Leukemia inhibitory factor is involved in tubular regeneration after experimental acute renal failure

Role of Interleukin-6 Family Cytokines in Organ Fibrosis

Background

Organ fibrosis remains an important cause of high incidence rate and mortality worldwide. The prominent role of interleukin-6 (IL-6) family members represented by IL-6 in inflammation has been extensively studied, and drugs targeting IL-6 have been used clinically. Because of the close relationship between inflammation and fibrosis, researches on the role of IL-6 family members in organ fibrosis are also gradually emerging.

Summary

In this review, we systematically reviewed the role of IL-6 family members in fibrosis and their possible mechanisms. We listed the role of IL-6 family members in organ fibrosis and drew two diagrams to illustrate the downstream signal transductions of IL-6 family members. We also summarized the effect of some IL-6 family members' antagonists in a table.

Key Messages

Fibrosis contributes to organ structure damage, organ dysfunction, and eventually organ failure. Although IL-6 family cytokines have similar downstream signal pathways, different members play various roles in an organ-specific manner which might be partly due to their different target cell populations. The pathogenic role of individual member in various diseases needs to be deciphered carefully.

Combining robust urine biomarkers to assess chronic kidney disease progression

BACKGROUND

Urinary biomarkers may improve the prediction of chronic kidney disease (CKD) progression. Yet, data reporting the applicability of most commercial biomarker assays to the detection of their target analyte in urine together with an evaluation of their predictive performance are scarce.

METHODS

30 commercial assays (ELISA) were tested for their ability to quantify the target analyte in urine using strict (FDA-approved) validation criteria. In an exploratory analysis, LASSO (Least Absolute Shrinkage and Selection Operator) logistic regression analysis was used to identify potentially complementary biomarkers predicting fast CKD progression, determined as the ⁵¹CrEDTA clearance-based measured glomerular filtration rate (mGFR) decline (>10% per year) in a subsample of 229 CKD patients (mean age, 61 years; 66% men; baseline mGFR, 38 mL/min) from the NephroTest prospective cohort.

FINDINGS

Among the 30 assays, directed against 24 candidate biomarkers, encompassing different pathophysiological mechanisms of CKD progression, 16 assays fulfilled the FDA-approved criteria. LASSO logistic regressions identified a combination of five biomarkers including CCL2, EGF, KIM1, NGAL, and TGF-α that improved the prediction of fast mGFR decline compared to the kidney failure risk equation variables alone: age, gender, mGFR, and albuminuria. Mean area under the curves (AUC) estimated from 100 re-samples was higher in the model with than without these biomarkers, 0.722 (95% confidence interval 0.652-0.795) vs. 0.682 (0.614-0.748), respectively. Fully-adjusted odds-ratios (95% confidence interval) for fast progression were 1.87 (1.22, 2.98), 1.86 (1.23, 2.89), 0.43 (0.25, 0.70), 1.10 (0.71, 1.83), 0.55 (0.33, 0.89), and 2.99 (1.89, 5.01) for albumin, CCL2, EGF, KIM1, NGAL, and TGF-α, respectively.

INTERPRETATION

This study provides a rigorous validation of multiple assays for relevant urinary biomarkers of CKD progression which combination may improve the prediction of CKD progression.

FUNDING

This work was supported by Institut National de la Santé et de la Recherche Médicale, Université de Paris, Assistance Publique Hôpitaux de Paris, Agence Nationale de la Recherche, MSDAVENIR, Pharma Research and Early Development Roche Laboratories (Basel, Switzerland), and Institut Roche de Recherche et Médecine Translationnelle (Paris, France).

Inhibition of a signaling modality within the gp130 receptor enhances tissue regeneration and mitigates osteoarthritis

Adult mammals are incapable of multitissue regeneration, and augmentation of this potential may shift current therapeutic paradigms. We found that a common co-receptor of interleukin 6 (IL-6) cytokines, glycoprotein 130 (gp130), serves as a major nexus integrating various context-specific signaling inputs to either promote regenerative outcomes or aggravate disease progression. Via genetic and pharmacological experiments in vitro and in vivo, we demonstrated that a signaling tyrosine 814 (Y814) within gp130 serves as a major cellular stress sensor. Mice with constitutively inactivated Y814 (F814) were resistant to surgically induced osteoarthritis as reflected by reduced loss of proteoglycans, reduced synovitis, and synovial fibrosis. The F814 mice also exhibited enhanced regenerative, not reparative, responses after wounding in the skin. In addition, pharmacological modulation of gp130 Y814 upstream of the SRC and MAPK circuit by a small molecule, R805, elicited a protective effect on tissues after injury. Topical administration of R805 on mouse skin wounds resulted in enhanced hair follicle neogenesis and dermal regeneration. Intra-articular administration of R805 to rats after medial meniscal tear and to canines after arthroscopic meniscal release markedly mitigated the appearance of osteoarthritis. Single-cell sequencing data demonstrated that genetic and pharmacological modulation of Y814 resulted in attenuation of inflammatory gene signature as visualized by the anti-inflammatory macrophage and nonpathological fibroblast subpopulations in the skin and joint tissue after injury. Together, our study characterized a molecular mechanism that, if manipulated, enhances the intrinsic regenerative capacity of tissues through suppression of a proinflammatory milieu and prevents pathological outcomes in injury and disease.

Leukemia inhibitory factor, a double-edged sword with therapeutic implications in human diseases

Leukemia inhibitory factor (LIF) is a pleiotropic cytokine of the interleukin-6 (IL-6) superfamily. LIF was initially discovered as a factor to induce the differentiation of myeloid leukemia cells and thus inhibit their proliferation. Subsequent studies have highlighted the multi-functions of LIF under a wide variety of physiological and pathological conditions in a highly cell-, tissue-, and context-dependent manner. Emerging evidence has demonstrated that LIF plays an essential role in the stem cell niche, where it maintains the homeostasis and regeneration of multiple somatic tissues, including intestine, neuron, and muscle. Further, LIF exerts a crucial regulatory role in immunity and functions as a protective factor against many immunopathological diseases, such as infection, inflammatory bowel disease (IBD), and graft-verse-host disease (GVHD). It is worth noting that while LIF displays a tumor-suppressive function in leukemia, recent studies have highlighted the oncogenic role of LIF in many types of solid tumors, further demonstrating the complexities and context-dependent effects of LIF. In this review, we summarize the recent insights into the roles and mechanisms of LIF in stem cell homeostasis and regeneration, immunity, and cancer, and discuss the potential therapeutic options for human diseases by modulating LIF levels and functions.

Leukemia inhibitory factor is a therapeutic target for renal interstitial fibrosis

BACKGROUND

The role of the IL6 family members in organ fibrosis, including renal interstitial fibrosis (TIF), has been widely explored. However, few studies have ever simultaneously examined them in the same cohort of patients. Besides, the role of leukemia inhibitory factor (LIF) in TIF remains unclear.

METHODS

RNA-seq data of kidney biopsies from chronic kidney disease (CKD) patients, in both public databases and our assays, were used to analyze transcript levels of IL6 family members. Two TIF mouse models, the unilateral ureteral obstruction (UUO) and the ischemia reperfusion injury (IRI), were employed to validate the finding. To assess the role of LIF in vivo, short hairpin RNA, lenti-GFP-LIF was used to knockdown LIF receptor (LIFR), overexpress LIF, respectively. LIF-neutralizing antibody was used in therapeutic studies. Whether urinary LIF could be used as a promising predictor for CKD progression was investigated in a prospective observation patient cohort.

