Macrophages promote renal fibrosis through direct and indirect mechanisms

Olfactory receptors contribute to progression of kidney fibrosis

Olfactory receptors (ORs) which are mainly known as odor-sensors in the olfactory epithelium are shown to be expressed in several non-sensory tissues. Despite the specified role of some of these receptors in normal physiology of the kidney, little is known about their potential effect in renal disorders. In this study, using the holistic view of systems biology, it was determined that ORs are significantly changed during the progression of kidney fibrosis. For further validation, common differentially expressed ORs resulted from reanalysis of two time-course microarray datasets were selected for experimental evaluation in a validated murine model of unilateral ureteral obstruction (UUO). Transcriptional analysis by real-time quantitative polymerase chain reaction demonstrated considerable changes in the expression pattern of Olfr433, Olfr129, Olfr1393, Olfr161, and Olfr622 during the progression of kidney fibrosis. For localization of these ORs, single-cell RNA-sequencing datasets of normal and UUO mice were reanalyzed. Results showed that Olfr433 is highly expressed in macrophages in day-2 and 7 post-injury in UUO mice and not in normal subgroups. Besides, like previous findings, Olfr1393 was shown to be expressed prominently in the proximal tubular cells of the kidney. In conclusion, our combinatorial temporal approach to the underlying mechanisms of chronic kidney disease highlighted the potential role of ORs in progression of fibrosis. The expression of Olfr433 in the macrophages provides some clue about its relation to molecular mechanisms promoted in the fibrotic kidney. The proposed ORs in this study could be the subject of further functional assessments in the future.

Macrophages are primed to transdifferentiate into fibroblasts in malignant ascites and pleural effusions

Cancer-associated fibroblasts (CAFs) play an important role in cancer progression. However, the origin of CAFs remains unclear. This study shows that macrophages in malignant ascites and pleural effusions (cavity fluid-associated macrophages: CAMs) transdifferentiate into fibroblast-like cells. CAMs obtained from gastrointestinal cancer patients were sorted by flow cytometry and cultured in vitro. CD45⁺CD14⁺ CAMs transdifferentiated into CD45^-CD90⁺ fibroblast-like cells that exhibited spindle shapes. Then, cDNA microarray analysis showed that the CD45^-CD90⁺ fibroblast-like cells (macrophage-derived CAFs: MDCAFs) had a fibroblast-specific gene expression signature and produced growth factors for epithelial cell proliferation. Human colon cancer cells transplanted into immunodeficient mice with MDCAFs formed larger tumors than cancer cells alone. Gene ontology analyses showed the involvement of TGFβ signaling and cell-matrix adhesion in MDCAFs, and transdifferentiation of CAMs into MDCAFs was canceled by inhibiting TGFβ and cell adhesion. Furthermore, the acquired genetic alterations in hematopoietic stem cells (HSCs) were shared in CAMs and MDCAFs. Taken together, CAMs could be a source of CAFs and might originate from HSCs. We propose the transdifferentiation process of CAMs into MDCAFs as a new therapeutic target for fibrosis associated with gastrointestinal cancer.

Advances in the Progression and Prognosis Biomarkers of Chronic Kidney Disease

Chronic kidney disease (CKD) is one of the increasingly serious public health concerns worldwide; the global burden of CKD is increasingly due to high morbidity and mortality. At present, there are three key problems in the clinical treatment and management of CKD. First, the current diagnostic indicators, such as proteinuria and serum creatinine, are greatly interfered by the physiological conditions of patients, and the changes in the indicator level are not synchronized with renal damage. Second, the established diagnosis of suspected CKD still depends on biopsy, which is not suitable for contraindication patients, is also traumatic, and is not sensitive to early progression. Finally, the prognosis of CKD is affected by many factors; hence, it is ineviatble to develop effective biomarkers to predict CKD prognosis and improve the prognosis through early intervention. Accurate progression monitoring and prognosis improvement of CKD are extremely significant for improving the clinical treatment and management of CKD and reducing the social burden. Therefore, biomarkers reported in recent years, which could play important roles in accurate progression monitoring and prognosis improvement of CKD, were concluded and highlighted in this review article that aims to provide a reference for both the construction of CKD precision therapy system and the pharmaceutical research and development.

Deficiency of IKKα in Macrophages Mitigates Fibrosis Progression in the Kidney after Renal Ischemia-Reperfusion Injury

Aims. Acute kidney injury (AKI) can lead to chronic kidney disease (CKD), and macrophages play a key role in this process. The aim of this study was to discover the role of IκB kinase α (IKKα) in macrophages in the process of AKI-to-CKD transition. Main Methods. We crossed lyz2-Cre mice with IKKα-floxed mice to generate mice with IKKα ablation in macrophages (Mac IKKα-/-). A mouse renal ischemia/reperfusion injury (IRI) model was induced by clamping the renal artery for 45 minutes. Treated mice were evaluated for blood biochemistry, tissue histopathology, and fibrosis markers. Macrophages were isolated from the peritoneal cavity for coculturing with tubular epithelial cells (TECs) and flow cytometry analysis. Key Findings. We found that fibrosis and kidney function loss after IRI were significantly alleviated in Mac IKKα-/- mice compared with wild-type (WT) mice. The expression of fibrosis markers and the infiltration of M2 macrophages were decreased in the kidneys of Mac IKKα-/- mice after IRI. The in vitro experiment showed that the IRI TECs cocultured with IKKα-/- macrophages (KO MΦs) downregulated the fibrosis markers accompanied by a downregulation of Wnt/β-catenin signaling. Significance. These data support the hypothesis that IKKα is involved in mediating macrophage polarization and increasing the expression of fibrosis-promoting inflammatory factors in macrophages. Therefore, knockdown of IKKα in macrophages may be a potential method that can be used to alleviate the AKI-to-CKD transition after IRI.

Bone marrow mesenchymal stem cell-derived exosomes improve renal fibrosis by reducing the polarisation of M1 and M2 macrophages through the activation of EP2 receptors

Renal fibrosis is the pathological outcome of most end‐stage renal diseases, yet there are still limited therapeutic options for it. In recent years, bone marrow mesenchymal stem cell‐derived exosomes (BM‐MSCs) have received much attention. Here, we investigate the therapeutic effect of BM‐MSCs on unilateral ureteral occlusion (UUO)‐induced interstitial fibrosis in the kidney by modulating prostaglandin E2 receptor 2 (EP2). Renal pathological changes were evident in the UUO group compared to the control group, with significantly increased expression of α‐smooth muscle actin (α‐SMA), fibronectin, Ep2 and F4/80⁺CD86⁺ and F4/80⁺CD206⁺ cells in the UUO group (p< 0.05). Pathological changes were alleviated and F4/80⁺CD86⁺ and F480/⁺CD206⁺ cells were reduced after exosome or EP2 agonist intervention compared to the UUO group. These data were further confirmed in vitro. Compared to the lipopolysaccharide (LPS) group and the LPS + exosome + Ah6809 group, the lipopolysaccharide (LPS) + exosome group and the LPS + butaprost group showed a significant decrease in α‐SMA expression, a decrease in the number of F4/80⁺CD86⁺ and F4/80⁺CD206⁺ cells, a decrease in interleukin (IL)‐6 and an increase in IL‐10 levels. Therefore, we conclude that BM‐MSCs can reduce the polarization of M1 and M2 macrophages by activating EP2 receptors, thereby ameliorating renal fibrosis.

Surface-engineered liposomes for dual-drug delivery targeting strategy against Methicillin-resistant Staphylococcus aureus (MRSA)

This study focused on the encapsulation of vancomycin (VAN) into liposomes coated with a red blood cell membrane with a targeting ligand, daptomycin–polyethylene glycol–1,2-distearoyl-sn-glycero-3-phosphoethanolamine, formed by conjugation of DAPT and N-hydroxysuccinimidyl-polyethylene glycol-1,2-distearoyl-sn-glycero-3-phosphoethanolamine. This formulation is capable of providing controlled and targeted drug delivery to the bacterial cytoplasm. We performed MALDI-TOF, NMR and FTIR analyses to confirm the conjugation of the targeting ligand via the formation of amide bonds. Approximately 45% of VAN could be loaded into the aqueous cores, whereas 90% DAPT was detected using UV–vis spectrophotometry. In comparison to free drugs, the formulations controlled the release of drugs for > 72 h. Additionally, as demonstrated using CLSM and flow cytometry, the resulting formulation was capable of evading detection by macrophage cells. In comparison to free drugs, red blood cell membrane–DAPT–VAN liposomes, DAPT liposomes, and VAN liposomes reduced the MIC and significantly increased bacterial permeability, resulting in > 80% bacterial death within 4 h. Cytotoxicity tests were performed in vitro and in vivo on mammalian cells, in addition to hemolytic activity tests in human erythrocytes, wherein drugs loaded into the liposomes and RBCDVL exhibited low toxicity. Thus, the findings of this study provide insight about a dual antibiotic targeting strategy that utilizes liposomes and red blood cell membranes to deliver targeted drugs against MRSA.

