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IntroductionEpidemiological studies have shown that patients who recovered from acute kidney injury (AKI) may subsequently develop chronic kidney disease (CKD). AKI is primarily caused by renal hypoxia, and it causes epigenetic alterations, known as hypoxic memory. 3-Deazaneplanocin A (Dznep), an inhibitor of histone modification, suppresses renal fibrosis and the expression of tissue inhibitor of metalloproteinases-2 (TIMP2), a profibrotic factor, in mouse ischemia–reperfusion models. The current study investigated the epigenetic regulation of TIMP2 in tubular cells.Methods and ResultsThe expression of TIMP2 was upregulated in human kidney 2 cells under hypoxic conditions and was suppressed by Dznep. ChIP-qPCR showed that Dznep reduced the expression of H3K4me3 at the promoter region of the TIMP2 gene under hypoxic condition. Formaldehyde-assisted isolation of regulatory elements-qPCR of the TIMP2 gene showed that Dznep reduced open chromatin area. In addition, based on ChIP-qPCR of hypoxia-inducible factor 1 alpha (HIF1α), Dznep inhibited the binding of HIF1α to the TIMP2 gene under hypoxic conditions.ConclusionDznep suppresses the expression of TIMP2 under hypoxic conditions by altering the histone methylations of the TIMP2 gene, decreasing open chromatin area, and inhibiting the binding of HIF1α to the TIMP2 gene.

Diabetic kidney disease (DKD) is the major cause of end-stage kidney disease. However, only renin-angiotensin system inhibitor with multidisciplinary treatments is effective for DKD. In 2019, sodium-glucose cotransporter 2 (SGLT2) inhibitor showed effica cy against DKD in Canagliflozin and Renal Events in Diabetes with Established Nephropathy Clinical Evaluation (CREDENCE) trial, adding a new treatment option. However, the progression of DKD has not been completely controlled. The patients with transient exposure to hyperglycemia develop diabetic complications, including DKD, even after normalization of their blood glu cose. Temporary hyperglycemia causes advanced glycation end product (AGE) accumulations and epigenetic changes as meta bolic memory. The drugs that improve metabolic memory are awaited, and AGE inhibitors and histone modification inhibitors are the focus of clinical and basic research. In addition, incretin-related drugs showed a renoprotective ability in many clinical tri als, and these trials with renal outcome as their primary endpoint are currently ongoing. Hypoxia-inducible factor prolyl hydrox ylase inhibitors recently approved for renal anemia may be renoprotective since they improve tubulointerstitial hypoxia. Further more, NF-E2-related factor 2 activators improved the glomerular filtration rate of DKD patients in Bardoxolone Methyl Treat ment: Renal Function in chronic kidney disease/Type 2 Diabetes (BEAM) trial and Phase II Study of Bardoxolone Methyl in Pa tients with Chronic Kidney Disease and Type 2 Diabetes (TSUBAKI) trial. Thus, following SGLT2 inhibitor, numerous novel drugs could be utilized in treating DKD. Future studies are expected to provide new insights.

A 21-year-old woman was referred to our hospital because of proteinuria and hematuria. She had occasional flank pain. A renal biopsy was performed and revealed a thin basement membrane. Therefore, she was diagnosed with thin basement membrane disease. However, the frequency of her flank pain increased. Since her left kidney was slightly larger than the right, nutcracker syndrome (NCS) was suspected. Renal vein ultrasonography and venography were performed, and NCS was confirmed. Her hematuria was multifactorial, and NCS can go unnoticed if there is a comorbidity that also causes hematuria.

