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Biomedical subjects

Charles E Alpers

Publications and source records attributed to Charles E Alpers.

At least 19 recordsLinked to original sources

Urinary clusterin as a biomarker of human kidney disease progression and response to the endothelin receptor antagonist atrasentan: An exploratory analysis from the SONAR trial.

The endothelin receptor antagonist atrasentan improved kidney outcomes in the SONAR trial for type 2 diabetes and chronic kidney disease (NCT01858532), though individual responses varied. To identify molecular biomarkers of atrasentan response and outcome, we conducted a nested case-control proteomics study (N = 180) within the SONAR trial population and identified urinary clusterin (uCLU) as the top candidate. Transcriptomic analyses of human kidney biopsies at tissue and single cell level from independent cohorts revealed higher CLU mRNA levels associated with worse kidney function and outcomes. An endothelin signaling activation score derived from pathway genes was reduced by atrasentan in mice with diabetic kidney disease. In the SONAR trial (N = 3,060) population, higher uCLU predicted worse outcomes, while atrasentan reduced uCLU by 42.6% over six weeks. Early uCLU changes independently predict improved kidney outcomes. In summary, uCLU is associated with kidney disease progression and response to atrasentan treatment, supporting its potential as a pharmacodynamic biomarker to target therapy.

Humans↗

Wiskott-Aldrich syndrome protein is required for regulatory T cell homeostasis.

Wiskott-Aldrich syndrome protein (WASp) is essential for optimal T cell activation. Patients with WAS exhibit both immunodeficiency and a marked susceptibility to systemic autoimmunity. We investigated whether alterations in Treg function might explain these paradoxical observations. While WASp-deficient (WASp(-/-)) mice exhibited normal thymic Treg generation, the competitive fitness of peripheral Tregs was severely compromised. The total percentage of forkhead box P3-positive (Foxp3(+)) Tregs among CD4(+) T cells was reduced, and WASp(-/-) Tregs were rapidly outcompeted by WASp(+) Tregs in vivo. These findings correlated with reduced expression of markers associated with self-antigen-driven peripheral Treg activation and homing to inflamed tissue. Consistent with these findings, WASp(-/-) Tregs showed a reduced ability to control aberrant T cell activation and autoimmune pathology in Foxp3(-/-)Scurfy (sf) mice. Finally, WASp(+) Tregs exhibited a marked selective advantage in vivo in a WAS patient with a spontaneous revertant mutation, indicating that altered Treg fitness likely explains the autoimmune features in human WAS.

Adoptive Transfer↗

Lung cancer induced in mice by the envelope protein of jaagsiekte sheep retrovirus (JSRV) closely resembles lung cancer in sheep infected with JSRV.

BACKGROUND: Jaagsiekte sheep retrovirus (JSRV) causes a lethal lung cancer in sheep and goats. Expression of the JSRV envelope (Env) protein in mouse lung, by using a replication-defective adeno-associated virus type 6 (AAV6) vector, induces tumors resembling those seen in sheep. However, the mouse and sheep tumors have not been carefully compared to determine if Env expression alone in mice can account for the disease features observed in sheep, or whether additional aspects of virus replication in sheep are important, such as oncogene activation following retrovirus integration into the host cell genome. RESULTS: We have generated mouse monoclonal antibodies (Mab) against JSRV Env and have used these to study mouse and sheep lung tumor histology. These Mab detect Env expression in tumors in sheep infected with JSRV from around the world with high sensitivity and specificity. Mouse and sheep tumors consisted mainly of well-differentiated adenomatous foci with little histological evidence of anaplasia, but at long times after vector exposure some mouse tumors did have a more malignant appearance typical of adenocarcinoma. In addition to epithelial cell tumors, lungs of three of 29 sheep examined contained fibroblastic cell masses that expressed Env and appeared to be separate neoplasms. The Mab also stained nasal adenocarcinoma tissue from one United States sheep, which we show was due to expression of Env from ovine enzootic nasal tumor virus (ENTV), a virus closely related to JSRV. Systemic administration of the AAV6 vector encoding JSRV Env to mice produced numerous hepatocellular tumors, and some hemangiomas and hemangiosarcomas, showing that the Env protein can induce tumors in multiple cell types. CONCLUSION: Lung cancers induced by JSRV infection in sheep and by JSRV Env expression in mice have similar histologic features and are primarily characterized by adenomatous proliferation of peripheral lung epithelial cells. Thus it is unnecessary to invoke a role for insertional mutagenesis, gene activation, viral replication, or expression of other viral gene products in sheep lung tumorigenesis, although these processes may play a role in other clinically less important sequelae of JSRV infection such as metastasis observed with variable frequency in sheep.