Tissue distribution and transcriptional regulation of CCN5 in the heart after myocardial infarction

CCN5 is a divergent member of the cellular communication network factor (CCN) family in that it lacks the carboxyl terminal cystine knot domain common to the other CCN family members. CCN5 has been reported to antagonize the profibrotic actions of CCN2 and to inhibit myocardial collagen deposition and fibrosis in chronic pressure overload of the heart. However, what mechanisms that regulate CCN5 activity in the heart remain unknown. Recombinant, replication defective adenovirus encoding firefly luciferase under control of the human CCN5 promoter was prepared and used to investigate what mechanisms regulate CCN5 transcription in relevant cells. Tissue distribution of CCN5 in hearts from healthy mice and from mice subjected to myocardial infarction was investigated. Contrary to the profibrotic immediate early gene CCN2, we find that CCN5 is induced in the late proliferation and maturation phases of scar healing. CCN5 was identified principally in endothelial cells, fibroblasts, smooth muscle cells, and macrophages. Our data show that CCN5 gene transcription and protein levels are induced by catecholamines via β₂-adrenergic receptors. Myocardial induction of CCN5 was further confirmed in isoproterenol-infused mice. We also find that CCN5 transcription is repressed by TNF-α, an inflammatory mediator highly elevated in early phases of wound healing following myocardial infarction. In conclusion, CCN5 predominates in endothelial cells, fibroblasts, and macrophages of the differentiating scar tissue and its transcription is conversely regulated by β₂-adrenergic agonists and TNF-α.

The mTOR inhibitor everolimus attenuates tacrolimus-induced renal interstitial fibrosis in rats

AIMS

Tacrolimus-a widely used immunosuppressant to prevent allograft rejection after organ transplantation-is nephrotoxic, increasing the risk of kidney injury accompanied by kidney fibrosis. The mammalian target of rapamycin (mTOR) inhibitor, everolimus, is an immunosuppressant used together with tacrolimus. Although mTOR signaling inhibition has been demonstrated to exhibit antifibrotic effects, the efficacy of everolimus against tacrolimus-induced kidney fibrosis has not been explored. Therefore, we evaluated the protective effects of everolimus against tacrolimus-induced kidney fibrosis.

MAIN METHODS

To assess antifibrotic effect of everolimus against tacrolimus-induced kidney fibrosis, male Wistar rats were subcutaneously administered vehicle or tacrolimus (5 mg/kg per day) and/or everolimus (0.2 mg/kg per day) for 2 weeks after bilateral renal ischemia for 45 min. The antifibrotic effect of everolimus was also assessed using rat kidney fibroblast cell line (NRK-49F).

KEY FINDINGS

Tacrolimus administration increased predominant profibrotic cytokine transforming growth factor-β (TGF-β) and fibroblast activation marker α-smooth muscle actin (α-SMA) expression and promoted the infiltration of macrophages in the kidney cortex, resulting in renal interstitial fibrosis in rats. Tacrolimus increased serum creatinine, blood urea nitrogen, kidney injury molecule-1 (KIM-1), and kidney injuries, such as tubular dilation, vacuolization, and glomerular atrophy. Everolimus administration attenuated tacrolimus-induced kidney fibrosis and the associated abnormalities. Everolimus strongly suppressed TGF-β-induced kidney fibroblast activation and extracellular matrix protein expression by the mTOR signaling inhibition.

SIGNIFICANCE

We demonstrated that everolimus attenuates tacrolimus-induced renal interstitial fibrosis in rats. Owing to its protective effect against tacrolimus-induced kidney fibrosis, everolimus may be useful when used concomitantly with tacrolimus.

Clinical evaluation of colony-stimulating factor 1 receptor inhibitors

Signaling through colony-stimulating factor 1 receptor (CSF1R) regulates the development, differentiation, and activation of mononuclear phagocytic cells. Inhibition of this pathway provides an opportunity for therapeutic intervention in diseases in which these cells play a pathogenic role, including cancers, inflammation, fibrosis, and others. Multiple monoclonal antibodies and small molecule inhibitors targeting CSF1R or its known ligands CSF1 and IL-34 have been clinically tested and are generally well tolerated with side effects associated with on-target macrophage inhibition or depletion. To date, clinical activity of CSF1R inhibitors has been primarily observed in diffuse-type tenosynovial giant cell tumors, a disease characterized by genetic alterations in CSF1 leading to dysregulated CSF1R signaling. Expanded development into novel indications such as chronic graft vs host disease may provide new opportunities to further explore areas where a role for CSF1R dependent monocytes and macrophages has been established. This review presents key findings from the clinical development of 12 CSF1/CSF1R targeted therapies as monotherapy or in combination with immune checkpoint inhibitors and chemotherapy.

Targeting monocytes/macrophages in fibrosis and cancer diseases: Therapeutic approaches

Over almost 140 years since their identification, the knowledge about macrophages has unbelievably evolved. The 'big eaters' from being thought of as simple phagocytic cells have been recognized as master regulators in immunity, homeostasis, healing/repair and organ development. Long considered to originate exclusively from bone marrow-derived circulating monocytes, macrophages have been also demonstrated to be the first immune cells colonizing tissues in the developing embryo and persisting in adult life by self-renewal, as long-lived tissue resident macrophages. Therefore, heterogeneous populations of macrophages with different ontogeny and functions co-exist in tissues. Macrophages act as sentinels of homeostasis and are intrinsically programmed to lead the wound healing and repair processes that occur after injury. However, in certain pathological circumstances macrophages get dysfunctional, and impaired or aberrant macrophage activities become key features of diseases. For instance, in both fibrosis and cancer, that have been defined 'wounds that do not heal', dysfunctional monocyte-derived macrophages overall play a key detrimental role. On the other hand, due to their plasticity these cells can be 're-educated' and exert anti-fibrotic and anti-cancer functions. Therefore macrophages represent an important therapeutic target in both fibrosis and cancer diseases. The current review will illustrate new insights into the role of monocytes/macrophages in these devastating diseases and summarize new therapeutic strategies and applications of macrophage-targeted drug development in their clinical setting.

STAT6 Deficiency Attenuates Myeloid Fibroblast Activation and Macrophage Polarization in Experimental Folic Acid Nephropathy

Renal fibrosis is a pathologic feature of chronic kidney disease, which can lead to end-stage kidney disease. Myeloid fibroblasts play a central role in the pathogenesis of renal fibrosis. However, the molecular mechanisms pertaining to myeloid fibroblast activation remain to be elucidated. In the present study, we examine the role of signal transducer and activator of transcription 6 (STAT6) in myeloid fibroblast activation, macrophage polarization, and renal fibrosis development in a mouse model of folic acid nephropathy. STAT6 is activated in the kidney with folic acid nephropathy. Compared with folic-acid-treated wild-type mice, STAT6 knockout mice had markedly reduced myeloid fibroblasts and myofibroblasts in the kidney with folic acid nephropathy. Furthermore, STAT6 knockout mice exhibited significantly less CD206 and PDGFR-β dual-positive fibroblast accumulation and M2 macrophage polarization in the kidney with folic acid nephropathy. Consistent with these findings, STAT6 knockout mice produced less extracellular matrix protein, exhibited less severe interstitial fibrosis, and preserved kidney function in folic acid nephropathy. Taken together, these results have shown that STAT6 plays a critical role in myeloid fibroblasts activation, M2 macrophage polarization, extracellular matrix protein production, and renal fibrosis development in folic acid nephropathy. Therefore, targeting STAT6 may provide a novel therapeutic strategy for fibrotic kidney disease.

IRF-4 deficiency reduces inflammation and kidney fibrosis after folic acid-induced acute kidney injury

The chronic phase following toxin-induced acute kidney injury (AKI) is characterized by robust inflammation and progressive kidney fibrosis. Interferon regulatory factor 4 (IRF-4) is a type of multifunctional transcription factor that has been deeply linked to inflammation and fibrotic diseases. However, the role of IRF-4 in kidney damage and renal fibrosis after toxin-induced AKI remain to be explored. In this work, we examined the effect of IRF-4 deficiency on inflammation and kidney fibrosis in an AKI-chronic kidney disease (CKD) transition model induced by folic acid (FA) injury. We showed that FA treatment resulted in severe acute tubular injury followed by inflammatory reaction and interstitial fibrosis in wild-type mice. A sharp elevation of IRF-4 levels was observed in FA-injured kidneys. IRF-4 knockout led to a substantial reduction of extracellular matrix (ECM) proteins deposition and inhibited myofibroblasts transformation in the kidneys of mice subjected to FA treatment. In addition, IRF-4 ablation impaired F4/80+ macrophages and CD3+ T lymphocytes infiltration into the FA-injured kidneys. Loss of IRF-4 reduced the production of inflammatory molecules such as CXCL16, IL-18, IL-6, and TGF-β1 in the kidneys in response to FA stress. Following FA injury, the kidneys of IRF-4 knockout mice had fewer bone marrow-derived myofibroblasts than wild-type controls. Moreover, IRF-4 disruption inhibited macrophages to myofibroblasts differentiation in the kidneys in response to FA stimuli. In vitro, IL-4 stimulated expression of α-smooth muscle actin and ECM proteins and promoted M2 macrophages to myofibroblasts transition in mouse bone marrow-derived monocytes, which was abolished in the absence of IRF-4. Thus, we identified an important role of IRF-4 in the pathogenesis of progressive CKD following FA-induced AKI.

