Kazuho Honda

Morphological Changes in the Peritoneal Vasculature of Patients on CAPD with Ultrafiltration Failure

Vascular changes in the peritoneum were histochemically assessed in patients on continuous ambulatory peritoneal dialysis (CAPD) with ultrafiltration failure. Light microscopy showed extensive interstitial fibrosis, mesothelial denudation and vascular changes. Morphological changes in the vasculature were observed at different levels. The specific changes in the vasculature in these patients were characterized by severe fibrosis and hyalinization of the media of venules. Immunofluorescence microscopy revealed extensive deposition of such extracellular matrices as type IV collagen and laminin in the vascular wall. Electron microscopy revealed a significant increase in collagenous fibers and degeneration of smooth muscle cells in the media. However, the endothelial cells at the levels of vasculature affected were relatively well preserved. These pathological alterations in the vasculature in CAPD patients with ultrafiltration failure suggest that certain toxic factors, such as a high osmolar dialysate or low pH of dialysate, had affected the peritoneal vasculature from the adventitial side rather than the endothelial side. These vascular changes in the peritoneum are thought to be irreversible, associated with deterioration of peritoneal function, and to cause ultrafiltration failure in the patients on long-term CAPD therapy.

Impact of uremia, diabetes, and peritoneal dialysis itself on the pathogenesis of peritoneal sclerosis: a quantitative study of peritoneal membrane morphology.

BACKGROUND AND OBJECTIVES Peritoneal interstitial fibrosis and hyalinizing vasculopathy were induced by peritoneal dialysis and other associated conditions (e.g., uremia). A quantitative method for peritoneal biopsy evaluation is required to investigate possible causative factors and severity of the peritoneal dialysis-related peritoneal alterations. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Peritoneal biopsy specimens from 173 uremic (before peritoneal dialysis) and 80 peritoneal dialysis patients with or without impaired ultrafiltration capacity were evaluated by average peritoneal thickness of submesothelial compact zone measured at five randomly selected points of peritoneum and by lumen/vessel diameter ratio at postcapillary venule. RESULTS The average peritoneal thickness was increased in uremic patients and progressively thickened as the duration of peritoneal dialysis prolonged. The lumen/vessel diameter ratio was lower in uremia than normal and progressively decreased as the duration of peritoneal dialysis prolonged. In pre-peritoneal dialysis peritoneum, patients with diabetes showed significant decrease in lumen/vessel diameter ratio compared with patients without diabetes. The average peritoneal thickness was significantly higher in patients with impaired ultrafiltration capacity than in patients with maintained ultrafiltration capacity; however, no significant difference was observed in the postcapillary venule thickness and lumen/vessel diameter ratio between the two groups. CONCLUSIONS The average peritoneal thickness and lumen/vessel diameter ratio were useful morphologic parameters to quantify the severity of the peritoneal alterations in uremic and peritoneal dialysis patients. Uremia and diabetes had an impact on the pathogenesis of peritoneal sclerosis in pre-peritoneal dialysis peritoneum. Peritoneal dialysis treatment itself had a much stronger impact on the progression of peritoneal sclerosis.

Role of Dok-1 and Dok-2 in myeloid homeostasis and suppression of leukemia

Dok-1 and Dok-2 are closely related rasGAP-associated docking proteins expressed preferentially in hematopoietic cells. Although they are phosphorylated upon activation of many protein tyrosine kinases (PTKs), including those coupled with cytokine receptors and oncogenic PTKs like Bcr-Abl, their physiological roles are largely unidentified. Here, we generated mice lacking Dok-1 and/or Dok-2, which included the double-deficient mice succumbed to myeloproliferative disease resembling human chronic myelogenous leukemia (CML) and chronic myelomonocytic leukemia. The double-deficient mice displayed medullary and extramedullary hyperplasia of granulocyte/macrophage progenitors with leukemic potential, and their myeloid cells showed hyperproliferation and hypo-apoptosis upon treatment and deprivation of cytokines, respectively. Consistently, the mutant myeloid cells showed enhanced Erk and Akt activation upon cytokine stimulation. Moreover, loss of Dok-1 and/or Dok-2 induced blastic transformation of chronic phase CML-like disease in mice carrying the bcr-abl gene, a cause of CML. These findings demonstrate that Dok-1 and Dok-2 are key negative regulators of cytokine responses and are essential for myeloid homeostasis and suppression of leukemia.

