Pivotal role of CD4+ T cells in renal fibrosis following ureteric obstruction

Renal tubular epithelial cell quality control mechanisms as therapeutic targets in renal fibrosis

Renal fibrosis is a devastating consequence of progressive chronic kidney disease, representing a major public health challenge worldwide. The underlying mechanisms in the pathogenesis of renal fibrosis remain unclear, and effective treatments are still lacking. Renal tubular epithelial cells (RTECs) maintain kidney function, and their dysfunction has emerged as a critical contributor to renal fibrosis. Cellular quality control comprises several components, including telomere homeostasis, ubiquitin-proteasome system (UPS), autophagy, mitochondrial homeostasis (mitophagy and mitochondrial metabolism), endoplasmic reticulum (ER, unfolded protein response), and lysosomes. Failures in the cellular quality control of RTECs, including DNA, protein, and organelle damage, exert profibrotic functions by leading to senescence, defective autophagy, ER stress, mitochondrial and lysosomal dysfunction, apoptosis, fibroblast activation, and immune cell recruitment. In this review, we summarize recent advances in understanding the role of quality control components and intercellular crosstalk networks in RTECs, within the context of renal fibrosis.

Epithelial cell states associated with kidney and allograft injury

The kidney epithelium, with its intricate arrangement of highly specialized cell types, constitutes the functional core of the organ. Loss of kidney epithelium is linked to the loss of functional nephrons and a subsequent decline in kidney function. In kidney transplantation, epithelial injury signatures observed during post-transplantation surveillance are strong predictors of adverse kidney allograft outcomes. However, epithelial injury is currently neither monitored clinically nor addressed therapeutically after kidney transplantation. Several factors can contribute to allograft epithelial injury, including allograft rejection, drug toxicity, recurrent infections and postrenal obstruction. The injury mechanisms that underlie allograft injury overlap partially with those associated with acute kidney injury (AKI) and chronic kidney disease (CKD) in the native kidney. Studies using advanced transcriptomic analyses of single cells from kidney or urine have identified a role for kidney injury-induced epithelial cell states in exacerbating and sustaining damage in AKI and CKD. These epithelial cell states and their associated expression signatures are also observed in transplanted kidney allografts, suggesting that the identification and characterization of transcriptomic epithelial cell states in kidney allografts may have potential clinical implications for diagnosis and therapy.

From inflammation to renal fibrosis: A one-way road in autoimmunity?

Renal fibrosis is now recognized as a main determinant of renal pathology to include chronic kidney disease. Deposition of pathological matrix in the walls of glomerular capillaries, the interstitial space, and around arterioles predicts and contributes to the functional demise of the nephron and its surrounding vasculature. The recent identification of the major cell populations of fibroblast precursors in the kidney interstitium such as pericytes and tissue-resident mesenchymal stem cells, or bone-marrow-derived macrophages, and in the glomerulus such as podocytes, parietal epithelial and mesangial cells, has enabled the study of the fibrogenic process thought the lens of involved immunological pathways. Besides, a growing body of evidence is supporting the role of the lymphatic system in modulating the immunological response potentially leading to inflammation and ultimately renal damage. These notions have moved our understanding of renal fibrosis to be recognized as a clinical entity and new main player in autoimmunity, impacting directly the management of patients.

Interleukin-10 enhances recruitment of immune cells in the neonatal mouse model of obstructive nephropathy

Urinary tract obstruction during renal development leads to inflammation, leukocyte infiltration, tubular cell death, and interstitial fibrosis. Interleukin-10 (IL-10) is an anti-inflammatory cytokine, produced mainly by monocytes/macrophages and regulatory T-cells. IL-10 inhibits innate and adaptive immune responses. IL-10 has a protective role in the adult model of obstructive uropathy. However, its role in neonatal obstructive uropathy is still unclear which led us to study the role of IL-10 in neonatal mice with unilateral ureteral obstruction (UUO). UUO serves as a model for congenital obstructive nephropathies, a leading cause of kidney failure in children. Newborn Il-10-/- and C57BL/6 wildtype-mice (WT) were subjected to complete UUO or sham-operation on the 2nd day of life. Neonatal kidneys were harvested at day 3, 7, and 14 of life and analyzed for different leukocyte subpopulations by FACS, for cytokines and chemokines by Luminex assay and ELISA, and for inflammation, programmed cell death, and fibrosis by immunohistochemistry and western blot. Compared to WT mice, Il-10-/- mice showed reduced infiltration of neutrophils, CD11bhi cells, conventional type 1 dendritic cells, and T-cells following UUO. Il-10-/- mice with UUO also showed a reduction in pro-inflammatory cytokine and chemokine release compared to WT with UUO, mainly of IP-10, IL-1α, MIP-2α and IL-17A. In addition, Il-10-/- mice showed less necroptosis after UUO while the rate of apoptosis was not different. Finally, α-SMA and collagen abundance as readout for fibrosis were similar in Il-10-/- and WT with UUO. Surprisingly and in contrast to adult Il-10-/- mice undergoing UUO, neonatal Il-10-/- mice with UUO showed a reduced inflammatory response compared to respective WT control mice with UUO. Notably, long term changes such as renal fibrosis were not different between neonatal Il-10-/- and neonatal WT mice with UUO suggesting that IL-10 signaling is different in neonates and adults with UUO.

TLR2 mediates renal apoptosis in neonatal mice subjected experimentally to obstructive nephropathy

Urinary tract obstruction during renal development leads to inflammation, tubular apoptosis, and interstitial fibrosis. Toll like receptors (TLRs) expressed on leukocytes, myofibroblasts and renal cells play a central role in acute inflammation. TLR2 is activated by endogenous danger signals in the kidney; its contribution to renal injury in early life is still a controversial topic. We analyzed TLR2 for a potential role in the neonatal mouse model of congenital obstructive nephropathy. Inborn obstructive nephropathies are a leading cause of end-stage kidney disease in children. Thus, newborn Tlr2-/- and wild type (WT) C57BL/6 mice were subjected to complete unilateral ureteral obstruction (UUO) or sham-operation on the 2nd day of life. The neonatal kidneys were harvested and analyzed at days 7 and 14 of life. Relative expression levels of TLR2, caspase-8, Bcl-2, Bax, GSDMD, GSDME, HMGB1, TNF, galectin-3, α-SMA, MMP-2, and TGF-β proteins were quantified semi-quantitatively by immunoblot analyses. Tubular apoptosis, proliferation, macrophage- and T-cell infiltration, tubular atrophy, and interstitial fibrosis were analyzed immunohistochemically. Neonatal Tlr2-/- mice kidneys exhibited less tubular and interstitial apoptosis as compared to those of WT C57BL/6 mice after UUO. UUO induced neonatally did trigger pyroptosis in kidneys, however to similar degrees in Tlr2-/- and WT mice. Also, tubular atrophy, interstitial fibrosis, tubular proliferation, as well as macrophage and T-cell infiltration were unremarkable. We conclude that while TLR2 mediates apoptosis in the kidneys of neonatal mice subjected to UUO, leukocyte recruitment, interstitial fibrosis, and consequent neonatal obstructive nephropathy might lack a TLR2 involvement.