FINDINGS

Among IL6 family members, LIF is the most upregulated one in both human and mouse renal fibrotic lesions. The mRNA level of LIF negatively correlated with eGFR with the strongest correlation and the smallest P value. Baseline urinary concentrations of LIF in CKD patients predict the risk of CKD progression to end-stage kidney disease by Kaplan-Meier analysis. In mouse TIF models, knockdown of LIFR alleviated TIF; conversely, overexpressing LIF exacerbated TIF. Most encouragingly, visible efficacy against TIF was observed by administering LIF-neutralizing antibodies to mice. Mechanistically, LIF-LIFR-EGR1 axis and Sonic Hedgehog signaling formed a vicious cycle between fibroblasts and proximal tubular cells to augment LIF expression and promote the pro-fibrotic response via ERK and STAT3 activation.

INTERPRETATION

This study discovered that LIF is a noninvasive biomarker for the progression of CKD and a potential therapeutic target of TIF.

FUNDINGS

Stated in the Acknowledgements section of the manuscript.

Meprin β expression modulates the interleukin-6 mediated JAK2-STAT3 signaling pathway in ischemia/reperfusion-induced kidney injury

Meprin metalloproteinases have been implicated in the pathophysiology of ischemia/reperfusion (IR)-induced kidney injury. Previous in vitro data showed that meprin β proteolytically processes interleukin-6 (IL-6) resulting in its inactivation. Recently, meprin-β was also shown to cleave the IL-6 receptor. The goal of this study was to determine how meprin β expression impacts IL-6 and downstream modulators of the JAK2-STAT3-mediated signaling pathway in IR-induced kidney injury. IR was induced in 12-week-old male wild-type (WT) and meprin β knockout (βKO) mice and kidneys obtained at 24 h post-IR. Real-time PCR, western blot, and immunostaining/microscopy approaches were used to quantify mRNA and protein levels respectively, and immunofluorescence counterstaining with proximal tubule (PT) markers to determine protein localization. The mRNA levels for IL-6, CASP3 and BCL-2 increased significantly in both genotypes. Interestingly, western blot data showed increases in protein levels for IL-6, CASP3, and BCL-2 in the βKO but not in WT kidneys. However, immunohistochemical data showed increases in IL-6, CASP3, and BCL-2 proteins in select kidney tubules in both genotypes, shown to be PTs by immunofluorescence counterstaining. IR-induced increases in p-STAT-3 and p-JAK-2 in βKO at a global level but immunoflourescence counterstaining demonstrated p-JAK2 and p-STAT3 increases in select PT for both genotypes. BCL-2 increased only in the renal corpuscle of WT kidneys, suggesting a role for meprins expressed in leukocytes. Immunohistochemical analysis confirmed higher levels of leukocyte infiltration in WT kidneys when compared to βKO kidneys. The present data demonstrate that meprin β modulates IR-induced kidney injury in part via IL-6/JAK2/STAT3-mediated signaling.

Cyclo(Val-Pro) and Cyclo(Leu-Hydroxy-Pro) from Pseudomonas sp. (ABS-36) alleviates acute and chronic renal injury under in vitro and in vivo models (Ischemic reperfusion and unilateral ureter obstruction)

The study aimed to identify small molecules having potentiality in alleviating renal injury. Two natural compounds cyclo(Val-Pro) (1) and cyclo(Leu-Hydroxy-Pro) (2) were first evaluated under acute renal injury model of ischemic reperfusion at different doses of 25, 50 and 75 mg/kg body weight. Further, the compounds were subjected to antimycin A-induced ischemic in vitro study (NRK-52E cell lines). Both the compounds significantly decreased plasma IL-1β levels (P < 0.05). Also, the mRNA expression levels of inflammatory markers (TNF-α, IL-6 and IL-1β) and renal injury markers (KIM-1, NGAL, α-GST and π-GST) in the renal tissues were significantly alleviated (P < 0.01) along with the improvement in histological damage and control over neutrophil infiltration as a result of ischemic reperfusion. The in vitro study revealed the protective effect against antimycin A-induced cytotoxicity (P < 0.05) and antiapoptotic effect acting through the regulation of Bax, caspase 3 (pro and cleaved) and BCL2 with reduction in Annexin⁺PI⁺ cells. Further, the compound cyclo(Val-Pro) (1) was evaluated (50 mg/kg body weight dose) in chronic unilateral ureter obstruction model of renal injury in mice and TGF-β-induced in vitro fibrotic model (NRK-49F cell lines). Cyclo(Val-Pro) (1) significantly reduced the expression levels of fibrotic markers (collagen-1, α-SMA and TGF-β) and showed marked alleviation of renal fibrosis (sirius red staining). Also, the proliferation of TGF-β-induced NRK-49F cells was significantly reduced along with decreased levels of collagen-1 and α-SMA in immunohistochemistry studies. In conclusion, the compounds significantly abrogated ischemic injury by inhibiting renal inflammation and tubular epithelial apoptosis. Further, cyclo (Val-Pro) (1) exhibited significant anti-fibrotic activity through the inhibition of fibroblast activation and proliferation. Thus, these proline-based cyclic dipeptides are recommended as drug leads for treating renal injury.

The spatially resolved transcriptional profile of acute T cell-mediated rejection in a kidney allograft

Analysis of the transcriptional profile of graft biopsies represents a promising strategy to study T cell-mediated-rejection (TCMR), also known as acute cellular rejection. However, bulk RNA sequencing of graft biopsies may not capture the focal nature of acute rejection. Herein, we used the whole exome GeoMX Digital Space Profiling platform to study five tubular and three glomerular regions of interest in the kidney graft biopsy from a patient with a chronic-active TCMR episode and in analogous areas from two different normal kidney control biopsies. All kidney sections were from paraffin blocks. Overall, inflammatory genes were significantly upregulated in the tubular areas of the TCMR biopsy and showed an enrichment for gene-ontology terms associated with T-cell activation, differentiation, and proliferation. Enrichment analysis of the 100 genes with the highest coefficient of variation across the TCMR tubular regions of interest revealed that these highly variable genes are involved in kidney development and injury and interestingly do not associate with the 2019 Banff classification pathology scores within the individual regions of interest. Spatial transcriptomics allowed us to unravel a previously unappreciated variability across different areas of the TCMR biopsy related to the graft response to the alloimmune attack, rather than to the immune cells. Thus, our approach has the potential to decipher clinically relevant, new pathogenic mechanisms, and therapeutic targets in acute cellular rejection and other kidney diseases with a focal nature.

DNA repair factor KAT5 prevents ischemic acute kidney injury through glomerular filtration regulation

The “preconditioning effect” in AKI is a phenomenon in which an episode of ischemia-reperfusion results in tolerance to subsequent ischemia-reperfusion injury. However, its relationship between DNA damage repair has not been elucidated. Here, we show the role of KAT5 in the preconditioning effect. Preconditioning attenuated DNA damage in proximal tubular cells with elevated KAT5 expression. Ischemia-reperfusion (IR) injuries were exacerbated, and preconditioning effect vanished in proximal tubular-cell-specific KAT5 knockout mice. Investigation of tubuloglomerular feedback (TGF) by MALDI-IMS and urinary adenosine revealed that preconditioning caused attenuated TGF at least in part via KAT5. In addition, K-Cl cotransporter 3 (KCC3) expression decreased in damaged proximal tubular cells, which may be involved in accelerated TGF following IR. Furthermore, KAT5 induced KCC3 expression by maintaining chromatin accessibility and binding to the KCC3 promoter. These results suggest a novel mechanism of the preconditioning effect mediated by the promotion of DNA repair and attenuation of TGF through KAT5.