Association between Single-Nucleotide Polymorphisms in Selectin Genes and Immunoglobulin A Nephropathy

Although intensive efforts have been undertaken to elucidate the genetic background of immunoglobulin A nephropathy (IgAN), genetic factors associated with the pathogenesis of this disease are still not well understood. We designed a case-control association study that was based on linkage disequilibrium among single-nucleotide polymorphisms (SNPs) in the selectin gene cluster on chromosome 1q24-25, and we found two SNPs in the E-selectin gene (SELE8 and SELE13) and six SNPs in the L-selectin gene (SELL1, SELL4, SELL5, SELL6, SELL10, and SELL11) that were significantly associated with IgAN in Japanese patients. All eight SNPs were in almost complete linkage disequilibrium. SELE8 and SELL10 caused amino acid substitutions from His to Tyr and from Pro to Ser (chi2=9.02, P=.0026, odds ratio = 2.73 [95% confidence interval [CI] 1.38--5.38] for His-to-Tyr substitutions; chi2=17.4, P=.000031, odds ratio = 3.61 [95% CI 1.91--6.83] for Pro-to-Ser substitutions), and SELL1 could affect promoter activity of the L-selectin gene (chi2=19.5, P=.000010, odds ratio = 3.77 [95% CI 2.02--7.05]). The TGT haplotype at these three loci was associated significantly with IgAN (chi2=18.67, P=.000016, odds ratio = 1.88 [95% CI 1.41--2.51]). Our results suggest that these eight SNPs in selectin genes may be useful for screening populations susceptible to the IgAN phenotype that involves interstitial infiltration.

Association of single-nucleotide polymorphisms in the polymeric immunoglobulin receptor gene with immunoglobulin A nephropathy (IgAN) in Japanese patients

AbstractImmunoglobulin A nephropathy (IgAN) is a primary glomerulonephritis of common incidence world-wide whose etiology and pathogenesis remain unresolved, although genetic factors are assumed to be involved in the development and progression of this disease. To identify genetic variations that might confer susceptibility to IgAN, we performed a case-control association study involving 389 Japanese IgAN patients and 465 controls. Genome-wide analysis of approximately 80,000 single-nucleotide polymorphisms (SNPs) identified a significant association between IgAN and six SNPs located in the PIGR (polymeric immuoglobulin receptor) gene at chromosome 1q31-q41. One of them, PIGR-17, caused an amino-acid substitution from alanine to valine at codon 580 (χ2=13.05, P=0.0003, odds ratio [OR] =1.59, 95% confidence interval [95% CI] =1.24–2.05); the OR of minor homozygotes to others was 2.71 (95% CI = 1.31–5.61). Another SNP, PIGR-2, could affect promoter activity (χ2 = 11.95, P=0.00055, OR=1.60, 95% CI=1.22–2.08); the OR of minor homozygotes to others was 2.08 (95% CI=0.94–4.60). Pairwise analyses demonstrated that all six SNPs were in almost complete linkage disequilibrium. Biopsy specimens from IgAN patients were positively stained by antibody against the secretory component of PIGR, but corresponding tissues from non-IgAN patients were not. Our results suggest that a gene associated with susceptibility to IgAN lies within or close to the PIGR gene locus on chromosome 1q in the Japanese population.

Glomerular expression of cell-cycle-regulatory proteins in human crescentic glomerulonephritis

Abstract To elucidate the mechanism underlying crescentic formation, we assessed the phenotypic characterization and cell-cycle protein expression in human crescentic glomerulonephritis (CRGN). Kidney tissue specimens taken from CRGN patients (10 patients with pauci-immune type rapidly progressive glomerulonephritis (RPGN), 2 patients with Henoch-Schönlein purpura nephritis, and 1 patient with IgA nephropathy) were examined immunohistochemically. Most of the cellular components of the crescents expressed cytokeratin, whereas few cells expressed PHM-5. CD68-positive cells were minor components of cellular crescents, indicating that the major principal cellular component of the crescents is made up of cells with the parietal glomerular epithelial cell (PEC) phenotype. Additionally, serial section analysis revealed that Ki-67-positive cells in the crescents were frequently cyclin-A positive and Bcl-2 positive, but seldom cyclin-B1 positive. Moreover, the expression of cyclin-dependent kinase inhibitor p27Kip1 was low in the cellular crescents, despite being exclusively positive in podocytes within the same section. We concluded that the major component of the cellular crescents is made up of PECs and that apparent expression of cyclins and Bcl-2 and restrained expression of p27Kip1 may be synergistically associated with the development of cellular crescents in human CRGN.

