Role of Aberrantly Activated Lysophosphatidic Acid Receptor 1 Signaling Mediated Inflammation in Renal Aging

The increasing load of senescent cells is a source of aging, and chronic inflammation plays a pivotal role in cellular senescence. In addition, senescent renal tubular epithelial cells are closely associated with renal aging. Lysophosphatidic acid (LPA) is a bioactive lipid mainly produced by the catalytic action of autotaxin (ATX), and its ligation to LPA receptor-1 (LPAR1) is associated with chronic inflammation and renal fibrosis; however, its role in renal aging is unclear. Male 2-, 12-, and 24-month-old C57BL/6 mice and Human renal proximal tubular epithelial cells (HRPTEpiC) were used in the present study. DNA damage and oxidative stress-induced senescence were simulated using doxorubicin (DOXO) and H2O2, respectively. The aged kidney showed decreased renal function, increased fractional mesangial area, and tubulointerstitial fibrosis. Both aged kidney and senescent cells showed increased levels of LPAR1, Nuclear factor κB (NF-κB), and inflammatory cytokines. In addition, LPAR1-knockdown reduced NF-κB and subsequent inflammatory cytokine induction, and NF-κB-knockdown resulted in decreased LPAR1 expression. Our study revealed a positive feedback loop between LPAR1 and NF-κB, which reinforces the role of inflammatory response, suggesting that blocking of aberrantly activated LPAR1 may reduce excessive inflammation, thereby providing a new possible therapeutic strategy to attenuate renal aging.

Clinicopathological and prognostic study of IgA-dominant postinfectious glomerulonephritis

Background The clinicopathological and prognostic features of IgA-dominant postinfectious glomerulonephritis and its difference from the primary IgA nephropathy remains to be investigated. Methods The clinical and pathological data of 6542 patients who underwent renal biopsy from 2009 to 2020 in our hospital were reviewed and 50 patients who met the selection criteria of IgA-dominant postinfectious glomerulonephritis were enrolled to conduct a retrospective and observational single-center study. The selection criteria were: meet the characteristics of IgA dominance or codominance in immunofluorescence, and conform to 3 of the following 5 criteria: 1.Clinical or laboratory evidence show that there is infection before or at the onset of glomerulonephritis; 2.The level of serum complement decreased; 3.Renal pathology is consistent with endocapillary proliferative glomerulonephritis; 4. Glomerular immunofluorescence staining showed complement C3 dominance or codominance; 5. Hump-like subepithelial immune complex deposition was observed under electron microscopy. According to age, sex, renal function (estimated glomerular filtration rate, eGFR) and follow-up time, the control group was constructed with 1:3 matched cases of primary IgA nephropathy. The clinicopathological and prognostic differences between the two groups were analyzed. Results The most common histological pattern of IgA-dominant postinfectious glomerulonephritis was acute endocapillary proliferative glomerulonephritis and exudative glomerulonephritis. Immunofluorescence showed mainly IgA deposition or IgA deposition only, mainly deposited in the mesangial area (deposition rate 100 %), with typical C3 high-intensity staining (intensity++~+++), mainly deposited in the mesangial area (deposition rate 92.0 %). The fluorescence intensity of kappa is usually not weaker than lambda. The probability of the appearance of typical hump-like electron deposition under electron microscopy is low. Compared to primary IgA nephropathy, patients with IgA-dominant postinfectious glomerulonephritis had higher proportion of crescents (p = 0. 005) and endocapillary hypercellularity (p < 0.001) in pathological manifestations. Using serum creatinine level doubled of the baseline or reached end-stage renal disease as the endpoint, the prognosis of IgA-dominant postinfectious glomerulonephritis patients was worse than that of primary IgA nephropathy patients (p = 0.013). Conclusions The clinicopathological features of patients with IgA-dominant postinfectious glomerulonephritis was different from that of primary IgA nephropathy, and the prognosis was worse.

Distribution pattern of mesangial C4d deposits as predictor of kidney failure in IgA nephropathy

