Mesangial phenotypic changes associated with cellular lesions in primary focal segmental glomerulosclerosis

A novel de novo truncating TRIM8 variant associated with childhood-onset focal segmental glomerulosclerosis without epileptic encephalopathy: a case report

BACKGROUND

Heterozygous truncating variants in the Tripartite motif containing 8 (TRIM8) gene have been reported to cause epileptic encephalopathy, both with and without proteinuria. A recent study showed a lack of TRIM8 protein expression, with suppressor of cytokine signaling 1 (SOCS1) overexpression, in podocytes and tubules from a patient with a TRIM8 variant, who presented with epileptic encephalopathy and focal segmental glomerulosclerosis (FSGS). To date, no patients with TRIM8 variants who presented with nephrotic syndrome but without neurological manifestations have been described.

CASE PRESENTATION

An 8-year-old girl presented with nephrotic syndrome, without epilepsy or developmental delay. Her kidney biopsy specimens showed FSGS and cystic dilatations of the distal tubules. Whole-exome sequencing identified a novel de novo heterozygous variant in the C-terminal encoding portion of TRIM8 (c.1461C > A), resulting in a premature stop codon (p.Tyr487*). Reverse transcription-polymerase chain reaction using peripheral blood mononuclear cells identified the mRNA sequence of the mutant allele, which confirmed an escape from nonsense-mediated mRNA decay. Immunofluorescence studies showed a lack of TRIM8 expression in glomerular and tubular cells and cystic dilatation of distal tubules. Immunohistochemical studies showed overexpression of SOCS1 in glomerular and tubular cells.

CONCLUSIONS

We reported a patient with FSGS, associated with a de novo heterozygous TRIM8 variant, without any neurological manifestations. Our results expanded the clinical phenotypic spectrum of TRIM8 variants.

Usefulness of atherogenic index of plasma for estimating reduced eGFR risk: insights from the national health and nutrition examination survey

AIMS

Previous studies have identified Atherogenic index of plasma (AIP) as a simple measure of atherosclerosis. Because atherosclerosis plays a role in the development of renal damage, our study aims to evaluate the effect of AIP on the risk of reduced eGFR and assess its usefulness to refine the risk stratification of reduced estimated glomerular filtration rate (eGFR).

METHODS

Our study included 15,836 participants from the National Health and Nutritional Survey (NHANES) 2009-2016. Association was investigated by logistic regression. AIP was calculated as log (triglycerides/high-density lipoprotein cholesterol). Reduced eGFR was determined as eGFR < 60 ml/min per 1.73 m*2.

RESULTS

The prevalence of reduced eGFR was 8.01%. In the full model, each SD increase of AIP leaded to 27.4% additional risk for reduced eGFR. After dividing AIP into quartiles, the fourth quartile had a 1.649 times risk than the first quartile. Moreover, smooth curve fitting suggested that the risk of reduced eGFR elevated linearly with the increase of AIP. Subgroup analysis demonstrated that the association between AIP and reduced eGFR was robust in sex, body mass index, hypertension, and diabetes subpopulation, but the association was significantly stronger in black race and people aged less than 50 years old. Additionally, AUC displayed an advancement when introducing AIP into established risk factors (0.875 cs. 0.897, P < 0.001), category-free net reclassification index (0.249, 95% CI: 0.192-0.306, P < 0.001) and integrated discrimination index (0.007, 95% CI: 0.004-0.009, P < 0.001) also suggested the improvement from AIP.

CONCLUSION

The present work suggested a linear association between AIP and reduced eGFR. Furthermore, the results showed that the association was stronger in black race and people aged less than 50 years old. Most importantly, our work implicated the usefulness of AIP to refine the risk stratification of reduced eGFR.

The impact of monocyte to high-density lipoprotein ratio on reduced renal function: insights from a large population

Aim: To investigate whether monocyte to HDL cholesterol ratio (MHR) can improve the risk stratification of reduced renal function by estimating atherosclerosis. Patients & methods: The cross-sectional study included 8159 subjects (males: 45.73%, mean age: 54.12 years) from Northeast China in 2013. Results: Each standard deviation increase of MHR brought 42.9% additional risk of reduced renal function in males. In females, MHR strongly correlated with reduced renal function before it reached a breakpoint (MHR = 0.25). Additionally, net reclassification improvement identified the value of MHR (0.199; 95% CI: 0.030–0.369; p = 0.021) to improve the risk classification of renal function reduction. Conclusion: This study implicates that MHR is independently associated with reduced renal function and can refine the risk stratification of renal function reduction.