Soluble Osteopontin and Vascular Calcification in Hemodialysis Patients

Background: Vascular calcification often occurs in patients with uremia. As osteopontin (OPN) is not only involved in the physiological but also the pathological calcification of tissues, OPN may be associated with the pathogenesis of aortic calcification in hemodialysis (HD) patients. Methods: We examined the expression of OPN in atherosclerotic aortas of HD patients. In addition, we performed a prospective longitudinal study by using CT scans to detect aortic calcifications and by measuring the plasma OPN concentration by ELISA in HD patients (20 men, 16 women; mean age 55.2 ± 21.3 years) and in healthy volunteers (18 men, 17 women; mean age 54.0 ± 13.2 years). Results: By immunohistochemical staining, OPN was abundantly localized in atherosclerotic plaques of HD patients. The macrophages surrounding the atheromatous plaques were identified as the OPN-expressing cells. We furthermore found that the concentration of soluble plasma OPN was significantly higher in HD patients as compared with the concentrations in age-matched healthy volunteers (837.3 ± 443.2 vs. 315.1 ± 117.4 ng/ml, p < 0.01). The OPN concentration was positively correlated with the aortic calcification index in HD patients (r = 0.749, p < 0.01). Conclusion: These data suggest that OPN, secreted by macrophages, plays a role in the calcification of atheromatous plaques in HD patients.

Mice lacking Dok-1, Dok-2, and Dok-3 succumb to aggressive histiocytic sarcoma.

Histiocytic sarcoma (HS), a rare hematological malignancy, is an aggressive neoplasm that responds poorly to therapy. The molecular etiology and pathology of this disease remain unclear, hampering the development of an effective therapy, and there remains a need for more, and more realistic, animal models. HS cells typically show a histiocytic (ie, tissue macrophage-like) morphology and express histiocyte/macrophage markers in the absence of lymphocyte markers. In this study, we report that Dok-1−/−Dok-2−/−Dok-3−/− mice develop HS, but do not exhibit elevated incidence of other types of tumors. These mutant mice showed earlier mortality than wild-type (WT) or the other mutant mice, and this mortality was associated with HS. In total, 17 of 21 tumor-bearing Dok-1−/−Dok-2−/−Dok-3−/− mice necropsied at 25–66 weeks of age showed multiple organ spread, with osteolytic lesions and orthotopic invasion from the bone marrow to skeletal muscle. Tumors from the mice were transplantable. In addition, all Dok-1−/−Dok-2−/−Dok-3−/− mice, but only a small proportion of Dok-3−/− mice and no Dok-1−/−Dok-2−/− mice, exhibited abnormal accumulation of macrophages in the lung on necropsy at 8–12 weeks of age. Macrophages derived from Dok-1−/−Dok-2−/−Dok-3−/− mice displayed an exaggerated proliferative response to macrophage colony-stimulating factor (M-CSF) or granulocyte- macrophage colony-stimulating factor (GM-CSF) compared with WT and mutant controls. Together, these findings indicate that Dok-1, Dok-2, and Dok-3 cooperatively suppress aggressive HS, and commend Dok-1−/−Dok-2−/−Dok-3−/− mice as a useful model for the study of this neoplasia.

Neutral Solution Low in Glucose Degradation Products Is Associated with Less Peritoneal Fibrosis and Vascular Sclerosis in Patients Receiving Peritoneal Dialysis

♦ Background: The effects of novel biocompatible peritoneal dialysis (PD) solutions on human peritoneal membrane pathology have yet to be determined. Quantitative evaluation of human peritoneal biopsy specimens may reveal the effects of the new solutions on peritoneal membrane pathology. ♦ Methods: Peritoneal specimens from 24 PD patients being treated with either acidic solution containing high-glucose degradation products [GDPs (n = 12)] or neutral solution with low GDPs (n = 12) were investigated at the end of PD. As controls, pre-PD peritoneal specimens, obtained from 13 patients at PD catheter insertion, were also investigated. The extent of peritoneal fibrosis, vascular sclerosis, and advanced glycation end-product (AGE) accumulation were evaluated by quantitative or semi-quantitative methods. The average densities of CD31-positive vessels and podoplanin-positive lymphatic vessels were also determined. ♦ Results: Peritoneal membrane fibrosis, vascular sclerosis, and AGE accumulation were significantly suppressed in the neutral group compared with the acidic group. The neutral group also showed lower peritoneal equilibration test scores and preserved ultrafiltration volume. The density of blood capillaries, but not of lymphatic capillaries, was significantly increased in the neutral group compared with the acidic and pre-PD groups. ♦ Conclusions: Neutral solutions with low GDPs are associated with less peritoneal membrane fibrosis and vascular sclerosis through suppression of AGE accumulation. However, contrary to expectation, blood capillary density was increased in the neutral group. The altered contents of the new PD solutions modified peritoneal membrane morphology and function in patients undergoing PD.

Latent IgA deposition from donor kidney is the major risk factor for recurrent IgA nephropathy in renal transplantation

Abstract:  Background:  Previous studies have recognized risk factors for recurrent IgA nephropathy (r‐IgAN) in renal transplantation. However the clinical significance of latent IgA deposition from the donor kidney remains to be determined.