Complement-binding anti-HLA antibodies and kidney-allograft survival.

BACKGROUND: Anti-HLA antibodies hamper successful transplantation, and activation of the complement cascade is involved in antibody-mediated rejection. We investigated whether the complement-binding capacity of anti-HLA antibodies plays a role in kidney-allograft failure. METHODS: We enrolled patients who received kidney allografts at two transplantation centers in Paris between January 1, 2005, and January 1, 2011, in a population-based study. Patients were screened for the presence of circulating donor-specific anti-HLA antibodies and their complement-binding capacity. Graft injury phenotype and the time to kidney-allograft loss were assessed. RESULTS: The primary analysis included 1016 patients. Patients with complement-binding donor-specific anti-HLA antibodies after transplantation had the lowest 5-year rate of graft survival (54%), as compared with patients with non-complement-binding donor-specific anti-HLA antibodies (93%) and patients without donor-specific anti-HLA antibodies (94%) (P<0.001 for both comparisons). The presence of complement-binding donor-specific anti-HLA antibodies after transplantation was associated with a risk of graft loss that was more than quadrupled (hazard ratio, 4.78; 95% confidence interval [CI], 2.69 to 8.49) when adjusted for clinical, functional, histologic, and immunologic factors. These antibodies were also associated with an increased rate of antibody-mediated rejection, a more severe graft injury phenotype with more extensive microvascular inflammation, and increased deposition of complement fraction C4d within graft capillaries. Adding complement-binding donor-specific anti-HLA antibodies to a traditional risk model improved the stratification of patients at risk for graft failure (continuous net reclassification improvement, 0.75; 95% CI, 0.54 to 0.97). CONCLUSIONS: Assessment of the complement-binding capacity of donor-specific anti-HLA antibodies appears to be useful in identifying patients at high risk for kidney-allograft loss.

Antibody-mediated vascular rejection of kidney allografts: a population-based study.

BACKGROUND: Rejection of allografts has always been the major obstacle to transplantation success. We aimed to improve characterisation of different kidney-allograft rejection phenotypes, identify how each one is associated with anti-HLA antibodies, and investigate their distinct prognoses. METHODS: Patients who underwent ABO-compatible kidney transplantations in Necker Hospital and Saint-Louis Hospital (Paris, France) between Jan 1, 1998, and Dec 31, 2008, were included in our population-based study. We assessed patients who provided biopsy samples for acute allograft rejection, which was defined as the association of deterioration in function and histopathological lesions. The main outcome was kidney allograft loss-ie, return to dialysis. To investigate distinct rejection patterns, we retrospectively assessed rejection episodes with review of graft histology, C4d in allograft biopsies, and donor-specific anti-HLA antibodies. FINDINGS: 2079 patients were included in the main analyses, of whom 302 (15%) had acute biopsy-proven rejection. We identified four distinct patterns of kidney allograft rejection: T cell-mediated vascular rejection (26 patients [9%]), antibody-mediated vascular rejection (64 [21%]), T cell-mediated rejection without vasculitis (139 [46%]), and antibody-mediated rejection without vasculitis (73 [24%]). Risk of graft loss was 9·07 times (95 CI 3·62-19·7) higher in antibody-mediated vascular rejection than in T cell-mediated rejection without vasculitis (p<0·0001), compared with an increase of 2·93 times (1·1-7·9; P=0·0237) in antibody-mediated rejection without vasculitis and no significant rise in T cell-mediated vascular rejection (hazard ratio [HR] 1·5, 95% CI 0·33-7·6; p=0·60). INTERPRETATION: We have identified a type of kidney rejection not presently included in classifications: antibody-mediated vascular rejection. Recognition of this distinct phenotype could lead to the development of new treatment strategies that could salvage many kidney allografts. FUNDING: None.

A clinicopathologic study of thrombotic microangiopathy in IgA nephropathy.