Mesangial C4d deposits have been associated with worse outcomes in Western patients with IgA nephropathy (IgAN), but there is limited data in Asians. Previously, a high proportion of stained glomeruli was often required for the classification of C4d positive (C4d+ve). Positive staining in lower proportion of staining would be classified as C4d-ve. This retrospective study evaluated the prognostic value of C4d+ve using a less stringent definition (one C4d+ve glomerulus) in Thai patients with IgAN (n = 120). Baseline findings and outcomes were compared between those with more extensive C4d staining patterns and those with more restricted staining. Clinico-pathologic parameters and risk for kidney outcomes (kidney failure or decline GFR50%) were compared between C4d+ve versus C4d-ve, and between different patterns: Focal (< 50%) versus Diffuse (≥ 50% of glomeruli); or Global (≥ 50) versus Segmental (< 50% of mesangial area). The hazard ratios were estimated using Cox proportional hazard models for Model 1 (Oxford score+ C4d) and Model 2 (Model 1+ clinical factors). C4d+ve (n = 81) had lower eGFR, more global sclerosis, and interstitial fibrosis than C4d-ve at baseline. The 5-year kidney survival for C4d+ve was lower (53.7%) than C4d-ve (89.7%); P = 0.0255. By univariate analysis, T1, T2, C4d+ve, eGFR<60, proteinuria were predictors of kidney outcome. By multivariate analysis, proteinuria, T1, T2 and C4d+ve were independent predictors (Model 2 HR (95% CI) C4d+ve: 3.24 (1.09–9.58), p = 0.034). Segmental had lower eGFR, higher tubulointerstitial fibrosis, and segmental sclerosis compared to Global pattern. Clinicopathological parameters were not different between Focal and Diffuse patterns. Outcomes were similar between staining patterns. In conclusion, C4d staining may be a valuable marker of poor prognosis in Asian patients with IgAN. Less stringent criteria for C4d+ve should be considered as no differences in outcomes were observed between more extensive staining with less extensive patterns. More studies are needed to identify the optimum criteria for C4d+ve.

Continuous hypergammaglobulinemia and proteinuria after the recovery of the visceral Leishmaniasis: a case report

Background Kidney involvement of visceral Leishmaniasis is previously reported, but knowledge is limited. Hypergammaglobulinemia is common in visceral leishmaniasis patients. Whether hypergammaglobulinemia after leishmaniasis depletion can cause kidney injury is not well reported yet. Case presentation We reported a patient who recovered from visceral Leishmaniasis but showed persistent hypergammaglobulinemia and elevated urinary protein. Kidney biopsy showed glomerular hypertrophy with mild segmental mesangial proliferation without tubulointerstitial involvement in light microscopy. No immune complex deposit was found in the mesangial area by neither immunofluorescent staining nor electronic microscope. Increased lysosomes were observed in proximal tubules by electronic microscope. Valsartan was administered to decrease urinary protein, and no immune-suppressive therapy was added. The urinary protein and serum IgG level gradually dropped, and serum creatinine level remained stable during three- month follow up. Conclusions Hypergammaglobulinemia is unlikely to cause renal structural or functional damage in the short term. Angiotensin blockade significantly reduced urine protein, with a minor effect on IgG elimination.

A Case of Systemic Lupus Erythematosus and Antineutrophil Cytoplasmic Antibodies-Associated Vasculitis Overlap Syndrome

An overlap of systemic lupus erythematosus (SLE) and antineutrophil cytoplasmic antibodies- (ANCA-) associated vasculitis (AAV) is extremely rare: approximately 40 cases have been reported to date. A literature review indicates that they are more common in women in their forties, and simultaneous onset has been reported in 69% of cases. In addition, both lupus nephritis and ANCA-associated glomerulonephritis were observed on renal biopsy. This report presents the case of a 35-year-old woman with an 8-month history of polyarthralgia who was admitted to our hospital. She was diagnosed with SLE due to typical clinical presentation of the disease: polyarthritis, lymphocytopenia, hypocomplementemia, presence of antinuclear and anti-dsDNA antibodies, and proteinuria. However, purpura were scattered, and the titer of antimyeloperoxidase-antineutrophil cytoplasmic antibodies (MPO-ANCA) was high. A skin biopsy revealed leukocytoclastic vasculitis that involved poor immune complex deposition. A renal biopsy showed necrotizing glomerulonephritis with cellular and fibrocellular crescent formation that involved deposition of IgM and C3c only in the mesangial area and the peripheral capillaries. Additionally, no electron-dense deposits were observed under electron microscopy. These pathological findings were consistent with AAV rather than with SLE. Therefore, we finally diagnosed the patient with both SLE and microscopic polyangiitis. After treatment with methylprednisolone and intravenous cyclophosphamide pulse therapies, renal function improved and MPO-ANCA levels decreased. In cases of suspected overlap between SLE and AAV, appropriate diagnosis and treatment are important.

microRNA-630 Regulates Underglycosylated IgA1 Production in the Tonsils by Targeting TLR4 in IgA Nephropathy