Accelerative action of topical piperonylic acid on mice full thickness wound by modulating inflammation and collagen deposition

Epidermal growth factor (EGF) promotes cell growth, proliferation, and survival in numerous tissues. Piperonylic acid, a metabolite present in peppers (Piper nigrum L. and Piper longum L.), can bind to the epidermal growth factor receptor (EGFR) and induce an intracellular signaling cascade leading to the transcription of genes responsible for these actions, especially in keratinocytes. These cells are fundamental in maintaining cutaneous homeostasis and are the first to be damaged in the case of a wound. Thus, we hypothesized that piperonylic acid improves wound healing. C57BL6/J male mice were submitted to dorsal skin wounds caused by a 6 mm punch and treated topically with piperonylic acid or vehicle. The wounds were evaluated macro- and microscopically, and tissue samples were collected for immunofluorescence and real-time PCR analyses on days 6, 9 and 19 post-injury. Topical piperonylic acid improved wound healing from day 6 post-injury until closure. This phenomenon apparently occurred through EGFR activation. In addition, piperonylic acid modulated the gene expression of interleukin (Il)-6, il-1β, tumor necrosis factor (Tnf)-α, il-10, monocyte chemoattractant protein (Mcp)-1 and insulin-like growth factor (Igf)-1, which are important for the healing process. By day 19 post-injury, the new tissue showed greater deposition of type I collagen and a morphology closer to intact skin, with more dermal papillae and hair follicles. We conclude that piperonylic acid may be a viable option for the treatment of skin wounds.

Crosstalk between cancer-associated fibroblasts and immune cells in the tumor microenvironment: new findings and future perspectives

Cancer-associated fibroblasts (CAFs), a stromal cell population with cell-of-origin, phenotypic and functional heterogeneity, are the most essential components of the tumor microenvironment (TME). Through multiple pathways, activated CAFs can promote tumor growth, angiogenesis, invasion and metastasis, along with extracellular matrix (ECM) remodeling and even chemoresistance. Numerous previous studies have confirmed the critical role of the interaction between CAFs and tumor cells in tumorigenesis and development. However, recently, the mutual effects of CAFs and the tumor immune microenvironment (TIME) have been identified as another key factor in promoting tumor progression. The TIME mainly consists of distinct immune cell populations in tumor islets and is highly associated with the antitumor immunological state in the TME. CAFs interact with tumor-infiltrating immune cells as well as other immune components within the TIME via the secretion of various cytokines, growth factors, chemokines, exosomes and other effector molecules, consequently shaping an immunosuppressive TME that enables cancer cells to evade surveillance of the immune system. In-depth studies of CAFs and immune microenvironment interactions, particularly the complicated mechanisms connecting CAFs with immune cells, might provide novel strategies for subsequent targeted immunotherapies. Herein, we shed light on recent advances regarding the direct and indirect crosstalk between CAFs and infiltrating immune cells and further summarize the possible immunoinhibitory mechanisms induced by CAFs in the TME. In addition, we present current related CAF-targeting immunotherapies and briefly describe some future perspectives on CAF research in the end.

Transforming Growth Factor-β1/Smad Signaling in Glomerulonephritis and Its Association with Progression to Chronic Kidney Disease

INTRODUCTION

Transforming growth factor-β1 (TGF-β1) is a multifunctional cytokine, with diverse roles in fibrosis and inflammation, which acts through Smad signaling in renal pathology. We intended to investigate the expression of TGF-β/Smad signaling in glomerulonephritis (GN) and to assess its role as risk factor for progression to chronic kidney disease (CKD).

METHODS

We evaluated the immunohistochemical expression of TGF-β1, phosphorylated Smad3 (pSmad3), and Smad7 semiquantitatively and quantitatively using computerized image analysis program in different compartments of 50 renal biopsies with GN, and the results were statistically analyzed with clinicopathological parameters. We also examined the associations among their expressions, the impact of their co-expression, and their role in progression to CKD.

RESULTS

TGF-β1 expression correlated positively with segmental glomerulosclerosis (p= 0.025) and creatinine level at diagnosis (p = 0.002), while pSmad3 expression with interstitial inflammation (p = 0.024). In glomerulus, concomitant expressions of high Smad7 and medium pSmad3 were observed to be correlated with renal inflammation, such as cellular crescent (p = 0.011), intense interstitial inflammation (p = 0.029), and lower serum complement (C) 3 (p = 0.028) and C4 (p = 0.029). We also reported a significant association between pSmad3 expression in glomerular endothelial cells of proliferative GN (p = 0.045) and in podocytes of nonproliferative GN (p = 0.005). Finally, on multivariate Cox-regression analysis, TGF-β1 expression (hazard ratio = 6.078; 95% confidence interval: 1.168-31.627; p = 0.032) was emerged as independent predictor for CKD.

DISCUSSION/CONCLUSION

TGF-β1/Smad signaling is upregulated with specific characteristics in different forms of GN. TGF-β1 expression is indicated as independent risk factor for progression to CKD, while specific co-expression pattern of pSmad3 and Smad7 in glomerulus is correlated with renal inflammation.

The Role of Macrophages in Kidney Fibrosis

The phenotypic heterogeneity and functional diversity of macrophages confer on them complexed roles in the development and progression of kidney diseases. After kidney injury, bone marrow-derived monocytes are rapidly recruited to the glomerulus and tubulointerstitium. They are activated and differentiated on site into pro-inflammatory M1 macrophages, which initiate Th1-type adaptive immune responses and damage normal tissues. In contrast, anti-inflammatory M2 macrophages induce Th2-type immune responses, secrete large amounts of TGF-β and anti-inflammatory cytokines, transform into αSMA+ myofibroblasts in injured kidney, inhibit immune responses, and promote wound healing and tissue fibrosis. Previous studies on the role of macrophages in kidney fibrosis were mainly focused on inflammation-associated injury and injury repair. Apart from macrophage-secreted profibrotic cytokines, such as TGF-β, evidence for a direct contribution of macrophages to kidney fibrosis is lacking. However, under inflammatory conditions, Wnt ligands are derived mainly from macrophages and Wnt signaling is central in the network of multiple profibrotic pathways. Largely underinvestigated are the direct contribution of macrophages to profibrotic signaling pathways, macrophage phenotypic heterogeneity and functional diversity in relation to kidney fibrosis, and on their cross-talk with other cells in profibrotic signaling networks that cause fibrosis. Here we aim to provide an overview on the roles of macrophage phenotypic and functional diversity in their contribution to pro-fibrotic signaling pathways, and on the therapeutic potential of targeting macrophages for the treatment of kidney fibrosis.

Ongoing Exposure to Peritoneal Dialysis Fluid Alters Resident Peritoneal Macrophage Phenotype and Activation Propensity

Peritoneal dialysis (PD) is a more continuous alternative to haemodialysis, for patients with chronic kidney disease, with considerable initial benefits for survival, patient independence and healthcare costs. However, long-term PD is associated with significant pathology, negating the positive effects over haemodialysis. Importantly, peritonitis and activation of macrophages is closely associated with disease progression and treatment failure. However, recent advances in macrophage biology suggest opposite functions for macrophages of different cellular origins. While monocyte-derived macrophages promote disease progression in some models of fibrosis, tissue resident macrophages have rather been associated with protective roles. Thus, we aimed to identify the relative contribution of tissue resident macrophages to PD induced inflammation in mice. Unexpectedly, we found an incremental loss of homeostatic characteristics, anti-inflammatory and efferocytic functionality in peritoneal resident macrophages, accompanied by enhanced inflammatory responses to external stimuli. Moreover, presence of glucose degradation products within the dialysis fluid led to markedly enhanced inflammation and almost complete disappearance of tissue resident cells. Thus, alterations in tissue resident macrophages may render long-term PD patients sensitive to developing peritonitis and consequently fibrosis/sclerosis.

Natural killer T cell/IL-4 signaling promotes bone marrow-derived fibroblast activation and M2 macrophage-to-myofibroblast transition in renal fibrosis

Renal fibrosis is a histological manifestation of chronic kidney disease. Natural killer T (NKT) cells have a critical role in the pathogenesis of fibrotic disorder. However, the role of NKT cells in regulating kidney fibrosis remains largely unknown. In the current study, we showed that the percentages of NKT⁺ cells and NKT⁺-IL-4⁺ cells were notably increased in folic acid (FA) and obstructive nephropathy. CD1d deficiency protected mice from renal fibrosis induced by FA and obstructive injury. Specifically, Loss of CD1d reduced bone marrow-derived myofibroblasts and CD206⁺/α-smooth muscle actin⁺ cells in the kidneys of injured mice. But mice treated with α-galactosylceramide (α-GC, a specific activator of NKT cells) developed more severe fibrosis, accumulated more myeloid myofibroblasts and M2 macrophages-myofibroblasts transition (M2MMT) cells in FA injured kidneys. Furthermore, IL-4 expression was markedly reduced in CD1d deficiency mice but increased in α-GC-treated mice. Administration of IL-4 abrogates the inhibiting effect of CD1d deficiency on renal fibrosis, bone marrow-derived fibroblasts activation, and M2MMT in FA injured kidneys. Conversely, pharmacological inhibition of IL-4 attenuated the development of renal fibrosis, decreased bone marrow-derived myofibroblasts, and suppressed M2MMT. Thus, this study revealed a novel role of NKT cells in the bone marrow-derived fibroblasts activation and M2MMT during renal fibrosis. Targeting NKT cell/IL-4 signaling may be an effective treatment for renal fibrosis.

