Publications by authors named "Ichikawa I"

In the United States, through nation-wide discussions, the procedures for handling allegations of research misconduct are now well established. Procedures are geared toward carefully treating both complainants and respondents fairly in accordance with the US framework. Other countries, which have their own cultural and legal framework, also need fair and legally compatible procedures for conducting investigations of allegations of research misconduct.

View Article and Find Full Text PDF

In 2017, the University of Hong Kong and the University of California San Diego co-hosted the first Asian meeting of the recently formed Asia Pacific Research Integrity (APRI) network in Hong Kong. Aligned with planning meetings in 2015 and 2016 funded in part by the US Office of Research Integrity (ORI), the Hong Kong meeting was designed by a multi-national planning committee to address pressing challenges in research integrity: improving multi-national communication; exchanging information on managing misconduct investigations; and sharing best practices to promote research integrity. To create a sustainable, robust international partnership to promote research integrity in the region, the purpose of this 2017 meeting was to foster multi-national awareness, understanding, and opportunities for collaboration.

View Article and Find Full Text PDF

People with autism spectrum disorder (ASD) frequently show the symptoms of oversensitivity to sound (hyperacusis). Although the previous studies have investigated methods for quantifying hyperacusis in ASD, appropriate physiological signs for quantifying hyperacusis in ASD remain poorly understood. Here, we investigated the relationship of loudness tolerance with the threshold of the stapedial reflex and with contralateral suppression of the distortion product otoacoustic emissions, which has been suggested to be related to hyperacusis in people without ASD.

View Article and Find Full Text PDF

Immunoglobulin A nephropathy (IgAN) is the most common form of primary glomerulonephritis in many parts of the world. Although previous genome-wide association studies (GWAS) identified the major susceptibility loci for IgAN, the causal genes currently remain unknown. We performed a GWAS using 23 465 microsatellite (MS) markers to identify genes related to IgAN in a Japanese population.

View Article and Find Full Text PDF

The renal tissue renin-angiotensin system is activated in chronic kidney diseases. We previously demonstrated that intrarenal ANG II is synthesized primarily from liver-derived angiotensinogen filtered through the glomerulus and that podocyte injury increases the passage of angiotensinogen into the tubular lumen and generation of ANG II. In the present study, we tested the effect of cessation of glomerular filtration by ureteral obstruction on renal ANG II generation in kidneys with podocyte injury under two experimental conditions.

View Article and Find Full Text PDF

Background/aims: TSPAN8 encoding tetraspanin-8 was identified as a candidate gene for immunoglobulin A nephropathy (IgAN) by a genome-wide association study using microsatellites in the Japanese population. Tetraspanin-8 is a cell surface protein that contributes to the migration and invasion of epithelial cells.

Methods: We performed immunohistochemistry for tetraspanin-8 on human renal biopsy specimens associated with IgAN, antineutrophil cytoplasmic antibody-associated nephropathy and interstitial nephritis, as well as normal renal tissue.

View Article and Find Full Text PDF

Background: Recent studies have reported that podocytes are postnatally generated from progenitor cells localized in Bowman's capsule or in the bone marrow. In the present study, we investigated whether or not podocyte regeneration is important in the repair of injured glomeruli after mild podocyte injury in mice.

Methods: Mild podocyte injury was induced in NEP25 mice (n = 8) by injecting an immunotoxin, LMB2 (0.

View Article and Find Full Text PDF

Intrarenal angiotensin II is increased in kidney diseases independently of plasma angiotensin II and is thought to promote progressive deterioration of renal architecture. Here we investigated the mechanism of enhanced renal angiotensin II generation in kidney glomerular diseases. For this, kidney- or liver-specific angiotensinogen gene (Agt) knockout was superimposed on the mouse model of inducible podocyte injury (NEP25).

View Article and Find Full Text PDF

Background: Mice carrying the null-mutated Foxc1 gene frequently develop an anomalous double collecting system. These mice provide an ideal opportunity to specify the role of ectopic budding in the development of congenital anomalies of the kidney and urinary tract.

Methods: Tissue specimens were collected from Foxc1(ch/ch) mutants at several embryonic stages and at birth.

View Article and Find Full Text PDF

Background: Regression is an important process in the normal development of many organs. In this study, we investigated whether glomerular regression occurs after normal glomerulogenesis and determined the time course for this process.

Methods: Glomerular number was analyzed in normal mouse kidneys at postnatal day (P)7, P10, P14, P18, P21, P25, and P28 by the gold standard fractionator/dissector method, which involves exhausting the kidney tissue.

View Article and Find Full Text PDF

Angiotensin II content in the kidney is much higher than in the plasma, and it increases more in kidney diseases through an uncertain mechanism. Because the kidney abundantly expresses angiotensinogen mRNA, transcriptional dysregulation of angiotensinogen within the kidney is one potential cause of increased renal angiotensin II in the setting of disease. Here, we observed that kidney-specific angiotensinogen knockout mice had levels of renal angiotensinogen protein and angiotensin II that were similar to those levels of control mice.

View Article and Find Full Text PDF

Background: We previously showed that angiotensin type 1 receptor (AT1) blocker (ARB) attenuates glomerular injury in Nphs1-hCD25 (NEP25) transgenic mice, a model of selective podocyte injury. However, subsequent studies in NEP25 mice with podocyte-specific deficiency of AT1 revealed that the protective effects of ARB are not through the podocyte AT1, thereby raising the possibility that the protective effects of ARB involve mineralocorticoids.

Methods: NEP25 mice were treated with the mineralocorticoid receptor blocker (MRB) spironolactone (25 mg/kg/day, n = 10), the ARB losartan (250 mg/kg/day, n = 11), both (ARB+MRB, n = 8) or vehicle (Vehicle, n = 9) from day -7 to day 9 of induction of podocyte injury.