Progression of renal fibrosis in congenital CKD model rats with reduced number of nephrons

A congenital reduction in the number of nephrons is a critical risk factor for both onset of chronic kidney disease (CKD) and its progression to end-stage kidney disease (ESKD). Hypoplastic kidney (HPK) rats have only about 20% of the normal number of nephrons and show progressive CKD. This study used an immunohistological method to assess glomerular and interstitial pathogenesis in male HPK rats aged 35-210days. CD68 positive-macrophages were found to infiltrate into glomeruli in HPK rats aged 35 and 70days and to infiltrate into interstitial tissue in rats aged 140 and 210days. HPK rats aged 35 and 70days showed glomerular hypertrophy, loss of normal linear immunostaining of podocine, and increased expression of PDGFr-β, TGF-β, collagens, and fibronectin, with all of these alterations gradually deteriorating with age. α-SMA-positive myofibroblasts were rarely detected in glomerular tufts, whereas α-SMA-positive glomerular parietal epithelium (GPE) cells were frequently observed along Bowman's capsular walls. The numbers of PDGFr-β-positive fibroblasts in interstitial tissue were increased in rats aged 35days and older, whereas interstitial fibrosis, characterized by the increased expression of tubular PDGF-BB, the appearance of myofibroblasts doubly positive for PDGFr-β and α-SMA, and increased expression of collagens and fibronectin, were observed in rats aged 70 and older. These results clearly indicate that congenital CKD with only 20% of nephrons cause renal fibrosis in rats.

Serum myeloid-related protein 8/14 in minimal change- and glomerulonephritis-related nephrotic syndrome

BACKGROUND

Myeloid-related protein 8/14 (MRP8/14) forms stable heterodimers and is the major calcium-binding protein secreted by activated granulocytes and monocytes. We evaluated whether serum MRP8/14 level is a useful indicator for a differential diagnosis of glomerulonephritis (GN)- and minimal change disease (MC)- related nephrotic syndrome (NS).

METHODS

Serum MRP8/14 complex was evaluated in 37 NS patients with MC or GN. These patients were divided into two groups. Group 1 consisted of 13 NS patients with MC, and group 2 consisted of 24 NS patients with GN. Group 2 was further divided into four subgroups: IgA nephropathy (IgAN; n = 5), Henoch-Schönlein purpura nephritis (HSPN; n = 6), focal segmental glomerulosclerosis (FSGS; n = 12), and acute GN Poststreptococcal acute glomeruloNephritis (PSAGN; n = 1).

RESULTS

The clinical manifestations, laboratory findings, serum MRP8/14 level, and renal accumulation of MRP8 were investigated for each group. No significant inter-group differences were observed for serum total protein, serum albumin, or blood urea nitrogen and urinary protein excretions. Mean serum MRP8/14 in the IgAN, HSPN, FSGS, and PSAGN groups was higher than in group 1. Further, the mean glomerular and interstitial MRP8 staining scores in the IgAN, HSPN, and PSAGN groups were higher than in group 1.

CONCLUSIONS

Serum MRP8/14 level may be a useful indicator for differential diagnosis between GN- and MC- related NS.

Podocyte injury-driven lipid peroxidation accelerates the infiltration of glomerular foam cells in focal segmental glomerulosclerosis