The Mechanism of CD8+ T Cells for Reducing Myofibroblasts Accumulation during Renal Fibrosis

Renal fibrosis is a hallmark of chronic kidney disease (CKD) and a common manifestation of end-stage renal disease that is associated with multiple types of renal insults and functional loss of the kidney. Unresolved renal inflammation triggers fibrotic processes by promoting the activation and expansion of extracellular matrix-producing fibroblasts and myofibroblasts. Growing evidence now indicates that diverse T cells and macrophage subpopulations play central roles in the inflammatory microenvironment and fibrotic process. The present review aims to elucidate the role of CD8⁺ T cells in renal fibrosis, and identify its possible mechanisms in the inflammatory microenvironment.

Recent advances on the mechanisms of kidney stone formation (Review)

Kidney stone disease is one of the oldest diseases known to medicine; however, the mechanisms of stone formation and development remain largely unclear. Over the past decades, a variety of theories and strategies have been developed and utilized in the surgical management of kidney stones, as a result of recent technological advances. Observations from the authors and other research groups suggest that there are five entirely different main mechanisms for kidney stone formation. Urinary supersaturation and crystallization are the driving force for intrarenal crystal precipitation. Randall's plaques are recognized as the origin of calcium oxalate stone formation. Sex hormones may be key players in the development of nephrolithiasis and may thus be potential targets for new drugs to suppress kidney stone formation. The microbiome, including urease-producing bacteria, nanobacteria and intestinal microbiota, is likely to have a profound effect on urological health, both positive and negative, owing to its metabolic output and other contributions. Lastly, the immune response, and particularly macrophage differentiation, play crucial roles in renal calcium oxalate crystal formation. In the present study, the current knowledge for each of these five aspects of kidney stone formation is reviewed. This knowledge may be used to explore novel research opportunities and improve the understanding of the initiation and development of kidney stones for urologists, nephrologists and primary care.

Monocyte and macrophage derived myofibroblasts: Is it fate? A review of the current evidence

Since the discovery of the myofibroblast over 50 years ago, much has been learned about its role in wound healing and fibrosis. Its origin, however, remains controversial, with a number of progenitor cells being proposed. Macrophage-myofibroblast transition (MMT) is a recent term coined in 2014 that describes the mechanism through which macrophages, derived from circulating monocytes originating in the bone marrow, transformed into myofibroblasts and contributed to kidney fibrosis. Over the past years, several studies have confirmed the existence of MMT in various systems, suggesting that MMT could potentially occur in all fibrotic conditions and constitute a reasonable therapeutic target to prevent progressive fibrotic disease. In this perspective, we examined recent evidence supporting the notion of MMT in both human disease and experimental models across organ systems. Mechanistic insight from these studies and information from in vitro studies is provided. The findings substantiating plausible MMT showcased the co-expression of macrophage and myofibroblast markers, including CD68 or F4/80 (macrophage) and α-SMA (myofibroblast), in fibroblast-like cells. Furthermore, fate-mapping experiments in murine models exhibiting myeloid-derived myofibroblasts in the tissue further provide direct evidence for MMT. Additionally, we provide some evidence from single cell RNA sequencing experiments confirmed by fluorescent in situ hybridisation studies, showing monocyte/macrophage and myofibroblast markers co-expressed in lung tissue from patients with fibrotic lung disease. In conclusion, MMT is likely a significant contributor to myofibroblast formation in wound healing and fibrotic disease across organ systems. Circulating precursors including monocytes and the molecular mechanisms governing MMT could constitute valid targets and provide insight for the development of novel antifibrotic therapies; however, further understanding of these processes is warranted.

Pharmacological inhibition of SETD7 by PFI-2 attenuates renal fibrosis following folic acid and obstruction injury

Renal fibrosis is the common pathological hallmark of chronic kidney disease, and SET domain containing lysine methyltransferase 7 (SETD7) promote considerably renal fibrosis. However, the signaling mechanisms underlying SETD7 driving renal fibrosis are not fully understood. Here, we investigated the role of SETD7 in M2 macrophages-myofibroblasts transition and the myeloid fibroblasts activation in folic acid and obstruction-induced renal fibrosis. Mice treated with PFI-2, an inhibitor of SETD7, presented less bone marrow-derived myofibroblasts, fewer CD206+/α-smooth muscle actin + cells and developed less renal fibrosis (P＜0.01). Furthermore, SETD7 inhibition reduced the infiltration of inflammatory cells and decreased the production of pro-inflammatory cytokines and chemokines in the kidneys after folic acid treatment (P＜0.01). Finally, SETD7 inhibition suppressed the accumulation of NF-κB p65+ cells in folic acid nephropathy (P＜0.01). Taken together, SETD7 mediates M2 macrophages-myofibroblasts transition, bone marrow-derived myofibroblasts activation, and inflammation response in the development of renal fibrosis.

Targeting immune cell metabolism in kidney diseases

Insights into the relationship between immunometabolism and inflammation have enabled the targeting of several immunity-mediated inflammatory processes that underlie infectious diseases and cancer or drive transplant rejection, but this field remains largely unexplored in kidney diseases. The kidneys comprise heterogeneous cell populations, contain distinct microenvironments such as areas of hypoxia and hypersalinity, and are responsible for a functional triad of filtration, reabsorption and secretion. These distinctive features create myriad potential metabolic therapeutic targets in the kidney. Immune cells have crucial roles in the maintenance of kidney homeostasis and in the response to kidney injury, and their function is intricately connected to their metabolic properties. Changes in nutrient availability and biomolecules, such as cytokines, growth factors and hormones, initiate cellular signalling events that involve energy-sensing molecules and other metabolism-related proteins to coordinate immune cell differentiation, activation and function. Disruption of homeostasis promptly triggers the metabolic reorganization of kidney immune and non-immune cells, which can promote inflammation and tissue damage. The metabolic differences between kidney and immune cells offer an opportunity to specifically target immunometabolism in the kidney.

The PAR-1 antagonist vorapaxar ameliorates kidney injury and tubulointerstitial fibrosis

Protease-activated receptor (PAR)-1 has emerged as a key profibrotic player in various organs including kidney. PAR-1 activation leads to deposition of extracellular matrix (ECM) proteins in the tubulointerstitium and induction of epithelial-mesenchymal transition (EMT) during renal fibrosis. We tested the anti-fibrotic potential of vorapaxar, a clinically approved PAR-1 antagonist for cardiovascular protection, in an experimental kidney fibrosis model of unilateral ureteral obstruction (UUO) and an AKI-to-chronic kidney disease (CKD) transition model of unilateral ischemia-reperfusion injury (UIRI), and dissected the underlying renoprotective mechanisms using rat tubular epithelial cells. PAR-1 is activated mostly in the renal tubules in both the UUO and UIRI models of renal fibrosis. Vorapaxar significantly reduced kidney injury and ameliorated morphologic changes in both models. Amelioration of kidney fibrosis was evident from down-regulation of fibronectin (Fn), collagen and α-smooth muscle actin (αSMA) in the injured kidney. Mechanistically, inhibition of PAR-1 inhibited MAPK ERK1/2 and transforming growth factor-β (TGF-β)-mediated Smad signaling, and suppressed oxidative stress, overexpression of pro-inflammatory cytokines and macrophage infiltration into the kidney. These beneficial effects were recapitulated in cultured tubular epithelial cells in which vorapaxar ameliorated thrombin- and hypoxia-induced TGF-β expression and ECM accumulation. In addition, vorapaxar mitigated capillary loss and the expression of adhesion molecules on the vascular endothelium during AKI-to-CKD transition. The PAR-1 antagonist vorapaxar protects against kidney fibrosis during UUO and UIRI. Its efficacy in human CKD in addition to CV protection warrants further investigation.

TSC1 Affects the Process of Renal Ischemia-Reperfusion Injury by Controlling Macrophage Polarization

Renal ischemia-reperfusion injury (IRI) contributes to acute kidney injury (AKI), increases morbidity and mortality, and is a significant risk factor for chronic kidney disease (CKD). Macrophage infiltration is a common feature after renal IRI, and infiltrating macrophages can be polarized into the following two distinct types: M1 macrophages, i.e., classically activated macrophages, which can not only inhibit infection but also accelerate renal injury, and M2 macrophages, i.e., alternatively activated macrophages, which have a repair phenotype that can promote wound healing and subsequent fibrosis. The role of TSC1, which is a negative regulator of mTOR signaling that regulates macrophage polarization in inflammation-linked diseases, has been well documented, but whether TSC1 contributes to macrophage polarization in the process of IRI is still unknown. Here, by using a mouse model of renal ischemia-reperfusion, we found that myeloid cell-specific TSC1 knockout mice (termed Lyz-TSC1 cKO mice) had higher serum creatinine levels, more severe histological damage, and greater proinflammatory cytokine production than wild-type (WT) mice during the early phase after renal ischemia-reperfusion. Furthermore, the Lyz-TSC1 cKO mice showed attenuated renal fibrosis during the repair phase of IRI with decreased levels of M2 markers on macrophages in the operated kidneys, which was further confirmed in a cell model of hypoxia-reoxygenation (H/R) in vitro. Mechanistically, by using RNA sequencing of sorted renal macrophages, we found that the expression of most M1-related genes was upregulated in the Lyz-TSC1 cKO group (Supplemental Table 1) during the early phase. However, C/EBPβ and CD206 expression was decreased during the repair phase compared to in the WT group. Overall, our findings demonstrate that the expression of TSC1 in macrophages contributes to the whole process of IRI but serves as an inflammation suppressor during the early phase and a fibrosis promoter during the repair phase.