Adenocarcinoma↗

Localization of TGF-beta signaling intermediates Smad2, 3, 4, and 7 in developing and mature human and mouse kidney.

Smad proteins are signaling intermediates of the TGF-beta superfamily and are involved in a range of biological activities including development and immune responses. We studied the expression of TGF-beta-receptor activated Smads (Smad2 and Smad3), the common partner Smad (Smad4), an inhibitory Smad (Smad7), and the activated (phosphorylated) Smad2 (pSmad2) in developing and adult kidneys of humans and mice. These studies demonstrate associated expression of these Smads in multiple renal cell types in all developmental stages and in mature non-diseased kidneys. Smad expression is in general most widespread at the earliest stages of nephron development and diminishes as components of the nephrons become more differentiated. Paucity of Smad expression in mesangial cells in contrast to widespread expression of these Smads in glomerular visceral epithelial cells in both developing and mature kidneys was remarkable. Divergent and less extensive expression of Smad4, compared with other Smad proteins, was also demonstrated in tubules of human kidneys. Based on the observed expression patterns, these findings demonstrate, for the first time, expression of the TGF-beta-receptor-activated Smad2 and Smad3, the common mediator Smad4, and the inhibitory Smad7 in the developing human fetal kidney, extending observations previously made in rodent systems to humans.

Adult↗

Bone morphogenetic protein 4: potential regulator of shear stress-induced graft neointimal atrophy.

OBJECTIVE: Placement in baboons of a distal femoral arteriovenous fistula increases shear stress through aortoiliac polytetrafluoroethylene (PTFE) grafts and induces regression of a preformed neointima. Atrophy of the neointima might be controlled by shear stress-induced genes, including the bone morphogenetic proteins (BMPs). We have investigated the expression and function of BMPs 2, 4, and 5 in the graft neointima and in cultured baboon smooth muscle cells (SMCs). METHODS: Baboons received bilateral aortoiliac PTFE grafts and 8 weeks later, a unilateral femoral arteriovenous fistula. RESULTS: Quantitative polymerase chain reaction showed that high shear stress increased BMP2, 4, and 5 messenger RNA (mRNA) in graft intima between 1 and 7 days, while noggin (a BMP inhibitor) mRNA was decreased. BMP4 most potently (60% inhibition) inhibited platelet-derived growth factor-stimulated SMC proliferation compared with BMP2 and BMP5 (31% and 26%, respectively). BMP4 also increased SMC death by 190% +/- 10%. Noggin reversed the antiproliferative and proapoptotic effects of BMP4. Finally, Western blotting confirmed BMP4 protein upregulation by high shear stress at 4 days. BMP4 expression demonstrated by in situ hybridization was confined to endothelial cells. CONCLUSIONS: Increased BMPs (particularly BMP4) coupled with decreased noggin may promote high shear stress-mediated graft neointimal atrophy by inhibiting SMC proliferation and increasing SMC death.

Animals↗

Membranous glomerulopathy with spherules: an uncommon variant with obscure pathogenesis.

BACKGROUND: Occasional case reports of membranous glomerulopathy described unique subepithelial accumulations of an unusual type of immune deposit composed of spherular structures. The identity of such structures as nuclear pores has been suggested, but not established. METHODS: We identified a cohort of patients (n = 14, including 1 patient with disease recurrence in an allograft) who presented with nephrotic syndrome and had renal biopsy specimens with light and immunofluorescence microscopic findings characteristic of membranous glomerulopathy. These patients were distinguished by ultrastructural studies that showed glomerular capillary wall accumulations of subepithelial immune deposits composed of uniform spherular structures, while lacking the typical granular electron-dense deposits seen in membranous glomerulopathy. The molecular identity of these spherular structures as nuclear pores was tested by using immunofluorescence microscopy and immunohistochemistry with mouse monoclonal antinuclear pore antibodies (Covance, Princeton, NJ) and anti-Nuclear Pore-O-Linked Glycoprotein (Affinity BioReagents Inc, Golden, CO) antibodies. RESULTS: Measurement of spherular structures by using high-magnification electron microscopy showed an average diameter of 84.5 nm, which correlated well with accepted diameters of nuclear pores (80 to 120 nm). Immunofluorescence microscopy and immunoperoxidase staining with both antibodies showed characteristic beaded staining of nuclear membranes of multiple cell types within normal control kidney, but no staining of immune-type deposits within glomerular basement membranes. CONCLUSION: These cases form a rare, but distinctive, morphological subclass of membranous glomerulopathy. The antigenic specificity of immune deposits in these cases remains elusive.