Transcriptomic analysis reveals partial epithelial-mesenchymal transition and inflammation as common pathogenic mechanisms in hypertensive nephrosclerosis and Type 2 diabetic nephropathy

Hypertensive nephrosclerosis (HN) and Type 2 diabetic nephropathy (T2DN) are the leading causes of chronic kidney disease (CKD). To explore shared pathogenetic mechanisms, we analyzed transcriptomes of kidney biopsies from patients with HN or T2DN. Total RNA was extracted from 10 μm whole kidney sections from patients with HN, T2DN, and normal controls (Ctrl) (n = 6 for each group) and processed for RNA sequencing. Differentially expressed (log2 fold change >1, adjusted p < 0.05) genes (DEG) and molecular pathways were analyzed, and selected results were validated by immunohistochemistry (IHC). ELISA on serum samples was performed on a related cohort consisting of patients with biopsy-proven HN (n = 13) and DN (n = 9), and a normal control group (n = 14). Cluster analysis on RNA sequencing data separated diseased and normal tissues. RNA sequencing revealed that 88% (341 out of 384) of DEG in HN were also altered in T2DN, while gene set enrichment analysis (GSEA) showed that over 90% of affected molecular pathways, including those related to inflammation, immune response, and cell-cycle regulation, were similarly impacted in both HN and T2DN samples. The increased expression of genes tied to interleukin signaling and lymphocyte activation was more pronounced in HN, while genes associated with extracellular matrix organization were more evident in T2DN. Both HN and T2DN tissues exhibited significant upregulation of genes connected with inflammatory responses, T-cell activity, and partial epithelial to mesenchymal transition (p-EMT). Immunohistochemistry (IHC) further confirmed T-cell (CD4+ and CD8+ ) infiltration in the diseased tissues. Additionally, IHC revealed heightened AXL protein expression, a key regulator of inflammation and p-EMT, in both HN and T2DN, while serum analysis indicated elevated soluble AXL levels in patients with both conditions. These findings underline the shared molecular mechanisms between HN and T2DN, hinting at the potential for common therapeutic strategies targeting both diseases.

Identification of immune-related molecular clusters and diagnostic markers in chronic kidney disease based on cluster analysis

Background: Chronic kidney disease (CKD) is a heterogeneous disease with multiple etiologies, risk factors, clinical manifestations, and prognosis. The aim of this study was to identify different immune-related molecular clusters in CKD, their functional immunological properties, and to screen for promising diagnostic markers. Methods: Datasets of 440 CKD patients were obtained from the comprehensive gene expression database. The core immune-related genes (IRGs) were identified by weighted gene co-expression network analysis. We used unsupervised clustering to divide CKD samples into two immune-related subclusters. Then, functional enrichment analysis was performed for differentially expressed genes (DEGs) between clusters. Three machine learning methods (LASSO, RF, and SVM-RFE) and Venn diagrams were applied to filter out 5 significant IRGs with distinguished subtypes. A nomogram diagnostic model was developed, and the prediction effect was verified using calibration curve, decision curve analysis. CIBERSORT was applied to assess the variation in immune cell infiltration among clusters. The expression levels, immune characteristics and immune cell correlation of core diagnostic markers were investigated. Finally, the Nephroseq V5 was used to assess the correlation among core diagnostic markers and renal function. Results: The 15 core IRGs screened were differentially expressed in normal and CKD samples. CKD was classified into two immune-related molecular clusters. Cluster 2 is significantly enriched in biological functions such as leukocyte adhesion and regulation as well as immune activation, and has a severe immune prognosis compared to cluster 1. A nomogram diagnostic model with reliable prediction of immune-related clusters was developed based on five signature genes. The core diagnostic markers LYZ, CTSS, and ISG20 were identified as playing an important role in the immune microenvironment and were shown to correlate meaningfully with immune cell infiltration and renal function. Conclusion: Our study identifies two subtypes of CKD with distinct immune gene expression patterns and provides promising predictive models. Along with the exploration of the role of three promising diagnostic markers in the immune microenvironment of CKD, it is anticipated to provide novel breakthroughs in potential targets for disease treatment.

The antifibrotic and anti-inflammatory effects of FZHY prescription on the kidney in rats after unilateral ureteral obstruction

PURPOSE

To explore the potential impact of traditional Chinese herb FuZhengHuaYuJiangZhuTongLuo recipe (FZHY) on renal interstitial fibrosis (RIF) in chronic kidney disease (CKD) at cellular and molecular levels.

METHODS

Unilateral ureteral obstruction (UUO) rats were established as the RIF model in vivo. The rats were given intragastric administration with FZHY once a day for consecutive 7, 14 and 21 days, respectively. The renal function parameters and inflammation indicators in kidney tissues were measured using enzyme-linked immunosorbent assay, the CD4+/CD8+ T cells in peripheral blood was detected using flow cytometry, the renal fibrosis degree was estimated using Masson's staining, and the fibrosis-related genes' expression was detected using quantitative polymerase chain reaction, western blotting, and immunohistochemistry analyses.

RESULTS

FZHY prescription reduced the serum creatinine and blood urea nitrogen, decreased the levels of c-reactive protein, interleukin-1, interleukin-6 and tumor necrosis factor-α in kidney tissues, and increased the ratio of CD4+/CD8+ T cells in peripheral blood. FZHY prescription suppressed the renal tissue fibrosis and reduced the levels of laminin, fibronectin, collagen I and collagen III.

CONCLUSIONS

FZHY prescription suppressed the renal fibrosis and improved the condition of "Healthy Qi Deficiency and Evil Qi Excess" in rats with UUO, which may provide an effective method for CKD treatment.

Acquired lymphedema: Molecular contributors and future directions for developing intervention strategies

Lymphedema is a debilitating chronic disease that mostly develops as an adverse reaction to cancer treatment modalities such as chemotherapy, surgery, and radiotherapy. Lymphedema also appears to be a deteriorating consequence of roundworm infections, as best represented by filariasis. According to its origin, lymphedema is classified as primary lymphedema and acquired lymphedema. The latter is an acquired condition that, hitherto, received a considerably low attention owing to the less number of fatal cases been reported. Notably, despite the low mortality rate in lymphedema, it has been widely reported to reduce the disease-free survival and thus the quality of life of affected patients. Hence, in this review, we focused on acquired lymphedema and orchestration of molecular interplays associated with either stimulation or inhibition of lymphedema development that were, in vast majority, clearly depicted in animal models with their specific and distinct technical approaches. We also discussed some recent progress made in phytochemical-based anti-lymphedema intervention strategies and the specific mechanisms underlying their anti-lymphedema properties. This review is crucial to understand not only the comprehensive aspects of the disease but also the future directions of the intervention strategies that can address the quality of life of affected patients rather than alleviating apparent symptoms only.

Metabolic signatures of immune cells in chronic kidney disease

Immune cells play a key role in maintaining renal dynamic balance and dealing with renal injury. The physiological and pathological functions of immune cells are intricately connected to their metabolic characteristics. However, immunometabolism in chronic kidney disease (CKD) is not fully understood. Pathophysiologically, disruption of kidney immune cells homeostasis causes inflammation and tissue damage via triggering metabolic reprogramming. The diverse metabolic characteristics of immune cells at different stages of CKD are strongly associated with their different pathological effect. In this work, we reviewed the metabolic characteristics of immune cells (macrophages, natural killer cells, T cells, natural killer T cells and B cells) and several non-immune cells, as well as potential treatments targeting immunometabolism in CKD. We attempt to elaborate on the metabolic signatures of immune cells and their intimate correlation with non-immune cells in CKD.

Intratumoral fibrosis and patterns of immune infiltration in clear cell renal cell carcinoma

Background

Intratumoral fibrosis was positively correlated with histological grade of renal clear cell carcinoma (ccRCC) and intratumoral inflammation. However, the association of intratumoral fibrosis with the immune infiltration of ccRCC was few evaluated.