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KAT5-mediated DNA damage repair acts against ischemia-reperfusion (IR) injuries

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K-Cl cotransporter3 (KCC3) expression is decreased in damaged proximal tubular cells

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Decreased KCC3 may lead to AKI via acceleration of tubuloglomerular feedback

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KAT5 induces KCC3 expression through an epigenetic mechanism

The emerging role of leukemia inhibitory factor in cancer and therapy

Leukemia inhibitory factor (LIF) is a multi-functional cytokine of the interleukin-6 (IL-6) superfamily. Initially identified as a factor that inhibits the proliferation of murine myeloid leukemia cells, LIF displays a wide variety of important functions in a cell-, tissue- and context-dependent manner in many physiological and pathological processes, including regulating cell proliferation, pluripotent stem cell self-renewal, tissue/organ development and regeneration, neurogenesis and neural regeneration, maternal reproduction, inflammation, infection, immune response, and metabolism. Emerging evidence has shown that LIF plays an important but complex role in human cancers; while LIF displays a tumor suppressive function in some types of cancers, including leukemia, LIF is overexpressed and exerts an oncogenic function in many more types of cancers. Further, targeting LIF has been actively investigated as a novel strategy for cancer therapy. This review summarizes the recent advances in the studies on LIF in human cancers and its potential application in cancer therapy. A better understanding of the role of LIF in different types of cancers and its underlying mechanisms will help to develop more effective strategies for cancer therapy.

Identification of Novel Biomarker for Early Detection of Diabetic Nephropathy

Diabetic nephropathy (DN) is one of the most common complications of diabetes mellitus. After development of DN, patients will progress to end-stage renal disease, which is associated with high morbidity and mortality. Here, we developed early-stage diagnostic biomarkers to detect DN as a strategy for DN intervention. For the DN model, Zucker diabetic fatty rats were used for DN phenotyping. The results revealed that DN rats showed significantly increased blood glucose, blood urea nitrogen (BUN), and serum creatinine levels, accompanied by severe kidney injury, fibrosis and microstructural changes. In addition, DN rats showed significantly increased urinary excretion of kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL). Transcriptome analysis revealed that new DN biomarkers, such as complementary component 4b (C4b), complementary factor D (CFD), C-X-C motif chemokine receptor 6 (CXCR6), and leukemia inhibitory factor (LIF) were identified. Furthermore, they were found in the urine of patients with DN. Since these biomarkers were detected in the urine and kidney of DN rats and urine of diabetic patients, the selected markers could be used as early diagnosis biomarkers for chronic diabetic nephropathy.

Kidney-intrinsic factors determine the severity of ischemia/reperfusion injury in a mouse model of delayed graft function

Delayed graft function due to transplant ischemia/reperfusion injury adversely affects up to 50% of deceased-donor kidney transplant recipients. However, key factors contributing to the severity of ischemia/reperfusion injury remain unclear. Here, using a clinically relevant mouse model of delayed graft function, we demonstrated that donor genetic background and kidney-intrinsic MyD88/Trif-dependent innate immunity were key determinants of delayed graft function. Functional deterioration of kidney grafts directly corresponded with the duration of cold ischemia time. The graft dysfunction became irreversible after cold ischemia time exceeded six hours. When cold ischemia time reached four hours, kidney grafts displayed histological features reflective of delayed graft function seen in clinical kidney transplantation. Notably, kidneys of B6 mice exhibited significantly more severe histological and functional impairment than kidneys of C3H or BALB/c mice, regardless of recipient strains or alloreactivities. Furthermore, allografts of B6 mice also showed an upregulation of IL-6, neutrophil gelatinase-associated lipocalin, and endoplasmic reticulum stress genes, as well as an increased influx of host neutrophils and memory CD8 T-cells. In contrast, donor MyD88/Trif deficiency inhibited neutrophil influx and decreased the expression of IL-6 and endoplasmic reticulum stress genes, along with improved graft function and prolonged allograft survival. Thus, kidney-intrinsic factors involving genetic characteristics and innate immunity serve as critical determinants of the severity of delayed graft function. This preclinical murine model allows for further investigations of the mechanisms underlying delayed graft function.

Opioid Preconditioning Modulates Repair Responses to Prevent Renal Ischemia-Reperfusion Injury

Progression to renal damage by ischemia-reperfusion injury (IRI) is the result of the dysregulation of various tissue damage repair mechanisms. Anesthetic preconditioning with opioids has been shown to be beneficial in myocardial IRI models. Our main objective was to analyze the influence of pharmacological preconditioning with opioids in renal function and expression of molecules involved in tissue repair and angiogenesis. Experimental protocol includes male rats with 45 min ischemia occluding the left renal hilum followed by 24 h of reperfusion with or without 60 min preconditioning with morphine/fentanyl. We analyzed serum creatinine and renal KIM-1 expression. We measured circulating and intrarenal VEGF. Immunohistochemistry for HIF-1 and Cathepsin D (CTD) and real-time PCR for angiogenic genes HIF-1α, VEGF, VEGF Receptor 2 (VEGF-R2), CTD, CD31 and IL-6 were performed. These molecules are considered important effectors of tissue repair responses mediated by the development of new blood vessels. We observed a decrease in acute renal injury mediated by pharmacological preconditioning with opioids. Renal function in opioid preconditioning groups was like in the sham control group. Both anesthetics modulated the expression of HIF-1, VEGF, VEGF-R2 and CD31. Preconditioning negatively regulated CTD. Opioid preconditioning decreased injury through modulation of angiogenic molecule expression. These are factors to consider when establishing strategies in pathophysiological and surgical processes.

Periostin Promotes Cell Proliferation and Macrophage Polarization to Drive Repair after AKI

BACKGROUND

The matricellular protein periostin has been associated with CKD progression in animal models and human biopsy specimens. Periostin functions by interacting with extracellular matrix components to drive collagen fibrillogenesis and remodeling or by signaling through cell-surface integrin receptors to promote cell adhesion, migration, and proliferation. However, its role in AKI is unknown.

METHODS

We used mice with conditional tubule-specific overexpression of periostin or knockout mice lacking periostin expression in the renal ischemia-reperfusion injury model, and primary cultures of isolated tubular cells in a hypoxia-reoxygenation model.

RESULTS

Tubular epithelial cells showed strong production of periostin during the repair phase of ischemia reperfusion. Periostin overexpression protected mice from renal injury compared with controls, whereas knockout mice showed increased tubular injury and deteriorated renal function. Periostin interacted with its receptor, integrin-β1, to inhibit tubular cell cycle arrest and apoptosis in in vivo and in vitro models. After ischemia-reperfusion injury, periostin-overexpressing mice exhibited diminished expression of proinflammatory molecules and had more F4/80⁺ macrophages compared with knockout mice. Macrophages from periostin-overexpressing mice showed increased proliferation and expression of proregenerative factors after ischemia-reperfusion injury, whereas knockout mice exhibited the opposite. Coculturing a macrophage cell line with hypoxia-treated primary tubules overexpressing periostin, or treating such macrophages with recombinant periostin, directly induced macrophage proliferation and expression of proregenerative molecules.

CONCLUSIONS

In contrast to the detrimental role of periostin in CKD, we discovered a protective role of periostin in AKI. Our findings suggest periostin may be a novel and important mediator of mechanisms controlling renal repair after AKI.