IgA nephropathy (IgAN) is the most common primary glomerular disease. The characteristic pathology involves immune complexes formed by the deposition of IgA1 and underglycosylated IgA1 aggregates in the mesangial area, which may be accompanied by the deposition of IgG and/or IgM and complement components. However, the molecular mechanisms of IgAN remain unclear. In the present study, microarray analysis showed that the expression of microRNA-630 (miR-630) was significantly reduced in palatal tonsils from IgAN patients compared with chronic tonsillitis. Additionally, bioinformatic analysis showed that Toll-like receptor 4 (TLR4) was the predicted target gene of miR-630 and was regulated by miR-630. When miR-630 was overexpressed in palatal tonsil mononuclear cells from IgAN patients, the expression of TLR4 was reduced and the content of IgA1 in the cell culture supernatant was decreased, and the level of galactosylation in the IgA1 hinge region was increased. Moreover, immunohistochemical analysis showed that the expression of TLR4 in IgAN patients was significantly increased. After knocking down the expression of TLR4, both the concentration of IgA1 and the binding force of IgA1 with broad bean lectin were significantly reduced in IgAN. Furthermore, the mechanism study demonstrated that TLR4 might regulate the expression of IL-1β and IL-8 through NF-κB signaling pathway to modulate the concentration of IgA1 and the glycosylation level of IgA1. This interesting finding may offer new insight into the molecular mechanism of IgAN.

Delayed diagnosis of Angioimmunoblast T-cell lymphoma presenting with type II Cryoglobulinemia and acute kidney injury: a case report and narrative review of the literature

Background Angioimmunoblastic T cell lymphoma (AITL) is an infrequent hematological malignancy with variable and often atypical presentations. The presence of dysproteinemia, autoantibodies and systemic involvement in AITL has often led to a delay in diagnosis or even misdiagnosis in practice. We herewith present a case of AITL that primarily presented with acute kidney injury associated with type II Cryoglobulinemia, the underlying cause was only identified 8 months after the emergence of initial symptoms. Case presentation A 67-year old woman presented with 2-month history of intermittent joint pain and a 3-day history of bilateral lower limb edema and acute kidney injury. Initial laboratory investigations showed marked hypocomplementemia with positive autoantibodies of ANA, anti-cardiolipin-IgM and direct antiglobulin. The serum and urinary Immunofixation and serum cryoglobulin tests were negative, while the serum free κ to λ light chain ratio was 0.231. A renal biopsy showed a diffuse proliferative glomerulonephritis with intracapillary pseudothrombi formation. There were orderly arranged microtubular structures of 20–35 nm in diameter in the subendothelial and mesangial area on electron microscopy. Shortly afterwards, the patient developed tingling affecting her finger tips and weak hands and legs. A diagnosis of cryoglobulinemia complicated with cryoglobulinemic glomerulonephritis and polyneuropathy was made. She responded well to methylprednisolone, plasma exchange and rituximab. However, 3 months later, she presented with generalized pruritic rash, weight loss, and inguinal lymphadenopathy. A subsequent inguinal excisional lymph node biopsy at month 8 revealed AITL as the underlying disease. Conclusions AITL and its associated B cell dysregulation can give rise to autoimmunity and cryoglobulinemia which may conceal itself as the underlying disorder. In various clinical scenarios of auto-immune diseases, it is advisable that the clinicians should take into consideration the multi-faceted lymphoma.

Intravenous administration of Streptococcus mutans induces IgA nephropathy-like lesions

Background IgA nephropathy (IgAN) is one of the most frequently occurring types of chronic glomerulonephritis. Previous analyses have revealed that a major pathogen of dental caries, Streptococcus mutans [which expresses collagen-binding protein (Cnm) on its surface], is involved in the pathogenesis of IgAN. Methods Cnm-positive S. mutans isolated from a patient with IgAN was intravenously administered to specific pathogen-free Sprague–Dawley rats to evaluate their kidney conditions. Results The urinary protein level of the S. mutans group reached a plateau at 30 days, with increased numbers of mesangial cells and an increased mesangial matrix. The numbers of rats with IgA-positive and/or C3-positive glomeruli were significantly greater in the S. mutans group than in the control group at 45 days (P < 0.05). Electron microscopy analyses revealed electron-dense depositions in the mesangial area among rats in the S. mutans group. There were significantly more CD68-positive cells (macrophages) in the glomeruli of the S. mutans group than in the glomeruli of the control group during the late phase (P < 0.05), similar to the findings in patients with IgAN. Conclusion Our results suggested that intravenous administration of Cnm-positive S. mutans caused transient induction of IgAN-like lesions in rats.