Methods

We used the second harmonic generation (SHG)-based imaging technology and evaluated the intratumoral fibrosis in ccRCC, and then divided the patients into the high fibrosis group (HF) and the low fibrosis group (LF). Meanwhile, the Kaplan–Meier survival curve analysis was performed to analyze the relationship between intratumoral fibrosis and the disease-free survival rate. Antibody arrays were used for seeking difference in cytokines and immune infiltration between the HF group (N = 11) and LF group (N = 11). The selected immune infiltration marker was then verified by immunohistochemistry (IHC) staining in 45 ccRCC samples.

Results

Out of 640 cytokines and immune infiltration markers, we identified 115 proteins that were significantly different in quantity between ccRCC and adjacent normal tissues. In addition, the Venn diagram indicated that six proteins, including Cytotoxic T-Lymphocyte Associated Protein 4 (CTLA4), were significantly associated with intratumoral fibrosis (p < 0.05). The GO/KEGG enrichment analysis indicated that the proteins associated with intratumoral fibrosis were involved in the immunity and tumor-infiltrating lymphocytes. The expression of the CTLA4 was negatively correlated with collagen level, confirmed by IHC staining of CTLA4 (p < 0.05).

Conclusions

The study indicated that the intratumoral fibrosis level was negatively correlated with the expression of CTLA4 in the tumor immune microenvironment of the ccRCC, which posed the potential value of targeting the stroma of the tumor, a supplement to immunotherapy. However, the specific mechanism of this association is still unclear and needs further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09765-0.

Signaling pathways of chronic kidney diseases, implications for therapeutics

Chronic kidney disease (CKD) is a chronic renal dysfunction syndrome that is characterized by nephron loss, inflammation, myofibroblasts activation, and extracellular matrix (ECM) deposition. Lipotoxicity and oxidative stress are the driving force for the loss of nephron including tubules, glomerulus, and endothelium. NLRP3 inflammasome signaling, MAPK signaling, PI3K/Akt signaling, and RAAS signaling involves in lipotoxicity. The upregulated Nox expression and the decreased Nrf2 expression result in oxidative stress directly. The injured renal resident cells release proinflammatory cytokines and chemokines to recruit immune cells such as macrophages from bone marrow. NF-κB signaling, NLRP3 inflammasome signaling, JAK-STAT signaling, Toll-like receptor signaling, and cGAS-STING signaling are major signaling pathways that mediate inflammation in inflammatory cells including immune cells and injured renal resident cells. The inflammatory cells produce and secret a great number of profibrotic cytokines such as TGF-β1, Wnt ligands, and angiotensin II. TGF-β signaling, Wnt signaling, RAAS signaling, and Notch signaling evoke the activation of myofibroblasts and promote the generation of ECM. The potential therapies targeted to these signaling pathways are also introduced here. In this review, we update the key signaling pathways of lipotoxicity, oxidative stress, inflammation, and myofibroblasts activation in kidneys with chronic injury, and the targeted drugs based on the latest studies. Unifying these pathways and the targeted therapies will be instrumental to advance further basic and clinical investigation in CKD.

Siglec-F-expressing neutrophils are essential for creating a pro-fibrotic microenvironment in the renal fibrosis

The roles of neutrophils in renal inflammation are currently unclear. On examining these cells in the unilateral ureteral obstruction murine model of chronic kidney disease, we found that the injured kidney bore a large and rapidly expanding population of neutrophils that expressed the eosinophil marker Siglec-F. We first confirmed that these cells were neutrophils. Siglec-F+ neutrophils were recently detected for the first time by several studies on other disease contexts. We then showed that (i) these cells were derived from conventional neutrophils in the renal vasculature by TGF-β1 and GM-CSF, (ii) they differed from their parent cells by more frequent hypersegmentation, higher expression of pro-fibrotic inflammatory cytokines, and, notably, expression of Collagen 1, and (iii) their depletion reduced collagen deposition and disease progression, but adoptive transfer increased renal fibrosis. These findings have thus unveiled a subtype of neutrophils that participate in renal fibrosis and maybe a new therapeutic target in chronic kidney disease.

Mineralocorticoid Receptor Antagonism Prevents the Synergistic Effect of Metabolic Challenge and Chronic Kidney Disease on Renal Fibrosis and Inflammation in Mice

Obesity and/or metabolic diseases are frequently associated with chronic kidney disease and several factors associated with obesity may contribute to proteinuria and extracellular matrix production. Mineralocorticoid receptor antagonists have proven their clinical efficacy in diabetic kidney disease with preclinical data suggesting that they may also be efficient in non-diabetic chronic kidney disease associated to metabolic diseases. In the present study we developed a novel mouse model combining severe nephron reduction and High Fat Diet challenge that led to chronic kidney disease with metabolic alterations. We showed that the Mineralocorticoid Receptor antagonist canrenoate improved metabolic function, reduced albuminuria and prevented the synergistic effect of high fat diet on renal fibrosis and inflammation in chronic kidney disease mice.

Nesfatin-1 treatment preserves antioxidant status and attenuates renal fibrosis in rats with unilateral ureteral obstruction

BACKGROUND

Nesfatin-1 (NES-1), an anorexigenic peptide, was reported to have anti-inflammatory and anti-apoptotic actions in several inflammation models.

METHODS

To elucidate potential renoprotective effects of NES-1, unilateral ureteral obstruction (UUO) was induced in male Sprague Dawley rats by ligating left ureters. The rats were injected intraperitoneally with either saline (SL) or NES-1 (10 μg/kg/day) for 7 or 14 days (n = 8 in each group). On the 7th or 14th day, obstructed kidneys were removed for the isolation of leukocytes for flow-cytometric analysis and for the assessments of biochemical and histopathological changes.

RESULTS

Opposite to glutathione levels, renal myeloperoxidase activity in the SL-treated UUO group was significantly increased compared to sham-operated group, while NES-1 treatment abolished the elevation. The percentages of CD8+/CD4+ T-lymphocytes infiltrating the obstructed kidneys were increased in SL-treated groups but treatment with NES-1 did not prevent lymphocyte infiltration. Elevated TNF-a levels in SL-treated UUO group was decreased with NES-1. Although total degeneration scores were similarly increased in all UUO groups, tubular dilatation scores were significantly increased in UUO groups and lowered by NES-1 only in the 7-day treated group. Elevated interstitial fibrosis scores in the SL-treated groups were decreased in both 7- and 14-day NES-1 treated groups, while alpha smooth muscle actin (α-SMA) and apoptosis scores were depressed in both NES-1 treated groups.

CONCLUSION

The present data demonstrate that UUO-induced renal fibrosis is ameliorated by NES-1, which appears to involve the inhibition of neutrophil infiltration and thereby amelioration of oxidative stress and inflammation. These data suggest that NES-1 may have a regulatory role in protecting the kidneys against obstruction-induced renal injury.