An injectable micelle-hydrogel hybrid for localized and prolonged drug delivery in the management of renal fibrosis

Localized delivery, comparing to systemic drug administration, offers a unique alternative to enhance efficacy, lower dosage, and minimize systemic tissue toxicity by releasing therapeutics locally and specifically to the site of interests. Herein, a localized drug delivery platform ("plum‒pudding" structure) with controlled release and long-acting features is developed through an injectable hydrogel ("pudding") crosslinked via self-assembled triblock polymeric micelles ("plum") to help reduce renal interstitial fibrosis. This strategy achieves controlled and prolonged release of model therapeutics in the kidney for up to three weeks in mice. Following a single injection, local treatments containing either anti-inflammatory small molecule celastrol or anti-TGFβ antibody effectively minimize inflammation while alleviating fibrosis via inhibiting NF-κB signaling pathway or neutralizing TGF-β1 locally. Importantly, the micelle-hydrogel hybrid based localized therapy shows enhanced efficacy without local or systemic toxicity, which may represent a clinically relevant delivery platform in the management of renal interstitial fibrosis.

TGF-β1 Signaling: Immune Dynamics of Chronic Kidney Diseases

Chronic kidney disease (CKD) is a major cause of morbidity and mortality worldwide, imposing a great burden on the healthcare system. Regrettably, effective CKD therapeutic strategies are yet available due to their elusive pathogenic mechanisms. CKD is featured by progressive inflammation and fibrosis associated with immune cell dysfunction, leading to the formation of an inflammatory microenvironment, which ultimately exacerbating renal fibrosis. Transforming growth factor β1 (TGF-β1) is an indispensable immunoregulator promoting CKD progression by controlling the activation, proliferation, and apoptosis of immunocytes via both canonical and non-canonical pathways. More importantly, recent studies have uncovered a new mechanism of TGF-β1 for de novo generation of myofibroblast via macrophage-myofibroblast transition (MMT). This review will update the versatile roles of TGF-β signaling in the dynamics of renal immunity, a better understanding may facilitate the discovery of novel therapeutic strategies against CKD.

Eplerenone Attenuates Fibrosis in the Contralateral Kidney of UUO Rats by Preventing Macrophage-to-Myofibroblast Transition

Severe renal fibrosis often occurs in obstructive kidney disease, not only in the obstructed kidney but also in the contralateral kidney, causing renal dysfunction. Although the mechanisms of injury in obstructed kidney have been studied for years, the pathogenesis of fibrosis in the contralateral kidney remains largely unknown. Here, we examined long-term unilateral ureteral obstruction (UUO) model in male Sprague-Dawley rats and found that macrophage-to-myofibroblast transition (MMT) is contributing to renal fibrosis in the contralateral kidney of UUO rats. Interestingly, this process was attenuated by treatment of eplerenone, a specific blocker of the mineralocorticoid receptor (MR). In-vitro, stimulating MR in primary cultured or cell line macrophages enhances MMT, which were also inhibited by MR blockade. Collectively, these findings provide a plausible mechanism for UUO-induced injury in the contralateral kidney, suggesting the benefit of using MR blockage as a part of treatment to UUO to protect the contralateral kidney thereby preserve renal function.

UUO induces lung fibrosis with macrophage-myofibroblast transition in rats

Progression of chronic kidney disease (CKD) to uremia is often accompanied by varying degrees of lung damage and this is also an important cause of death. Although there are many studies on the mechanism of lung injury, it is not clearly understood. Inflammatory macrophages may associated with fibrosis in the lungs. Here, we investigated the role of macrophage-myofibroblast transition (MMT) in lung fibrosis with unilateral ureteral obstruction (UUO) rats. We found that cells undergoing MMT accounted for an important part of the myofibroblast population, and correlated with lung fibrosis, MMT cells in lungs have a predominant M2 phenotype, and this process was attenuated after treatment with eplerenone. In conclusion, our studies provide a possible mechanism for UUO-induced kidney damage and lung injury, indicating the possibility of using eplerenone, a mineralocorticoid receptor blocker, to treat UUO to reduce kidney damage and protect lung function.

Chronic Inflammation and Radiation-Induced Cystitis: Molecular Background and Therapeutic Perspectives

Radiation cystitis is a potential complication following the therapeutic irradiation of pelvic cancers. Its clinical management remains unclear, and few preclinical data are available on its underlying pathophysiology. The therapeutic strategy is difficult to establish because few prospective and randomized trials are available. In this review, we report on the clinical presentation and pathophysiology of radiation cystitis. Then we discuss potential therapeutic approaches, with a focus on the immunopathological processes underlying the onset of radiation cystitis, including the fibrotic process. Potential therapeutic avenues for therapeutic modulation will be highlighted, with a focus on the interaction between mesenchymal stromal cells and macrophages for the prevention and treatment of radiation cystitis.

Pterostilbene, a Bioactive Component of Blueberries, Alleviates Renal Interstitial Fibrosis by Inhibiting Macrophage-Myofibroblast Transition

Pterostilbene (PTB) is a derivative of resveratrol present in grapes and blueberries. PTB is structurally similar to resveratrol, possessing properties such as being analgesic, anti-aging, antidiabetic, anti-inflammatory, anti-obesity, anti-oxidation, cholesterol-reductive, and neuroprotective. However, there have not been reports on the effect of PTB on macrophage-myofibroblast transition (MMT) induced fibrosis in kidney. In this study, we investigated the antifibrotic effects of PTB on the in vivo mouse unilateral ureteral obstruction (UUO) model and in vitro MMT cells. Kidneys subjected to UUO with PTB treatment were collected for the investigation of PTB mediating MMT derived renal interstitial fibrosis. We conducted kidney RNA-seq transcriptomes and TGF-[Formula: see text]1-induced bone marrow-derived macrophages assays to determine the mechanisms of PTB. We found that PTB treatment suppressed the interstitial fibrosis in UUO mice. PTB also attenuated the number of MMT cells in vivo and in vitro. The transcriptomic analysis showed that CXCL10 may play a central role in the process of PTB-treated renal fibrosis. The siRNA-mediated CXCL10 knockdown decreased the number of MMT cells in TGF-[Formula: see text]1-induced bone marrow-derived macrophages. Our results suggested that PTB attenuated renal interstitial fibrosis by mediating MMT by regulating transcriptional activity of CXCL10.

[High-salt exposure induces macrophage polarization to promote proliferation and phenotypic transformation of co-cultured renal fibroblasts]

OBJECTIVE

To investigate high-salt exposure-induced polarization of mononuclear macrophages and the changes in proliferation and phenotypic transformation of renal fibroblasts in a co-culture system.

METHODS

Cultured mononuclear macrophages were exposed to high salt (161 mmol/L Na +) for 2 h and the surface markers of M0, M1 and M2-type macrophages were detected with RT-qPCR. The culture medium of the macrophages in normal and high-salt groups was collected for detection of the mRNA and protein levels of IL-6 and TGF-β1 using RT-qPCR and ELISA. A co-culture system of high salt-exposed macrophages and renal fibroblasts (NRK-49F) was established using a Transwell chamber, and the changes in proliferation and migration of NRK-49F cells were examined using EdU assay and Transwell assay, respectively. Western blotting was performed to detect the expressions of collagen I, collagen III and collagen α-SMA in NRK-49F cells.

RESULTS

The high salt-exposed macrophages showed significantly increased mRNA levels of M2-type macrophage surface markers mannose receptor and arginase (P < 0.05). The results of EdU and Transwell assays showed that NRK-49F cells co-cultured with high salt-exposed macrophages exhibited significantly increased proliferation and migration ability (P < 0.05). Co-culture with high salt-exposed macrophages resulted in significantly enhanced protein expressions of collagen I, collagen III and α-SMA in NRK-49F cells (P < 0.05) and significantly increased levels of IL-6 and TGF-β1 in the culture medium (P < 0.05).

CONCLUSIONS

High-salt exposure induces polarization of mononuclear macrophages into M2-type macrophages and promotes secretion of IL-6 and TGF-β1 by the macrophages to induce the proliferation and phenotypic transformation of NRK-49F cells.