Intracapillary foam cell infiltration with podocyte alterations is a characteristic pathology of focal segmental glomerulosclerosis (FSGS). We investigated the possible role of podocyte injury in glomerular macrophage and foam cell infiltration in a podocyte-selective injury model (NEP25 mice) and hypercholesterolemic model [low-density lipoprotein receptor deficiency (LDLR(-/-)) mice] with doxorubicin-induced nephropathy. Acute podocyte selective injury alone failed to induce glomerular macrophages in the NEP25 mice. However, in the doxorubicin-treated hypercholesterolemic LDLR(-/-) mice, glomerular macrophages/foam cells significantly increased and were accompanied by lipid deposition and the formation and ingestion of oxidized phospholipids (oxPLs). Glomerular macrophages significantly correlated with the amount of glomerular oxPL. The NEP25/LDLR(-/-) mice exhibited severe hypercholesterolemia, glomerular lipid deposition, and renal dysfunction. Imaging mass spectrometry revealed that a major component of oxidized low-density lipoprotein, lysophosphatidylcholine 16:0 and 18:0, was present only in the glomeruli of NEP25/LDLR(-/-) mice. Lysophosphatidylcholine 16:0 stimulated mesangial cells and macrophages, and lysophosphatidylcholine 18:0 stimulated glomerular endothelial cells to express adhesion molecules and chemokines, promoting macrophage adhesion and migration in vitro. In human FSGS, glomerular macrophage-derived foam cells contained oxPLs accompanied by the expression of chemokines in the tuft. In conclusion, glomerular lipid modification represents a novel pathology by podocyte injury, promoting FSGS. Podocyte injury-driven lysophosphatidylcholine de novo accelerated glomerular macrophage-derived foam cell infiltration via lysophosphatidylcholine-mediated expression of adhesion molecules and chemokines in glomerular resident cells.

The expression of cytoskeletal proteins in kidney specimens of children with primary focal segmental glomerulosclerosis

Several studies have evaluated cytoskeletal proteins as prognostic factors for some types of nephrotic syndrome. However, studies concerning children with FSGS are scarce. This study was done to evaluate the glomerular, tubular, and interstitial expression of vimentin, desmin, and alpha smooth muscle actin (α-SMA) in kidney specimens of children with FSGS. Clinical and histologic data of 31 children with FSGS were reviewed. Thirty one formalin-fixed, paraffin-embedded kidney biopsy sections (3 μm) were selected for immunohistochemical staining. Double immunohistochemistry using a microwave-based two-color staining was applied. The mean age at onset in male and female was 56.3 ± 41.4 and 78.0 ± 60.4 months, respectively. The duration of follow-up was 46.3 ± 56.5 months. Interstitial fibrosis and tubular atrophy were reported in 42% and 54% of the patients, respectively. The latest evaluated mean blood pressure was significantly correlated with the expression of both vimentin and α-SMA in the interstitium (P < 0.05). However, we were not able to demonstrate any cytoskeletal protein expression as an independent predictor for renal survival. Further studies with larger sample size and longer follow-up periods are warranted to investigate the prognostic values of other histopathologic features in pediatrics with FSGS.

[Quantification of sclerotic renal glomeruli during the aging process in humans]

INTRODUCTION

The aim of our research was to quantify the presence of totally sclerotized glomeruli during the aging process.

MATERIAL AND METHODS

The study material were kidney tissue samples taken from fifty-six cadavers, their age ranging from 20 to over 70 years. They were classified in six age groups: I (20-29), II (30-39), III (40-49); IV (50-59); V (60-69) and VI (older than 70). The tissue samples were routinely histologically processed and then cut into the slices 5 mm thick, which were then stained and stereologically analyzed under the microscope with a projection screen (Reichert Visopan) with 10 x lens magnification and multipurpose test system M42 application. The analysis was carried out on 20 fields of vision per one sample. The numerical density of completely sclerotic and other glomeruli was measured, and the resulting percentages were obtained from this parameter.

RESULTS

Completely sclerotic glomeruli were not found in the first group. They were observed in the II aging group (5%) for the first time. Their numerical density and percentage increased during the aging process and was 18% in the IV, 25% in the V and maximally 37.5% in the VI aging group.

CONCLUSION

Finally, the above cited results pointed to the increase of completely sclerotized and the decreased presence of normal glomeruli during the aging process.

Bradykinin receptor 1 activation exacerbates experimental focal and segmental glomerulosclerosis

Focal and segmental glomerulosclerosis (FSGS) is one of the most important causes of end-stage renal failure. The bradykinin B1 receptor has been associated with tissue inflammation and renal fibrosis. To test for a role of the bradykinin B1 receptor in podocyte injury, we pharmacologically modulated its activity at different time points in an adriamycin-induced mouse model of FSGS. Estimated albuminuria and urinary protein to creatinine ratios correlated with podocytopathy. Adriamycin injection led to loss of body weight, proteinuria, and upregulation of B1 receptor mRNA. Early treatment with a B1 antagonist reduced albuminuria and glomerulosclerosis, and inhibited the adriamycin-induced downregulation of podocin, nephrin, and α-actinin-4 expression. Moreover, delayed treatment with antagonist also induced podocyte protection. Conversely, a B1 agonist aggravated renal dysfunction and even further suppressed the levels of podocyte-related molecules. Thus, we propose that kinin has a crucial role in the pathogenesis of FSGS operating through bradykinin B1 receptor signaling.