Cxcl10 deficiency attenuates renal interstitial fibrosis through regulating epithelial-to-mesenchymal transition

IFN-γ-inducible protein 10 (IP-10, CXCL10) has been widely demonstrated to be involved in multiple kidney pathological processes. However, the role of CXCL10 in renal fibrosis remains unclear. In this study, Cxcl10-deficient (Cxcl10-/-) mice were used to generate the unilateral ureteral obstruction (UUO) model. The level of renal fibrosis and inflammatory cell infiltration was examined in vivo and the effects of CXCL10 on EMT process of HK-2 cells was investigated in vitro. We observed that the injury degree of renal tissue and the collagen deposition levels were lighter and the expression of α-SMA, collagen I and fibronectin was significantly reduced in Cxcl10-/- mice, while the expression of E-cadherin was increased. However, interstitial F4/80-positive macrophages and CD4-positive T lymphocytes were unaffected by knockout of Cxcl10. Furthermore, IFN-γ or CXCL10 stimulation could obviously promote the expression of α-SMA, collagen I, fibronectin and reduce the expression of E-cadherin in HK-2 cells, which could be inhibited by transfection of Cxcl10-siRNA. Our findings suggested Cxcl10 knockout could reduce renal dysfunction and inhibit renal fibrosis through regulating EMT process of renal tubular epithelial cells in murine UUO model. These results may provide a novel insight into the mechanism and a potential therapy target of renal fibrosis.

Neutrophil Gelatinase-Associated Lipocalin From Macrophages Plays a Critical Role in Renal Fibrosis Via the CCL5 (Chemokine Ligand 5)-Th2 Cells-IL4 (Interleukin 4) Pathway

NGAL (neutrophil gelatinase-associated lipocalin; or lipocalin 2, Lcn2) is a novel mineralocorticoid target in the cardiovascular system. We showed that Lcn2 gene invalidation protects against proteinuria and renal injury upon mineralocorticoid excess and we hypothesized that NGAL produced from macrophages promotes the expression of chemoattractant molecules involved these renal lesions. The role of NGAL was analyzed using myeloid-specific (MΦ KO NGAL) Lcn2 knockout mice challenged with uni-nephrectomy, aldosterone, and salt (NAS) for 6 weeks. The role of the CCL5 (chemokine ligand 5) and IL4 (interleukin 4) in kidney fibrosis was studied by administration of the CCL5 receptor antagonist maraviroc or by injections of an anti-IL4 neutralizing antibody. In CTL mice, NAS increased the renal expression of extracellular matrix proteins, such as collagen I, αSMA, and fibronectin associated with interstitial fibrosis which were blunted in MΦ KO NGAL mice. The expression of CCL5 was blunted in sorted macrophages from MΦ KO NGAL mice challenged by NAS and in macrophages obtained from KO NGAL mice and challenged ex vivo with aldosterone and salt. The pharmacological blockade of the CCL5 receptor reduced renal fibrosis and the CD4⁺ Th cell infiltration induced by NAS. Neutralization of IL4 in NAS mice blunted kidney fibrosis and the overexpression of profibrotic proteins, such as collagen I, αSMA, and fibronectin. In conclusion, NGAL produced by macrophages plays a critical role in renal fibrosis and modulates the CCL5/IL4 pathway in mice exposed to mineralocorticoid excess.

Kidney VISTA prevents IFNγ-IL-9 axis-mediated tubulointerstitial fibrosis after acute glomerular injury

Severe glomerular injury ultimately leads to tubulointerstitial fibrosis that determines patient outcome, but the immunological molecules connecting these processes remain undetermined. The present study addressed whether V-domain Ig suppressor of T cell activation (VISTA), constitutively expressed in kidney macrophages, plays a protective role in tubulointerstitial fibrotic transformation after acute antibody-mediated glomerulonephritis. After acute glomerular injury using nephrotoxic serum, tubules in the VISTA-deficient (Vsir–/–) kidney suffered more damage than those in WT kidneys. When interstitial immune cells were examined, the contact frequency of macrophages with infiltrated T cells increased and the immunometabolic features of T cells changed to showing high oxidative phosphorylation and fatty acid metabolism and overproduction of IFN-γ. The Vsir–/– parenchymal tissue cells responded to this altered milieu of interstitial immune cells as more IL-9 was produced, which augmented tubulointerstitial fibrosis. Blocking antibodies against IFN-γ and IL-9 protected the above pathological process in VISTA-depleted conditions. In human samples with acute glomerular injury (e.g., antineutrophil cytoplasmic autoantibody vasculitis), high VISTA expression in tubulointerstitial immune cells was associated with low tubulointerstitial fibrosis and good prognosis. Therefore, VISTA is a sentinel protein expressed in kidney macrophages that prevents tubulointerstitial fibrosis via the IFN-γ/IL-9 axis after acute antibody-mediated glomerular injury.

MHC class II in renal tubules plays an essential role in renal fibrosis

Immunomodulation is considered a potential therapeutic approach for chronic kidney disease (CKD). Although it has been previously reported that CD4⁺ T cells contribute to the development of renal fibrosis, the role of MHC class II (MHCII) in the development of renal fibrosis remains largely unknown. The present study reports that the expression of MHCII molecules in renal cortical tubules is upregulated in mouse renal fibrosis models generated by unilateral ureter obstruction (UUO) and folic acid (FA). Proximal tubule epithelial cells (PTECs) are functional antigen-presenting cells that promote the proliferation of CD4⁺ T cells in an MHCII-dependent manner. PTECs from mice with renal fibrosis had a stronger ability to induce T cell proliferation and cytokine production than control cells. Global or renal tubule-specific ablation of H2-Ab1 significantly alleviated renal fibrosis following UUO or FA treatment. Renal expression of profibrotic genes showed a consistent reduction in H2-Ab1 gene-deficient mouse lines. Moreover, there was a marked increase in renal tissue CD4⁺ T cells after UUO or FA treatment and a significant decrease following renal tubule-specific ablation of H2-Ab1. Furthermore, renal tubule-specific H2-Ab1 gene knockout mice exhibited higher proportions of regulatory T cells (Tregs) and lower proportions of Th2 cells in the UUO- or FA-treated kidneys. Finally, Immunohistochemistry (IHC) studies showed increased renal expression of MHCII and the profibrotic gene α smooth muscle actin (α-SMA) in CKD patients. Together, our human and mouse data demonstrate that renal tubular MHCII plays an important role in the pathogenesis of renal fibrosis.

Comparison of two different toxin-induced kidney fibrosis models in terms of inflammatory responses

Chronic kidney disease (CKD) is characterized by persistent abnormalities in kidney function, accompanied by structural changes. Interstitial fibrosis, characterized by the accumulation of extracellular matrix (ECM) proteins, is frequently detected during CKD development. Given the multiple underlying causes of CKD, numerous animal models have been developed to advance our understanding of human nephropathy. Herein, we compared two reliable toxin-induced mouse kidney fibrosis models in terms of fibrosis and inflammation. Administration of folic acid (250 mg/kg, intraperitoneal injection) or an adenine diet (0.25 % for three weeks) afforded similar effects on kidney function, as detected by increased serum nitrogen levels. In addition, the kidneys exhibited a similar extent of tubule dilation and kidney damage. The degree of fibrosis was compared using various biological methods. Although both models developed a significant fibrotic phenotype, the adenine diet-fed model showed a marginally higher increase in fibrosis than the folic acid model, as reflected by increased kidney ECM gene and protein levels. We further compared inflammatory responses in the kidneys. Interestingly, pro-inflammatory responses, including cytokine expression and immune cell infiltration, were significantly increased in adenine diet-fed kidneys. Furthermore, collagen expression was identified in the macrophage-infiltrated region, implying the importance of inflammation in fibrogenesis. Collectively, we observed that the adenine diet-fed kidney fibrosis model presented a higher inflammatory response with increased fibrosis when compared with the folic acid-induced kidney fibrosis model, indicating the importance of the inflammatory response in fibrosis development.

