Tadashi Kamata

Increased Frequency of Surface IgA-Positive Plasma Cells in the Intestinal Lamina Propria and Decreased IgA Excretion in Hyper IgA (HIGA) Mice, a Murine Model of IgA Nephropathy with Hyperserum IgA

Because abnormalities of mucosal immunity have been suggested in human IgA nephropathy, we examined the involvement of mucosal immunity in IgA deposition to the kidney in hyper IgA (HIGA) mice, which was established as a mouse model for human IgA nephropathy with hyperserum IgA. The number of surface IgA+B220− lymphocytes in the intestinal lamina propria (LP) of HIGA mice increased 2.7-fold at 30 wk of age as compared with those at 10 wk of age, whereas normal mice did not show such increase. The surface IgA+B220− LP lymphocytes spontaneously secreted IgA in culture. Morphological studies showed that the surface IgA+B220− lymphocytes of murine intestinal LP are identical with plasma cells (PCs). About 20% of IgA+B220− PC in LP expressed both Mac-1 and CD19, suggesting that they may derive from peritoneal B-1 cells. Cell cycle study on intestinal IgA-PCs using bromodeoxyuridine revealed no difference between HIGA mice and normal mice, suggesting that the high frequency of IgA-producing PCs in HIGA mice is not due to enhanced proliferation or prolonged survival of IgA-producing PCs in LP. In addition, IgA secretion into the gut lumen of HIGA mice decreased drastically (to one forth) with aging. These data suggest that the increased number of intestinal IgA-producing PCs and the down-regulation of IgA excretion into the intestinal lumen might synergistically contribute to the hyperserum IgA in HIGA mice and resultant IgA deposition to the kidney.

Evaluation of Markers to Estimate Volume Status in Hemodialysis Patients: Atrial Natriuretic Peptide, Inferior Vena Cava Diameter, Blood Volume Changes and Filtration Coefficients of Microvasculature

Abstract:  Relationships among five markers of volume status—cardio–thoracic ratio (CTR), atrial natriuretic peptide (ANP), inferior vena cava diameter at quiet expiration (IVCe), blood volume change (▵BV/TUF) during ultrafiltration and filtration coefficients of microvasculature (Lpst)—were investigated. Fifty stable hemodialysis patients were enrolled. The CTR was measured before hemodialysis (HD), and ultrasonic measurement of IVCe and sample collection for ANP were performed shortly after HD. Lpst and ▵BV/TUF were calculated using a CRIT‐LINE monitor. Overhydrated patients determined by each marker (OVERctr, OVERivc, OVERanp, OVERlp and OVERbv) were compared. The agreement of volume status determined by each marker was assessed by κ value, and the sensitivity and specificity of each marker to distinguish overhydrated patients were analyzed by a receiver‐operating characteristic (ROC) curve. IVCe, ANP, ▵BV/TUF and Lpst, significantly correlated with each other. The correlation coefficients of Lpst with IVCe, ANP and ▵BV/TUF were higher than the others. The κ value between ANP and Lpst was the highest. OVERanp was the highest, then OVERlp, OVERivc and OVERbv, in this order. The OVERlp and OVERivc patients were completely included in OVERanp. All patients, except one OVERbv patient, were included in OVERlp. The relatively high distinguishing ability of Lpst was demonstrated by ROC analysis. These results suggest that the determination of overhydration solely by ANP was an overestimation and by ▵BV/TUF was an underestimation. The relatively high correlation coefficients of Lpst with other markers, as well as its distinguishing ability, suggest that Lpst fluctuates in close relation to other markers.

Evaluation of estimated creatinine clearance before steady state in acute kidney injury by creatinine kinetics

BackgroundA simple method to calculate estimated creatinine clearance using two serum creatinine concentration (Cr) values in acute kidney injury (AKI) was developed (eCrCl-AKI). We aimed to evaluate its accuracy and to clarify its contribution to the classification of AKI.MethodsWe validated the errors in eCrCl-AKI in a simulation study after various reductions in creatinine clearance (CrCl) at various levels of chronic kidney disease (CKD). We compared the eCrCl-AKI-based classification of RIFLE criteria with the Cr-based classification or that proposed by Waikar and Bonventre. The regression equations of eCrCl-AKI on time were determined and Cr values were reconstructed by creatinine kinetics substituting CrCl with eCrCl-AKI in actual patients.ResultsMost errors in eCrCl-AKI were relatively small (from −13.6 to +7.9%) with the exception of two Cr values that straddled the changing trend of Cr. The classification according to RIFLE criteria based on Cr was unstable and did not enable adequate classification, especially in milder reductions of CrCl with advanced CKD. The classification based on eCrCl-AKI was stable and enabled adequate classification. There were good agreements between measured Cr and reconstructed Cr with eCrCl-AKI. The regression equations of eCrCl-AKI revealed changes of renal function that were unexpected only from fluctuations of Cr.ConclusionseCrCl-AKI can provide relatively accurate estimates for fluctuating CrCl. eCrCl-AKI enables more stable and earlier classification of AKI than Cr, at least in the simulation study. The more widespread use of eCrCl-AKI in actual clinical settings of AKI is necessary to evaluate this formula.