Renal tubulointerstitial hypoxia is recognized as a final common pathway of chronic kidney disease and is considered a promising drug target. However, hypoxia in the tubules is not well examined because of limited detection methods. Here, we devised a method to visualize renal tubular oxygen tension with spatial resolution at a cellular level using the cell-penetrating phosphorescent probe, BTPDM1 (an iridium-based cationic lipophilic dye), and confocal phosphorescence lifetime imaging microscopy to precisely assess renal hypoxia. Imaging with BTPDM1 revealed an oxygen gradient between S1 and S2 segments in mouse kidney. We also demonstrated that our microscopy system can detect subtle changes of hypoxemia and reoxygenation, and the acquired phosphorescence lifetime can be converted to partial pressure of oxygen. This new method allows, for the first time, visualization of intravital oxygen gradients at the renal surface with high spatial resolution. Thus, the confocal phosphorescence lifetime imaging microscopy platform, combined with BTPDM1, will promote an accurate understanding of tissue hypoxia, including renal hypoxia.

Tubulointerstitial fibrosis has been recently reported to be caused by the collapse of the epigenetic regulation of kidney diseases. We examined whether pharmacological inhibition of histone modification is effective against renal fibrosis. DZNep (3-deazaneplanocin A) was originally developed as an anti-cancer drug to inhibit the repressive histone mark, H3K27me3. We used a model of chronic tubulointerstitial fibrosis induced by unilateral ischaemia/reperfusion and administered DZNep intravenously to the mice for 8 weeks. We found DZNep contributes to the reduction of tubulointerstitial fibrosis. We selected only tubular cells from in vivo samples using laser-capture microdissection because epigenetic regulation is specific to the cell types, and we focused on the changes in the tubular cells. We performed a genome-wide analysis of tubular cells using high-throughput sequencing (RNA-seq) to identify novel epigenetic factors associated with renal fibrosis. We found that pro-fibrotic genes such as COL3A1 (collagen type 3a1) and TIMP2 (tissue inhibitor of metalloproteinase 2) were suppressed by DZNep in vivo. In addition, pro-fibrotic genes such as COL4A1 (collagen type 4a1), TIMP2 and MMP14 were down-regulated by DZNep in vitro. In conclusion, we found that pharmacological epigenetic modification by DZNep decreased the expression levels of fibrogenic genes in tubular cells and inhibited tubulointerstitial fibrosis.

Kidney aging is a multifactorial process. Using genome-wide database analysis, Rowland et al. identified testis-specific Y-encoded–like protein 5 as a candidate age-related renal gene, and reported that with aging, testis-specific Y-encoded–like protein 5 expression decreases in response to increased testis-specific Y-encoded–like protein 5 promoter methylation. Genome-wide databases are readily available, and we should carefully analyze them to find a mechanism to fight kidney aging on the experiments using cells and animals, not just in silico calculations.

Acute kidney injury (AKI) was previously thought to be a merely transient event; however, recent epidemiological evidence supports the existence of a causal relationship between AKI episodes and subsequent progression to chronic kidney disease (CKD). Although the pathophysiology of this AKI-to-CKD transition is not fully understood, it is mediated by the interplay among multiple components of the kidney including tubular epithelial cells, endothelial cells, pericytes, inflammatory cells, and myofibroblasts. Epigenetic alterations including histone modification, DNA methylation, non-coding RNAs, and chromatin conformational changes, are also expected to be largely involved in the pathophysiology as a “memory” of the initial injury that can persist and predispose to chronic progression of fibrosis. Each epigenetic modification has a great potential as a therapeutic target of AKI-to-CKD transition; timely and target-specific epigenetic interventions to the various temporal stages of AKI-to-CKD transition will be the key to future therapeutic applications in clinical practice. This review elaborates on the latest knowledge of each mechanism and the currently available therapeutic agents that target epigenetic modification in the context of AKI-to-CKD transition. Further studies will elucidate more detailed mechanisms and novel therapeutic targets of AKI-to-CKD transition.