Lymphocytes: Versatile Participants in Acute Kidney Injury and Progression to Chronic Kidney Disease

Background: Acute kidney injury (AKI) remains a major global public health concern due to its high morbidity and mortality. The progression from AKI to chronic kidney disease (CKD) makes it a scientific problem to be solved. However, it is with lack of effective treatments. Summary: Both innate and adaptive immune systems participate in the inflammatory process during AKI, and excessive or dysregulated immune responses play a pathogenic role in renal fibrosis, which is an important hallmark of CKD. Studies on the pathogenesis of AKI and CKD have clarified that renal injury induces the production of various chemokines by renal parenchyma cells or resident immune cells, which recruits multiple-subtype lymphocytes in circulation. Some infiltrated lymphocytes exacerbate injury by proinflammatory cytokine production, cytotoxicity, and interaction with renal resident cells, which constructs the inflammatory environment and induces further injury, even death of renal parenchyma cells. Others promote tissue repair by producing protective cytokines. In this review, we outline the diversity of these lymphocytes and their mechanisms to regulate the whole pathogenic stages of AKI and CKD; discuss the chronological responses and the plasticity of lymphocytes related to AKI and CKD progression; and introduce the potential therapies targeting lymphocytes of AKI and CKD, including the interventions of chemokines, cytokines, and lymphocyte frequency regulation in vivo, adaptive transfer of ex-expanded lymphocytes, and the treatments of gut microbiota or metabolite regulations based on gut-kidney axis. Key Message: In the process of AKI and CKD, T helper (Th) cells, innate, and innate-like lymphocytes exert mainly pathogenic roles, while double-negative T (DNT) cells and regulatory T cells (Tregs) are confirmed to be protective. Understanding the mechanisms by which lymphocytes mediate renal injury and renal fibrosis is necessary to promote the development of specific therapeutic strategies to protect from AKI and prevent the progression of CKD.

Endothelin receptors in renal interstitial cells do not contribute to the development of fibrosis during experimental kidney disease

Renal interstitial fibrosis is characterized by the development of myofibroblasts, originating from resident renal and immigrating cells. Myofibroblast formation and extracellular matrix production during kidney damage are triggered by various factors. Among these, endothelins have been discussed as potential modulators of renal fibrosis. Utilizing mouse models of adenine nephropathy (AN) and unilateral ureter occlusion (UUO), this study aimed to investigate the contribution of endothelin signaling in stromal mesenchymal resident renal interstitial cells. We found in controls that adenine feeding and UUO caused marked upregulations of endothelin-1 (ET-1) gene expression in endothelial and in tubular cells and a strong upregulation of ET_A-receptor (ET_A-R) gene expression in interstitial and mesangial cells, while the gene expression of ET_B-receptor (ET_B-R) did not change. Conditional deletion of ET_A-R and ET_B-R gene expression in the FoxD1 stromal cell compartment which includes interstitial cells significantly reduced renal ET_A-R gene expression and moderately lowered renal ET_B-R gene expression. ET receptor (ET-R) deletion exerted no apparent effects on kidney development nor on kidney function. Adenine feeding and UUO led to similar increases in profibrotic and proinflammatory gene expression in control as well as in ET_A^flflET_B^flfl FoxD1^Cre+ mice (ET-Ko). In summary, our findings suggest that adenine feeding and UUO activate endothelin signaling in interstitial cells which is due to upregulated ET_A-R expression and enhanced renal ET-1 production Our data also suggest that the activation of endothelin signaling in interstitial cells has less impact for the development of experimentally induced 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.

Potential Therapeutic Targets for Cisplatin-Induced Kidney Injury: Lessons from Other Models of AKI and Fibrosis

The effectiveness of cisplatin, a mainstay in the treatment of many solid organ cancers, is hindered by dose-limiting nephrotoxicity. Cisplatin causes AKI in 30% of patients. Patients who do not develop AKI by clinical standards during treatment are still at risk for long-term decline in kidney function and the development of CKD. The connection between AKI and CKD has become increasingly studied, with renal fibrosis a hallmark of CKD development. To prevent both the short- and long-term effects of cisplatin, researchers must use models that reflect both types of pathology. Although a lot is known about cisplatin-induced AKI, very little is known about the mechanisms by which repeated low levels of cisplatin lead to fibrosis development. In this review, strategies used in various rodent models to prevent kidney injury, its progression to fibrosis, or both, are examined to gain mechanistic insights and identify potential therapeutic targets for cisplatin-induced kidney pathologies. Reviewing the results from these models highlights the diverse and highly complex role of cell death, cell senescence, endoplasmic reticulum stress, autophagy, and immune cell activation in acute and chronic kidney injuries. The use of several models of kidney injury is needed for development of agents that will prevent all aspects of cisplatin-induced kidney injury.

Twist1 in T Lymphocytes Augments Kidney Fibrosis after Ureteral Obstruction

Background

Twist1 is a basic helix-loop-helix domain-containing transcription factor that participates in diverse cellular functions, including epithelial-mesenchymal transition and the cellular immune response. Although Twist1 plays critical roles in the initiation and progression of kidney diseases, the effects of Twist1 in the T lymphocyte on the progression of renal fibrosis require elucidation.

Methods

129/SvEv mice with a floxed allele for the gene encoding Twist1 or TNFα were bred with CD4-Cre mice to yield CD4-Cre⁺ Twist1^flox/flox (Twist1-TKO) or CD4-Cre⁺ TNF^flox/flox (TNF-TKO) mice with robust, but selective, deletion of Twist1 or TNFα mRNA in T cells, respectively. Twist1 TKO, TNF TKO, and WT controls underwent UUO with assessment of kidney fibrosis and T-cell phenotype at 14 days.

Results

Compared with WT controls, obstructed kidneys from Twist1 TKO mice had attenuated extracellular matrix deposition. Despite this diminished fibrosis, Twist1 TKO obstructed kidneys contained more CD8⁺ T cells than in WTs. These intrarenal CD8⁺ T cells exhibited greater activation and higher levels of TNFα expression than those from WT obstructed kidneys. Further, we found that selective deletion of TNFα from T cells exaggerated renal scar formation and injury after UUO, highlighting the capacity of T-cell TNF to constrain fibrosis in the kidney.

Conclusions

Twist1 in T cells promotes kidney fibrogenesis, in part, by curtailing the renal accumulation of TNF-elaborating T cells.

Periodontitis aggravates renal inflammatory response in a mouse model of renal fibrosis

OBJECTIVES

To assess the effects of periodontitis on renal interstitial fibrosis in a mouse model.

MATERIALS AND METHODS

Thirty C57BL/6 male mice were divided into control, periodontitis (PD), unilateral ureteral ligation (UUO) and PD+UUO groups. Unilateral ureteral ligation was performed 6 days after periodontitis. After 2 weeks, all mice were sacrificed, and samples were collected for the assessment of gene expression, immune cells, biochemical indicators and renal pathology.

RESULTS

Expression of tumour necrosis factor-α, interleukin-1β, and Ly6G in the kidneys in the PD+UUO group was significantly greater than in the UUO group. The percentage of CD11b⁺ Ly6G⁺ cells was significantly higher in the PD+UUO than in the UUO group. Fibrotic areas in the kidneys in the PD+UUO group were slightly, but not significantly, greater than those in the UUO group. Kidneys from the PD+UUO group showed markedly higher gene expression of matrix metalloproteinase-9, but not α-smooth muscle actin or collagen I, than those in the UUO group. There were no significant differences in blood urea nitrogen, serum creatinine and uric acid between the PD+UUO and UUO groups.