Adult↗

The cyclin-dependent kinase inhibitor p21 limits murine mesangial proliferative glomerulonephritis.

BACKGROUND: Mesangial cell (MC) proliferation underlies increased matrix accumulation in glomerulonephritis (GN), and the resolution of MC proliferation occurs largely through apoptosis. Proliferation and apoptosis are controlled by specific cell cycle proteins, where cyclin-dependent kinase (CDK) inhibitors such as p21 bind target cyclin-CDK complexes. However, the role of p21 in acute mesangial proliferative GN is not known. This study was conducted to test the hypothesis that p21 regulates MC proliferation and apoptosis in anti-MC serum-induced GN. METHODS: Age and sex matched wild-type (p21+/+) and p21-deficient (p21-/-) mice were injected with sheep anti-MC serum. Renal function (BUN, urinary albumin excretion), histology, DNA synthesis (BrdU. Ki-67) and apoptosis (TUNEL) were quantified at day 6 and day 12 (n = 6-8/time point). RESULTS: In p21+/+ mice, anti-MC-serum induced mild MC proliferative GN, and glomerular p21 expression was increased. Renal function was worse in nephric p21-/- mice. PAS and silver staining revealed that p21-/- mice had typical features of MC proliferative GN with focal segmental tuft necrosis, focal mesangiolysis and focal mesangial hypercellularity. Occasional features of podocyte injury (swelling, vacuolization) were noted. Double immunostaining confirmed increased mesangial cell DNA synthesis in nephritic p21-/- mice at day 6. In contrast, there was no difference in glomerular apoptosis in nephritic p21+/+ and p21-/- mice at each time point. Glomerular lesions were accompanied by severe glomerular and tubulointerstitial fibrosis in p21-/- mice. CONCLUSIONS: This data shows that the CDK-inhibitor p21 regulates the MC proliferative response to immune-mediated injury. In contrast, p21 does not alter the apoptotic response, resulting in a delayed resolution in nephritic p21-/- mice.

Animals↗

Expanding the pathologic spectrum of light chain deposition disease: a rare variant with clinical follow-up of 7 years.

We report an unusual histologic manifestation of light chain deposition disease in a 69-year-old female patient, who presented with nephrotic syndrome and an increased serum creatinine. The renal biopsy findings by light and electron microscopy suggested a glomerulonephritis with massive immune-complex deposition, such as lupus nephritis. However, the overall clinical scenario was inconsistent with lupus. Subsequent tests revealed multiple myeloma confirmed by bone marrow biopsy and identification of a monoclonal kappa light chain immunoglobulin by serum and urine immunoelectrophoresis and immunofixation. Additional immunohistochemistry of the first biopsy also demonstrated strong kappa light chain staining of the glomerular capillary walls and mesangium but not lambda light chain or IgG staining. The patient responded well to therapy and was asymptomatic until nearly 7 years later. A repeat biopsy revealed similar findings to the first biopsy with the addition of immunofluorescence microscopy, which confirmed the prominent kappa light chain staining of the glomeruli, tubular basement membranes, and interstitium with corresponding electron-dense deposits visualized by electron microscopy. This case represents an unusual histologic variant of light chain deposition disease, which to our knowledge has not been previously described and further expands the wide clinicopathologic spectrum within the diagnostic entity of light chain deposition disease.

Aged↗

IgA nephropathy with crescents in kidney transplant recipients.