Attenuation of endocrine-exocrine pancreatic communication in type 2 diabetes: pancreatic extracellular matrix ultrastructural abnormalities

Ultrastructural observations reveal a continuous interstitial matrix connection between the endocrine and exocrine pancreas, which is lost due to fibrosis in rodent models and humans with type 2 diabetes mellitus (T2DM). Widening of the islet-exocrine interface appears to result in loss of desmosomes and adherens junctions between islet and acinar cells and is associated with hypercellularity consisting of pericytes and inflammatory cells in T2DM pancreatic tissue. Organized fibrillar collagen was closely associated with pericytes, which are known to differentiate into myofibroblasts-pancreatic stellate cells. Of importance, some pericyte cellular processes traverse both the connecting islet-exocrine interface and the endoacinar interstitium of the exocrine pancreas. Loss of cellular paracrine communication and extracellular matrix remodeling fibrosis in young animal models and humans may result in a dysfunctional insulino-acinar-ductal-incretin gut hormone axis, resulting in pancreatic insufficiency and glucagon-like peptide deficiency, which are known to exist in prediabetes and overt T2DM in humans.

PPAR{alpha} attenuates the proinflammatory response in activated mesangial cells

The activated mesangial cell is an important therapeutic target for the control of glomerulonephritis. The peroxisome proliferator-activated receptor alpha (PPARalpha) has attracted considerable attention for its anti-inflammatory effects; however, its roles in the mesangial cells remain unknown. To determine the anti-inflammatory function of PPARalpha in mesangial cells, wild-type and Ppara-null cultured mesangial cells were exposed to lipopolysaccharide (LPS). LPS treatment caused enhanced proinflammatory responses in the Ppara-null cells compared with wild-type cells, as revealed by the induction of interleukin-6, enhanced cell proliferation, and the activation of the nuclear factor (NF)-kappaB signaling pathway. In wild-type cells resistant to inflammation, constitutive expression of PPARalpha was undetectable. However, LPS treatment induced the significant appearance and substantial activation of PPARalpha, which would attenuate the proinflammatory responses through its antagonizing effects on the NF-kappaB signaling pathway. The induction of PPARalpha was coincident with the appearance of alpha-smooth muscle actin, which might be associated with the phenotypic changes of mesangial cells. Moreover, another examination using LPS-injected wild-type mice demonstrated the appearance of PPARalpha-positive cells in glomeruli, suggesting in vivo correlation with PPARalpha induction. These results suggest that PPARalpha plays crucial roles in the attenuation of inflammatory response in activated mesangial cells. PPARalpha might be a novel therapeutic target against glomerular diseases.

Clinical features and mutational survey of NPHS2 (podocin) in Japanese children with focal segmental glomerulosclerosis who underwent renal transplantation

Recurrent FSGS is a major challenge in the field of nephrology. To clarify the role of NPHS2 defects in the pathogenesis of FSGS recurrence, we sequenced all eight exons of NPHS2 in 11 Japanese pediatric FSGS patients with or without post-transplant recurrence. All patients had biopsy-proven primary FSGS, had no family history of renal diseases or consanguinity, were steroid-resistant, and received living-related renal transplantation. The mean age at onset was 5.0 +/- 3.1 yr and mean age at renal transplantation was 10.4 +/- 4.1 yr. Mutational analysis of NPHS2 was performed using polymerase chain reaction and direct sequencing. We found a synonymous T/C polymorphism at alanine 318 (GCC to GCT) in seven of 11 patients but no other causative NPHS2 mutations. FSGS recurred immediately after transplant in seven patients, while the remaining four patients had no recurrence for 3.2-5.8 yr. There were no differences between recurrent and non-recurrent patients in the onset age and the interval from onset to ESRD. In conclusion, we detected no causative NPHS2 mutations in Japanese pediatric FSGS patients with or without post-transplant recurrence. Further studies on the involvement of other genes are required to better understand recurrent FSGS.