Chronic kidney disease presents a complex and distinct pathological landscape in men and women, yet this difference is poorly understood. microRNAs are powerful molecular regulators of pathophysiology in the kidney and other organs. We previously reported a significant upregulation of miR-146b-5p in the 5/6 nephrectomy rat model of chronic kidney disease. Here we investigated the sex-specific contribution of miR-146b-5p to renocardiac pathology by generating a novel miR-146b(−/−) rat and characterized the expression of miR-146b-5p in both wild-type and knockout animals. The 5/6 nephrectomy or sham surgery was performed on rats of each genotype and sex. Renal pathology was examined through gross histology, plasma and urinary analysis of electrolytes and metabolites, and by chronic blood pressure monitoring. Cardiac pathology was monitored via echocardiography and pressure-volume analysis. The miR-146b(−/−) rats show functional knockout of miR-146b-5p in both the kidney and heart. While 5/6 nephrectomy induced tissue hypertrophy, miR-146b(−/−) female rats displayed exacerbated renal hypertrophy. Additionally, miR-146b(−/−) female rats exhibited a marked elevation of renal fibrosis and significant renal dysfunction yet lower blood pressure and less pronounced cardiac remodeling. These phenotypic differences were not exhibited in miR-146b(−/−) male rats. Ovariectomy ameliorated renal pathology and abolished genotypic differences. In vitro examination of transforming growth factor-β signaling in combination with miR-146b-5p manipulation supports a role for miR-146b-5p in mediating the protective benefit of estrogen from renal pathologies. Thus, our data highlight an important role of miR-146b-5p in modulating kidney disease progression and provide new avenues for the study of sex-specific pathology

The number of patients with kidney failure has increased in recent years. Different factors contribute to the progression of chronic kidney disease, including glomerular sclerosis, atherosclerosis of the renal arteries and tubulointerstitial fibrosis. Tubulointerstitial injury is induced by hypoxia and other inflammatory signals, leading to fibroblast activation. Technological advances using high-throughput sequencing has enabled the determination ofthe expression profile of almost all genes, revealing that gene expression is intricately regulated by DNA methylation, histone modification, changes in chromosome conformation, long non-coding RNAs and microRNAs. These epigenetic modifications are stored as cellular epigenetic memory. Epigenetic memory leads to adult-onset disease or ageing in the long term and may possibley play an important role in the kidney disease process. Herein we emphasize the importance of clarifying the molecular mechanisms underlying epigenetic modifications because this may lead to the development of new therapeutic targets in kidney disease. This article is protected by copyright. All rights reserved.

Background: Kidney injury, including chronic kidney disease and acute kidney injury, is a worldwide health problem. Hypoxia and transforming growth factor-β (TGF-β) are well-known factors that promote kidney injury. Hypoxia-inducible factor (HIF) and SMAD3 are their main downstream transcriptional factors. Hypoxia-HIF pathway and TGF-β/SMAD3 pathway play a crucial role in the progression of kidney injury. However, reports on their interactions are limited, and the global transcriptional regulation under their control is almost unknown. Methods: Kidney tubular epithelial cells were cultured and stimulated by hypoxia and TGF-β. We detected global binding sites of HIF-1α and SMAD3 in cells using chromatin immunoprecipitation-sequencing (ChIP-Seq), and measured the gene expression using RNA-sequencing (RNA-Seq). ChIP-quantitative PCR (qPCR) was used to quantitatively evaluate bindings of SMAD3. Results: ChIP-Seq revealed that 2,065 and 5,003 sites were bound by HIF-1α and SMAD3, respectively, with 614 sites co-occupied by both factors. RNA-Seq showed that hypoxia and TGF-β stimulation causes synergistic upregulation of 249 genes, including collagen type I alpha 1 (COL1A1) and serpin peptidase inhibitor, clade E, member 1, which are well-known to be involved in fibrosis. Ontology of the 249 genes implied that the interaction of HIF-1α and SMAD3 is related to biological processes such as fibrosis. ChIP-qPCR of SMAD3 at HIF-1α binding sites near COL1A1 and SERPINE1 indicated that HIF-1α promotes the bindings of SMAD3, which is induced by TGF-β. Conclusions: These findings suggest that HIF-1α induced by hypoxia activates the TGF-β/SMAD3 pathway. This mechanism may promote kidney injury, especially by upregulating genes related to fibrosis.