BACKGROUND: Crescentic glomerulonephritis is an uncommon finding in renal allografts. Recurrence or de novo mesangial deposition of immunoglobulin A (IgA) in renal allografts most often is clinically benign, but some case reports have shown that IgA nephropathy in renal allografts can present as crescentic glomerulonephritis and may lead to rapid deterioration of graft function and/or graft loss. METHODS: We reviewed diagnoses of all allograft biopsies at University of Washington Medical Center (Seattle, WA) from 1989 to 2003 and found 33 cases of glomerulonephritis with crescents. Eight of these cases were the result of recurrent or de novo IgA nephropathy. Clinical and pathological features of these patients were reviewed. RESULTS: Six of 8 cases with crescents were the result of recurrent IgA nephropathy, and 2 cases were presumptive de novo IgA nephropathy. Of the 8 patients with IgA nephropathy with crescents, 6 patients presented clinically with increasing serum creatinine levels; 4 patients, with proteinuria; and 4 patients, with hematuria. In 6 patients, there was 10% to 30% involvement of glomeruli, with crescents partially or completely filling urinary spaces. The other patients showed lesser (approximately 7% of sampled glomeruli) involvement. Four patients with IgA nephropathy with crescents developed renal failure and returned to hemodialysis therapy. Three patients had a benign clinical course, with stabilization of renal function. One patient was lost to follow-up. CONCLUSION: We identified a cohort of patients with glomerulonephritis with crescents in renal allografts with IgA nephropathy as the cause. In half the affected patients, this led to early progressive renal insufficiency and return to hemodialysis therapy.

Adult↗

Pathogenic mechanisms in membranoproliferative glomerulonephritis.

PURPOSE OF REVIEW: This review considers new information on the pathogenesis of a long recognized and poorly understood form of glomerular injury, membranoproliferative glomerulonephritis. This disease has received growing attention as it is the principal renal manifestation of hepatitis C virus infection, which has become pandemic worldwide. RECENT FINDINGS: This review briefly describes three murine models of membranoproliferative glomerulonephritis suitable for pathogenesis studies. We consider recent evidence implicating innate immune mechanisms in immune and autoimmune-mediated glomerulonephritis, and recent data pointing to the alternative pathway of complement activation in the amplification of glomerulonephritic injury. SUMMARY: Understanding the contribution of complement activation and innate immunity to the evolution of membranoproliferative glomerulonephritis promises to provide new therapeutic targets for this disease. Inhibitors of the complement cascade are already being tested in clinical trials as therapeutic interventions for some human glomerular diseases. Successful tests of this approach in membranoproliferative glomerulonephritis are still awaited. Our understanding of how the innate immune system modulates glomerulonephritis is still in an early stage, and future studies should be directed at identifying targets and specific interventions that may also benefit patients with this disease.

Animals↗

Multifunctionality of PAI-1 in fibrogenesis: evidence from obstructive nephropathy in PAI-1-overexpressing mice.

BACKGROUND: Plasminogen activator inhibitor-1 (PAI-1) has been implicated in the pathogenesis of chronic kidney disease based on its up-regulated expression and on the beneficial effects of PAI-1 inhibition or depletion in experimental models. PAI-1 is a multifunctional protein and the mechanisms that account for its profibrotic effects have not been fully elucidated. METHODS: The present study was designed to investigate PAI-1-dependent fibrogenic pathways by comparing the unilateral ureteral obstruction model (UUO) (days 3, 7, and 14) in PAI-1-overexpressing mice (PAI-1 tg) to wild-type mice, both on a C57BL6 background. RESULTS: Following UUO, total kidney PAI-1 mRNA and/or protein levels were significantly higher in the PAI-1 tg mice (N= 6 to 8/group) and fibrosis severity was significantly worse (days 3, 7, and 14), measured both as Sirius red-positive interstitial area (e.g., 10 +/- 3.2% vs. 4.5 +/- 1.0%) (day 14) and total kidney collagen (e.g., 11.1 +/- 1.7 vs. 6.2 +/- 1.3 microg/mg) (day 14). By day 14, the expression of two normal tubular proteins, E-cadherin and Ksp-cadherin, were significantly lower in the PAI-1 tg mice (3.2 +/- 0.5% vs. 11.7 +/- 5.9% and 2.6 +/- 1.6) vs. 6.2 +/- 0.8%, respectively), implying more extensive tubular damage. At least four fibrogenic pathways were differentially expressed in the PAI-1 tg mice. First, interstitial macrophage recruitment was more intense (P < 0.05 days 3 and 14). Second, interstitial myofibroblast density was greater (P < 0.05 days 3 and 7) despite similar numbers of proliferating tubulointerstitial cells. Third, transforming growth factor-beta1 (TGF-beta1) and collagen I mRNA were significantly higher. Finally, urokinase activity was significantly lower (P < 0.05 days 7 and 14) despite similar mRNA levels. Gene microarray studies documented that that the deletion of this single profibrotic gene had far-reaching consequences on renal cellular responses to chronic injury. CONCLUSION: These data provide further evidence that PAI-1 is directly involved in interstitial fibrosis and tubular damage via two primary overlapping mechanisms: early effects on interstitial cell recruitment and late effects associated with decreased urokinase activity.