TGF-beta-regulated collagen type I accumulation: role of Src-based signals

Transforming growth factor-beta (TGF-beta) stimulates myofibroblast transdifferentiation, leading to type I collagen accumulation and fibrosis. We investigated the function of Src in TGF-beta-induced collagen I accumulation. In human mesangial cells, PTyr416 Src (activated Src) was 3.3-fold higher in TGF-beta-treated cells than in controls. Src activation by TGF-beta was blocked by rottlerin and by a dominant negative mutant of protein kinase Cdelta (PKCdelta), showing that TGF-beta activates Src by a PKCdelta-based mechanism. Pharmacological inhibitors and a dominant negative Src mutant prevented the increase in collagen type I secretion in cells exposed to TGF-beta. Similarly, on-target Src small interference RNA (siRNA) prevented type I collagen secretion in response to TGF-beta, but off-target siRNA complexes had no effect. It is well established in mesangial cells that upregulation of type I collagen by TGF-beta requires extracellular signal-regulated kinase 1/2 (ERK1/2), and we found that activation of ERK1/2 by TGF-beta requires Src. In conclusion, these results suggest that stimulation of collagen type I secretion by TGF-beta requires a PKCdelta-Src-ERK1/2 signaling motif.

Glomerular expression of transforming growth factor-beta (TGF-beta) isoforms in mice lacking CD2-associated protein

Mice lacking CD2-associated protein (CD2AP-/-) develop glomerular lesions resembling human focal segmental glomerulosclerosis (FSGS) between 3-4 weeks of age and die approximately 2 weeks later from massive proteinuria and renal failure. The mechanisms involved in the glomerular injury in this model are unclear. In this study, we used laser capture microdissection (LCM) and real-time PCR, and examined expression of TGF-ss isoforms in CD2AP-/- mice at the level of isolated glomeruli. Total RNA yield from cryosections of 30 glomeruli was 10.71 ng (SD, 5.45) in CD2AP+/+ group (n =7), and 4.20 ng (SD, 2.04) in CD2AP-/- group (n =8), p =0.008. Expression of TGF-ss1 mRNA was increased 1.5-fold in the whole kidney (p =0.030), and twofold in isolated CD2AP-/- glomeruli (p =0.026). Whole kidney mRNA of TGF-ss receptor I (RI) and II (RII) was not different in CD2AP-/- and CD2AP+/+ animals, but it was increased in CD2AP-/- glomerular samples by 4.38-fold (p =0.001) and 11.37-fold (p =0.0163), respectively. By using LCM we confirmed increased glomerular expression levels of TGF-ss isoforms previously described by our group in glomeruli isolated by sieving in CD2AP KO mice and underscored the importance of local factors in the development of glomerulosclerosis.

Shared expression of phenotypic markers in systemic sclerosis indicates a convergence of pericytes and fibroblasts to a myofibroblast lineage in fibrosis

The mechanisms by which microvascular damage leads to dermal fibrosis in diffuse cutaneous systemic sclerosis (dcSSc) are unclear. We hypothesized that microvascular pericytes constitute a cellular link between microvascular damage and fibrosis by transdifferentiating into myofibroblasts. We used a combination of immunohistochemistry and double immunofluorescence labelling of frozen skin biopsies taken from normal and dcSSc patients to determine whether a phenotypic link between pericytes and myofibroblasts exists in dcSSc. Using α-smooth muscle actin, the ED-A splice variant of fibronectin (ED-A FN) and Thy-1 to identify myofibroblasts, we demonstrated the presence of myofibroblasts in fibrotic dcSSc skin. Myofibroblasts were totally absent from control skin, atrophic stage dcSSc skin and non-lesional skin. Using double immunofluorescence labelling, both myofibroblasts and pericytes were shown to express ED-A FN and Thy-1 in dcSSc skin but not in control skin. Proliferating cell nuclear antigen was also expressed by myofibroblasts and pericytes in dcSSc skin while being absent in control skin. These observations suggest that the presence of myofibroblasts may represent a transitional phase during the fibrotic stages of dcSSc and that Thy-1^+ve pericytes participate in the fibrogenic development of dcSSc by synthesizing ED-A FN, which may be associated with a proliferation and transition of pericytes and fibroblasts to myofibroblasts, thus linking microvascular damage and fibrosis.