Inhibition of Fatty Acid-Binding Protein 4 Attenuated Kidney Fibrosis by Mediating Macrophage-to-Myofibroblast Transition

The macrophage-to-myofibroblast transition (MMT) process is an important pathway that contributing to renal interstitial fibrosis (RIF). Fatty acid–binding protein 4 (FABP4) deteriorated RIF via promoting inflammation in obstructive nephropathy. However, the clinical significance of FABP4 in fibrotic kidney disease remains to be determined and little is known of the FABP4 signaling in MMT. Biopsy specimens of chronic kidney disease patients and kidneys subjected to unilateral ureteral obstruction (UUO) of FABP4-deficient mice or FABP4 inhibitor-treated mice were collected for the investigation of FABP4 mediating MMT of RIF. We conducted kidney RNA-seq transcriptomes and TGF-β1-induced bone marrow–derived macrophage (BMDM) assays to determine the mechanisms of FABP4. We found that FABP4 expression correlated with RIF in biopsy specimens and the injured kidneys of UUO mice where FABP4 was co-expressed with MMT cells. In UUO mice, FABP4 deficiency and a highly selective FABP4 inhibitor BMS309403 treatment both suppressed RIF. FABP4 ablation also attenuated the UUO-induced number of MMT cells and serum amyloid A1 (Saa1) expression. The siRNA-mediated Saa1 knockdown decreased the number of MMT cells in vitro. In conclusion, FABP4 is an important factor contributing to RIF by mediating MMT, and genetic/pharmacological inhibition of FABP4 provides a novel approach for the treatment of kidney fibrosis.

Tocilizumab mimotope alleviates kidney injury and fibrosis by inhibiting IL-6 signaling and ferroptosis in UUO model

AIMS

Previously we identified four Tocilizumab mimotopes and antibodies induced by these mimotopes could bind to IL-6R (interleukin-6 receptor) and regulate the downstream signaling pathways. On the basis of obtained research data, we sought to investigate whether the therapeutic strategies by Tocilizumab mimotope vaccination could be effective in the renal fibrosis model and show the desired activity by inhibiting IL-6 signaling in current study.

MAIN METHODS

We immunized the mice with the Tocilizumab mimotope and then performed the unilateral ureteric obstruction (UUO) surgery. Masson-trichrome staining and immunohistochemistry were performed to evaluate the renal fibrosis. The activations and differentiations of F4/80+ cells in the spleens and kidneys were detected by flow cytometry, immunohistochemistry and immunofluorescence. Signaling pathways involved IL-6, pro-fibrotic and ferroptosis were analyzed by immunoblot assay. The free iron and lipid oxidation end product were performed by Prussian blue staining and immunohistochemistry. The injury and apoptosis in the kidneys were evaluated by immunofluorescence.

KEY FINDINGS

The results showed the mimotope vaccination could reduce the level of fibrosis, injury and apoptosis by down-regulating the pro-fibrotic proteins, alleviating the activations and differentiations of macrophage F4/80+ cells in UUO models. IL-6/ERK signaling pathway was inhibited with the mimotope vaccination. The ferroptosis inhibited proteins significantly increased after the mimotope vaccination. On the contrary, the levels of free iron and lipid oxidation end product were observed to decrease in the mimotope treatment group.

SIGNIFICANCE

Our results suggested that the Tocilizumab mimotope vaccination might be an alternative therapy to against renal fibrosis.

C-C chemokine receptor type 2 mediates glomerular injury and interstitial fibrosis in focal segmental glomerulosclerosis

BACKGROUND

Glomerulosclerosis and tubulointerstitial fibrosis are hallmarks of chronic kidney injury leading to end-stage renal disease. Inflammatory mechanisms contribute to glomerular and interstitial scarring, including chemokine-mediated recruitment of leucocytes. In particular, accumulation of C-C chemokine receptor type 2 (CCR2)-expressing macrophages promotes renal injury and fibrotic remodelling in diseases like glomerulonephritis and diabetic nephropathy. The functional role of CCR2 in the initiation and progression of primary glomerulosclerosis induced by podocyte injury remains to be characterized.

METHODS

We analysed glomerular expression of CCR2 and its chemokine ligand C-C motif chemokine ligand 2 (CCL2) in human focal segmental glomerulosclerosis (FSGS). Additionally, CCL2 expression was determined in stimulated murine glomeruli and glomerular cells in vitro. To explore pro-inflammatory and profibrotic functions of CCR2 we induced adriamycin nephropathy, a murine model of FSGS, in BALB/c wild-type and Ccr2-deficient mice.

RESULTS

Glomerular expression of CCR2 and CCL2 significantly increased in human FSGS. In adriamycin-induced FSGS, progressive glomerular scarring and reduced glomerular nephrin expression was paralleled by induced glomerular expression of CCL2. Adriamycin exposure stimulated secretion of CCL2 and tumour necrosis factor-α (TNF) in isolated glomeruli and mesangial cells and CCL2 in parietal epithelial cells. In addition, TNF induced CCL2 expression in all glomerular cell populations, most prominently in podocytes. In vivo, Ccr2-deficient mice with adriamycin nephropathy showed reduced injury, macrophage and fibrocyte infiltration and inflammation in glomeruli and the tubulointerstitium. Importantly, glomerulosclerosis and tubulointerstitial fibrosis were significantly ameliorated.

CONCLUSIONS

Our data indicate that CCR2 is an important mediator of glomerular injury and progression of FSGS. CCR2- targeting therapies may represent a novel approach for its treatment.

C57BL/6 mice require a higher dose of cisplatin to induce renal fibrosis and CCL2 correlates with cisplatin-induced kidney injury

C57BL/6 mice are one of the most commonly used mouse strains in research, especially in kidney injury studies. However, C57BL/6 mice are resistant to chronic kidney disease-associated pathologies, particularly the development of glomerulosclerosis and interstitial fibrosis. Our laboratory and others developed a more clinically relevant dosing regimen of cisplatin (7 mg/kg cisplatin once a week for 4 wk and mice euthanized at day 24) that leads to the development of progressive kidney fibrosis in FVB/n mice. However, we found that treating C57BL/6 mice with this same dosing regimen does not result in kidney fibrosis. In this study, we demonstrated that increasing the dose of cisplatin to 9 mg/kg once a week for 4 wk is sufficient to consistently induce fibrosis in C57BL/6 mice while maintaining animal survival. In addition, we present that cohorts of C57BL/6 mice purchased from Jackson 1 yr apart and mice bred in-house display variability in renal outcomes following repeated low-dose cisplatin treatment. Indepth analyses of this intra-animal variability revealed C-C motif chemokine ligand 2 as a marker of cisplatin-induced kidney injury through correlation studies. In addition, significant immune cell infiltration was observed in the kidney after four doses of 9 mg/kg cisplatin, contrary to what has been previously reported. These results indicate that multiple strains of mice can be used with our repeated low-dose cisplatin model with dose optimization. Results also indicate that littermate control mice should be used with this model to account for population variability.

Trichostatin A Alleviates Renal Interstitial Fibrosis Through Modulation of the M2 Macrophage Subpopulation

Mounting evidence indicates that an increase in histone deacetylation contributes to renal fibrosis. Although inhibition of histone deacetylase (HDAC) can reduce the extent of fibrosis, whether HDAC inhibitors exert the antifibrotic effect through modulating the phenotypes of macrophages, the key regulator of renal fibrosis, remains unknown. Moreover, the functional roles of the M2 macrophage subpopulation in fibrotic kidney diseases remain incompletely understood. Herein, we investigated the role of HDAC inhibitors on renal fibrogenesis and macrophage plasticity. We found that HDAC inhibition by trichostatin A (TSA) reduced the accumulation of interstitial macrophages, suppressed the activation of myofibroblasts and attenuated the extent of fibrosis in obstructive nephropathy. Moreover, TSA inhibited M1 macrophages and augmented M2 macrophage infiltration in fibrotic kidney tissue. Interestingly, TSA preferentially upregulated M2c macrophages and suppressed M2a macrophages in the obstructed kidneys, which was correlated with a reduction of interstitial fibrosis. TSA also repressed the expression of proinflammatory and profibrotic molecules in cultured M2a macrophages and inhibited the activation of renal myofibroblasts. In conclusion, our study was the first to show that HDAC inhibition by TSA alleviates renal fibrosis in obstructed kidneys through facilitating an M1 to M2c macrophage transition.

M2 Macrophages Promote Collagen Expression and Synthesis in Laryngotracheal Stenosis Fibroblasts

OBJECTIVE

Macrophages exhibit distinct phenotypes and are dysregulated in a model of iatrogenic laryngotracheal stenosis (iLTS). Increased populations of alternatively activated or M2 macrophages have been demonstrated. However, the role of these macrophages is unknown. The aims of this study are: 1) define the macrophage population in iLTS in the context of classically activated or M1 and M2 macrophage phenotypes, and 2) characterize the effect of monocyte-derived M1 and M2 macrophages on normal airway and LTS-derived fibroblasts (FBs) in vitro.

STUDY DESIGN

Comparative analysis; in vitro controlled study.