Thrombotic microangiopathy (TMA) occurs in IgA nephropathy, but its clinical significance is not well described. We retrospectively examined a series of 128 patients diagnosed with IgA nephropathy between 2002 and 2008 who had a mean follow-up of 44±27 months. In our series, 53% presented with lesions of TMA, acute or organized, in arteries and/or arterioles. Among patients with TMA, 4% were normotensive, 25% had controlled hypertension, and 71% had uncontrolled hypertension. Of those with uncontrolled hypertension, 26% had malignant hypertension. Histologically, the group with TMA had a significantly greater percentage of sclerotic glomeruli and worse tubulointerstitial fibrosis than those of the group without TMA. However, a significant minority of patients had near-normal histology, with minimal tubular atrophy (20%) and/or <20% interstitial fibrosis (24%). TMA rarely occurred in the absence of significant proteinuria. During follow-up, a doubling of serum creatinine or ESRD occurred in all patients with laboratory evidence of TMA, in 42% of those with morphologic evidence but no laboratory evidence of TMA, and in 11% of those without TMA. In summary, lesions of TMA are frequent in IgA nephropathy and may occur in normotensive patients with near-normal renal histology. Although the pathophysiologic mechanisms involved remain undetermined, the current study rules out severe hypertension or advanced renal disease as sole causes.

Donor-specific antibodies accelerate arteriosclerosis after kidney transplantation.

In biopsies of renal allografts, arteriosclerosis is often more severe than expected based on the age of the donor, even without a history of rejection vasculitis. To determine whether preformed donor-specific antibodies (DSAs) may contribute to the severity of arteriosclerosis, we examined protocol biopsies from patients with (n=40) or without (n=59) DSA after excluding those with any evidence of vasculitis. Among DSA-positive patients, arteriosclerosis significantly progressed between month 3 and month 12 after transplant (mean Banff cv score 0.65 ± 0.11 to 1.12 ± 0.10, P=0.014); in contrast, among DSA-negative patients, we did not detect a statistically significant progression during the same timeframe (mean Banff cv score 0.65 ± 0.11 to 0.81 ± 0.10, P=not significant). Available biopsies at later time points supported a rate of progression of arteriosclerosis in DSA-negative patients that was approximately one third that in DSA-positive patients. Accelerated arteriosclerosis was significantly associated with peritubular capillary leukocytic infiltration, glomerulitis, subclinical antibody-mediated rejection, and interstitial inflammation. In conclusion, these data support the hypothesis that donor-specific antibodies dramatically accelerate post-transplant progression of arteriosclerosis.

Focal segmental glomerulosclerosis plays a major role in the progression of IgA nephropathy. II. Light microscopic and clinical studies.

It is well known that lesions morphologically identical with focal segmental glomerulosclerosis (FSGS) may appear in IgA nephropathy (IgAN). Capsular adhesions without underlying abnormalities in the tuft, often the first sign of FSGS, are frequent in IgAN. In this retrospective study, a new cohort of 128 adult patients with IgAN was used to validate the new Oxford classification system of IgAN, and shown to have highly significant associations with clinical and outcome parameters. We then used these patients to determine the extent to which IgAN could be accounted for in terms of FSGS. Some form of lesion consistent with FSGS, notably hyalinosis and collapsing glomerulopathy, was found in 101 of these patients. No glomerular lesions were found in 16 patients, and 11 had mild lesions not definable as FSGS. Those with FSGS had significantly worse renal survival at 80 months than those without. Comparison of pure forms of FSGS (excluding collapsing glomerulopathy) with cases of FSGS having other glomerular lesions (mesangial hyperplasia, endocapillary hypercellularity, glomerular necroses, extracapillary proliferation) revealed that those with FSGS and other superimposed lesions did significantly worse than cases of pure FSGS at 80 months following diagnosis. Importantly, patients with pure FSGS had relatively poor survival even without other superimposed glomerular abnormalities. Thus, the majority of cases of IgAN can be interpreted as representing one or another variant of FSGS. Hence, interpreting IgAN in terms of FSGS emphasizes the role that podocyte lesions may play in the pathogenesis and progression of this disease.

Focal segmental glomerulosclerosis plays a major role in the progression of IgA nephropathy. I. Immunohistochemical studies.