How Does Higher Ultrafiltration within the Conventional Clinical Range Impact the Volume Status of Hemodialysis Patients

Aims: The higher ultrafiltration (UF) induces poor outcomes. The impact of higher UF on the volume status was investigated. Methods: 60 hemodialysis (HD) patients were divided into three groups according to the ratio of total UF to post-dialysis body weight (TUF/PDW) (<3%, 3–5%, ≥5%). ANP, the ratio of extracellular water to total body water and excess fluid mass (ExF/PDW) by bioimpedance spectroscopy, inferior vena cava diameter by ultrasound were measured at the end of HD. The ratio of post-HD blood volume to pre-HD (BVpost/BVpre) and standardized filtration coefficients (Lpst) of the microvasculature in the vicinity of PDW were calculated. Results: Only Lpst and BVpost/BVpre showed significant differences among the three groups. A stepwise multiple linear regression model revealed that BVpost/BVpre was correlated with TUF/PDW, ExF/PDW and Lpst (R = 0.778, p < 0.001), independently. Conclusion: Higher UF causes decreases in BVpost/BVpre and Lpst. BVpost/BVpre was determined by TUF/PDW, ExF/PDW and Lpst.

Quantitative trait loci (QTL) analysis reveals a close linkage between the hinge region and trimeric IgA dominancy in a high IgA strain (HIGA) of ddY mice

Polymerization of IgA has been suggested as one of the causes of mesangial deposition in IgA nephropathy. HIGA mice are an inbred model of IgA nephropathy, established by selective mating of ddY mice. This strain is characterized by a unique profile of the IgA molecule that is dominantly polymeric and has high serum levels with intense IgA deposition on the mesangium. We carried out quantitative trait loci (QTL) analysis, using F2 generations by crossing HIGA with BALB/c mice. Significant linkage of polymeric IgA in serum samples was identified around D12Mit263, which is close to the gene of the immunoglobulin heavy chain on chromosome 12. The amino acid sequence of the α heavy chain revealed marked differences between BALB/c and HIGA mice. Furthermore, most differences were focussed on the hinge region. The DBA/2J strain, which has the same amino acid sequence in the hinge region as the HIGA strain, also showed polymeric IgA dominance but low IgA levels in sera. Size fraction analysis revealed that these polymeric IgA showed trimer dominance in both DBA/2J and HIGA mice. In conclusion, the hinge region plays a key role in trimeric IgA formation in HIGA mice.

Ultrastructural Localization of Dominantly Increased Fibronectin in the Markedly Thickened Glomerular Basement Membrane in a Selectively Mated Murine High IgA Strain (HIGA Mice)

To clarify which matrix component(s) contributes to glomerular sclerosis with mesangial IgA deposits in a murine high serum IgA strain (HIGA) derived from ddY mice, morphological and immunopathological analyses of glomeruli were performed in comparison with original ddY and BALB/c mice as controls. Significantly increased thickness of the glomerular basement membrane (GBM), especially the lamina densa, was observed in HIGA mice. Immunofluorescent staining showed marked increases in levels of fibronectin and laminin in both the mesangium and capillary wall in aged HIGA mice. Analysis of the distribution of immunogold-labeled antibody in GBM revealed a significant increase (p < 0.0001) and specific orientation of fibronectin in the endothelial side, which suggested that mesangial fibronectin produced at high levels due to IgA deposition extended to the endothelial side of GBM and contributed to the thickening of GBM with further development to glomerulosclerosis in the HIGA mice.

The evaluation of filtration coefficients of microvasculature for the assessment of fluid status in hemodialysis patients.

Purpose Bioimpedance spectroscopy (BIS) is widely used to assess fluid status in hemodialysis (HD) patients. Our purpose is to evaluate filtration coefficients (Lpst) as an alternative test to assess fluid status by utilizing BIS as a reference test. Methods 106 HD patients (determined group) were divided into two groups with (EX group: 53) or without excess fluid mass (ExF). ExF calculated from extracellular water and intracellular water measured by BIS. Multiple linear regression equation of Lpst was made using ExF (ExF/DW) and ultrafiltration rate (UFR/DW) to adjust Lpst (AdjLpst). The cut-off values of the tests for detection of EX were determined by receiver-operator characteristic curve analysis. Lpst, AdjLpst, serum atrial natriuretic peptide concentration (ANP), ultrasonically measured inferior vena cava diameter (IVCe/BSA), and blood volume change (ΔBV/TUF/DW) were examined. The detection abilities of these tests were evaluated in the distinct 61 patients (evaluated group). Results Patients of the EX group numbered 29 in the evaluated group. The correlation between AdjLpst and ExF/DW was the highest. The sensitivity of AdjLpst and specificity of Lpst were the highest. The specificity of AdjLpst was equivalent to that of Lpst. Unadjusted and adjusted odds ratios of AdjLpst were the higher (20.80, 95% CI, 5.61-77.10, 16.06, 95% CI 4.00-64.59, respectively) than those of the other tests. Conclusions AdjLpst can detect patients of the EX group more accurately than other tests. Because AdjLpst is related to plasma refilling, it may indicate removable fluid overload. AdjLpst in conjunction with BIS may contribute to more adequate fluid management.