METHODS

Immunohistochemical analysis of human iLTS and control specimens was performed to define the macrophage population. In vitro, M1, and M2 macrophages were polarized using M-CSF + Interferon-gamma and lipopolysaccharide or Interleukin-4, respectively. FBs isolated from laryngotracheal scar (LTS-FBs) and normal tracheal airway (NA-FBs) in eight patients with iLTS were cocultured with polarized macrophages. Fibrosis gene expression, soluble collagen production, and proliferation were assessed.

RESULTS

Immunohistochemical analysis revealed increased CD11b + cells (macrophage marker) in laryngotracheal scar specimens (18.3% vs. 8.5%, P = .03) and predominant CD206 (M2) costaining versus CD86 (M1) (51.5% vs. 9.8%, n = 10, P = .001). In vitro, NA-FBs cultured with M2 macrophages demonstrated a 2.41-fold increase in collagen-1 expression (P = .05, n = 8) and an increase in soluble collagen (9.98 vs. 8.875, mean difference: 1.11 95%, confidence interval 0.024-2.192, n = 8, P = .015).

CONCLUSION

Increased populations of CD11b cells are present in iLTS specimens and are predominantly CD206+, indicating an M2 phenotype. In vitro, M2 macrophages promoted collagen expression in airway FBs. Targeting macrophages may represent a therapeutic strategy for attenuating fibrosis in iLTS.

LEVEL OF EVIDENCE

NA Laryngoscope, 131:E346-E353, 2021.

Neural transcription factor Pou4f1 promotes renal fibrosis via macrophage-myofibroblast transition

Unresolved inflammation can lead to tissue fibrosis and impaired organ function. Macrophage-myofibroblast transition (MMT) is one newly identified mechanism by which ongoing chronic inflammation causes progressive fibrosis in different forms of kidney disease. However, the mechanisms underlying MMT are still largely unknown. Here, we discovered a brain-specific homeobox/POU domain protein Pou4f1 (Brn3a) as a specific regulator of MMT. Interestingly, we found that Pou4f1 is highly expressed by macrophages undergoing MMT in sites of fibrosis in human and experimental kidney disease, identified by coexpression of the myofibroblast marker, α-SMA. Unexpectedly, Pou4f1 expression peaked in the early stage in renal fibrogenesis in vivo and during MMT of bone marrow-derived macrophages (BMDMs) in vitro. Mechanistically, chromatin immunoprecipitation (ChIP) assay identified that Pou4f1 is a Smad3 target and the key downstream regulator of MMT, while microarray analysis defined a Pou4f1-dependent fibrogenic gene network for promoting TGF-β1/Smad3-driven MMT in BMDMs at the transcriptional level. More importantly, using two mouse models of progressive renal interstitial fibrosis featuring the MMT process, we demonstrated that adoptive transfer of TGF-β1-stimulated BMDMs restored both MMT and renal fibrosis in macrophage-depleted mice, which was prevented by silencing Pou4f1 in transferred BMDMs. These findings establish a role for Pou4f1 in MMT and renal fibrosis and suggest that Pou4f1 may be a therapeutic target for chronic kidney disease with progressive renal fibrosis.

Berberine attenuates severity of chronic pancreatitis and fibrosis via AMPK-mediated inhibition of TGF-β1/Smad signaling and M2 polarization

Berberine (BR) acts as an AMP-activated protein kinase (AMPK) activator which possesses antioxidant and anti-inflammatory properties. In this study, we have investigated the effects of BR against cerulein-induced chronic pancreatitis (CP) via inhibition of TGF-β/Smad signaling and M2 macrophages polarization in AMPK dependent manner. Cerulein-induced CP mice were treated with BR (3 and 10 mg/kg), intraperitoneally every day for 21 days. Our results indicated that, BR treatment (10 mg/kg) significantly reduced oxidative-nitrosative stress, histological alterations, inflammatory cells infiltration and collagen deposition in pancreatic tissue. BR treatment also prevented cerulein-induced pancreatic stellate cells (PSCs) activation and extracellular matrix (ECM) deposition via downregulation of α-SMA, collagen1a, collagen3a and fibronectin expression. Mechanistically, treatment with BR significantly activated AMPK signaling as compared to cerulein-challenged mice. Further, administration of BR also inhibited TGF-β/Smad signaling and macrophages polarization in cerulein-induced CP in-vivo models and TGF-β1 stimulated RAW 264.7 macrophages in-vitro. Together, our results strongly suggest that BR treatment protected against cerulein-induced CP and associated fibrosis progression by inhibiting TGF-β1/Smad signaling and M2 macrophages polarization in an AMPK dependent manner.

Sulforaphane elicts dual therapeutic effects on Renal Inflammatory Injury and crystal deposition in Calcium Oxalate Nephrocalcinosis

Intrarenal calcium oxalate (CaOx) crystals induce renal tubular epithelial cells (TECs) injury and inflammation, which involve Toll-like receptor 4 (TLR4)/interferon regulatory factor 1 (IRF1) signaling. Additionally, infiltrating macrophages (Mϕs) might influence intrarenal CaOx crystals and CaOx-induced renal injury. Although the roles of nuclear factor erythroid 2-related factor 2 (Nrf2) in regulating inflammation and macrophage polarization are well characterized, its potential mechanisms in regulating CaOx nephrocalcinosis remain undefined.

Methods: We used a Gene Expression Omnibus dataset to analyze gene-expression profiles. Luciferase reporter, western blot, quantitative polymerase chain reaction, immunofluorescence staining, fluorescence in situ hybridization, positron emission tomography computed tomography imaging, flow cytometry, and chromatin immunoprecipitation assays were employed to study the mechanism of miR-93-TLR4/IRF1 regulation by Nrf2. Anti-inflammatory activity and regulation of macrophage polarization by Nrf2 were investigated in vitro and in vivo.

Results: We found that stone-mediated kidney inflammation significantly affected stone growth, and that sulforaphane attenuated CaOx nephrocalcinosis-induced kidney injury and renal CaOx crystals deposition. Additionally, Nrf2 levels significantly increased and negatively correlated with TLR4 and IRF1 levels in a mouse model of CaOx nephrocalcinosis following sulforaphane treatment. Moreover, Nrf2 suppressed TLR4 and IRF1 levels and decreased M1-macrophage polarization which induced by supernatants from COM-stimulated TECs in vitro. In terms of mechanism, transcription factor analyses, microRNA microarray, and chromatin immunoprecipitation assays showed that Nrf2 exhibited positive transcriptional activation of miR-93-5p. In addition, Luciferase reporter, qRT-PCR, and western blot validated that miR-93-5p targets TLR4 and IRF1 mRNA. Furthermore, suppressed miR-93-5p expression partially reversed Nrf2-dependent TLR4/IRF1 downregulation.

Conclusions: The results suggested that sulforaphane might promote M2Mϕ polarization and inhibit CaOx nephrocalcinosis-induced inflammatory injury to renal tubular epithelial cells via the Nrf2-miR-93-TLR4/IRF1 pathway in vitro and in vivo.

Oxidative stress induces monocyte-to-myofibroblast transdifferentiation through p38 in pancreatic ductal adenocarcinoma

BACKGROUND

Cancer-associated fibroblasts (CAFs) are among the most prominent cells during the desmoplastic reaction in pancreatic ductal adenocarcinoma (PDAC). However, CAFs are heterogeneous and the precise origins are not fully elucidated. This study aimed to explore whether monocytes can transdifferentiate into fibroblasts in PDAC and evaluate the clinical significance of this event.

METHODS

CD14⁺ monocytes were freshly isolated from human peripheral blood. Immunofluorescence, reverse transcription-quantitative PCR, western blot, flow cytometry and enzyme-linked immunosorbent assay were used to detect the expression of αSMA, fibronectin, and other relevant molecules. In addition, latex beads with a mean particle size of 2.0 µm were used to assess the phagocytic capacity. Moreover, RNA sequencing (RNA-seq) was performed to identify the differences induced by H₂ O₂ and the underlying mechanisms.

RESULTS

Immunofluorescence identified αSMA and fibroblast-specific protein 1 expression by tumor-associated macrophages in PDAC. The in vitro experiment revealed that oxidative stress (H₂ O₂ or radiation) induced monocyte-to-myofibroblast transdifferentiation (MMT), as identified by upregulated αSMA expression at both the RNA and protein levels. In addition, compared with freshly isolated monocytes, human monocyte-derived macrophages increased fibronectin expression. RNA-seq analysis identified p53 activation and other signatures accompanying this transdifferentiation; however, the p53 stabilizer nutlin-3 induced αSMA expression through reactive oxygen species generation but not through the p53 transcription/mitochondria-dependent pathway, whereas the p38 inhibitor SB203580 could partially inhibit αSMA expression. Finally, MMT produced a unique subset of CAFs with reduced phagocytic capacity that could promote the proliferation of pancreatic cancer cells.

CONCLUSIONS

Oxidative stress in the tumor microenvironment could induce MMT in PDAC, thus inducing reactive stroma, modulating immunosuppression, and promoting tumor progression. Reducing oxidative stress may be a promising future therapeutic regimen.