A combined low-density lipoprotein apheresis and prednisone therapy for steroid-resistant primary focal segmental glomerulosclerosis in children

BACKGROUND

Treatment of steroid-resistant (SR) primary focal segmental glomerulosclerosis (FSGS) remains a major challenge in nephrology. A prospective study was conducted to clarify the therapeutic role of low-density lipoprotein apheresis (LDL-A) in 11 nephrotic children with SR and cyclosporine A (CsA)-resistant primary FSGS.

METHODS

Based on entry criteria, all 11 eligible patients had biopsy-proven primary FSGS presenting with nephrotic syndrome (NS) and were resistant to steroid and conventional-dose CsA therapy. LDL-A was performed twice a week for 3 weeks (first course), then weekly for 6 weeks (second course). Beginning from the second LDL-A course, a dosage of 1 mg/kg/d of prednisone was administered for 6 weeks, then tapered.

RESULTS

Seven patients experienced remission of NS, 5 of whom achieved complete remission within 4 weeks after initiating prednisone therapy with LDL-A. These 5 patients maintained normal renal function during follow-up (median, 4.4 years). Of 2 patients with partial remission, 1 patient maintained stable renal function during follow-up (4.5 years), whereas the other patient showed a gradual decline in renal function and progressed to end-stage renal failure (ESRF) 7.8 years after LDL-A therapy. Four patients who were considered to experience treatment failure had persistent NS and progressed to ESRF in 1.3 years (median) after LDL-A therapy. Complete remission (n = 5) was associated with significantly more highly selective proteinuria compared with treatment failure (n = 4).

CONCLUSION

This study suggests that combined LDL-A and prednisone therapy can be a valuable addition to therapeutic options for treating patients with SR-FSGS. The role of LDL-A in treating these patients deserves to be assessed further in larger randomized controlled trials.

Effect of enalapril and losartan on the events that precede diabetic nephropathy in rats

BACKGROUND

Mesangial cell proliferation, phenotype change, and increased transforming growth factor-beta (TGF-beta) precede mesangial expansion in diabetic rats. Experiments using mesangial cell culture have shown that angiotensin II increases TGF-beta production by these cells. The aim of the present study was to investigate the effect of enalapril and losartan on the events that precede diabetic nephropathy in rats. It was also analyzed if the determination of urinary TGF-beta could be a mean for the evaluation of therapeutic efficacy in this disease.

METHODS

Eighty-two female Wistar rats were made diabetic by intravenous injection of streptozotocin diluted in citrate buffer, and citrate buffer alone was injected into the control group (N = 34). Ten days later, the right kidney was removed. Thirty diabetic rats were treated with enalapril, DMN + E, in drinking water (20 mg/L) and 24 with losartan, DMN + L (50 mg/L). Urinary TGF-beta was determined 90 days after STZ or buffer injection, the animals were killed, and the kidneys were removed for histological and immunohistochemical studies.

RESULTS

The immunostaining for TGF-beta and fibronectin in the cortical tubulointerstitium and glomeruli was higher in untreated diabetic rats (p < 0.001). Treatment with enalapril or losartan reduced this increase. The urinary TGF-beta excretion (pg/mg urinary creatinine) was 48.6 +/- 5.9 in control animals, 603.9 +/- 80.41 in untreated diabetic rats, 279.3 +/- 47.0 in diabetic rats treated with enalapril, and 243.7 +/- 40.0 in rats treated with losartan.

CONCLUSIONS

We concluded that enalapril or losartan treatment can modify events that precede diabetic nephropathy by reducing TGF-beta and fibronectin expression in glomeruli and tubulointerstitium as well as urinary TGF-beta content.

Significance of early phenotypic change of glomerular podocytes detected by Pax2 in primary focal segmental glomerulosclerosis