IgA nephropathy (IgAN) often shows lesions morphologically identical with those of focal segmental glomerulosclerosis (FSGS). In order to determine the possible role of FSGS in IgAN lesions, we measured glomerular capsular adhesions, often the first step toward FSGS, in biopsies from 127 patients with IgAN, 100 with lupus nephritis, and 26 with primary FSGS. Capsular adhesions with no lesions in the underlying tuft, consistent with podocyte abnormality or loss, were found regularly in FSGS and IgAN, but infrequently in lupus. Fifteen biopsies of patients with IgAN were studied immunohistochemically using markers for podocytes, Bowman's parietal epithelial cells, proliferating cells, and macrophages. Cytokeratins CK-8 and C2562 differentiated normal podocytes (negative) from parietal epithelial cells (variably positive). There was focal loss of the podocyte markers synaptopodin, glomerular epithelial protein 1 (GLEPP-1), nephrin, and vascular endothelial growth factor (VEGF), particularly at sites of capsular adhesions in otherwise histologically normal glomeruli. Cells displaying the parietal epithelial cell markers PAX2 (paired box gene 2) and the cytokeratins were also positive for the proliferating cell marker, proliferating cell nuclear antigen. These cells gathered at sites of adhesion, and in response to active lesions in the tuft, grew inward along the adhesion onto the tuft, forming a monolayer positive for parietal markers and the podocyte marker Wilms tumor protein-1 (WT-1). These cells deposited a layer of collagen over the sclerosing tuft. Thus, all biopsies of patients with IgAN had changes basically identical to those classically described in FSGS. Hence, our study strongly suggests that podocytopathy of a type similar to that in primary FSGS occurs frequently in IgAN.

Preexisting donor-specific HLA antibodies predict outcome in kidney transplantation.

The clinical importance of preexisting HLA antibodies at the time of transplantation, identified by contemporary techniques, is not well understood. We conducted an observational study analyzing the association between preexisting donor-specific HLA antibodies (HLA-DSA) and incidence of acute antibody-mediated rejection (AMR) and survival of patients and grafts among 402 consecutive deceased-donor kidney transplant recipients. We detected HLA-DSA using Luminex single-antigen assays on the peak reactive and current sera. All patients had a negative lymphocytotoxic cross-match test on the day of transplantation. We found that 8-year graft survival was significantly worse (61%) among patients with preexisting HLA-DSA compared with both sensitized patients without HLA-DSA (93%) and nonsensitized patients (84%). Peak HLA-DSA Luminex mean fluorescence intensity (MFI) predicted AMR better than current HLA-DSA MFI (P = 0.028). As MFI of the highest ranked HLA-DSA detected on peak serum increased, graft survival decreased and the relative risk for AMR increased: Patients with MFI >6000 had >100-fold higher risk for AMR than patients with MFI <465 (relative risk 113; 95% confidence interval 31 to 414). The presence of HLA-DSA did not associate with patient survival. In conclusion, the risk for both AMR and graft loss directly correlates with peak HLA-DSA strength. Quantification of HLA antibodies allows stratification of immunologic risk, which should help guide selection of acceptable grafts for sensitized patients.

Accelerated arteriosclerosis: a form of transplant arteriopathy.

PURPOSE OF REVIEW: Terminology for posttransplant renal arterial lesions is confusing, with multiple terms being applied, the more common among them being the comprehensive terms, transplant arteriosclerosis and transplant atherosclerosis; endarteritis, for intimal lesions with an inflammatory component; and finally for advanced lesions with or without intimal inflammation, transplant arteriopathy. However, these latter lesions may present the appearance of banal arteriosclerosis, albeit more advanced expected on the basis of donor age. This review explores the distinctions to be drawn among these various descriptive terms. RECENT FINDINGS: Cell-mediated arterial lesions due to T-cell cell-endothelial interactions and antibody-mediated lesions, due to antiendothelial cell antibodies, show many common features: myofibroblasts, some of recipient origin, laying down extracellular matrix. However, they differ in that cell-mediated intimal lesions initially have a prominent leukocytic component, usually absent in antibody-mediated lesions. The antibodies most frequently implicated are antihuman leukocyte antigen class I and class 2 antibodies. With the exception of a sometimes more cellular intima and initial absence of dense collagen and elastic fibers, these latter lesions resemble those of arteriosclerosis of aging. SUMMARY: Many instances of lesions designated as transplant arteriopathy are morphologically similar or identical to typical renal arteriosclerosis and could equally be regarded as accelerated arteriosclerosis.