The fate of myofibroblasts during the development of fibrosis in Crohn's disease

Intestinal fibrosis is a devastating complication in patients with inflammatory bowel disease. Its characteristics include the loss of regular peristalsis and nutrition absorption, excessive deposition of extracellular matrix (ECM) components, thickness of intestinal lumen due to the formation of strictures and of scar tissue. As a major cell type involved in fibrogenesis, the myofibroblasts have already been shown to have a plastic and heterogeneous function in producing abundant collagen, fibronectin and connective tissue growth factor. The primary sources of ECM-producing and vimentin-positive myofibroblasts come from different precursor cells, including bone marrow-derived mesenchymal cells, fibrocytes, pericytes, epithelial to mesenchymal transition and endothelial to mesenchymal transition. Recent immunological research findings suggest that numerous cytokines and chemokines made from macrophages, in addition to T cells and other myeloid cell types, are also important drivers of myofibroblast differentiation and hence of the activation of myofibroblast-mediated transforming growth factor and collagen production. In this review we discuss the origins, roles and cell signaling of myofibroblasts during the development of fibrosis in different organs, particularly in Crohn's disease. Finally, we suggest that the epigenetic and immunological regulation of myofibroblast differentiation may provide a novel antifibrotic strategy in the near future.

Resolvin D1 and D2 inhibit tumour growth and inflammation via modulating macrophage polarization

Plastic polarization of macrophage is involved in tumorigenesis. M1-polarized macrophage mediates rapid inflammation, entity clearance and may also cause inflammation-induced mutagenesis. M2-polarized macrophage inhibits rapid inflammation but can promote tumour aggravation. ω-3 long-chain polyunsaturated fatty acid (PUFA)-derived metabolites show a strong anti-inflammatory effect because they can skew macrophage polarization from M1 to M2. However, their role in tumour promotive M2 macrophage is still unknown. Resolvin D1 and D2 (RvD1 and RvD2) are docosahexaenoic acid (DHA)-derived docosanoids converted by 15-lipoxygenase then 5-lipoxygenase successively. We found that although dietary DHA can inhibit prostate cancer in vivo, neither DHA (10 μmol/L) nor RvD (100 nmol/L) can directly inhibit the proliferation of prostate cancer cells in vitro. Unexpectedly, in a cancer cell-macrophage co-culture system, both DHA and RvD significantly inhibited cancer cell proliferation. RvD1 and RvD2 inhibited tumour-associated macrophage (TAM or M2d) polarization. Meanwhile, RvD1 and RvD2 also exhibited anti-inflammatory effects by inhibiting LPS-interferon (IFN)-γ-induced M1 polarization as well as promoting interleukin-4 (IL-4)-mediated M2a polarization. These differential polarization processes were mediated, at least in part, by protein kinase A. These results suggest that regulation of macrophage polarization using RvDs may be a potential therapeutic approach in the management of prostate cancer.

Post-Ischemic Renal Fibrosis Progression Is Halted by Delayed Contralateral Nephrectomy: The Involvement of Macrophage Activation

(1) Background: Successful treatment of acute kidney injury (AKI)-induced chronic kidney disease (CKD) is unresolved. We aimed to characterize the time-course of changes after contralateral nephrectomy (Nx) in a model of unilateral ischemic AKI-induced CKD with good translational utility. (2) Methods: Severe (30 min) left renal ischemia-reperfusion injury (IRI) or sham operation (S) was performed in male Naval Medical Research Institute (NMRI) mice followed by Nx or S one week later. Expression of proinflammatory, oxidative stress, injury and fibrotic markers was evaluated by RT-qPCR. (3) Results: Upon Nx, the injured kidney hardly functioned for three days, but it gradually regained function until day 14 to 21, as demonstrated by the plasma urea. Functional recovery led to a drastic reduction in inflammatory infiltration by macrophages and by decreases in macrophage chemoattractant protein-1 (MCP-1) and tumor necrosis factor-alpha (TNF-α) mRNA and most injury markers. However, without Nx, a marked upregulation of proinflammatory (TNF-α, IL-6, MCP-1 and complement-3 (C3)); oxidative stress (nuclear factor erythroid 2-related factor 2, NRF2) and fibrosis (collagen-1a1 (Col1a1) and fibronectin-1 (FN1)) genes perpetuated, and the injured kidney became completely fibrotic. Contralateral Nx delayed the development of renal failure up to 20 weeks. (4) Conclusion: Our results suggest that macrophage activation is involved in postischemic renal fibrosis, and it is drastically suppressed by contralateral nephrectomy ameliorating progression.

Intraglomerular Monocyte/Macrophage Infiltration and Macrophage-Myofibroblast Transition during Diabetic Nephropathy Is Regulated by the A2B Adenosine Receptor

Diabetic nephropathy (DN) is considered the main cause of kidney disease in which myofibroblasts lead to renal fibrosis. Macrophages were recently identified as the major source of myofibroblasts in a process known as macrophage–myofibroblast transition (MMT). Adenosine levels increase during DN and in vivo administration of MRS1754, an antagonist of the A_2B adenosine receptor (A_2BAR), attenuated glomerular fibrosis (glomerulosclerosis). We aimed to investigate the association between A_2BAR and MMT in glomerulosclerosis during DN. Kidneys/glomeruli of non-diabetic, diabetic, and MRS1754-treated diabetic (DM+MRS1754) rats were processed for histopathologic, transcriptomic, flow cytometry, and cellular in vitro analyses. Macrophages were used for in vitro cell migration/transmigration assays and MMT studies. In vivo MRS1754 treatment attenuated the clinical and histopathological signs of glomerulosclerosis in DN rats. Transcriptomic analysis demonstrated a decrease in chemokine-chemoattractants/cell-adhesion genes of monocytes/macrophages in DM+MRS1754 glomeruli. The number of intraglomerular infiltrated macrophages and MMT cells increased in diabetic rats. This was reverted by MRS1754 treatment. In vitro cell migration/transmigration decreased in macrophages treated with MRS1754. Human macrophages cultured with adenosine and/or TGF-β induced MMT, a process which was reduced by MRS1754. We concluded that pharmacologic blockade of A_2BAR attenuated some clinical signs of renal dysfunction and glomerulosclerosis, and decreased intraglomerular macrophage infiltration and MMT in DN rats.

TGF-β in renal fibrosis: triumphs and challenges

Renal fibrosis is a hallmark of chronic kidney disease. Although considerable achievements in the pathogenesis of renal fibrosis have been made, the underlying mechanisms of renal fibrosis remain largely to be explored. Now we have reached the consensus that TGF-β is a master regulator of renal fibrosis. Indeed, TGF-β regulates renal fibrosis via both canonical and noncanonical TGF-β signaling. Moreover, ongoing renal inflammation promotes fibrosis as inflammatory cells such as macrophages, conventional T cells and mucosal-associated invariant T cells may directly or indirectly contribute to renal fibrosis, which is also tightly regulated by TGF-β. However, anti-TGF-β treatment for renal fibrosis remains ineffective and nonspecific. Thus, research into mechanisms and treatment of renal fibrosis remains highly challenging.

Kidney allograft fibrosis: what we learned from latest translational research studies

To add new molecular and pathogenetic insights into the biological machinery associated to kidney allograft fibrosis is a major research target in nephrology and organ transplant translational medicine. Interstitial fibrosis associated to tubular atrophy (IF/TA) is, in fact, an inevitable and progressive process that occurs in almost every type of chronic allograft injury (particularly in grafts from expanded criteria donors) characterized by profound remodeling and excessive production/deposition of fibrillar extracellular matrix (ECM) with a great clinical impact. IF/TA is detectable in more than 50% of kidney allografts at 2 years. However, although well studied, the complete cellular/biological network associated with IF/TA is only partially evaluated. In the last few years, then, thanks to the introduction of new biomolecular technologies, inflammation in scarred/fibrotic parenchyma areas (recently acknowledged by the BANFF classification) has been recognized as a pivotal element able to accelerate the onset and development of the allograft chronic damage. Therefore, in this review, we focused on some new pathogenetic elements involved in graft fibrosis (including epithelial/endothelial to mesenchymal transition, oxidative stress, activation of Wnt and Hedgehog signaling pathways, fatty acids oxidation and cellular senescence) that, in our opinion, could become in future good candidates as potential biomarkers and therapeutic targets.

Diverse Role of TGF-β in Kidney Disease

Inflammation and fibrosis are two pathological features of chronic kidney disease (CKD). Transforming growth factor-β (TGF-β) has been long considered as a key mediator of renal fibrosis. In addition, TGF-β also acts as a potent anti-inflammatory cytokine that negatively regulates renal inflammation. Thus, blockade of TGF-β inhibits renal fibrosis while promoting inflammation, revealing a diverse role for TGF-β in CKD. It is now well documented that TGF-β1 activates its downstream signaling molecules such as Smad3 and Smad3-dependent non-coding RNAs to transcriptionally and differentially regulate renal inflammation and fibrosis, which is negatively regulated by Smad7. Therefore, treatments by rebalancing Smad3/Smad7 signaling or by specifically targeting Smad3-dependent non-coding RNAs that regulate renal fibrosis or inflammation could be a better therapeutic approach. In this review, the paradoxical functions and underlying mechanisms by which TGF-β1 regulates in renal inflammation and fibrosis are discussed and novel therapeutic strategies for kidney disease by targeting downstream TGF-β/Smad signaling and transcriptomes are highlighted.