Renal anemia is caused by the deficiency of endogenous erythropoietin (Epo) due to renal dysfunction. We think that it is possible to slow the progression of chronic kidney disease (CKD) in case we initiate Epo early in pre-dialysis patients, especially in the non-diabetic population. Erythropoiesis stimulating agent (ESA) treatments targeting mild anemia (10-12 g/dl) can decrease the risk of occurrence of cardiovascular disease (CVD) in patients with hypertension, diabetes mellitus and congestive heart failure. As the large randomized controlled trials such as Cardiovascular Risk Reduction by Early Anemia Treatment with Epoetin Beta, Correction of Hemoglobin and Outcomes in Renal Insufficiency and Trial to Reduce Cardiovascular Events with Aranesp Thearpy in the Western countries suggested, we do not recommend high doses of ESA to achieve the target hemoglobin (Hb) level. The target Hb of >13 g/dl might lead to increase in the risk of CVD although maintaining a high Hb of >12 g/dl without ESA is not harmful for CKD patients. It is desirable to determine the target Hb in dialysis patients depending on their ages. Renal anemia should be monitored constantly to start ESA and iron replacement therapy at an appropriate time, while avoiding their excess in order to minimize the occurrence of CVD and other complications. Taken all the international guidelines and our clinical experiences together, we should consider administration of ESA when the Hb level becomes

Previously acute kidney injury (AKI) had been believed to be a transient event, and recovery from AKI had been thought to lead to no consequences. However, recent epidemiological studies have shown that even if there is complete recovery of the kidney function, AKI can eventually result in chronic kidney disease (CKD) and eventually in end-stage kidney disease in the long term. Transition of AKI to CKD is mediated by multiple mechanisms, including aberrant cell cycle arrest and hypoxia. Hypoxia of the kidney is induced by rarefaction of the peritubular capillaries after AKI episodes, and induces inflammation and fibrosis. It should also be noted that epigenetic changes are closely related to hypoxia, and epigenetic changes induced by hypoxia, called “hypoxic memory” can explain the AKI-to-CKD transition in the long term after complete recovery from the initial AKI episode. Targeting hypoxia and subsequent epigenetic changes are promising strategies to block the transition from AKI to CKD.

Chronic tubulointerstitial hypoxia plays an important role as the final common pathway to end‐stage renal disease. HIF‐1 (hypoxia‐inducible factor‐1) is a master transcriptional factor under hypoxia, regulating downstream target genes. Genome‐wide analysis of HIF‐1 binding sites using high‐throughput sequencers has clarified various kinds of downstream targets and made it possible to demonstrate the novel roles of HIF‐1. Our aim of this study is to identify novel HIF‐1 downstream epigenetic targets which may play important roles in the kidney. Immortalized tubular cell lines (HK2; human kidney‐2) and primary cultured cells (RPTEC; renal proximal tubular cell lines) were exposed to 1% hypoxia for 24–72 h. We performed RNA‐seq to clarify the expression of mRNA and long non‐coding RNA (lncRNA). We also examined ChIP‐seq to identify HIF‐1 binding sites under hypoxia. RNA‐seq identified 44 lncRNAs which are up‐regulated under hypoxic condition in both cells. ChIP‐seq analysis demonstrated that HIF‐1 also binds to the lncRNAs under hypoxia. The expression of novel lncRNA, DARS‐AS1 (aspartyl‐tRNA synthetase anti‐sense 1), is up‐regulated only under hypoxia and HIF‐1 binds to its promoter region, which includes two hypoxia‐responsive elements. Its expression is also up‐regulated with cobalt chloride exposure, while it is not under hypoxia when HIF‐1 is knocked down by siRNA. To clarify the biological roles of DARS‐AS1, we measured the activity of caspase 3/7 using anti‐sense oligo of DARS‐AS1. Knockdown of DARS‐AS1 deteriorated apoptotic cell death. In conclusion, we identified the novel lncRNAs regulated by HIF‐1 under hypoxia and clarified that DARS‐AS1 plays an important role in inhibiting apoptotic cell death in renal tubular cells.