CONCLUSIONS

Periodontitis increases the renal inflammatory response without showing a significant influence on renal interstitial fibrosis or renal function in the UUO mouse model.

Two identified subsets of CD8 T cells in obstructed kidneys play different roles in inflammation and fibrosis

Inflammation plays a crucial role in initiating renal fibrosis after injury. The infiltration of inflammatory cells, such as CD4⁺ T cells and macrophages, contributes to renal fibrosis following ureteric obstruction. However, the function of CD8⁺ T cells in obstructed kidneys remains unclear. Although CD8⁺ T cell depletion intensifies renal fibrosis by decreasing IFN-γ and increasing IL-4 in the kidneys, the change and role of CD8 T cell populations following environmental changes during renal fibrosis are largely unknown. Here, we identified two CD8 T cell subsets in mouse obstructed kidneys with unilateral ureteric obstruction and revealed their different functions in building an inflammatory or profibrotic environment. Following renal fibrosis, the phenotypes of infiltrated CD8 T cells were mainly Tc1 (CD44⁺CD25^-CD62L^-) at the early inflammation stage and then changed to Tc2 (CD44⁺CD25^highCD62L^low). Tc1 and Tc2 secreted IFN-γ, contributing to the decrease in the Th2-induced over-polarization of M2 macrophages and fibrosis. Moreover, Tc2 secreted pro- and anti-inflammation factors and decreased the inflammatory responses of other cells to control inflammation and fibrosis. This work and our previous study showed that CD8 T cells could balance out inflammation by controlling its level in renal fibrosis.

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.

Placental Mesenchymal Stromal Cells (PMSCs) and PMSC-Derived Extracellular Vesicles (PMSC-EVs) Attenuated Renal Fibrosis in Rats with Unilateral Ureteral Obstruction (UUO) by Regulating CD4+ T Cell Polarization

Purpose

Recent evidence has shown that CD4⁺ T helper (Th) cells are involved in renal inflammation and fibrosis. However, whether renal fibrosis can be alleviated by intervening in the polarization of CD4⁺ T cells remains unknown. Our research investigated the effects of intravenously administered placenta mesenchymal stromal cells (PMSCs) or treatment with extracellular EVs (EVs) derived from PMSCs (PMSC-EVs) on the polarization of CD4⁺ T cells in rats with unilateral ureteral obstruction (UUO). We further verified how PMSCs affect inflammatory factor secretion and the levels of regulatory T (Treg) and Th17 CD4⁺ T cells in vitro.

Materials and Methods

We evaluated renal interstitial inflammation and fibrosis by pathological section staining, tested the polarization of CD4⁺ T cells (Th17 and Treg phenotypes) by flow cytometry (FCM) and immunohistochemistry, and detected the cytokines secreted by CD4⁺ T cells by enzyme-linked immunosorbent assay (ELISA).

Results

Compared with that of control rats, the renal tissue of PMSC-treated rats exhibited lower renal Masson scores and more Foxp3⁺ cell infiltration, with a significantly decreased IL17A⁺CD4⁺ T cell/CD4⁺ T cell ratio and a significantly elevated anti-inflammatory cytokine (IL-10) level. When CD4⁺ T cells were cocultured with PMSCs, CD4⁺IL17A⁺ cell percentages were decreased in a UUO model after 7 days of coculture with PMSCs. The secretion of TGF-β and IL-10 was significantly increased (P < 0.05), while the secretion of IFN-γ, IL-17, and IL-6 was significantly decreased (P < 0.05) in the PMSC coculture group. Moreover, after treatment with PMSC-EVs, tubulointerstitial fibrosis was alleviated, and Foxp3⁺/IL-17⁺ cell infiltration was increased in the kidneys of UUO model animals on day 7.

Conclusions

PMSCs can convert the inflammatory environment into an anti-inflammatory environment by affecting the polarization of CD4⁺ T cells and macrophages, inhibiting the inflammatory factors IFN-γ and IL-17, and upregulating the expression of the anti-inflammatory factors TGF-β and IL-10, ultimately leading to renal protection. Such functions may be mediated by the paracrine activity of PMSC-EVs.

Cyclophilin A Promotes Inflammation in Acute Kidney Injury but Not in Renal Fibrosis

Cyclophilin A (CypA) is a highly abundant protein in the cytoplasm of most mammalian cells. Beyond its homeostatic role in protein folding, CypA is a Damage-Associated Molecular Pattern which can promote inflammation during tissue injury. However, the role of CypA in kidney disease is largely unknown. This study investigates the contribution of CypA in two different types of kidney injury: acute tubular necrosis and progressive interstitial fibrosis. CypA (Ppia) gene deficient and wild type (WT) littermate controls underwent bilateral renal ischaemia/reperfusion injury (IRI) and were killed 24 h later or underwent left unilateral ureteric obstruction (UUO) and were killed 7 days later. In the IRI model, CypA^−/− mice showed substantial protection against the loss of renal function and from tubular cell damage and death. This was attributed to a significant reduction in neutrophil and macrophage infiltration since CypA^−/− tubular cells were not protected from oxidant-induced cell death in vitro. In the UUO model, CypA^−/− mice were not protected from leukocyte infiltration or renal interstitial fibrosis. In conclusion, CypA promotes inflammation and acute kidney injury in renal IRI, but does not contribute to inflammation or interstitial fibrosis in a model of progressive kidney fibrosis.

Role of chemokines, innate and adaptive immunity

Polycystic Kidney Disease (PKD) triggers a robust immune system response including changes in both innate and adaptive immunity. These changes involve immune cells (e.g., macrophages and T cells) as well as cytokines and chemokines (e.g., MCP-1) that regulate the production, differentiation, homing, and various functions of these cells. This review is focused on the role of the immune system and its associated factors in the pathogenesis of PKDs as evidenced by data from cell-based systems, animal models, and PKD patients. It also highlights relevant pre-clinical and clinical studies that point to specific immune system components as promising candidates for the development of prognostic biomarkers and therapeutic strategies to improve PKD outcomes.

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.

Lymphatic Vessels Enhancing Adaptive Immunity Deteriorates Renal Inflammation and Renal Fibrosis

Background

Lymphatic vessels transport lymph away from microvascular beds into the cardiovascular system. The basic function of the lymphatic system include absorption of water and macromolecules in the interstitial fluid, which plays an important role in maintaining osmotic balance of the body. Recent studies have shown that lymphangiogenesis is associated with tumor metabolism, injury repair, and chronic inflammation, and deteriorates disease progression via immune cell trafficking.

Summary

Renal interstitial lymph-angiogenesis is found in patients with chronic kidney disease and a series of animal models of renal fibrosis. Lymphatic vessels transfer antigen and antigen-presenting cells from peripheral tissues to lymph nodes, which initiates adaptive immunity and in turn deteriorates renal inflammation and renal fibrosis, even in non-autoimmune renal diseases.

Key Messages

This review summarizes the latest findings on how lymphatics participate in the progression of chronic kidney disease. This discussion will serve to highlight the role of adaptive immunity in non-infectious and non-autoimmune nephropathy, in order to provide new ideas and methods for prevention and treatment of kidney diseases.