Influence of renal ischaemia-reperfusion injury on renal neutrophil gelatinase-associated lipocalin receptor (24p3R) in rats

The neutrophil gelatinase-associated lipocalin (NGAL) receptor (24p3R) is expressed in distal nephron and contributes to the endocytosis of NGAL in urine. This study was undertaken to evaluate an influence of renal ischaemia-reperfusion injury on 24p3R. Unilateral renal pedicle was clamped for 0, 10, 20, 30, or 45 minutes in male Wistar rats. Urine was collected for 24 hours after reperfusion, and ischaemic kidney and blood sample were obtained. Apparent histological injury in the ischaemic kidney was detected in the 30 and 45 minutes-treated groups. Urinary NGAL excretion elevated in rats with renal ischaemia for more than 20 minutes, while serum creatinine increased in rats for more than 30 minutes of ischaemia. Renal protein expression of NGAL did not significantly change. Renal mRNA expressions of megalin and cubilin, which are expressed at renal proximal tubules and uptake NGAL, decreased in animals with renal ischaemia for more than 20 minutes. Renal protein expression of 24p3R, which is expressed at renal distal tubules and uptake NGAL, decreased in rats with renal ischaemia for 45 min. This study showed for the first time that renal 24p3R decreased in response to renal ischaemia. As relatively longer renal ischaemia (45 minutes) decreased renal 24p3R protein and increased urinary NGAL excretion, the down-regulation of 24p3R protein might contribute to the elevated urinary excretion of NGAL in rats with unilateral ischaemia-reperfusion injury.

Leukemia inhibitory factor promotes the regeneration of rat uterine horns with full-thickness injury

Severe uterine injuries may lead to infertility or pregnancy complications. There is a lack of effective methods to restore the structure and function of seriously injured uteri. Leukemia inhibitory factor (LIF), which plays a crucial role in blastocyst implantation, promotes the process of regeneration after injury in several different tissues. In this study, we explored the effect of LIF on the regeneration of rat uterine horns following full-thickness injury. One hundred and twenty four female Sprague-Dawley rats were assigned to three groups, including a sham-operated group (n = 34 uterine horns), a PBS/collagen group (n = 90 uterine horns), and a LIF/collagen group (n = 124 uterine horns). The regenerated uterine horns were collected at 1, 2, 4, 8, or 12 weeks after the surgery. The results showed that LIF/collagen scaffolds increased the number of endometrial cells and neovascularization 2 weeks after uterine full-thickness defect in excision sites (p < 0.001 vs PBS/collagen). Eight weeks after the surgery, the number of endometrial glands was dramatically higher in the LIF/collagen scaffolds group (35.2 ± 4.1/field) than in the PBS/collagen scaffolds (15.1 ± 1.4/field). The percentage of a-smooth muscle actin (a-SMA)-positive areas in the LIF/collagen scaffolds (88.8% ± 9.8%) was also significantly higher than that in the PBS/collagen group (52.9% ± 3.7%). Moreover, LIF improved the pregnancy rate and fetus number. We also found that LIF inhibited the infiltration of inflammatory cells and down-regulated the pro-inflammatory cytokine IL-12 expression while up-regulating the anti-inflammatory cytokine IL-10 expression in the injured part of the uterine horns. Our results indicate that LIF promotes regeneration of the uterus after injury, and this is at least partially due to its immunomodulatory properties. In addition, it is worth to explore further the possibility for LIF/collagen to be an alternative therapeutic approach for uterine damage in the clinic in near future.

Current Knowledge of IL-6 Cytokine Family Members in Acute and Chronic Kidney Disease

Healthy kidneys are important for the efficient regulation of metabolism. However, there is an ever increasing population of patients suffering from both acute and chronic kidney diseases that disrupt this homeostasis. This review will explore the emerging roles that interleukin 6 (IL-6) cytokine family members play in the pathogenesis of kidney disease. The IL-6 family of cytokines are involved in a diverse range of physiological functions. In relation to kidney disease, their involvement is no less diverse. Evidence from both preclinical and clinical sources show that IL-6 cytokine family members can play either a deleterious or protective role in response to kidney disease. This appears to be dependent on the type of kidney disease in question or the specific cytokine. Current attempts to use or target IL-6 cytokine family members as therapies of kidney diseases will be highlighted throughout this review. Finally, the involvement of IL-6 cytokine family members in kidney disease will be presented in the context of three regularly overlapping conditions: obesity, hypertension and diabetes.

Interleukin-6 contributes to the increase in fibroblast growth factor 23 expression in acute and chronic kidney disease

The high serum fibroblast growth factor 23 (FGF23) levels in patients with acute kidney injury (AKI) and chronic kidney disease (CKD) are associated with increased morbidity and mortality. Mice with folic acid-induced AKI had an increase in bone FGF23 mRNA expression together with an increase in serum FGF23 and several circulating cytokines including interleukin-6 (IL-6). Dexamethasone partially prevented the increase in IL-6 and FGF23 in the AKI mice. IL-6 knock-out mice fed an adenine diet to induce CKD failed to increase bone FGF23 mRNA and had a muted increase in serum FGF23 levels, compared with the increases in wild-type mice with CKD. Therefore, IL-6 contributes to the increase in FGF23 observed in CKD. Hydrodynamic tail injection of IL-6/soluble IL-6 receptor (sIL-6R) fusion protein hyper IL-6 (HIL-6) plasmid increased serum FGF23 levels. Circulating sIL-6R levels were increased in both CKD and AKI mice, suggesting that IL-6 increases FGF23 through sIL-6R-mediated trans-signaling. Renal IL-6 mRNA expression was increased in mice with either AKI or CKD, suggesting the kidney is the source for the increased serum IL-6 levels in the uremic state. HIL-6 also increased FGF23 mRNA in calvaria organ cultures and osteoblast-like UMR106 cells in culture, demonstrating a direct effect of IL-6 on FGF23 expression. HIL-6 increased FGF23 promoter activity through STAT3 phosphorylation and its evolutionarily conserved element in the FGF23 promoter. Thus, IL-6 increases FGF23 transcription and contributes to the high levels of serum FGF23 in both acute and chronic kidney disease.

Interleukin-6 Signaling Pathway and Its Role in Kidney Disease: An Update

Interleukin-6 (IL-6) is a pleiotropic cytokine that not only regulates the immune and inflammatory response but also affects hematopoiesis, metabolism, and organ development. IL-6 can simultaneously elicit distinct or even contradictory physiopathological processes, which is likely discriminated by the cascades of signaling pathway, termed classic and trans-signaling. Besides playing several important physiological roles, dysregulated IL-6 has been demonstrated to underlie a number of autoimmune and inflammatory diseases, metabolic abnormalities, and malignancies. This review provides an overview of basic concept of IL-6 signaling pathway as well as the interplay between IL-6 and renal-resident cells, including podocytes, mesangial cells, endothelial cells, and tubular epithelial cells. Additionally, we summarize the roles of IL-6 in several renal diseases, such as IgA nephropathy, lupus nephritis, diabetic nephropathy, acute kidney injury, and chronic kidney disease.