Chronic kidney disease (CKD) is placing an increasing burden on patients and societies because no decisive therapy has been established. Tubulointerstitial lesions accompanied by fibrosis, inflammatory cells, and capillary rarefaction not only characterize, but also aggravate renal dysfunction in CKD. In this setting, renal cells, particularly tubular cells, suffer from hypoxia caused by the imbalance of blood perfusion and oxygen demand despite their adaptive responses represented by upregulation of hypoxia-inducible factors (HIFs). Fibrosis is a pathological state characterized by excess extracellular matrix (ECM) deposition, which is also a hallmark and causative factor of many chronic diseases including CKD. Recent studies have suggested that the dominant origin of ECM-producing myofibroblasts (MFs) may be pericytes, which are indispensable cells for maintaining proper capillary functions, as they wrap capillaries and stabilize them through a fine-tuned interplay with endothelial cells. During fibrosis, pericytes are activated and detach from capillaries before conversion into MFs, which compromises capillaries and worsens hypoxia. We also discuss how hypoxia and HIFs affect fibrogenesis. Given that hypoxia is caused by insufficient angiogenesis and that fibrosis results from pericyte loss, restoration of pericytes should be an intriguing target for overcoming both hypoxia and fibrosis. We propose the deactivation of MFs to recover lost pericytes as a promising therapy for CKD.

MicroRNA (miR) are small noncoding RNA molecules that regulate gene expression and play important roles during kidney development, homeostasis, and disease. Novel contributions to the field of cell death, cell cycle, and miR regulation in the kidney have come from the Laboratory of Dong, and in the

Aim: In end-stage renal disease (ESRD) patients, left ventricular hypertrophy (LVH) is common and a risk for cardiovascular events. LVH is geometrically classified into two major groups, concentric and eccentric, and accumulating evidence suggests eccentric LVH has a more negative effect than concentric LVH on ESRD outcome. However, there have been very few studies on the cardiac findings from ESRD patient autopsy in which the relationship between LVH geometry and mortality was analyzed. Methods: An observational study was performed with the autopsy findings in 30 haemodialysis patient cases between 2001 and 2006 at Mitsui Memorial Hospital, Tokyo. Between those who died of a cardiovascular cause and those who died of non-cardiovascular causes, we compared the heart/bodyweight ratio, left ventricular dilatation, and the extent of fibrosis of the left ventricle. Results: Heart/bodyweight ratio was significantly higher (P

70歳，男性．糖尿病性腎症を原疾患とし，15年の透析歴がある．1995年頃から下血を主訴に他院で消化管精査行うも出血源特定できず．AB型Rh(－）と特殊な血液型のため製剤入手に苦慮した．精査加療目的で2006年6月当院初診．小腸内視鏡上，Treitz靭帯を越えて3mの部分の拍動性の出血性病変に対してAPC焼灼とクリップで止血を行った．その後も2006年11月，2007年8月，9月に同様のエピソードがあり，内視鏡上，別部位に出血を認めたが，同様の処置を行い止血が可能であった．本例では，頻回の再発を認め，また入手困難な血液型であったため治療に苦慮したが，小腸内視鏡による止血を得た．ESRD患者は消化管出血の頻度が高く，上部下部内視鏡上，出血源が特定できず診断，治療が困難なことも多い．小腸内視鏡はこうした例でも開腹術を行わずに止血が得られ，有効な手段である．