MMP-9-positive neutrophils are essential for establishing profibrotic microenvironment in the obstructed kidney of UUO mice

AIM

Matrix metalloproteinase-9 (MMP9) plays a profibrotic role in renal fibrosis. Neutrophils produce MMP9 in many pathologic models. However, the effect of neutrophil on the progression of renal fibrosis and the relationship of MMP9 to the infiltration of neutrophils into the kidney remain unknown.

METHODS

The surgery of unilateral ureter obstruction (UUO) was performed in male C57BL/6 mice. Kidneys were collected for analyses on days 0, 1, 3, 5 or 7 following surgery. The inflammatory cells were analysed by flow cytometry. The mRNA and protein levels of renal fibrosis factor and inflammatory factor were measured by qRT-PCR, immumofluorescence and western blot analysis.

RESULTS

In a mouse kidney model of UUO, neutrophil infiltration significantly increased and neutrophil accumulation reached the highest level at 5 days after the injury. In the obstructed kidney, depleting neutrophils decreased the expression of inflammatory factors, inhibited the accumulation of macrophages including type 2 macrophages and suppressed renal fibrosis. Almost all neutrophils produced MMP9 at the early stage of kidney obstruction. MMP9 attracted neutrophils and inflammatory cells because inhibiting MMP9 suppressed the infiltration of neutrophils and other inflammatory cells and reduced renal fibrosis, regardless of using MMP9 neutralizing antibody or MMP9 inhibitor or different intervening periods of days (0-6, 0-3 or 3-6 were applied after kidney obstruction).

CONCLUSION

MMP9 promotes neutrophil infiltration by increasing the inflammatory level, macrophage accumulation and renal fibrosis in the obstructed kidney. Inhibiting MMP9 or depleting neutrophils in the early stage of acute kidney injury can relieve the progression of kidney fibrosis.

Proximal Tubule Translational Profiling during Kidney Fibrosis Reveals Proinflammatory and Long Noncoding RNA Expression Patterns with Sexual Dimorphism

BACKGROUND

Proximal tubule injury can initiate CKD, with progression rates that are approximately 50% faster in males versus females. The precise transcriptional changes in this nephron segment during fibrosis and potential differences between sexes remain undefined.

METHODS

We generated mice with proximal tubule-specific expression of an L10a ribosomal subunit protein fused with enhanced green fluorescent protein. We performed unilateral ureteral obstruction surgery on four male and three female mice to induce inflammation and fibrosis, collected proximal tubule-specific and bulk cortex mRNA at day 5 or 10, and sequenced samples to a depth of 30 million reads. We applied computational methods to identify sex-biased and shared molecular responses to fibrotic injury, including up- and downregulated long noncoding RNAs (lncRNAs) and transcriptional regulators, and used in situ hybridization to validate critical genes and pathways.

RESULTS

We identified >17,000 genes in each proximal tubule group, including 145 G-protein-coupled receptors. More than 700 transcripts were differentially expressed in the proximal tubule of males versus females. The >4000 genes displaying altered expression during fibrosis were enriched for proinflammatory and profibrotic pathways. Our identification of nearly 150 differentially expressed proximal tubule lncRNAs during fibrosis suggests they may have unanticipated regulatory roles. Network analysis prioritized proinflammatory and profibrotic transcription factors such as Irf1, Nfkb1, and Stat3 as drivers of fibrosis progression.

CONCLUSIONS

This comprehensive transcriptomic map of the proximal tubule revealed sexually dimorphic gene expression that may reflect sex-related disparities in CKD, proinflammatory gene modules, and previously unappreciated proximal tubule-specific bidirectional lncRNA regulation.

Lymphangiogenesis in kidney and lymph node mediates renal inflammation and fibrosis

Lymphangiogenesis is associated with chronic kidney disease (CKD) and occurs following kidney transplant. Here, we demonstrate that expanding lymphatic vessels (LVs) in kidneys and corresponding renal draining lymph nodes (RDLNs) play critical roles in promoting intrarenal inflammation and fibrosis following renal injury. Our studies show that lymphangiogenesis in the kidney and RDLN is driven by proliferation of preexisting lymphatic endothelium expressing the essential C-C chemokine ligand 21 (CCL21). New injury-induced LVs also express CCL21, stimulating recruitment of more CCR7⁺ dendritic cells (DCs) and lymphocytes into both RDLNs and spleen, resulting in a systemic lymphocyte expansion. Injury-induced intrarenal inflammation and fibrosis could be attenuated by blocking the recruitment of CCR7⁺ cells into RDLN and spleen or inhibiting lymphangiogenesis. Elucidating the role of lymphangiogenesis in promoting intrarenal inflammation and fibrosis provides a key insight that can facilitate the development of novel therapeutic strategies to prevent progression of CKD-associated fibrosis.

Stimulating Type 1 Angiotensin Receptors on T Lymphocytes Attenuates Renal Fibrosis

Most forms of chronic kidney disease culminate in renal fibrosis that heralds organ failure. In contrast to the protective effects of globally blocking type 1 angiotensin (AT₁) receptors throughout the body, activating AT₁ receptors directly on immune cells may serve protective functions. However, the effects of stimulating the T-cell AT₁ receptor on the progression of renal fibrosis remain unknown. In this study, mice with T-cell-specific deletion of the dominant murine AT₁ receptor isoform Lck-Cre Agtra^flox/flox [total knockout (TKO)] and wild-type (WT) controls were subjected to the unilateral ureteral obstruction model of kidney fibrosis. Compared with WT controls, obstructed kidneys from TKO mice at day 14 had increased collagen 1 deposition. CD4⁺ T cells, CD11b⁺Ly6C^hi myeloid cells, and mRNA levels of Th1 inflammatory cytokines are elevated in obstructed TKO kidneys, suggesting that augmented Th1 responses in the TKO mice may exaggerate renal fibrosis by driving proinflammatory macrophage differentiation. In turn, T-bet deficient (T-bet knockout) mice lacking Th1 responses have attenuated collagen deposition after unilateral ureteral obstruction. We conclude that activating the AT₁ receptor on T cells mitigates renal fibrogenesis by inhibiting Th1 differentiation and renal accumulation of profibrotic macrophages.

Inflammatory Mediators and Renal Fibrosis

Renal inflammation is the initial, healthy response to renal injury. However, prolonged inflammation promotes the fibrosis process, which leads to chronic pathology and eventually end-stage kidney disease. There are two major sources of inflammatory cells: first, bone marrow-derived leukocytes that include neutrophils, macrophages, fibrocytes and mast cells, and second, locally activated kidney cells such as mesangial cells, podocytes, tubular epithelial cells, endothelial cells and fibroblasts. These activated cells produce many profibrotic cytokines and growth factors that cause accumulation and activation of myofibroblasts, and enhance the production of the extracellular matrix. In particular, activated macrophages are key mediators that drive acute inflammation into chronic kidney disease. They produce large amounts of profibrotic factors and modify the microenvironment via a paracrine effect, and they also transdifferentiate to myofibroblasts directly, although the origin of myofibroblasts in the fibrosing kidney remains controversial. Collectively, understanding inflammatory cell functions and mechanisms during renal fibrosis is paramount to improving diagnosis and treatment of chronic kidney disease.

T-Helper 2 Lymphocyte Immunophenotype Is Associated With Iatrogenic Laryngotracheal Stenosis

OBJECTIVE/HYPOTHESIS

This prospective controlled human and murine study assessed the presence of inflammatory cells and cytokines to test the hypothesis that immune cells are associated with fibroproliferation in iatrogenic laryngotracheal stenosis (iLTS).

