARD expression in myofibroblasts, implicating its significance in the stress response of myofibroblasts to injury. In vivo experimental validation further demonstrated elevated PYCARD expression in RF, accompanied by infiltration of Foxp3+ regulatory T cells.

Conclusions

Our findings suggest that pyroptosis plays a pivotal role in orchestrating the immune microenvironment of RF. This study provides valuable insights into the pathogenesis of RF and highlights potential targets for future therapeutic interventions.

Interaction of estradiol and renin-angiotensin system with microRNAs-21 and -29 in renal fibrosis: focus on TGF-β/smad signaling pathway

Kidney fibrosis is one of the complications of chronic kidney disease (CKD (and contributes to end-stage renal disease which requires dialysis and kidney transplantation. Several signaling pathways such as renin-angiotensin system (RAS), microRNAs (miRNAs) and transforming growth factor-β1 (TGF-β1)/Smad have a prominent role in pathophysiology and progression of renal fibrosis. Activation of classical RAS, the elevation of angiotensin II (Ang II) production and overexpression of AT1R, develop renal fibrosis via TGF-β/Smad pathway. While the non-classical RAS arm, Ang 1-7/AT2R, MasR reveals an anti-fibrotic effect via antagonizing Ang II. This review focused on studies illustrating the interaction of RAS with sexual female hormone estradiol and miRNAs in the progression of renal fibrosis with more emphasis on the TGF-β signaling pathway. MiRNAs, especially miRNA-21 and miRNA-29 showed regulatory effects in renal fibrosis. Also, 17β-estradiol (E2) is a renoprotective hormone that improved renal fibrosis. Beneficial effects of ACE inhibitors and ARBs are reported in the prevention of renal fibrosis in patients. Future studies are also merited to delineate the new therapy strategies such as miRNAs targeting, combination therapy of E2 or HRT, ACEis, and ARBs with miRNAs mimics and antagomirs in CKD to provide a new therapeutic approach for kidney patients.

The nuclear factor kappa B signaling pathway is a master regulator of renal fibrosis

Renal fibrosis is increasingly recognized as a global public health problem. Acute kidney injury (AKI) and chronic kidney disease (CKD) both result in renal fibrosis. Oxidative stress and inflammation play central roles in progressive renal fibrosis. Oxidative stress and inflammation are closely linked and form a vicious cycle in which oxidative stress induces inflammation through various molecular mechanisms. Ample evidence has indicated that a hyperactive nuclear factor kappa B (NF-ƙB) signaling pathway plays a pivotal role in renal fibrosis. Hyperactive NF-ƙB causes the activation and recruitment of immune cells. Inflammation, in turn, triggers oxidative stress through the production of reactive oxygen species and nitrogen species by activating leukocytes and resident cells. These events mediate organ injury through apoptosis, necrosis, and fibrosis. Therefore, developing a strategy to target the NF-ƙB signaling pathway is important for the effective treatment of renal fibrosis. This Review summarizes the effect of the NF-ƙB signaling pathway on renal fibrosis in the context of AKI and CKD (immunoglobulin A nephropathy, membranous nephropathy, diabetic nephropathy, hypertensive nephropathy, and kidney transplantation). Therapies targeting the NF-ƙB signaling pathway, including natural products, are also discussed. In addition, NF-ƙB-dependent non-coding RNAs are involved in renal inflammation and fibrosis and are crucial targets in the development of effective treatments for kidney disease. This Review provides a clear pathophysiological rationale and specific concept-driven therapeutic strategy for the treatment of renal fibrosis by targeting the NF-ƙB signaling pathway.

Application of nanotechnology in the treatment of glomerulonephritis: current status and future perspectives

Glomerulonephritis (GN) is the most common cause of end-stage renal failure worldwide; in most cases, it cannot be cured and can only delay the progression of the disease. At present, the main treatment methods include symptomatic therapy, immunosuppressive therapy, and renal replacement therapy. However, effective treatment of GN is hindered by issues such as steroid resistance, serious side effects, low bioavailability, and lack of precise targeting. With the widespread application of nanoparticles in medical treatment, novel methods have emerged for the treatment of kidney diseases. Targeted transportation of drugs, nucleic acids, and other substances to kidney tissues and even kidney cells through nanodrug delivery systems can reduce the systemic effects and adverse reactions of drugs and improve treatment effectiveness. The high specificity of nanoparticles enables them to bind to ion channels and block or enhance channel gating, thus improving inflammation. This review briefly introduces the characteristics of GN, describes the treatment status of GN, systematically summarizes the research achievements of nanoparticles in the treatment of primary GN, diabetic nephropathy and lupus nephritis, analyzes recent therapeutic developments, and outlines promising research directions, such as gas signaling molecule nanodrug delivery systems and ultrasmall nanoparticles. The current application of nanoparticles in GN is summarized to provide a reference for better treatment of GN in the future.