血液透析に不可欠のバスキュラーアクセスの必要条件は，安定した血液透析が可能で，心負荷の点で患者のQOLを損なわないことである．今回，血液透析導入時のバスキュラーアクセス選択について背景因子を検討した．2003年と2004年に当院で血液透析導入した94名において，プライマリーアクセスとして動静脈内シャント（以下AVF）は79例（85％）であった．AVF以外の15例は，心機能低下（10例），動静脈の問題（8例）のいずれかまたは両者を有していた．動脈表在化を選択した低心機能の患者は比較的長期にわたり安定した維持透析が可能であった．また，長期型バスキュラーカテーテルを選択した4例は心機能低下のほか，麻酔の侵襲が危惧される全身状態不良例であった．長期型バスキュラーカテーテル4例はいずれも，1～29か月で死亡していたが，その原因は感染ではなく，すべて原病の増悪あるいは突然死であった．アクセス選択に影響する患者因子は心機能，動脈硬化症の進行，前腕静脈の荒廃，加齢であった．

Hypoxia appears to have an important role in pathological conditions in many organs such as kidney; however, a method to quantify intracellular oxygen tension in vivo has not been well established. In this study, we established an optical method to quantify oxygen tension in mice kidneys using a cationic lipophilic phosphorescence probe, BTPDM1, which has an intracellular oxygen concentration-sensitive phosphorescence lifetime. Since this probe is distributed inside the tubular cells of the mice kidney, we succeeded in detecting acute renal hypoxic conditions and chronic kidney disease. This technique enabled us to estimate intracellular partial pressures of oxygen in vivo by extrapolating the calibration curve generated from cultured tubular cells. Since intracellular oxygen tension is directly related to cellular hypoxic reactions, such as the activation of hypoxia-inducible factors, our method will shed new light on hypoxia research in vivo.

Epigenetic mechanisms have been the focus of intensive research. De Marinis et al. demonstrated that high glucose levels exert stimulatory effects on activation histone marks, leading to the upregulation of thioredoxin-interacting protein ( TXNIP ) gene expression, which is proinflammatory. They also showed that the effect was reversed by the inhibition of histone acetyltransferase, suggesting a new therapeutic approach for improving diabetic kidney disease. Epigenetic changes are memorized as epigenetic memory that could exacerbate diabetic complications.

Patients with advanced chronic kidney disease are exposed to uremic toxins. In addition to causing uremic symptoms, uremic toxins accelerate the progression of renal failure. Indoxyl sulfate (IS) increases oxygen consumption in tubules, aggravating hypoxia of the kidney, and progression of the kidney disease. IS also induces endoplasmic reticulum stress and thereby contributes the progression of cellular damages in tubular epithelial cells. Hypoxia-inducible factor (HIF) is a master transcriptional regulator of adaptive responses against hypoxia and regulates expression of erythropoietin (EPO). IS suppresses EPO expression via HIF-dependent and HIF-independent manner. IS impedes the recruitment of transcriptional coactivators to HIF via upregulation of Cbp/p300-interacting transactivator with Glu/Asp-rich carboxy-terminal domain 2 through a mechanism of posttranscriptional messenger RNA stabilization. Furthermore, IS induces activating transcription factor 4 via endoplasmic reticulum stress, decreasing EPO expression. Although erythropoiesis-stimulating agent (ESA) resistance is generally defined as lack of responses to exogenous ESA administration, suppression of endogenous production of EPO under uremic conditions may aggravate ESA resistance. Uremia is associated with increased formation of advanced glycation end products (AGE). Studies of transgenic rats overexpressing glyoxalse 1 (GLO1), which detoxifies precursors of advanced glycation end products, demonstrated that glycative stress causes renal senescence and vascular endothelial dysfunction. Glycative stress also suppresses HIF activation making the kidney susceptible to hypoxia as a final common pathway to end-stage kidney disease.