In primary focal segmental glomerulosclerosis (FSGS), phenotypic alteration of podocytes is important for the development of cellular lesions (CLs), which precede glomerular scar formation. WT1 and Pax2 are transcription factors involved in kidney development and phenotypic regulation of glomerular epithelial cells. However, the role of WT1 and Pax2 in the development of CLs in primary FSGS is unclear. Using immunohistochemistry, the expression of WT1, Pax2, and cytokeratin (CK), an epithelial marker never found in normal podocytes, was examined in 35 biopsy samples of primary FSGS. Segmental lesions were categorized as: (1) classic segmental scar (CS), (2) CL, and (3) monolayer epithelial (ME) lesion. In normal glomeruli, WT1 was strongly positive in podocytes and weakly positive in parietal epithelium of Bowman's capsule. Pax2 was strongly positive in parietal epithelium of Bowman's capsule, but never expressed in podocytes. Expression of WT1, Pax2, and CK was scantly positive in CSs. WT1 expression was decreased in CLs compared with unaffected podocytes, but Pax2 and CK were strongly expressed in CLs and podocytes of morphologically unaffected tufts in cases with CLs. WT1 expression was strong, as well as Pax2 and CK, in ME lesions. Clinically, urinary protein levels were significantly greater, and the interval from clinical onset to biopsy was significantly shorter in patients with CLs. These results suggest that re-expression of Pax2 in podocytes resulting in phenotypic change to a different epithelial form is one of the important changes for the development of CLs and ME lesions. Alteration from WT1 to Pax2 in podocytes may have an important role in the initiation of glomerular injury in primary FSGS.

Alpha-smooth muscle actin and proliferating cell nuclear antigen expression in focal segmental glomerulosclerosis: functional and structural parameters of renal disease progression

The aim of the present study was to investigate the expression of alpha-smooth muscle actin (alpha-SM-actin) and proliferating cell nuclear antigen (PCNA) in renal cortex from patients with focal segmental glomerulosclerosis (FSGS) and their correlations with parameters of renal disease progression. We analyzed renal biopsies from 41 patients with idiopathic FSGS and from 14 control individuals. The alpha-SM-actin immunoreaction was evaluated using a score that reflected the changes in the extent and intensity of staining in the glomerular or cortical area. The PCNA reaction was quantified by counting the labeled cells of the glomeruli or renal cortex. The results, reported as median +/- percentile (25th; 75th), showed that the alpha-SM-actin scores in the glomeruli and tubulointerstitium from the renal cortex were 2.0 (2.0; 4.0) and 3.0 (3.0; 4.0), respectively, in patients with FSGS, and 0.5 (0.0; 1.0) and 0.0 (0.0; 0.5) in the controls. The number of PCNA-positive cells per glomerulus and graded field of tubulointerstitium from the renal cortex was 0.2 (0.0; 0.4) and 1.1 (0.3; 2.2), respectively, for patients with FSGS, and 0.0 (0.0; 0.5) and 0.0 (0.0; 0.0) for controls. The present data showed an increase of alpha-SM-actin and PCNA expression in glomeruli and renal cortex from FSGS patients. The extent of immunoreaction for alpha-SM-actin in the tubulointerstitial area was correlated with the intensity of proteinuria. However, there was no correlation between the kidney expression of these proteins and the reciprocal of plasma creatinine level or renal fibrosis. These findings suggest that the immunohistochemical alterations may be reversible.

Expression of alpha-smooth muscle actin and fibronectin in tubulointerstitial lesions of cats with chronic renal failure

OBJECTIVE

To examine renal expression of alpha-smooth muscle actin (alpha-SMA) and fibronectin in cats with tubulointerstitial nephritis (TIN) for use in predicting progression to renal fibrosis.

ANIMALS

19 cats with TIN and 9 cats without nephritis.

PROCEDURE

Serum creatinine and BUN concentrations were measured. Indices for glomerular extra-cellular matrix (ECM), tubular injury (TI), and fibronectin were determined in renal specimens to quantify the extent of injury and fibrotic lesions. Expression of alpha-SMA in renal tissue was immunohistochemically detected, and correlations were evaluated between the alpha-SMA index and other histologic and clinical variables.

RESULTS

The alpha-SMA index in tubulointerstitial areas (1.63 +/- 0.78) was significantly higher in cats with TIN, especially in the periglomerular and peritubular areas, than in cats without nephritis (0.20 +/- 0.14). The alpha-SMA index was significantly associated with the TI index (r2 = 0.70), fibronectin index (r2 = 0.95), BUN concentration (r = 0.64), and serum creatinine concentration () = 0.66). Of special interest was that interstitial alpha-SMA expression appeared evident in the kidneys at an early stage of TIN, prior to the onset of ECM deposition.