Single-cell sequencing dissects the transcriptional identity of activated fibroblasts and identifies novel persistent distal tubular injury patterns in kidney fibrosis

Examining kidney fibrosis is crucial for mechanistic understanding and developing targeted strategies against chronic kidney disease (CKD). Persistent fibroblast activation and tubular epithelial cell (TEC) injury are key CKD contributors. However, cellular and transcriptional landscapes of CKD and specific activated kidney fibroblast clusters remain elusive. Here, we analyzed single cell transcriptomic profiles of two clinically relevant kidney fibrosis models which induced robust kidney parenchymal remodeling. We dissected the molecular and cellular landscapes of kidney stroma and newly identified three distinctive fibroblast clusters with "secretory", "contractile" and "vascular" transcriptional enrichments. Also, both injuries generated failed repair TECs (frTECs) characterized by decline of mature epithelial markers and elevation of stromal and injury markers. Notably, frTECs shared transcriptional identity with distal nephron segments of the embryonic kidney. Moreover, we identified that both models exhibited robust and previously unrecognized distal spatial pattern of TEC injury, outlined by persistent elevation of renal TEC injury markers including Krt8 and Vcam1, while the surviving proximal tubules (PTs) showed restored transcriptional signature. We also found that long-term kidney injuries activated a prominent nephrogenic signature, including Sox4 and Hox gene elevation, which prevailed in the distal tubular segments. Our findings might advance understanding of and targeted intervention in fibrotic kidney disease.

Chemical components in cultivated Cordyceps sinensis and their effects on fibrosis

Objective

Cultivated Cordyceps sinensis powder has been used as clinical drug and healthy food to nourish the lung and kidney, which solves the problem of serious shortage of wild C. sinensis. This study aims to explore the chemical components and compared their anti-fibrotic effects in cultivated C. sinensis.

Methods

Nucleosides, sterols and polysaccharides were separated and purified from cultivated C. sinensis, and analyzed by high performance liquid chromatography, gas chromatography-mass spectrometry and chemical chromogenic methods, respectively. In high glucose-induced rat mesangial cell models, fibronectin and type 1 collagen were used as evaluation indicators.

Results

There were 10 kinds of nucleosides and one sterol in cultivated C. sinensis. The contents of nucleosides, sterols and polysaccharides in the cultivated C. sinensis were close to 2%, 0.55% and 4.4%, respectively. Furthermore, nucleoside, sterol and polysaccharide components exhibited varying degrees of anti-fibrotic activity. The nucleoside components and sterol components inhibited the expression of extracellular matrix more effectively in the three main components.

Conclusion

Cultivated C. sinensis remains the similar compounds with the wild C. sinensis, and nucleosides and sterols may be the main active substances that contribute to its anti-fibrotic effects. The project of this study may provide valuable information on further optimization of more effective remedies with few side effects based on cultivated C. sinensis.

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.

PDGFβ receptor-targeted delivery of truncated transforming growth factor β receptor type II for improving the in vitro and in vivo anti-renal fibrosis activity via strong inactivation of TGF-β1/Smad signaling pathway

Truncated transforming growth factor β receptor type II (tTβRII), serving as a trap for binding excessive transforming growth factor β1 (TGF-β1) by means of competing with wild-type TβRII, is a promising strategy for the treatment of kidney fibrosis. Platelet-derived growth factor β receptor (PDGFβR) is highly expressed in interstitial myofibroblasts in kidney fibrosis. This study identified the interaction between a novel tTβRII variant Z-tTβRII (PDGFβR-specific affibody ZPDGFβR fused to the N-terminus of tTβRII) and TGF-β1. Moreover, Z-tTβRII highly targeted to TGF-β1-activated NIH3T3 cells and UUO-induced fibrotic kidney, but less to normal cells, tissues, and organs. Furthermore, Z-tTβRII significantly inhibited cell proliferation and migration, and reduced fibrosis markers expression and phosphorylation level of Smad2/3 in activated NIH3T3 cells. Meanwhile, Z-tTβRII markedly alleviated the kidney histopathology and fibrotic responses, and inhibited the TGF-β1/Smad signaling pathway in UUO mice. Besides, Z-tTβRII showed good safety performance in the treatment of UUO mice. In conclusion, these results demonstrated that Z-tTβRII may be a potential candidate for a targeting therapy on renal fibrosis due to the high potential of fibrotic kidney-targeting and strong anti-renal fibrosis activity.