Clinical and morphological prognostic factors in membranous nephropathy: significance of focal segmental glomerulosclerosis.

BACKGROUND: Progression of idiopathic membranous glomerulonephritis (IMGN) to renal insufficiency depends on various clinical and laboratory factors that have been taken into account in most therapeutic trials based on such aggressive drugs as alkylating agents or cyclosporine. However, few studies have envisaged the prognostic significance of morphological factors and their importance for stratification of patients enrolled in therapeutic trials. METHODS: Records of patients with membranous glomerulonephritis (MGN) from 1976 to 2001 from five nephrology units were reviewed retrospectively. Secondary causes were ruled out, especially occult malignancy. Eligible cases were analyzed according to clinical profile, abundance of proteinuria, blood pressure, and standard renal pathological characteristics, including MGN staging, vascular lesions, and degree of interstitial fibrosis on a semiquantitative scale. Renal survival curves from renal insufficiency were calculated by the Kaplan-Meier method. Mean follow-up was 68 months. RESULTS: Initial multiple regression analysis showed that the most significant prognostic variable was the presence of focal segmental glomerulosclerosis (FSGS)-type glomerular lesions (P < 0.001), and patients therefore were divided into two groups: 42 patients had MGN only (group I) and 30 patients had superimposed FSGS (group II). Group II patients were more hypertensive, and all renal lesions were significantly more severe, with a higher mean stage of membranous lesions, more obsolescent glomeruli, greater mesangial proliferation, and worse interstitial fibrosis and vascular lesions. Renal survival for group II was significantly lower (P < 0.001, log-rank test). Only one remission occurred in group II, whereas 38% of group I patients experienced remission (P = 0.002). We pooled our results with those of three previous studies in the literature, totaling 282 patients (156 patients, MGN alone; 126 patients, MGN plus FSGS). Remission rates were 32% and 12.7%, respectively (P < 0.001). The prognostic value of hypertension was noted in three of the four series, including ours. CONCLUSION: FSGS lesions superimposed on IMGN are common and portend a significantly worse outcome in terms of nephrotic syndrome and renal insufficiency. Therefore, we consider that future therapeutic trials of IMGN should include case stratification based on the presence or absence of FSGS on pretreatment biopsy.

The impact of donor-specific anti-HLA antibodies on late kidney allograft failure.

Despite improvements in outcomes of renal transplantation, kidney allograft loss remains substantial, and is associated with increased morbidity, mortality and costs. Identifying the pathologic pathways responsible for allograft loss, and the attendant development of therapeutic interventions, will be one of the guiding future objectives of transplant medicine. One of the most important advances of the past decade has been the demonstration of the destructive power of anti-HLA alloantibodies and their association with antibody-mediated rejection (ABMR). Compelling evidence exists to show that donor-specific anti-HLA antibodies (DSAs) are largely responsible for the chronic deterioration of allografts, a condition previously attributed to calcineurin inhibitor toxicity and chronic allograft nephropathy. The emergence of sensitive techniques to detect DSAs, together with advances in the assessment of graft pathology, have expanded the spectrum of what constitutes ABMR. Today, subtler forms of rejection--such as indolent ABMR, C4d-negative ABMR, and transplant arteriopathy--are seen in which DSAs exert a marked pathological effect. In addition, arteriosclerosis, previously thought to be a bystander lesion related to the vicissitudes of aging, is accelerated in ABMR. Advances in our understanding of the pathological significance of DSAs and ABMR show their primacy in the mediation of chronic allograft destruction. Therapies aimed at B cells, plasma cells and antibodies will be important therapeutic options to improve the length and quality of kidney allograft survival.

Combined posttransplant prophylactic IVIg/anti-CD 20/plasmapheresis in kidney recipients with preformed donor-specific antibodies: a pilot study.