Up-Regulated TGF-β mRNA Expression in Splenic T Cells of High IgA-Prone Mice: A Murine Model of IgA Nephropathy with Glomerulosclerosis

Background/Aims: Recently, we established a high serum IgA-prone inbred (HIGA) mouse strain as a murine model of spontaneous IgA nephropathy by selective mating of high serum IgA ddY mice, and found that they showed enhanced production of glomerular extracellular matrix components with increased expression of TGF-β mRNA and protein in the kidneys. In this study, we examined the roles of lymphocytes in the development of high serum IgA in this strain. Methods: We performed flow cytometric analyses of T and B cells in splenic mononuclear cells (SMNCs) from these mice using BALB/c mice as normal controls. We also compared serum TGF-β1 concentrations and TGF-β mRNA expression levels in the B-cell-depleted (T-cell-rich) fraction of SMNCs in these mice. Results: HIGA mice showed significantly fewer CD3-positive cells compared with BALB/c mice when young, but not when aged. The CD4/CD8 ratio of HIGA mice was lower than that of BALB/c mice, but this difference was not significant. Although the number of B220-positive cells did not vary significantly, the ratio of surface IgA-positive B cells was significantly increased in both young and adult HIGA mice. The B-cell-depleted SMNCs from HIGA mice exhibited higher levels of expression of TGF-β and TGF-β1 mRNA than controls from a young age, which were maintained throughout life, but there were no differences in PDGF, MCP-1 or bFGF expression between these two strains. In contrast to local mRNA expression, serum TGF-β1 concentration was decreased in HIGA mice compared with BALB/c controls. Conclusion: These findings suggest that the mating procedure performed to establish HIGA mice selected for a unique phenotype of local up-regulation of TGF-β production in the kidneys, as well as T cells that may contribute to both the early and consistently high serum IgA expression and enhanced production of renal extracellular matrix components in HIGA mice. Additionally, TGF-β1 may act locally, not systemically, in a paracrine or autocrine manner.

Direct effects of simvastatin on proliferation and matrix accumulation in cultured murine mesangial cells

AbstractBackground. 3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors have been demonstrated to suppress glomerular injuries in various renal diseases. However, it is not fully clear whether HMG-CoA reductase inhibitors directly regulate matrix protein accumulation in mesangial cells. Methods. We investigated the effect of simvastatin (SIM), an HMG-CoA reductase inhibitor, on DNA synthesis in cultured murine mesangial cells stimulated by fetal calf serum (FCS). We then determined whether SIM affected the expression of regulatory factors of cell growth and matrix protein accumulation, using Northern analysis. Results. SIM dose-dependently inhibited FCS-induced DNA synthesis after 24 h of incubation. SIM treatment for 24 h suppressed the mRNA expression of platelet-derived growth factor (PDGF)-B chain, PDGF receptor β-subunit and c-myc, while the expression of transforming growth factor β (TGF-β) was not affected. Concerning matrix protein synthesis, the mRNA expression of type IV collagen was suppressed, whereas that of type III collagen was markedly upregulated. As for matrix turnover proteins, SIM had a markedly suppressive effect on the mRNA expression of plasminogen activator inhibitor-1 (PAI-1), with a constant expression of tissue-type plasminogen activator (tPA). Conclusions. These results indicate that SIM may sup-press mesangial cell proliferation in part through the downregulation of PDGF, PDGF-receptor, and c-myc mRNA expressions. In addition, the suppression of the synthesis of collagen IV and PAI-1 appears to be a direct inhibitory effect of SIM on glomerular matrix accumulation.

Ultrasound-guided cannulation of hemodialysis access

Because hemodialysis therapy cannot be performed without the cannulation of a vascular access, establishing a well-functioning vascular access is crucial. Recently, the number of patients with difficult arteriovenous (AV) fistula cannulation has increased due to changes in the epidemiology of the dialysis population. To address this issue, indications for real-time ultrasound-guided techniques have recently been reported. This review discusses methods of ultrasound-guided cannulation of dialysis access; it is difficult to cannulate a deep, small, or stiff vessel of an AV fistula on the first attempt with static ultrasound guidance in which the ultrasound probe remains stationary. Mastering a method in which the precise location of the needle tip can be continuously identified during the insertion by dynamic probe scanning is required. To achieve this, understanding the theory of ultrasound guidance, off/on-the-job training, and a sense of professionalism are important. The use of ultrasound also enables the safe catheter placement into a collapsed central vein and repeated direct puncture of a femoral vein. The latter reduces the risk of catheter-related blood stream infection by avoiding the use of an indwelling dual-lumen catheter. In conclusion, ultrasound-guided techniques enable precise vascular cannulation, which can result in significant patient and financial impact. The accumulation of further reports is required for the method to be acknowledged as the standard to cope with difficult vascular access for dialysis. As most of the latest ultrasound machines for procedural guidance are optimized for peripheral nerve block, a compact and affordable ultrasound device with image quality focused on vascular access is also needed.