CONCLUSION AND CLINICAL RELEVANCE

Analysis of results of histologic and clinical examinations revealed that interstitial alpha-SMA expression may have clinical importance and may be a useful early histologic marker for development of chronic renal failure in cats. An immunohistochemical examination for fibrogenic molecules (such as alpha-SMA expression) may provide fundamental information on the pathogenesis of early-stage renal disease and aid clinical management of cats with chronic renal failure, including TIN.

Phenotypic characteristics and cyclin-dependent kinase inhibitors repression in hyperplastic epithelial pathology in idiopathic focal segmental glomerulosclerosis

Hyperplastic glomerular epithelial lesion is an important determinant of the progression of idiopathic focal segmental glomerulosclerosis (FGS). The proliferation and differentiation of glomerular epithelial cells and parietal epithelial cells (PECs) are regulated differently by cyclin and cyclin-dependent kinase inhibitors (CKIs) during nephrogenesis. To access the cellular mechanism underlying epithelial hyperplasia in the development of FGS, the present study applied immunohistochemistry to 21 cases of FGS to demonstrate expression of cell-cycle molecules and phenotypic characterization in proliferative epithelial lesions in FGS. The materials included segmental sclerosis (18.1%), which was divided into monolayer epithelial lesions (64.6%) and cellular lesions (35.4%). All of the cellular lesions expressed cytokeratin, frequently with Ki-67 (82.4%) and less frequently with cyclin A (17.7%), but were invariably negative for podocyte markers (PHM-5 and synaptopodin) and CKIs (p27kip1 and p57kip2). Podocytes in nonsclerotic tuft in the same glomeruli with cellular lesions strongly expressed CKIs and podocyte markers. Moreover, electron microscopy showed that some large proliferating cells with prominent nucleoli have a broad cell base attached to Bowman's capsule. These cells have cilia and a junctional complex with neighboring hyperplastic cells, some of which directly cover the glomerular basement membrane. This suggests that cellular lesions are of PEC origin. Monolayer epithelial lesions also exclusively exhibited a PEC phenotype with reciprocal expression of podocyte markers and cytokeratin. In addition, CKIs are weakly expressed in monolayer epithelial lesions, suggesting a re-entry of cell-cycle quiescent. In conclusion, proliferation of PEC, sustained by repression of CKIs in nature and simultaneous activation of cyclin A, is the actual molecular background to the cellular lesions in FGS. Cellular lesions may result in monolayer epithelial lesions that retain the PEC phenotype and enter a common pathway to glomerulosclerosis.

Plasmapheresis as the sole therapy for rapidly progressive Henoch-Schönlein purpura nephritis in children

To clarify the therapeutic role of plasmapheresis (PP) for patients with Henoch-Schönlein purpura (HSP) nephritis, the clinical courses of nine children with a rapidly progressive type of HSP nephritis, who were treated with PP as the sole therapy, were retrospectively evaluated. All patients had nephrotic-range proteinuria (4.9 +/- 2.5 g/m2/d, mean +/- SD) and decreased glomerular filtration rate (GFR) (46.5 +/- 9.5 mL/min/1.73 m2) at the time of the initiation of PP. Biopsy specimens taken before PP showed large crescents involving more than 50% of the glomerular circumference in 56.8 +/- 6.9% of the glomeruli examined. The mean interval between disease onset and initiation of PP was 39.1 +/- 22.1 days. The PP regimen consisted of thrice-weekly treatment for 2 weeks, then weekly treatment for 6 weeks. No patients received any steroids or cytotoxic drugs, except for the use of steroids to manage severe abdominal pain. All patients responded promptly to PP with improvement in renal function, reduction of proteinuria, and subsidence of purpuric rash and abdominal pain. Six of nine patients showed further improvements without any other treatments; four had complete recovery, and two had only microscopic hematuria at the latest observation (follow-up period, 9.6 +/- 4.3 years). The remaining three patients showed a rebound increase of proteinuria after completion of PP; two of whom progressed to end-stage renal failure at 14.1 years and 1.8 years after disease onset. Because all patients had the most severe forms of nephritis, reported to carry a grave prognosis, this study suggests that PP as the sole therapy is effective in improving the prognosis of patients with rapidly progressive HSP nephritis, particularly if instituted early in the course of the disease. The role of PP in treating HSP nephritis deserves to be assessed further in larger randomized controlled trials.