Identification of Gene Transcripts Implicated in Peritoneal Membrane Alterations

♦ BACKGROUND: Permanent stimulation of the peritoneum during peritoneal dialysis (PD) is likely to result in increased expression of genes encoding proteins involved in inflammation and tissue remodeling. Peritoneal fibrosis and neoangiogenesis may develop. ♦ OBJECTIVE: To assess highly expressed genes potentially in volved in peritoneal alterations during PD treatment using an animal model. ♦ METHODS: A PD catheter was implanted in 36 male Wistar rats after 70% nephrectomy. The rats were divided into 3 groups, exposed to dialysis solution for 8 weeks, and sacrificed 2 weeks later. Group B was exposed to a buffer, group D was exposed to a 3.86% glucose-based dialysis solution, and in group D+H, a second hit of intraperitoneal blood on top of the dialysis solution was given to induce the development of peritoneal sclerosis. Before sacrifice, peritoneal function was assessed. Omental tissue was obtained for analysis of gene expression using RT-qPCR. ♦ RESULTS: Fibrosis scores, vessel counts, and peritoneal function parameters were not different between the groups. Genes involved in the transforming growth factor beta signaling pathway, cell proliferation, angiogenesis, and inflammation were more expressed (p < 0.05) in the D+H group. Almost no differences were found between the control groups. We identified 4 genes that were related to peritoneal transport. ♦ CONCLUSION: Already a mid-term peritoneal exposure, when no microscopical and functional alterations are present, provokes activation of gene pathways of cell proliferation, fibrosis, neoangiogenesis, and inflammation.

Leukemia inhibitory factor attenuates renal fibrosis through Stat3-miR-29c

Leukemia inhibitory factory (LIF), as a member of the IL-6 family, has been reported to ameliorate myocardial fibrosis and myocardial cell death. The purpose of the present study was to investigate the effect of LIF on renal fibrosis and its underlying mechanism. Our results showed, first, that LIF inhibited collagen type 1 and collagen type 3 expression induced by ANG II in NRK-49F (rat kidney fibroblast) cells and in mice with unilateral ureteral obstruction. Second, LIF induced Stat3 Tyr(705) phosphorylation and inhibited Stat3 Tyr(705) and Ser(727) phosphorylation induced by ANG II in NRK-49F cells. Third, LIF exerted an antirenal fibrosis effect mainly through activation of Stat3 Tyr(705) phosphorylation in NRK-49F cells. These effects of LIF were not observed in Stat3(-/-) cells. Finally, LIF-Stat3 upregulated microRNA-29c expression, and the latter downregulated collagen type 1 and collagen type 3 expression in NRK-49F cells and in mice with unilateral ureteral obstruction. In conclusion, LIF played a role in antirenal fibrosis by competitively activating Stat3 Tyr(705) phosphorylation, which upregulated microRNA-29c to suppress collagen expression.

Regenerative medicine for the kidney: renotropic factors, renal stem/progenitor cells, and stem cell therapy

The kidney has the capacity for regeneration and repair after a variety of insults. Over the past few decades, factors that promote repair of the injured kidney have been extensively investigated. By using kidney injury animal models, the role of intrinsic and extrinsic growth factors, transcription factors, and extracellular matrix in this process has been examined. The identification of renal stem cells in the adult kidney as well as in the embryonic kidney is an active area of research. Cell populations expressing putative stem cell markers or possessing stem cell properties have been found in the tubules, interstitium, and glomeruli of the normal kidney. Cell therapies with bone marrow-derived hematopoietic stem cells, mesenchymal stem cells, endothelial progenitor cells, and amniotic fluid-derived stem cells have been highly effective for the treatment of acute or chronic renal failure in animals. Embryonic stem cells and induced pluripotent stem cells are also utilized for the construction of artificial kidneys or renal components. In this review, we highlight the advances in regenerative medicine for the kidney from the perspective of renotropic factors, renal stem/progenitor cells, and stem cell therapies and discuss the issues to be solved to realize regenerative therapy for kidney diseases in humans.

Ablation of proximal tubular suppressor of cytokine signaling 3 enhances tubular cell cycling and modifies macrophage phenotype during acute kidney injury

Suppressor of cytokine signaling 3 (SOCS-3) is an important intracellular negative regulator of several signaling pathways. We found that SOCS-3 is highly expressed in renal proximal tubules during acute kidney injury. To test the impact of this, conditional proximal tubular knockout mice (SOCS-3(sglt2Δ/sglt2Δ)) were created. These mice had better kidney function than their wild-type counterparts in aristolochic acid nephropathy and after ischemia/reperfusion injury. Kidneys of these knockout mice showed significantly more proximal tubular cell proliferation during the repair phase. A direct effect of SOCS-3 on tubular cell cycling was demonstrated by in vitro experiments showing a JAK/STAT pathway-dependent antimitotic effect of SOCS-3. Furthermore, acute damaged kidneys of the knockout mice contained increased numbers of F4/80(+) cells. Phenotypic analysis of these F4/80(+) cells indicated a polarization from classically activated to alternatively activated macrophages. In vitro, SOCS-3-overexpressing renal epithelial cells directly induced classical activation in cocultured macrophages, supporting the observed in vivo phenomenon. Thus, upregulation of SOCS-3 in stressed proximal tubules plays an important role during acute kidney injury by inhibition of reparative proliferation and by modulation of the macrophage phenotype. Antagonizing SOCS-3 could have therapeutic potential for acute kidney injury.

Protective role of JAK/STAT signaling against renal fibrosis in mice with unilateral ureteral obstruction

Inflammation is involved in renal fibrosis, a final common pathway for kidney diseases. To clarify how JAK/STAT/SOCS system was involved in renal fibrosis, UUO was induced in BALB/c or SOCS3(+/-) mice in the presence or absence of JAK inhibitor-incorporated nanoparticle (pyridine6-PGLA). UUO increased pSTAT3 and subsequently elevated SOCS3 levels in the obstructed kidneys. pSTAT3 levels were further increased in SOCS3(+/-) mice. UUO-induced renal fibrosis was markedly suppressed in SOCS3(+/-) mice, while it was aggravated by pre-treatment with pyridine6-PGLA. Although there were no differences in renal mRNA levels of TGF-β and collagens between wild and SOCS3(+/-) mice, MMP-2 activity was enhanced in SOCS3(+/-) UUO mice. Activated MMP-2 was completely suppressed by pyridine6-PGLA-pre-treatment. TNF-α one of JAK/STAT activators, increased pSTAT3 levels and subsequently induced MMP-2 activation in proximal tubular cells. These results suggest that JAK/STAT3 signaling may play a role in repair process of renal fibrosis in UUO partly via MMP-2 activation.

Application of regenerative medicine for kidney diseases

Following recent advancements of stem cell research, the potential for organ regeneration using somatic stem cells as an ultimate therapy for organ failure has increased. However, anatomically complicated organs such as the kidney and liver have proven more refractory to stem cell-based regenerative techniques. At present, kidney regeneration is considered to require one of two approaches depending on the type of renal failure, namely acute renal failure (ARF) and chronic renal failure (CRF).The kidney has the potential to regenerate itself provided that the damage is not too severe and the kidney's structure remains intact. Regenerative medicine for ARF should therefore aim to activate or support this potent. In cases of the irreversible damage to the kidney, which is most likely in patients with CRF undergoing long-term dialysis, self-renewal is totally lost. Thus, regenerative medicine for CRF will likely involve the establishment of a functional whole kidney de novo. This article reviews the challenges and recent advances in both approaches and discusses the potential approach of these novel strategies for clinical application.