BACKGROUND: This study assesses the immunologic, functional, and histologic course of kidney recipients with preformed donor-specific alloantibodies (DSA) receiving deceased donor kidneys according to two prophylactic strategies that have been sequentially applied posttransplant. METHODS: The first strategy combined posttransplant quadritherapy/intravenous immunoglobulin (group 1, n=36) and the second added to the above protocol anti-CD20/plasmapheresis (group 2, n=18). All patients had a concomitant evaluation of glomerular filtration rate, protocol biopsies, and DSA mean intensity of fluorescence (MFI) at 3 month and 1 year posttransplant. RESULTS: Peak and day-0 class-I or II DSAmax-MFI were similar in both groups. The rate of acute antibody-mediated rejection (AMR) was similar in both groups (19.6% vs. 16.6%, respectively). At 1 year posttransplant, group 2 was characterized by lower microcirculation inflammation lesions (glomerulitis+capilaritis score of 1.8+/-0.2 vs. 2.7+/-0.2, respectively, P=0.03), a lower rate of transplant glomerulopathy (7% vs. 38%, P=0.02), and a lower rate of chronic AMR (41.3% vs. 13.3%, respectively, P=0.03). The decline in DSA-MFI from day 0 to 1 year was 44%+/-13% in group 1 compared with 80%+/-8% in group 2 (P=0.02). Finally, the 1-year glomerular filtration rate was 43+/-16 vs. 54+/-16 mL/min/1.73 m(2) in groups 1 and 2, respectively (P=0.04). CONCLUSION: This study raises the possibility that a more intensive day 0 prophylactic immunosuppressive strategy combining intravenous immunoglobulin/anti-CD20/plasmapheresis in this high-risk population, despite similar rates of early acute clinical humoral rejection, is associated with significant differences in long-term function and chronic AMR rate. Future prospective randomized studies are needed to assess the best strategies to be applied in light of the pretransplant immunologic risk stratification.

Hypertensive nephrosclerosis.

PURPOSE OF REVIEW: Hypertensive nephrosclerosis is the second most common cause of end-stage renal disease, however morphologic evidence on the subject is poorly understood. A perennial and vexing problem in understanding kidney hypertension is that correlations between hypertension and vascular and glomerular lesions are only moderate, in part because all of these lesions are present to a greater or lesser degree in the normotensive, aging kidney, with racial differences in severity further compounding the problem. This review looks at newer data on this topic. RECENT FINDINGS: Recent data suggest that there are two different processes leading to glomerulosclerosis, and the combination of the two begins to explain why global correlations between hypertension and morphologic lesions are destined to remain poor. Arterial stiffening with increased pulse pressure down as far as the afferent arteriolar level likely plays an important role in the progression of glomerular lesions. Loss of renal autoregulation with glomerular hypertrophy, hyperfiltration, and focal segmental glomerulosclerosis is now recognized to contribute significantly to nephrosclerosis, particularly in the black population. Ischemic glomerulosclerosis, however, may ultimately be the most important lesion, with consequent hypoxia in the parenchyma beyond, leading to tubular atrophy and interstitial fibrosis. SUMMARY: Hypertensive nephrosclerosis should be seen as a process with two principal modes of glomerular sclerosis, ischemic and hypertrophic, with consequent focal segmental glomerulosclerosis, contributing variably to renal failure according to race and level of hypertension.

Antiphospholipid syndrome in systemic lupus erythematosus.

Renal biopsies occasionally show a combination of thrombotic microangiopathy as a result of antiphospholipid syndrome and lupus nephritis. The thrombosis in this case preceded the onset of lupus probably by approximately 8 yr, consisting of repeated fetal loss and venous thrombosis. More severe disease may have both arterial and venous thrombotic manifestations, including pulmonary emboli and cerebrovascular lesions. The antiphospholipid syndrome bears no relationship to the class of lupus nephritis but is accompanied by more frequent and greater hypertension and greater azotemia and interstitial fibrosis, and is associated with worse outcomes than lupus nephritis without antiphospholipid syndrome.