Emerging delivery systems based on aqueous two-phase systems: A review

The aqueous two-phase system (ATPS) is an all-aqueous system fabricated from two immiscible aqueous phases. It is spontaneously assembled through physical liquid-liquid phase separation (LLPS) and can create suitable templates like the multicompartment of the intracellular environment. Delicate structures containing multiple compartments make it possible to endow materials with advanced functions. Due to the properties of ATPSs, ATPS-based drug delivery systems exhibit excellent biocompatibility, extraordinary loading efficiency, and intelligently controlled content release, which are particularly advantageous for delivering drugs in vivo . Therefore, we will systematically review and evaluate ATPSs as an ideal drug delivery system. Based on the basic mechanisms and influencing factors in forming ATPSs, the transformation of ATPSs into valuable biomaterials is described. Afterward, we concentrate on the most recent cutting-edge research on ATPS-based delivery systems. Finally, the potential for further collaborations between ATPS-based drug-carrying biomaterials and disease diagnosis and treatment is also explored.

Gasdermin D promotes hyperuricemia-induced renal tubular injury through RIG-I/caspase-1 pathway

Renal tubular epithelial cells injury is one of the most important pathological features in hyperuricemic nephropathy (HN). However, the involvement of gasdermin D (GSDMD)-mediated pyroptosis in HN remains obscure. We found GSDMD was upregulated in the kidney tissue of HN mice, which was accompanied by the loss of renal function, renal tubular fibrosis, and reduced body weight. These changes in HN mice were inhibited by GSDMD knockout. Knockdown of GSDMD inhibited the high uric acid-induced injury in cultured cells (NRK-52E). Mechanistically, co-immunoprecipitation showed that RIG-I exist in a complex with caspase-1. Overexpression of RIG-I induced increased expression of caspase-1 protein and caspase-1 activity. Caspase-1 interference significantly reduced the increase of caspase-1 activity and IL-1β production caused by RIG-I overexpression. Knockdown of RIG-I or caspase-1 decreased high uric acid-induced injury in NRK-52E. This work illustrates that targeting the RIG-I/caspase-1/GSDMD may provide potential therapeutic benefits to HN.

SLIT3-mediated fibroblast signaling: a promising target for antifibrotic therapies

The SLIT family (SLIT1-3) of highly conserved glycoproteins was originally identified as ligands for the Roundabout (ROBO) family of single-pass transmembrane receptors, serving to provide repulsive axon guidance cues in the nervous system. Intriguingly, studies involving SLIT3 mutant mice suggest that SLIT3 might have crucial biological functions outside the neural context. Although these mutant mice display no noticeable neurological abnormalities, they present pronounced connective tissue defects, including congenital central diaphragmatic hernia, membranous ventricular septal defect, and osteopenia. We recently hypothesized that the phenotype observed in SLIT3-deficient mice may be tied to abnormalities in fibrillar collagen-rich connective tissue. Further research by our group indicates that both SLIT3 and its primary receptor, ROBO1, are expressed in fibrillar collagen-producing cells across various nonneural tissues. Global and constitutive SLIT3 deficiency not only reduces the synthesis and content of fibrillar collagen in various organs but also alleviates pressure overload-induced fibrosis in both the left and right ventricles. This review delves into the known phenotypes of SLIT3 mutants and the debated role of SLIT3 in vasculature and bone. Present evidence hints at SLIT3 acting as an autocrine regulator of fibrillar collagen synthesis, suggesting it as a potential antifibrotic treatment. However, the precise pathway and mechanisms through which SLIT3 regulates fibrillar collagen synthesis remain uncertain, presenting an intriguing avenue for future research.