Enhancement of in vitro human tubulogenesis by endothelial cell-derived factors: implications for in vivo tubular regeneration after injury

Renal proximal tubular epithelium can regenerate after various insults. To examine whether the tubular repair process is regulated by surrounding peritubular capillaries, we established an in vitro human tubulogenesis model that mimics in vivo tubular regeneration after injury. In this model, HGF, a potent renotropic factor, dose dependently induced tubular structures in human renal proximal tubular epithelial cells cultured in gels. Consistent with regenerating tubular cells after injury, HGF-induced tubular structures expressed a developmental gene, Pax-2, and a mesenchymal marker, vimentin, and formed a lumen with aquaporin-1 expression. Electron microscopic analysis showed the presence of microvilli on the apical site of the lumen, suggesting that these structures are morphologically equivalent to renal tubules in vivo. When cocultured with human umbilical vein endothelial cells (HUVEC), HGF-induced tubular formation was significantly enhanced. This could not be reproduced by the addition of VEGF, basic FGF, or PDGF. Protein array revealed that HUVEC produced various matrix metalloproteinases (MMPs). The stimulatory effects of coculture with HUVEC or HUVEC-derived conditional medium were almost completely abolished by addition of the tissue inhibitor of metalloproteinase (TIMP)-1 or TIMP-2. These data suggest that endothelial cell-derived factors including MMPs play a critical role in tubulogenesis and imply a potential role of peritubular capillary endothelium as a source of factor(s) required for tubular recovery after injury.

Stem cells derived from human amniotic fluid contribute to acute kidney injury recovery

Stem cells isolated from human amniotic fluid are gaining attention with regard to their therapeutic potential. In this work, we investigated whether these cells contribute to tubular regeneration after experimental acute kidney injury. Cells expressing stem cell markers with multidifferentiative potential were isolated from human amniotic fluid. The regenerative potential of human amniotic fluid stem cells was compared with that of bone marrow-derived human mesenchymal stem cells. We found that the intravenous injection of 3.5 × 10(5) human amniotic fluid stem cells into nonimmune-competent mice with glycerol-induced acute kidney injury was followed by rapid normalization of renal function compared with injection of mesenchymal stem cells. Both stem cell types showed enhanced tubular cell proliferation and reduced apoptosis. Mesenchymal stem cells were more efficient in inducing proliferation than amniotic fluid-derived stem cells, which, in contrast, were more antiapoptotic. Both cell types were found to accumulate within the peritubular capillaries and the interstitium, but amniotic fluid stem cells were more persistent than mesenchymal stem cells. In vitro experiments demonstrated that the two cell types produced different cytokines and growth factors, suggesting that a combination of different mediators is involved in their biological actions. These results suggest that the amniotic fluid-derived stem cells may improve renal regeneration in acute kidney injury, but they are not more effective than mesenchymal stem cells.

Oncostatin M pathway plays a major role in the renal acute phase response

The acute phase response is traditionally characterized by hepatic synthesis of proteins as an inflammatory response to injury, with interleukin-6 (IL-6) being the key mediator. In contrast, microarray studies in human renal transplant implantation biopsies indicate a strong acute phase response in the deceased donor kidney, associated with a significant upregulation of oncostatin M receptor β (OSMR). The aim of this study was to determine whether the kidney can generate a strong acute phase response, mediated by the OSM/OSMR gateway. Genes associated with the IL-6 cytokine family and acute phase reactants were analyzed by real-time RT-PCR in four groups of human biopsies spanning a spectrum of renal injury. OSM, OSMR, and fibrinogen β (FGB) were progressively more highly expressed from prenephrectomy, living donor, deceased donor, to discarded donor kidneys, suggesting correlation with severity of injury and local renal synthesis. Acute phase response gene expression was analyzed in human proximal tubular cells in culture in response to OSM. OSM induced a significant increase in expression of FGB, OSMR, serpin peptidase inhibitor A1, IL-6, and lipopolysaccharide binding protein, and a decrease in IL-6R. These changes were largely attenuated by coincubation with an OSMR blocking antibody, indicating the OSM effect was mediated through OSMR. OSM also resulted in a significantly altered expression of acute phase genes compared with IL-6 or leukemia inhibitory factor, suggesting that OSM is the predominant cytokine mediating the renal tubular acute phase response. In conclusion, the renal parenchyma is capable of generating a strong acute phase response, likely mediated via OSM/OSMR.

Polarized secretion of leukemia inhibitory factor

Background

The direction of cytokine secretion from polarized cells determines the cytokine's cellular targets. Leukemia inhibitory factor (LIF) belongs to the interleukin-6 (IL-6) family of cytokines and signals through LIFR/gp130. Three factors which may regulate the direction of LIF secretion were studied: the site of stimulation, signal peptides, and expression levels. Stimulation with IL-1β is known to promote IL-6 secretion from the stimulated membrane (apical or basolateral) in the human intestinal epithelial cell line Caco-2. Since LIF is related to IL-6, LIF secretion was also tested in Caco-2 following IL-1β stimulation. Signal peptides may influence the trafficking of LIF. Two isoforms of murine LIF, LIF-M and LIF-D, encode different signal peptides which have been associated with different locations of the mature protein in fibroblasts. To determine the effect of the signal peptides on LIF secretion, secretion levels were compared in Madin-Darby canine kidney (MDCK) clones which expressed murine LIF-M or LIF-D or human LIF under the control of an inducible promoter. Low and high levels of LIF expression were also compared since saturation of the apical or basolateral route would reveal specific transporters for LIF.

Results

When Caco-2 was grown on permeable supports, LIF was secreted constitutively with around 40% secreted into the apical chamber. Stimulation with IL-1β increased LIF production. After treating the apical surface with IL-1β, the percentage secreted apically remained similar to the untreated, whereas, when the cells were stimulated at the basolateral surface only 20% was secreted apically. In MDCK cells, an endogenous LIF-like protein was detected entirely in the apical compartment. The two mLIF isoforms showed no difference in their secretion patterns in MDCK. Interestingly, about 70% of murine and human LIF was secreted apically from MDCK over a 400-fold range of expression levels within clones and a 200,000-fold range across clones.

Conclusion

The site of stimulation affected the polarity of LIF secretion, while, signal peptides and expression levels did not. Exogenous LIF is transported in MDCK without readily saturated steps.

Interleukin-18 binding protein transgenic mice are protected against ischemic acute kidney injury

IL-18 function is neutralized in IL-18 binding protein transgenic (IL-18BP Tg) mice. First, we determined whether IL-18BP Tg mice are protected against ischemic acute kidney injury (AKI). Ischemic AKI was induced by bilateral renal pedicle clamping. IL-18BP Tg mice were functionally and histologically protected against ischemic AKI as determined by blood urea nitrogen, serum creatinine, and acute tubular necrosis score. We have demonstrated that the injurious effect of IL-18 in the kidney is independent of neutrophils and lymphocytes. Thus the effect of IL-18 inhibition on renal macrophage infiltration was determined. The number of macrophages was significantly reduced in IL-18BP Tg compared with wild-type kidneys. To determine the cytokines and chemokines that are dependent on IL-18, we performed flow cytometry based assays. Multiple chemokines/cytokines, IL-3, IL-6, IL-15, IL-18, leukemia inhibitory factor, macrophage colony-stimulating factor, macrophage inflammatory protein-2, granulocyte-macrophage colony-stimulating factor, and monocyte chemotactic protein-1 were significantly increased in AKI vs. sham kidneys. Only CXCL1 (also known as KC or IL-8) was significantly increased in AKI vs. sham kidneys and significantly reduced in IL-18BP Tg AKI vs. wild-type AKI kidneys. To determine whether macrophages are the source of CXCL1 in the kidney, we depleted macrophages with liposomal encapsulated clodronate. CXCL1 was significantly decreased in macrophage-depleted vs. control AKI mice. In summary, in ischemic AKI in mice, 1) IL-18BP Tg mice are functionally and histologically protected, 2) macrophage infiltration in the kidney and CXCL1 are significantly reduced in IL-18BP Tg mice, and 3) macrophage depletion significantly reduces CXCL1 in the kidney. In conclusion, protection against ischemic AKI in IL-18BP Tg mice is associated with less macrophage infiltration and less production of CXCL1 in the kidney.