Parietal podocytes in normal human glomeruli.

Although parietal podocytes along the Bowman's capsule have been described by electron microscopy in the normal human kidney, their molecular composition remains unknown. Ten human normal kidneys that were removed for cancer were assessed for the presence and the extent of parietal podocytes along the Bowman's capsule. The expression of podocyte-specific proteins (podocalyxin, glomerular epithelial protein-1, podocin, nephrin, synaptopodin, and alpha-actinin-4), podocyte synthesized proteins (vascular endothelial growth factor and novH), transcription factors (WT1 and PAX2), cyclin-dependent kinase inhibitor p57, and intermediate filaments (cytokeratins and vimentin) was tested. In addition, six normal fetal kidneys were studied to track the ontogeny of parietal podocytes. The podocyte protein labeling detected parietal podocytes in all of the kidneys, was found in 76.6% on average of Bowman's capsule sections, and was prominent at the vascular pole. WT1 and p57 were expressed in some parietal cells, whereas PAX2 was present in all or most of them, so some parietal cells coexpressed WT1 and PAX2. Furthermore, parietal podocytes coexpressed WT1 and podocyte proteins. Cytokeratin-positive cells covered a variable part of the capsule and did not express podocyte proteins. Tuft-capsular podocyte bridges were present in 15.5 +/- 3.7% of the glomerular sections. Parietal podocytes often covered the juxtaglomerular arterioles and were present within the extraglomerular mesangium. Parietal podocytes were present in fetal kidneys. Parietal podocytes that express the same epitopes as visceral podocytes do exist along Bowman's capsule in the normal adult kidney. They are a constitutive cell type of the Bowman's capsule. Therefore, their role in physiology and pathology should be investigated.

Class IV-S versus class IV-G lupus nephritis: clinical and morphologic differences suggesting different pathogenesis.

BACKGROUND: A recently proposed reclassification of lupus nephritis divides class IV (diffuse proliferative) lupus nephritis into those cases with predominantly segmental proliferative lesions (class IV-S) and those with predominantly global proliferative lesions (class IV-G). This report explores the validity of this distinction and possible differences in pathogenesis between the 2 types of lesions. METHODS: Patients from a previously reported series of severe lupus nephritis, with initial biopsies (Bx1) and control biopsies (Bx2) at 6 months after induction therapy were reclassified according to the newly proposed classification. From the original series of 65 patients, 15 patients were reclassified as having class IV-S lesions and 31 patients class IV-G lesions. Clinical data at both biopsies and follow-up were available on all patients selected. RESULTS: Patients with IV-G lesions had worse proteinuria, lower serum hemoglobins, lower CH50s, and likely higher SCrs (P = .06) and lower C3s (P = .08) than class IV-S patients. Serum CH50 and C3 correlated negatively with severity of class IV-G lesions, but not at all with class IV-S lesions. Patients with class IV-G lesions had greater overall immune deposits and subendothelial deposits on IF and greater hyaline deposits on light microscopy. By contrast, class IV-S showed predominant mesangial deposits and a much higher rate of glomerular fibrinoid necroses (13.3 +/- 15.3% vs. 5.6 +/- 8.0% of viable glomeruli, P = .03). Other distinctions included the fact that membranoproliferative features were found only in class IV-G lesions, and glomerular monocyte/macrophages were much more frequent in this group than in class IV-S lesions (1.77 +/- 0.92 vs. 0.86 +/- 0.77, P = .008). Finally, class IV-G frequently involved all viable glomeruli (74.2% of cases), whereas segmental proliferative lesions never did (P < .0001). Survivals from doubling of SCr at 10 years did not differ between the 2 types at Bx1: 72.5% segmental versus 60.4% global, P= .53. However, among those with persistent lesions at Bx 2 (11 IV-S and 9 IV-G), there was a dramatic difference in 10-year survivals between IV-S lesions (63.6%) and IV-G lesions (0%), P = .08. CONCLUSION: There are definite clinical and morphologic differences between class IV-S and IV-G lesions. Data suggest that class IV-G lesions behave as an immune complex disease, having positive correlations with extent of immune deposits and negative correlations with serum complement levels, the model traditionally assumed for lupus nephritis as a whole. However, in class IV-S lesions, the presence of proportionally greater glomerular fibrinoid necroses and lack of correlation with extent of immune deposits suggest that these lesions may have a different pathogenesis.