METHODS

Inflammation was assessed by histology and immunofluorescence (IF), quantitative real-time polymerase chain reaction (qRT-PCR), and flow cytometry of cricotracheal resections of iLTS patients compared to normal controls. An iLTS murine model assessed the temporal relationship between inflammation and fibrosis.

RESULTS

iLTS specimens showed increased inflammation versus normal controls (159/high power field [hpf] vs. 119/hpf, P = 0.038), and increased CD3 + T-cells, CD4 + cells, and CD3+/CD4 + T-helper (T_H ) cells (all P < 0.05). The inflammatory infiltrate was located immediately adjacent to the epithelial surface in the superficial aspect of the thickened lamina propria. Human flow cytometry and qRT-PCR showed a significant increase in interleukin (IL)-4 gene expression, indicating a T_H 2 phenotype. Murine IF revealed a dense CD4 + T-cell inflammatory infiltrate on day 4 to 7 postinjury, which preceded the development of fibrosis. Murine flow cytometry and qRT-PCR studies mirrored the human ones, with increased T-helper cells and IL-4 in iLTS versus normal controls.

CONCLUSION

CD3/CD4 + T-helper lymphocytes and the proinflammatory cytokine IL-4 are associated with iLTS. The association of a T_H 2 immunophenotype with iLTS is consistent with findings in other fibroinflammatory disorders. The murine results reveal that the inflammatory infiltrate precedes the development of fibrosis. However, human iLTS specimens with well-developed fibrosis also contain a marked chronic inflammatory infiltrate, suggesting that the continued release of IL-4 by T-helper lymphocytes may continue to propagate iLTS.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:177-186, 2019.

Cellular and molecular mechanisms of kidney fibrosis

Renal fibrosis is the final pathological process common to any ongoing, chronic kidney injury or maladaptive repair. It is considered as the underlying pathological process of chronic kidney disease (CKD), which affects more than 10% of world population and for which treatment options are limited. Renal fibrosis is defined by excessive deposition of extracellular matrix, which disrupts and replaces the functional parenchyma that leads to organ failure. Kidney's histological structure can be divided into three main compartments, all of which can be affected by fibrosis, specifically termed glomerulosclerosis in glomeruli, interstitial fibrosis in tubulointerstitium and arteriosclerosis and perivascular fibrosis in vasculature. In this review, we summarized the different appearance, cellular origin and major emerging processes and mediators of fibrosis in each compartment. We also depicted and discussed the challenges in translation of anti-fibrotic treatment to clinical practice and discuss possible solutions and future directions.

CD4+ and CD8+ T Cells Exert Regulatory Properties During Experimental Acute Aristolochic Acid Nephropathy

Experimental aristolochic acid nephropathy is characterized by transient acute proximal tubule necrosis and inflammatory cell infiltrates followed by interstitial fibrosis and tubular atrophy. The respective role of T-cell subpopulations has never been studied in the acute phase of the mouse model, and was heretofore exclusively investigated by the use of several depletion protocols. As compared to mice injected with aristolochic acids alone, more severe acute kidney injury was observed after CD4⁺ or CD8⁺ T-cells depletion. TNF-alpha and MCP-1 mRNA renal expressions were also increased. In contrast, regulatory T-cells depletion did not modify the severity of the aristolochic acids induced acute kidney injury, suggesting an independent mechanism. Aristolochic acids nephropathy was also associated with an increased proportion of myeloid CD11b^highF4/80^mid and a decreased proportion of their counterpart CD11b^lowF4/80^high population. After CD4⁺ T-cell depletion the increase in the CD11b^highF4/80^mid population was even higher whereas the decrease in the CD11b^lowF4/80^high population was more marked after CD8+ T cells depletion. Our results suggest that CD4⁺ and CD8⁺ T-cells provide protection against AA-induced acute tubular necrosis. Interestingly, T-cell depletion was associated with an imbalance of the CD11b^highF4/80^mid and CD11b^lowF4/80^high populations.

Interferon gamma peptidomimetic targeted to interstitial myofibroblasts attenuates renal fibrosis after unilateral ureteral obstruction in mice

Renal fibrosis cannot be adequately treated since anti-fibrotic treatment is lacking. Interferon-γ is a pro-inflammatory cytokine with anti-fibrotic properties. Clinical use of interferon-γ is hampered due to inflammation-mediated systemic side effects. We used an interferon-γ peptidomimetic (mimγ) lacking the extracellular IFNγReceptor recognition domain, and coupled it to the PDGFβR-recognizing peptide BiPPB. Here we tested the efficacy of mimγ-BiPPB (referred to as “Fibroferon”) targeted to PDGFβR-overexpressing interstitial myofibroblasts to attenuate renal fibrosis without inducing inflammation-mediated side effects in the mouse unilateral ureter obstruction model.

Unilateral ureter obstruction induced renal fibrosis characterized by significantly increased α-SMA, TGFβ1, fibronectin, and collagens I and III protein and/or mRNA expression. Fibroferon treatment significantly reduced expression of these fibrotic markers. Compared to full-length IFNγ, anti-fibrotic effects of Fibroferon were more pronounced. Unilateral ureter obstruction-induced lymphangiogenesis was significantly reduced by Fibroferon but not full-length IFNγ. In contrast to full-length IFNγ, Fibroferon did not induce IFNγ-related side-effects as evidenced by preserved low-level brain MHC II expression (similar to vehicle), lowered plasma triglyceride levels, and improved weight gain after unilateral ureter obstruction.

In conclusion, compared to full-length IFNγ, the IFNγ-peptidomimetic Fibroferon targeted to PDGFβR-overexpressing myofibroblasts attenuates renal fibrosis in the absence of IFNγ-mediated adverse effects.

Personalized Proteomics in Proliferative Vitreoretinopathy Implicate Hematopoietic Cell Recruitment and mTOR as a Therapeutic Target

PURPOSE

To profile vitreous cytokine expression of proliferative vitreoretinopathy (PVR) patients.

DESIGN

Case-control study.

METHODS

Liquid biopsies were collected from 2 groups: control subjects (n = 3) undergoing pars plana vitrectomy to remove an epiretinal membrane (ERM), and test subjects (n = 7) with varying degrees of PVR. A high-throughput cytokine screen measured expression of 200 cytokines. Cytokine expression patterns were prospectively validated in separate cohorts of control patients and those with PVR-A, PVR-B, and PVR-C (n = 10 for each group). Expression changes were evaluated by analysis of variance (significant P value < .05), hierarchical cluster algorithm, and pathway analysis, to identify candidate pathways for prospective studies.

RESULTS

In PVR vitreous, 29 cytokines were upregulated compared to controls. Early PVR vitreous showed upregulation of T-cell markers, profibrotic cytokines, and cytokines downstream of mTOR activation (IL-2, IL-6, and IL-13), whereas in late PVR vitreous, cytokines driving monocyte responses and stem-cell recruitment (SDF-1) prevailed. Prospective validation confirmed the differential expression of specific cytokines from PVR-A to C.

CONCLUSIONS

Early PVR is characterized by activation of T cells and mTOR signaling, whereas advanced PVR is characterized by a chronic monocyte response. PVR might be treated by rational repositioning of existing drugs that target mTOR and IL-6. Our analysis demonstrates that successful therapeutic intervention will be highly dependent on the specific therapeutic target and the stage of PVR. This study provides insights into cytokines that will serve as biomarkers and therapeutic targets. These biomarkers will help design clinical trials that intervene at appropriate times.