IL-6/IL-6R axis plays a critical role in acute kidney injury

The response to tissue injury involves the coordination of inflammatory and repair processes. IL-6 expression correlates with the onset and severity of acute kidney injury (AKI), but its contribution to pathogenesis remains unclear. This study established a critical role for IL-6 in both the inflammatory response and the resolution of AKI. IL-6-deficient mice were resistant to HgCl2-induced AKI compared with wild-type mice. The accumulation of peritubular neutrophils was lower in IL-6-deficient mice than in wild-type mice, and neutrophil depletion before HgCl2 administration in wild-type mice significantly reduced AKI; these results demonstrate the critical role of IL-6 signaling in the injurious inflammatory process in AKI. Renal IL-6 expression and STAT3 activation in renal tubular epithelial cells significantly increased during the development of injury, suggesting active IL-6 signaling. Although a lack of renal IL-6 receptors (IL-6R) precludes the activation of classical signaling pathways, IL-6 can stimulate target cells together with a soluble form of the IL-6R (sIL-6R) in a process termed trans-signaling. During injury,serum sIL-6R levels increased three-fold, suggesting a possible role for IL-6 trans-signaling in AKI. Stimulation of IL-6 trans-signaling with an IL-6/sIL-6R fusion protein activated STAT3 in renal tubular epithelium and prevented AKI. IL-6/sIL-6R reduced lipid peroxidation after injury, suggesting that its protective effect may be largely mediated through amelioration of oxidative stress. In summary, IL-6 simultaneously promotes an injurious inflammatory response and, through a mechanism of trans-signaling, protects the kidney from further injury.

Epigenetic regulation of BMP7 in the regenerative response to ischemia

Kidneys damaged by ischemia have the potential to regenerate through a mechanism involving intrarenal induction of protective factors, including bone morphogenetic protein-7 (BMP7). Epigenetic changes, such as alterations in histone modifications, have also been shown to play a role in various pathologic conditions, but their involvement in ischemic injury and regeneration remains unknown. This study investigated whether changes in histone acetylation, regulated by histone acetyltransferase and histone deacetylase (HDAC), are induced by renal ischemia and involved in the regenerative response. Ischemia/reperfusion of the mouse kidney induced a transient decrease in histone acetylation in proximal tubular cells, likely as a result of a decrease in histone acetyltransferase activity as suggested by experiments with energy-depleted renal epithelial cells in culture. During recovery after transient energy depletion in epithelial cells, the HDAC isozyme HDAC5 was selectively downregulated in parallel with the return of acetylated histone. Knockdown of HDAC5 by RNAi significantly increased histone acetylation and BMP7 expression. BMP7 induction and HDAC5 downregulation in the recovery phase were also observed in proximal tubular cells in vivo after transient ischemia. These data indicate that ischemia induces dynamic epigenetic changes involving HDAC5 downregulation, which contributes to histone re-acetylation and BMP7 induction in the recovery phase. This highlights HDAC5 as a modulator of the regenerative response after ischemia and suggests HDAC5 inhibition may be a therapeutic strategy to enhance BMP7 expression.

Proteomics for biomarker discovery in acute kidney injury

Acute kidney injury (AKI), previously referred to as acute renal failure, represents a common and devastating problem in clinical medicine. Despite significant improvements in therapeutics, the mortality and morbidity associated with AKI remain high. A major reason for this is the lack of early markers for AKI, and hence an unacceptable delay in initiating therapy. Fortunately, the application of innovative technologies such as functional genomics and proteomics to human and animal models of AKI has uncovered several novel biomarkers and therapeutic targets. The most promising of these are chronicled in this review. These include the identification of biomarker panels in plasma (neutrophil gelatinase-associated lipocalin and cystatin C) and urine (neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, interleukin-18, cystatin C, alpha1-microglobulin, Fetuin-A, Gro-alpha, and meprin). It is likely that the AKI panels will be useful for timing the initial insult, and assessing the duration and severity of AKI. It is also probable that the AKI panels will distinguish between the various etiologies of AKI and predict clinical outcomes. It will be important in future studies to validate the sensitivity and specificity of these biomarker panels in clinical samples from large cohorts and from multiple clinical situations. Such studies will be facilitated markedly by the development of commercial tools for the reproducible measurement of biomarkers across different laboratories.

Snail1 is involved in the renal epithelial–mesenchymal transition

The pathological significance of the tubular epithelial-mesenchymal transition (EMT) in kidney diseases is becoming increasingly recognized, and the transcription factor Snail1 plays a critical role in EMT. The results of this study show that Snail1 mRNA and protein were upregulated in the tubular epithelial cells of the obstructed kidneys in a rat model of unilateral ureteral obstruction and in human proximal tubule HKC-8 cells treated with TGF-beta1. Glycogen synthase kinase-3beta (GSK-3beta) regulates the Snail1 level by degrading Snail1 protein. The level of the phosphorylated inactive form of GSK-3beta was increased in the tubular epithelial cells of the obstructed kidney. TGF-beta1 increased the phosphorylated form of GSK-3beta in HKC-8 cells, and inhibition of GSK-3beta by the selective inhibitors lithium and TDZD-8 caused Snail1 protein to accumulate. This study demonstrated that Snail1 is involved in renal tubular EMT and that TGF-beta1 regulates Snail1 at the transcription and protein degradation levels.

Molecular basis of pregnancy-induced breast cancer protection

We have postulated that the lifetime protective effect of an early pregnancy against breast cancer is due to the complete differentiation of the mammary gland characterized by a specific genomic signature imprinted by the physiological process of pregnancy. In the present work, we show evidence that the breast tissue of postmenopausal parous women has had a shifting of stem cell 1 to stem cell 2 with a genomic signature different from similar structures derived from postmenopausal nulliparous women that have stem cell 1. Those genes that are significantly different are grouped in major categories on the basis of their putative functional significance. Among them are those gene transcripts related to immune surveillance, DNA repair, transcription, chromatin structure/activators/co-activators, growth factor and signal transduction pathway, transport and cell trafficking, cell proliferation, differentiation, cell adhesion, protein synthesis and cell metabolism. From these data, it was concluded that during pregnancy there are significant genomic changes that reflect profound alterations in the basic physiology of the mammary gland that explain the protective effect against carcinogenesis. The implication of this knowledge is that when the genomic signature of protection or refractoriness to carcinogenesis is acquired by the shifting of stem cell 1 to stem cell 2, the hormonal milieu induced by pregnancy or pregnancy-like conditions is no longer required. This is a novel concept that challenges the current knowledge that a chemopreventive agent needs to be given for a long period to suppress a metabolic pathway or abrogate the function of an organ.