Morphometric study of arterioles and glomeruli in the aging kidney suggests focal loss of autoregulation.

BACKGROUND: In the past it was widely assumed that hyaline afferent arteriolosclerosis was responsible for ischemic glomerulosclerosis in the aging and hypertensive kidney. However, glomerular lesions of focal segmental glomerulosclerosis are now recognized in essential hypertension. Experimentally, such lesions are associated with loss of autoregulation of blood flow and glomerular hyperperfusion, as well as initial glomerular hypertrophy. These observations challenge the notion of ischemia as a unitary explanation for glomerulosclerosis. METHODS: A morphometric study was performed on normal portions of eight kidneys removed for tumors in aging, normotensive patients. Measurements were made of 126 pairs of afferent arterioles and their associated glomeruli. In addition, the amount of extracellular matrix (ECM) in the immediate periglomerular region was quantitated. RESULTS: Afferent arterioles were divided into three types according to the presence or absence of hyaline deposits and whether these did or did not obstruct the lumen. Arterioles with nonobstructive hyaline deposits had lumens over twice as large as those without deposits (482 +/- 240 micro2 vs. 204 +/- 160 micro2, P=0.0000). Their associated glomeruli had significantly greater total capillary area, particularly the hilar capillaries (1276 +/- 797 micro2 vs. 667 +/- 492 micro2, P=0.002), but with larger individual capillaries elsewhere as well (P=0.03). Arterioles with obstructive deposits differed from those with nonobstructive deposits by their smaller lumens (P=0.001) and walls (P=0.004), with a higher proportion of ECM in the periglomerular region (P=0.001), all consistent with a later stage of lesion. Glomeruli were divided into four basic types: normal, hypertrophic, glomeruli with features of focal segmental glomerulosclerosis (FSGS-type), and ischemic. Compared to normal glomeruli, hypertrophic glomeruli were larger, with greater total capillary area (P=0.0005), particularly the hilar capillaries (P=0.0000), and larger capillaries in the remainder of the tuft (P=0.003), but showed no evident lesions. FSGS-type glomeruli were also larger, with larger hilar capillaries (P=0.0005), but showed an increase in ECM due to sclerotic lesions (P=0.004). The remaining capillaries showed an inverse relation with the amount of mesangial matrix, showing a spectrum of sizes from enlarged to shrunken. As anticipated, ischemic glomeruli were significantly smaller than normal ones in every parameter measured. There was a strong association between hypertrophic/FSGS-type glomeruli and hyaline arteriolosclerosis, found in 90.3% of such glomeruli, versus 29.1% for the remaining glomeruli (P=0.0001). The great majority of hyaline deposits were of the nonobstructive variety (86.2%), but some were obstructive (13.8%), particularly in FSGS-type glomeruli, consistent with a more advanced lesion. CONCLUSIONS: We believe we have demonstrated in the aging kidney of humans the morphologic correlates of loss of autoregulation, occurring on a focal basis, with afferent arteriolar dilatation and increase in glomerular capillary size and subsequent focal segmental glomerulosclerosis. Hyaline arteriolosclerosis of the nonobstructive sort is strongly associated with these changes and may play a role in their pathogenesis.

Glomerular epithelial-mesenchymal transdifferentiation in pauci-immune crescentic glomerulonephritis.