Animals↗

Exogenous PDGF-D is a potent mesangial cell mitogen and causes a severe mesangial proliferative glomerulopathy.

The PDGF family consists of at least four members, PDGF-A, -B, -C, and -D. All of the PDGF isoforms bind and signal through two known receptors, PDGF receptor-alpha and PDGF receptor-beta, which are constitutively expressed in the kidney and are upregulated in specific diseases. It is well established that PDGF-B plays a pivotal role in the mediation of glomerular mesangial cell proliferation. However, little is known of the roles of the recently discovered PDGF-C and -D in mediating renal injury. In this study, adenovirus constructs encoding PDGF-B, -C, and -D were injected into mice. Mice with high circulating levels of PDGF-D developed a severe mesangial proliferative glomerulopathy, characterized by enlarged glomeruli and a striking increase in glomerular cellularity. The PDGF-B-overexpressing mice had a milder proliferative glomerulopathy, whereas the mice overexpressing PDGF-C and those that received adenovirus alone showed no measurable response. Mitogenicity of PDGF-D and -B for mesangial cells was confirmed in vitro. These findings emphasize the importance of engagement of PDGF receptor-beta in transducing mesangial cell proliferation and demonstrate that PDGF-D is a major mediator of mesangial cell proliferation. Finally, this approach has resulted in a unique and potentially valuable model of mesangial proliferative glomerulopathy and its resolution.

Animals↗

The classification of glomerulonephritis in systemic lupus erythematosus revisited.

The currently used classification reflects our understanding of the pathogenesis of the various forms of lupus nephritis, but clinicopathologic studies have revealed the need for improved categorization and terminology. Based on the 1982 classification published under the auspices of the World Health Organization (WHO) and subsequent clinicopathologic data, we propose that class I and II be used for purely mesangial involvement (I, mesangial immune deposits without mesangial hypercellularity; II, mesangial immune deposits with mesangial hypercellularity); class III for focal glomerulonephritis (involving <50% of total number of glomeruli) with subdivisions for active and sclerotic lesions; class IV for diffuse glomerulonephritis (involving > or = 50% of total number of glomeruli) either with segmental (class IV-S) or global (class IV-G) involvement, and also with subdivisions for active and sclerotic lesions; class V for membranous lupus nephritis; and class VI for advanced sclerosing lesions]. Combinations of membranous and proliferative glomerulonephritis (i.e., class III and V or class IV and V) should be reported individually in the diagnostic line. The diagnosis should also include entries for any concomitant vascular or tubulointerstitial lesions. One of the main advantages of the current revised classification is that it provides a clear and unequivocal description of the various lesions and classes of lupus nephritis, allowing a better standardization and lending a basis for further clinicopathologic studies. We hope that this revision, which evolved under the auspices of the International Society of Nephrology and the Renal Pathology Society, will contribute to further advancement of the WHO classification.

Biopsy↗

Chemokine receptor CCR1 but not CCR5 mediates leukocyte recruitment and subsequent renal fibrosis after unilateral ureteral obstruction.