P0966PLACENTAL GROWTH FACTOR DEFICIENCY AGGRAVATES DIABETIC NEPHROPATHY

Background and Aims Placental growth factor (PlGF) is a member of the vascular endothelial growth factor (VEGF) family. PlGF exerts favorable angiogenetic and lymphangiogenic activity by binding to VEGF-R1 and -R3, respectively. Due to its functional synergy with VEGF-A, it is required for a correct neovascularization during pathological conditions while inactivation of PlGF contributes to decrease of pathological angiogenesis. Because reduced angiogenesis and lymphagiogenesis that contribute to defective lipid drainage are implicated in the progression diabetic kidney disease, we investigated the role of PlGF in the development of diabetic nephropathy by using PlGF-knockout mice. Method Diabetes was induced by a low-dose streptozotocin injection in 9-week-old male C57BL/6J PlGF-KO and wild-type mice and biochemical and morphological parameters were examined at 12 weeks later. Results In diabetic PlGF-KO mice, fasting blood glucose and HbA1c levels increased significantly and the development of glomerular sclerosis and mesangial area expansion were accompanied by albuminuria. Diabetic PlGF-KO mice exhibited increased expression of type IV collagen, transforming growth factor-β1 and glomerular IHC staining for nephrin, PECAM-1 and WT-1-positive cells and VEGF-R1,-R2,-R3 expression decreased, suggesting decreased endothelial cell and podocyte structure. Intrarenal expression of pLKB1, and pAMPK decreased and that of PPARα, PGC1α, ERRα, p-eNOS, and urinary Nox concentration decreased while iNOS increased, indicating disturbed lipid metabolism and endothelial dysfunction in the same group. Increased intrarenal FFA, TG, and cholesterol concentration represents presence of lipid accumulation. F4/80- and TUNEL-positive cells increased, suggesting increased inflammatory cell infiltration and apoptosis. CD68 and arginase-II increased indicating that macrophage subtype M1 polarization is involved in the inflammatory process. Expression of Bcl2/bax decreased and that of SOD1 and 2 decreased, indicating increased apoptosis and oxidative stress, respectively. Increased expression of intrarenal 8-OHdG and urinary isoprostane level indicates increased oxidative stress. Conclusion Impaired angiogenesis and lymphangiogenesis are implicated in PlGF deficiency and this promotes lipotoxicity-induced inflammation, oxidative stress and deteriorates renal functional and phenotypic parameters in the diabetic kidney.

P0091DEEP LEARNING-BASED IMMUNOFLUORESCENCE ASSESSMENT OF GLOMERULAR DISEASES

Background and Aims Immunofluorescence (IF) tests of renal tissue are of great value in diagnosing most of the glomerular diseases. However, high quality IF tests and results interpretation by experienced pathologists are not universally available in different areas of China. The development of deep neural networks has been used to facilitate digital analysis of pathologic images recently. We proposed a novel Convolutional Residual Dense Network (CR-DenseNet) to facilitate IF assessment of renal biopsy samples. Method A dataset with 725 IF images, including 312 images of IgA nephropathy (IgAN), 319 images of idiopathic membranous nephropathy (IMN) and 94 images of type V lupus nephritis (LN V) diagnosed in Peking Union Medical College Hospital (PUMCH) from November, 2016 to March, 2018 were used for training and validation of CR-DenseNet. All the images were photographed using ANDOR, ZYLA, Japan. The resolution was 2560 × 2160 pixels. These images were carefully annotated for the distribution characteristics and final diagnosis by two renal pathologists independently. IgAN showed mesangial predominating deposition. IMN showed glomerular basement membrane (GBM) predominating deposition. LN V showed positive depositions in both mesangial area and GBM. These three groups were used for IF distribution identification training. In CR-DenseNet, convolutional residual dense blocks were introduced, each of them consisted of a dense block with a convolutional skip connection to fully exploit the dense local features. To identify the deposition location, we imposed a switch in the proposed model to handle an additional input for different types of tasks, which can provide glomerular contours approximated from the IF image foreground (Figure 1). Performance was evaluated using overall accuracy and F1 score. F1 was computed as 2×True Positive / (2×True Positive + False Positive + False Negative). The whole protocol was approved by Institutional Review Board of PUMCH (No. S-K913). Results Experimental results showed that the proposed CR-DenseNet model outperformed the state-of-the-art method. In identification of segmental and glomerular IF positive images, our model showed overall accuracy of 92.0%. The true positive rate and F1 score of segmental positive samples recognition were 90.1% and 0.889. The true positive rate and F1 score of glomerular recognition positive samples were 94.1% and 0.938. Furthermore, the overall accuracy of our model in identifying mesangial predominating deposition (IgAN), GBM predominating deposition (IMN) as well as positive depositions in both mesangial area and GBM (LN V) was 91.2%. The true positive rates of each above-mentioned deposition classification were 93.1%, 90.5% and 88.9%, respectively. The corresponding F1 scores were 0.964, 0.905 and 0.889. Conclusion Our preliminary data showed that CR-DenseNet model was quite powerful in making IF diagnosis of typical glomerular diseases for the first time.