BACKGROUND: Among the cellular changes occurring in renal fibrosis, epithelial-mesenchymal cell transdifferentiation or transition (EMT) is a phenomenon characterized in epithelial cells by loss of epithelial markers and acquisition of mesenchymal phenotype and of fibrosing properties. METHODS: To test the hypothesis that EMT is involved in human pauci-immune crescentic glomerulonephritis (PICGN), we studied 17 renal biopsies from 11 PICGN patients for: (i) proliferating cell nuclear antigen (PCNA) and cell cycle inhibitors (cyclin-dependent kinase inhibitors) p27 and p57; (ii) cell lineage phenotype markers: podocalyxin, synaptopodin and GLEPP-1 for podocytes; CD68 for macrophagic epitope; CD3 for T lymphocytes; alpha-smooth muscle actin (alpha-SMA) for myofibroblasts; vimentin for mesenchymal cells; and cytokeratins (CKs) for parietal epithelial cells (PECs); (iii) glomerular fibrosis by labelling collagens I, III and IV, and heat-shock protein 47 (HSP47), a marker of collagen-synthesizing cells; and (iv) co-localization of alpha-SMA, CK and HSP47 using confocal laser microscopy. RESULTS: The crescent cells proliferated greatly. They did not express p27 and p57. Different cell lineage markers could be identified in crescents: the major component was made of 'dysregulated' PECs negative for CK, followed by PECs positive for CK, macrophagic cells and myofibroblasts. Furthermore, some cells co-expressed CK and alpha-SMA. This latter co-expression suggests a transitional phase in the dynamic phenomenon of EMT. Therefore, proliferative and dysregulated glomerular epithelial cells could be a possible cellular source of myofibroblasts via EMT. In addition, HSP47 labelled many crescent cells and frequently co-localized in CK-positive epithelial cells and in alpha-SMA-positive myofibroblasts, indicating that these cells were involved in glomerular accumulation of collagens. CONCLUSION: EMT is a transient cellular phenomenon present in glomeruli in human PICGN contributing to the formation of myofibroblasts from epithelial cells and to glomerular fibrosis.

Outcome of relapse in lupus nephritis: roles of reversal of renal fibrosis and response of inflammation to therapy.

BACKGROUND: Renal relapse in lupus nephritis has been shown to have ominous prognostic significance with the majority of patients progressing to doubling of serum creatinine (CRX2). However, not all patients do so. This report explores the roles of response of inflammation to therapy and of glomerular scarring and interstitial fibrosis and their potential reversal to outcome of renal relapse. METHODS: Renal biopsies from 71 patients with lupus nephritis with an initial biopsy (Bx1) and systematic control biopsy (Bx2) after six months of therapy, as well as subsequent biopsies for clinical indications, were studied. The relationships of morphologic factors to renal relapse and its outcome as well as to CRX2 and end-stage renal disease (ESRD) were analyzed. Cox proportional hazards modeling was used to assess association of morphologic variables with outcomes. RESULTS: Renal interstitial fibrosis and glomerular segmental scarring were partially reversible in 17 and 11 patients, respectively. This decline was associated with an excellent prognosis, with only one patient in each group (5.9% and 9.1% respectively) progressing to CRX2. All 18 patients who progressed to CRX2 either failed to respond to therapy (7 patients) as defined by normalization of serum creatinine (SCr) and reduction of proteinuria to < or =1 g/day, or relapsed after initial response (11 patients), as defined by recent rise of SCr > 50% and/or proteinuria > 3.5 g/day. However, relapse also occurred in 11 of 47 other patients without progression to CRX2. These patients showed a greater initial response of inflammation and deposits to therapy and fibrous lesions partially reversed in the period prior to relapse, so that active lesions were superimposed on a lower level of chronic lesions. By contrast, chronic lesions mounted steadily in those who progressed to CRX2. Cox proportional hazards modeling indicated a strong association of inflammatory variables with renal relapse, CRX2 and ESRD. However, the extent of immunoglobulin deposits was not significantly associated with any outcome. Finally, we found that failure of disease to remit also is associated with a high rate of CRX2 (64.8% vs. 13.0%, P = 0.00034). CONCLUSIONS: Interstitial fibrosis and glomerular scarring in systemic lupus erythematosus are partially reversible, and this reversal is attended by an excellent outcome. The outcome of renal relapse is determined by the initial response of inflammatory and chronicity elements to therapy, those with prior partial reversal of interstitial and glomerular scarring having a good outcome, and those in whom fibrotic lesions have continued to increase and have a poor outcome. Inflammatory variables appear to be more important in determining outcome than immunoglobulin deposits.