As chemokine receptor CCR1 and CCR5 expression on circulating leukocytes is thought to contribute to leukocyte recruitment during renal fibrosis, the authors examined the effects of unilateral ureteral obstruction (UUO) in mice deficient for CCR1 or CCR5. Analysis of UUO kidneys from CCR1-deficient mice revealed a reduction of interstitial macrophages and lymphocytes (35% and 55%, respectively) compared with wild-type controls. CCR1-deficient mice had reduced CCR5 mRNA levels in UUO kidneys, which correlated with a reduction of CCR5+ T cell infiltrate as determined by flow cytometry. Interstitial fibroblasts, renal TGF-beta1 mRNA expression, interstitial volume, and collagen I deposits were all significantly reduced in CCR1-deficient mice. In contrast, renal leukocytes and fibrosis were unaffected in CCR5-deficient mice with UUO. However, if treated with the CCR1 antagonist BX471, CCR5-deficient mice showed a similar reduction of renal leukocytes and fibrosis as CCR1-deficient mice. To determine the underlying mechanism labeled macrophages and T cells isolated from either wild-type, CCR1-deficient, or CCR5-deficient mice were injected into wild-type mice with UUO. Three hours later, renal cell recruitment was reduced for CCR1-deficient cells or cells pretreated with BX471 compared with CCR5-deficient or wild-type cells. Thus, CCR1 but not CCR5 is required for leukocyte recruitment and fibrosis after UUO in mice. Therefore, CCR1 is a promising target for therapeutic intervention in leukocyte-mediated fibrotic tissue injury, e.g. progressive renal fibrosis.

Animals↗

Late onset of treatment with a chemokine receptor CCR1 antagonist prevents progression of lupus nephritis in MRL-Fas(lpr) mice.

Slowly progressive renal injury is the major cause for ESRD. The model of progressive immune complex glomerulonephritis in autoimmune MRL(lpr/lpr) mice was used to evaluate whether chemokine receptor CCR1 blockade late in the disease course can affect progression to renal failure. Mice were treated with subcutaneous injections of either vehicle or BX471, a nonpeptide CCR1 antagonist, three times a day from week 20 to 24 of age [corrected]. BX471 improved blood urea nitrogen levels (BX471, 35.1 +/- 5.3; vehicle, 73.1 +/- 39.6 mg/dl; P < 0.05) and reduced the amount of ERHR-3 macrophages, CD3 lymphocytes, Ki-67 positive proliferating cells, and ssDNA positive apoptotic cells in the interstitium but not in glomeruli. Cell transfer studies with fluorescence-labeled T cells that were pretreated with either vehicle or BX471 showed that BX471 blocks macrophage and T cell recruitment to the renal interstitium of MRL(lpr/lpr) mice. This was associated with reduced renal expression of CC chemokines CCL2, CCL3, CCL4, and CCL5 and the chemokine receptors CCR1, CCR2, and CCR5. Furthermore, BX471 reduced the extent of interstitial fibrosis as evaluated by interstitial smooth muscle actin expression and collagen I deposits, as well as mRNA expression for collagen I and TGF-beta. BX471 did not affect serum DNA autoantibodies, proteinuria, or markers of glomerular injury in MRL(lpr/lpr) mice. This is the first evidence that, in advanced chronic renal injury, blockade of CCR1 can halt disease progression and improve renal function by selective inhibition of interstitial leukocyte recruitment and fibrosis.

Animals↗

The classification of glomerulonephritis in systemic lupus erythematosus revisited.

The currently used classification reflects our understanding of the pathogenesis of the various forms of lupus nephritis, but clinicopathologic studies have revealed the need for improved categorization and terminology. Based on the 1982 classification published under the auspices of the World Health Organization (WHO) and subsequent clinicopathologic data, we propose that class I and II be used for purely mesangial involvement (I, mesangial immune deposits without mesangial hypercellularity; II, mesangial immune deposits with mesangial hypercellularity); class III for focal glomerulonephritis (involving <50% of total number of glomeruli) with subdivisions for active and sclerotic lesions; class IV for diffuse glomerulonephritis (involving > or =50% of total number of glomeruli) either with segmental (class IV-S) or global (class IV-G) involvement, and also with subdivisions for active and sclerotic lesions; class V for membranous lupus nephritis; and class VI for advanced sclerosing lesions. Combinations of membranous and proliferative glomerulonephritis (i.e., class III and V or class IV and V) should be reported individually in the diagnostic line. The diagnosis should also include entries for any concomitant vascular or tubulointerstitial lesions. One of the main advantages of the current revised classification is that it provides a clear and unequivocal description of the various lesions and classes of lupus nephritis, allowing a better standardization and lending a basis for further clinicopathologic studies. We hope that this revision, which evolved under the auspices of the International Society of Nephrology and the Renal Pathology Society, will contribute to further advancement of the WHO classification.

Humans↗