Neuropilin 1 promotes unilateral ureteral obstruction-induced renal fibrosis via RACK1 in renal tubular epithelial cells

Neuropilin 1 (NRP1) is a single-channel transmembrane glycoprotein whose role and mechanism in renal fibrosis remain incompletely elucidated. Therefore, we investigated the effect of NRP1 on renal fibrosis and its potential mechanism. NRP1 expression in the renal sections from patients with chronic kidney disease (CKD) and a unilateral ureteral obstruction (UUO) mouse model was detected. Nrp1 overexpression or knockdown plasmid was transfected into mice, TKPTS mouse kidney proximal tubular epithelial cells (TECs), and rat kidney fibroblasts, after which pathological injury evaluation and fibrosis marker detection were conducted. The direct interaction of the receptor of activated protein C kinase 1 (RACK1) with NRP1 was validated by immunoprecipitation and Western blot analysis. We found that the upregulated renal NRP1 expression in patients with CKD was located in proximal TECs, consistent with the degree of interstitial fibrosis. In the UUO mouse model, NRP1 expression was upregulated in the kidney, and overexpression of Nrp1 increased the mRNA and protein expression of fibronectin (Fn) and α-smooth muscle actin (α-SMA), whereas Nrp1 knockdown significantly reduced Fn and α-SMA expression and downregulated the inflammatory response. NRP1 promoted transforming growth factor β1 (TGF-β1)-induced profibrotic responses in the TKPTS cells and fibroblasts, and Nrp1 knockdown partially reversed these responses. Immunoprecipitation combined with liquid chromatography-tandem mass spectrometry verified that NRP1 can directly bind to RACK1, and Rack1 knockdown reversed the NRP1-induced fibrotic response. In summary, NRP1 may enhance the TGF-β1 pathway by binding to RACK1, thus promoting renal fibrosis.NEW & NOTEWORTHY Although a few studies have confirmed the correlation between neuropilin 1 (NRP1) and renal diseases, the mechanism of NRP1 in renal fibrosis remains unclear. Here, we investigated the effects of NRP1 on renal fibrosis through in vitro and in vivo experiments and explored the possible downstream mechanisms. We found that NRP1 can stimulate the TGF-β1 signaling pathway, possibly by binding to RACK1, thereby promoting renal fibrosis.

Identification of basement membrane markers in diabetic kidney disease and immune infiltration by using bioinformatics analysis and experimental verification

Diabetic kidney disease (DKD) is the leading cause of chronic kidney disease worldwide. Basement membranes (BMs) are ubiquitous extracellular matrices which are affected in many diseases including DKD. Here, the authors aimed to identify BM-related markers in DKD and explored the immune cell infiltration in this process. The expression profiles of three datasets were downloaded from the Gene Expression Omnibus database. BM-related differentially expression genes (DEGs) were identified and Kyoto encyclopaedia of genes and genomes pathway enrichment analysis were applied to biological functions. Immune cell infiltration and immune function in the kidneys of patients with DKD and healthy controls were evaluated and compared using the ssGSEA algorithm. The association of hub genes and immune cells and immune function were explored. A total of 30 BM-related DEGs were identified. The functional analysis showed that BM-related DEGs were notably associated with basement membrane alterations. Crucially, BM-related hub genes in DKD were finally identified, which were able to distinguish patients with DKD from controls. Moreover, the authors observed that laminin subunit gamma 1(LAMC1) expression was significantly high in HK2 cells treated with high glucose. Immunohistochemistry results showed that, compared with those in db/m mouse kidneys, the levels of LAMC1 in db/db mouse kidneys were significantly increased. The biomarkers genes may prove crucial for DKD treatment as they could be targeted in future DKD treatment protocols.

Nrf2/HO-1 as a therapeutic target in renal fibrosis

Chronic kidney disease (CKD) is one of the most prevalent chronic diseases and affects between 10 and 14 % of the world's population. The World Health Organization estimates that by 2040, the disease will be fifth in prevalence. End-stage CKD is characterized by renal fibrosis, which can eventually lead to kidney failure and death. Renal fibrosis develops due to multiple injuries and involves oxidative stress and inflammation. In the human body, nuclear factor erythroid 2-related factor 2 (Nrf2) plays an important role in the expression of antioxidant, anti-inflammatory, and cytoprotective genes, which prevents oxidative stress and inflammation damage. Heme oxygenase (HO-1) is an inducible homolog influenced by heme products and after exposure to cellular stress inducers such as oxidants, inflammatory chemokines/cytokines, and tissue damage as an outcome or downstream of Nrf2 activation. HO-1 is known for its antioxidative properties, which play an important role in regulating oxidative stress. In renal diseases-induced tissue fibrosis and xenobiotics-induced renal fibrosis, Nrf2/HO-1 has been targeted with promising results. This review summarizes these studies and highlights the interesting bioactive compounds that may assist in attenuating renal fibrosis mediated by HO-1 activation. In conclusion, Nrf2/HO-1 signal activation could have a renoprotective effect strategy against CKD caused by oxidative stress, inflammation, and consequent renal fibrosis.