Renal endothelin-converting enzyme (ECE)-1 is induced in experimental diabetes and following radiocontrast administration, conditions characterized by renal hypoxia, hypoxia-inducible factor (HIF) stabilization, and enhanced endothelin synthesis. Here we tested whether ECE-1 might be a HIF-target gene in vitro and in vivo. ECE-1 transcription and expression increased in cultured vascular endothelial and proximal tubular cell lines, subject to hypoxia, to mimosine or cobalt chloride. These interventions are known to stabilize HIF signaling by inhibition of HIF-prolyl hydroxylases. In rats, HIF-prolyl-hydroxylase inhibition by mimosine or FG-4497 increased HIF-1α immunostaining in renal tubules, principally in distal nephron segments. This was associated with markedly enhanced ECE-1 protein expression, predominantly in the renal medulla. A progressive and dramatic increase in ECE-1 immunostaining over time, in parallel with enhanced HIF expression, was also noted in conditional von Hippel-Lindau knockout mice. Since HIF and STAT3 are cross-stimulated, we triggered HIF expression by STAT3 activation in mice, transfected by or injected with a chimeric IL-6/IL-6-receptor protein, and found a similar pattern of enhanced ECE-1 expression. Chromatin immunoprecipitation sequence (ChIP-seq) and PCR analysis in hypoxic endothelial cells identified HIF binding at the ECE-1 promoter and intron regions. Thus, our findings suggest that ECE-1 may be a novel HIF-target gene.

Increasing evidence has demonstrated that chronic hypoxia in the tubulointerstitium results in irreversible chronic kidney diseases. Hypoxia inducible factor (HIF) is a transcriptional master regulator which takes control of gene expressions under hypoxia. Recently, HIF1 has been reported to organize a cluster of histone-modifying enzymes by binding to their promoter regions in various kinds of cell line. In order to clarify the epigenetic molecular mechanisms by HIF1, we examined the genome-wide analysis of HIF1-binding sites (ChIP-seq) in endothelial cells and HIF1 downstream target genes using DNA microarrays. ChIP-seq results demonstrated that HIF1 binds to the enhancer regions in addition to the promoter regions. We clarified that one of the HIF1 downstream genes, SLC2A3 (solute-carrier family 2A3, also known as glucose transporter 3: GLUT3), is regulated by changing chromosomal conformations under hypoxia via a cooperative combination of HIF1 and KDM3A(lysine(K) specific demethylase 3A), one of the histone demethylases. KDM3A is recruited to the SLC2A3 loci in an HIF1-dependent manner and demethylates histone repressive mark, H3K9me2, up-regulating its expression. In addition, we confirmed the interactions of HIF1 and KDM3A only under hypoxia using co-immunoprecipitation. These experimental results showed novel HIF1-dependent molecular mechanisms from an epigenetic viewpoint. It is important to elucidate the epigenetic mechanisms of chronic hypoxia in order to identify novel therapeutic approaches against chronic kidney disease.

Patients with long dialysis vintage have low cardiac output for various reasons. Although kidney transplantation is known to improve cardiac mortality, patients are sometimes evaluated as contraindicated for transplantation because of cardiac risk. We successfully performed kidney transplantation for a patient with a long dialysis vintage and dilated cardiomyopathy. Sequential (123)I-metaiodobenzylguanidine ((123)I-MIBG) scintigraphy suggested that amelioration of uraemia improved cardiac function. Kidney transplantation for patients with severely impaired cardiac function is safe and effective under careful perioperative monitoring irrespective of dialysis vintage. Sequential (123)I-MIBG scintigraphy can be used as an evaluation tool for the improvement in cardiac function.

Background: Although pegylated interferon (PEG-IFN) is now the standard treatment for chronic hepatitis C, there are few reports targeting dialysis patients and treatment protocol for hepatitis C virus (HCV) infection has not been determined, particularly in patients on peritoneal dialysis. Case: A 34-year-old woman with chronic hepatitis C started peritoneal dialysis because of progressive renal disease 2 years after peripheral blood stem cell transplantation for aplastic anaemia. The regimen was a single 6-h dwell of 2L glucose dialysate. Considering that her HCV genotype was 2a and that she was a candidate for cadaveric kidney transplant, we decided to treat her with PEG-IFN alpha-2a monotherapy 1 year after the beginning of peritoneal dialysis. We adopted a dose escalation strategy to minimize the total amount of PEG-IFN administration, thereby reducing the risk of adverse effects. Her HCV-RNA disappeared at the 17th week and sustained virus response was achieved thereafter. Only minor side effects were observed including flu-like symptoms and mild anaemia, and residual renal function remained stable during the treatment of 48 weeks (renal Kt/V; from 1.28 to 1.26). Conclusion: PEG-IFN monotherapy with dose modification may be a safe and effective treatment for HCV infection in patients undergoing peritoneal dialysis.