View Article and Find Full Text PDF

Background: Angiotensin I-converting enzyme inhibitors and angiotensin receptor blockers protect podocytes more effectively than other anti-hypertensive drugs. Transgenic rats overexpressing angiotensin II Type 1 (AT1) receptor selectively in podocytes have been shown to develop glomerulosclerosis. The prevailing hypothesis is that angiotensin II has a capacity of directly acting on the AT1 receptor of podocytes to induce injury.

View Article and Find Full Text PDF

Objective: Angiotensin II is a major determinant of atherosclerosis. Although macrophages are the most abundant cells in atherosclerotic plaques and express angiotensin II type 1 receptor (AT1), the pathophysiologic role of macrophage AT1 in atherogenesis remains uncertain. We examined the contribution of macrophage AT1 to accelerated atherosclerosis in an angiotensin II-responsive setting induced by uninephrectomy (UNx).

View Article and Find Full Text PDF

Loss of podocytes promotes glomerulosclerosis, but whether this results from a continued primary insult or a secondary mechanism triggered by the initial loss of podocytes is unknown. We generated chimeric mice in which only a subpopulation of podocytes expressed hCD25, which is the receptor for the immunotoxin LMB2. In addition, genetic labeling of hCD25-negative cells with human placental alkaline phosphatase allowed the study of these two distinct podocyte populations.

View Article and Find Full Text PDF

Our previous studies using puromycin aminonucleoside (PAN) established that podocyte damage leads to glomerular growth arrest during development and glomerulosclerosis later in life. This study examined the potential benefit of maintaining podocyte-derived VEGF in podocyte defense and survival after PAN injury using conditional transgenic podocytes and mice, in which human VEGF-A (hVEGF) transgene expression is controlled by tetracycline responsive element (TRE) promoter and reverse tetracycline transactivator (rtTA) in podocytes. In vitro experiments used primary cultured podocytes harvested from mice carrying podocin-rtTA and TRE-hVEGF transgenes, in which hVEGF can be induced selectively.

View Article and Find Full Text PDF

Background: Accelerated atherosclerosis and increased cardiovascular events are not only more common in chronic kidney disease (CKD) but are more resistant to therapeutic interventions effective in the general population. The oral charcoal adsorbent, AST-120, currently used to delay start of dialysis, reduces circulating and tissue uremic toxins, which may contribute to vasculopathy, including atherosclerosis. We, therefore, investigated whether AST-120 affects CKD-induced atherosclerosis.

View Article and Find Full Text PDF

Urine outflow obstruction activates a variety of profibrotic factors, including the intrarenal renin-angiotensin system. However, the obstruction also nullifies the transmural hydraulic pressure difference across the glomerular capillary wall, an established inducer of glomerulosclerosis. In the present study, we investigated whether, and by what mechanism, urine outflow obstruction affects the process of progressive glomerulosclerosis.

View Article and Find Full Text PDF

In the present study, we tested the hypothesis that the renoprotective effect of an angiotensin receptor blocker depends on the angiotensin II type 1 (AT(1)) receptor on podocytes. For this purpose, we generated podocyte-specific knockout mice for the AT(1) gene (Agtr1a) and crossed with NEP25, in which selective podocyte injury can be induced by immunotoxin, anti-Tac(Fv)-PE38. Four weeks after the addition of anti-Tac(Fv)-PE38, urinary albumin:creatinine ratio was not attenuated in Agtr1a knockout/NEP25 mice (n=18) compared with that in control NEP25 mice (n=13; 8.

View Article and Find Full Text PDF

Background: Composition of nonselective proteinuria includes several endogenous ligands of Toll-like receptors (TLRs) not normally present in Bowman's space, thus raising the possibility that TLRs are involved in proteinuria-mediated podocyte injury.

Methods: Kidneys of NEP25 mice, a model of glomerular sclerosis induced by podocyte-specific injury, were immunohistochemically evaluated for the presence of fibrin/fibrinogen, which are potent ligands for TLRs. A podocyte cell line was treated with fibrinogen or lipopolysaccharides and examined for expression of cytokines.

View Article and Find Full Text PDF

Objective: Patients with chronic kidney disease (CKD) have the highest risk for atherosclerotic cardiovascular disease (CVD). Current interventions have been insufficiently effective in lessening excess incidence and mortality from CVD in CKD patients versus other high-risk groups. The mechanisms underlying the heightened risk remain obscure but may relate to differences in CKD-induced atherogenesis, including perturbation of macrophage cholesterol trafficking.

View Article and Find Full Text PDF

Focal segmental glomerulosclerosis (FSGS) is a progressive renal disease, and the glomerular visceral cell hyperplasia typically observed in cellular/collapsing FSGS is an important pathological factor in disease progression. However, the cellular features that promote FSGS currently remain obscure. To determine both the origin and phenotypic alterations in hyperplastic cells in cellular/collapsing FSGS, the present study used a previously described FSGS model in p21-deficient mice with visceral cell hyperplasia and identified the podocyte lineage by genetic tagging.

View Article and Find Full Text PDF

Glomerular visceral epithelial cells (podocytes) contain interdigitated processes that form specialized intercellular junctions, termed slit diaphragms, which provide a selective filtration barrier in the renal glomerulus. Analyses of disease-causing mutations in familial nephrotic syndromes and targeted mutagenesis in mice have revealed critical roles of several proteins in the assembly of slit diaphragms. The nephrin-podocin complex is the main constituent of slit diaphragms.

View Article and Find Full Text PDF