Development of new therapies, including regeneration of the kidney, for chronic kidney diseases

The increasing number of patients on chronic hemodialysis is a great problem in the field of nephrology in Japan and Western countries. Current therapies for chronic kidney diseases (CKDs) can retard the progression of renal failure, but cannot completely stop their progression to endstage renal failure (ESRD). Many researchers are now studying new therapeutic targets for CKDs, by various methods. Furthermore, because organ donation for kidney transplantation is very limited in Japan, research on kidney regeneration is an important issue for the therapy of ESRD. To regenerate the kidney, stem cells and growth factors for the kidney are being extensively studied, although the clinical application of the results of these studies has not yet taken place.

Microarray analysis of a reversible model and an irreversible model of anti-Thy-1 nephritis

A single intravenous injection of anti-Thy-1 monoclonal antibody (mAb) 1-22-3 is known to cause reversible mesangial proliferative glomerulonephritis. However, mAb 1-22-3 injection followed by unilateral nephrectomy leads to progressive glomerulosclerosis and tubulointerstitial change with an irreversible course. To identify genes that play an important role in the irreversible progression of renal injury, we used microarray technology to identify differences in gene expression between these models. Rats were intravenously injected with mAb 1-22-3 1 week after unilateral nephrectomy (irreversible model) or a sham operation (reversible model), and rats were killed on days 4, 7, 14, 42, and 56 after the injection. complementary DNA probes prepared from kidney messenger RNAs were hybridized with oligonucleotide microarrays containing 4854 rat genes. The microarray identified 189 differentially expressed genes, having at least a two-fold difference in expression level between the two models, and they were classified into five clusters. One of the clusters consisted of genes whose expression was markedly upregulated in the irreversible model. This cluster included the genes encoding osteopontin, kidney injury molecule-1, and thymosin beta10. Increased expression of thymosin beta10 was localized mainly in macrophages in the fibrotic interstitium, and upregulation of thymosin beta10 expression was also observed in a unilateral ureteral obstruction model. The microarray analysis yielded information on the molecular mechanisms responsible for the difference in disease progression between the reversible and irreversible model of anti-Thy-1 nephritis. Thymosin beta10 may play an important role in the progression of kidney disease.

Adult kidney tubular cell population showing phenotypic plasticity, tubulogenic capacity, and integration capability into developing kidney

Using in vivo bromodeoxyuridine (BrdU) labeling, a tubular cell population (label-retaining tubular cells [LRTC]) was identified recently in normal adult kidneys, which contributes actively to the regeneration process of the kidney after injury. Here, these LRTC are characterized in vitro. The LRTC population was isolated from BrdU-treated rat kidney by FACS. Both LRTC and non-LRTC underwent proliferation and maintained an epithelial phenotype in the presence of tubulogenic growth factors such as EGF, TGF-alpha, IGF-I, and hepatocyte growth factor. It is interesting that LRTC also proliferated without epithelial markers expression in the presence of soluble factors derived from an embryonic kidney metanephric mesenchyme cell line. The type of extracellular matrix strongly influenced the phenotype of LRTC. Furthermore, in three-dimensional collagen gel culture, LRTC formed tubule-like or tubulocystic structures in response to growth factors (hepatocyte growth factor and fibroblast growth factor) that are known to induce kidney cell tubulogenesis in vitro and/or participate in renal regeneration in vivo. In contrast, non-LRTC did not form these structures. When transplanted into the metanephric kidney, LRTC but not non-LRTC were integrated into epithelial components of nephron, including the proximal tubular cells and the ureteric bud. They also differentiated into fibroblast-like cells. Collectively, these findings suggest that LRTC are an adult kidney tubular cell population that shows phenotypic plasticity, tubulogenic capacity, and integration capability into the developing kidney.

[Molecular mechanisms involved in kidney ischemia-reperfusion]

Acute renal failure (ARF) is still associated with high mortality. It is the consequence of a set of phenomena leading to a low glomerular filtration rate resulting, at least partly, from a misregulation of renal blood flow resulting itself from injuries at the epithelial and endothelial level. The outer medulla seems to be the region of the kidney the most affected by ischemia. Investigation at the histological level reveals a partial destruction of the renal epithelium generated by necrosis and/or apoptosis, loss of cell polarity, cell desquamation into the lumen and endothelial cell swelling. The recent advances in the comprehension of this pathology underline the major role of inflammation, which is probably responsible for the worsening and the persistence of ARF. Studies at the molecular level have pinpointed the implication of many signalling pathways such as apoptosis, G-protein signalling, various receptor and kinase activation. The characterisation of the molecular events involved in ARF should help in our approaches to prevent and treat ARF. The understanding of the adaptation mechanisms to ischemic stress (conditioning) is probably one of the most promising research area of this field in terms of medical applications.

Musculin/MyoR is expressed in kidney side population cells and can regulate their function

Musculin/MyoR is a new member of basic helix-loop-helix transcription factors, and its expression is limited to skeletal muscle precursors. Here, we report that musculin/MyoR is expressed in adult kidney side population (SP) cells and can regulate their function. SP phenotype can be used to purify stem cell–rich fractions. Microarray analysis clarified that musculin/MyoR was exclusively expressed in kidney SP cells, and the cells resided in the renal interstitial space. Musculin/MyoR-positive cells were decreased in acute renal failure, but infusion of kidney SP cells increased musculin/MyoR-positive cells and improved renal function. Kidney SP cells in reversible acute renal failure expressed a high level of renoprotective factors and leukemia inhibitory factor (LIF), but not in irreversible chronic renal failure. In cultured kidney SP cells, LIF stimulated gene expression of renoprotective factors, and down-regulation of musculin/MyoR augmented LIF-induced gene expression. Our results suggest that musculin/MyoR may play important roles not only in developmental processes but also in regenerative processes in adult tissue.

Leukemia inhibitory factor induces multi-lineage differentiation of adult stem-like cells in kidney via kidney-specific cadherin 16

Side population (SP) is reported to be a stem cell-rich population. In the presence of leukemia inhibitory factor (LIF), cultured kidney SP cells differentiated into multi-lineage in collagen gel but not in synthesized polymer that has no cell adhesion factor. In cultured kidney SP cells, gene expression of kidney-specific cadherin 16 was specifically upregulated in collagen gel but not in synthesized polymer. Moreover, decreasing cadherin 16 expression using siRNA abolished LIF-induced multi-lineage differentiation of kidney SP in collagen gel. These results indicated that LIF induced multi-lineage differentiation of adult stem-like cells in kidney via cadherin 16.

ESTABLISHMENT OF A LONG-TERM CULTURE SYSTEM FOR RAT COLON EPITHELIAL CELLS

The aim of this study was to establish a long-term culture system for rat colon epithelial cells. Colonic crypts were isolated by incubating a 4-cm-long rat colon segment cut longitudinally with an ethylenediaminetetraacetic acid [disodium salt]-containing buffer, taken up in conditioned medium from the normal rat kidney fibroblast cell line NRK (i.e., the supernatant of pure NRK cultures), directly plated on mitomycin C-treated NRK cells and subcultured with conditioned medium from NRK cells. Cells started to migrate out of the crypts shortly after plating them on NRK feeder layers. Some of the crypts fell apart during the isolation procedure, whereas the vast majority of them did it within 1 to 2 h after plating. The cells proliferated extremely slowly but continuously over a period of 4 mo and were epithelial because they expressed cytokeratin 19 and were stained by crystal violet at pH 2.8. In conclusion, the experimental system described in this study allows to maintain rat colon epithelial cells for up to 4 mo in culture and can be used to study the effects of a variety of tumor-modulating factors on growth and gene expression of normal colon epithelial cells in vitro.