Hypoxia-inducible factor (HIF) is a transcriptional master regulator that takes control of the gene expressions under hypoxia. Several lines of evidence have shown that chronic hypoxia in tubulointerstitium results in irreversible renal disease. Recently, HIF1 was reported to organize a cluster of histone-modifying enzymes by binding to their promoter regions in various kinds of cell lines. However, its function in renal disease remains largely unknown. We focused on the epigenetic regulation on the progression of chronic kidney disease and have reviewed the latest knowledge in this area with special emphasis on the involvement of HIF. For example, a set of HIF1 downstream target genes also were reported to be regulated by cooperative combination of HIF1 and histone demethylase. We suggest a novel epigenetic pathway that affects the final common pathway to end-stage renal disease in addition to the tubulointerstitial hypoxia. We emphasize the importance of figuring out the epigenetic mechanisms of renal failure to find the novel therapeutic approach of chronic kidney disease.

Hypoxia plays a crucial role in many pathophysiological conditions, including cancer biology, and hypoxia-inducible factor (HIF) regulates transcriptional responses under hypoxia. To elucidate the cellular responses to hypoxia, we performed chromatin immunoprecipitation with deep sequencing in combination with microarray analysis and identified HIF-1 targets. We focused on one of the novel targets, sperm-associated antigen 4 (SPAG4), whose function was unknown. SPAG4, an HIF-1-specific target, is up-regulated in various cultured cells under hypoxia. Examination of SPAG4 expression using a tissue microarray consisting of 190 human renal cell carcinoma (RCC) samples revealed that SPAG4 is an independent prognostic factor of cancer-specific mortality. Live-cell imaging revealed localization of SPAG4 at the intercellular bridge in telophase. We also studied cells in which SPAG4 was knocked down. Hypoxia enhances tetraploidy, which disturbs cell proliferation, and knockdown of SPAG4 increased tetraploid formation and decreased cell proliferation under both normoxic and hypoxic conditions. Studies using deletion mutants of SPAG4 also suggested the involvement of SPAG4 in cytokinesis. Microarray analysis confirmed dysregulation of cytokinesis-related genes by knockdown of SPAG4. In conclusion, SPAG4 is an independent prognostic factor in RCC and plays a crucial role in cytokinesis to defend against hypoxia-induced tetraploid formation. This defensive mechanism may promote survival of cancer cells under hypoxic conditions, thus leading to poor prognosis.

The recent and rapid advent of next-generation sequencing (NGS) has made this technology broadly available not only to researchers in various molecular and cellular biology fields but also to those in kidney disease. In this paper, we describe the usage of ChIP-seq (chromatin immunoprecipitation with sequencing) and RNA-seq for sample preparation and interpretation of raw data in the investigation of biological phenomenon in renal diseases. ChIP-seq identifies genome-wide transcriptional DNA-binding sites as well as histone modifications, which are known to regulate gene expression, in the intragenic as well as in the intergenic regions. With regard to RNA-seq, this process analyzes not only the expression level of mRNA but also splicing variants, non-coding RNA, and microRNA on a genome-wide scale. The combination of ChIP-seq and RNA-seq allows the clarification of novel transcriptional mechanisms, which have important roles in various kinds of diseases, including chronic kidney disease. The rapid development of these techniques requires an update on the latest information and methods of NGS. In this review, we highlight the merits and characteristics of ChIP-seq and RNA-seq and discuss the use of the genome-wide analysis in kidney disease.