Advancing the application of the analytical renal pathology system in allograft IgA nephropathy patients

BACKGROUND

The analytical renal pathology system (ARPS) based on convolutional neural networks has been used successfully in native IgA nephropathy (IgAN) patients. Considering the similarity of pathologic features, we aim to evaluate the performance of the ARPS in allograft IgAN patients and broaden its implementation.

METHODS

Biopsy-proven allograft IgAN patients from two different centers were enrolled for internal and external validation. We implemented the ARPS to identify glomerular lesions and intrinsic glomerular cells, and then evaluated its performance. Consistency between the ARPS and pathologists was assessed using intraclass correlation coefficients. The association of digital pathological features with clinical and pathological data was measured. Kaplan-Meier survival curve and cox proportional hazards model were applied to investigate prognosis prediction.

RESULTS

A total of 56 biopsy-proven allograft IgAN patients from the internal center and 17 biopsy-proven allograft IgAN patients from the external center were enrolled in this study. The ARPS was successfully applied to identify the glomerular lesions (F1-score, 0.696-0.959) and quantify intrinsic glomerular cells (F1-score, 0.888-0.968) in allograft IgAN patients rapidly and precisely. Furthermore, the mesangial hypercellularity score was positively correlated with all mesangial metrics provided by ARPS [Spearman's correlation coefficient (r), 0.439-0.472, and all p values < 0.001]. Besides, a higher allograft survival was noticed among patients in the high-level groups of the maximum and ratio of endothelial cells, as well as the maximum and density of podocytes.

CONCLUSION

We propose that the ARPS could be implemented in future clinical practice with outstanding capability.

The role of glomerular lesions in the prognosis of patients with acute kidney injury during hemorrhagic fever with renal syndrome

OBJECTIVE

This study aimed to explore the role of glomerular lesions in patients who suffered from acute kidney injury (AKI) during hemorrhagic fever with renal syndrome (HFRS).

METHODS

The study comprised 66 patients with AKI during HFRS treated at the National Clinical Research Center of Kidney Diseases of China, Jinling Hospital, from January 2014 to December 2018. According to the kidney pathological findings, the 66 patients were divided into two groups: the tubulointerstitial injury group (HFRS-TI group, n = 43) and the tubulointerstitial injury with glomerular lesions group (HFRS-GL group, n = 23). The clinical and pathological characteristics of the 66 patients were analyzed.

RESULTS

There were 9 cases of IgA nephropathy, 1 case of membranous nephropathy, 2 cases of diabetic nephropathy, and 11 cases of mesangial proliferative glomerulonephritis in the HFRS-GL group. There were more males in the HFRS-GL group than in the HFRS-TI group (92.3% vs. 69.8%, p < .05). A higher proportion of interstitial fibrosis (56.5% vs. 27.9%, p < .05) and more immunoglobulin and complement depositions (p < .001) were observed in the HFRS-GL group than in the HFRS-TI group. Rates of remission of AKI were lower in the HFRS-GL group than in the HFRS-TI group (73.9% vs. 95.3%, p < .05). The presence of glomerular lesions (HR = 5.636, 95% CI = 1.121-28.329, p = .036) and moderate tubulointerstitial injury (HR = 3.598, 95% CI = 1.278-10.125, p = .015) were found to be independent risk factors for kidney prognosis.

CONCLUSIONS

Patients with AKI during HFRS can have glomerular lesions or glomerulonephritis. Patients with AKI during HFRS who have glomerular lesions or moderate renal tubulointerstitial injury proven by kidney biopsy have a relatively poor kidney prognosis. A kidney biopsy can help determine long-term prognosis in patients with AKI during HFRS.

Heparin and calreticulin interact on the surface of early G0/G1 dividing rat mesangial cells to regulate hyperglycemic glucose-induced responses

Heparin can block pathological responses associated with diabetic nephropathy in animal models and human patients. Our previous studies showed that the interaction of heparin on the surface of rat mesangial cells (RMCs) entering G1 of cell division in hyperglycemic glucose: 1) blocked glucose uptake by glucose transporter 4; 2) inhibited cytosolic uridine diphosphate-glucose elevation that would occur within 6 h from G0/G1; and 3) prevented subsequent activation of hyaluronan synthesis in intracellular compartments and subsequent inflammatory responses. However, specific proteins that interact with heparin are unresolved. Here, we showed by live cell imaging that fluorescent heparin was rapidly internalized into the cytoplasm and then into the endoplasmic reticulum, Golgi, and nuclei compartments. Biotinylated-heparin was applied onto the surface of growth arrested G0/G1 RMCs in order to extract heparin-binding protein(s). SDS-PAGE gels showed two bands at ∼70 kDa in the extract that were absent when unlabeled heparin was used to compete. Trypsin digests of the bands were analyzed by MS and identified as calreticulin and prelamin A/C. Immunostaining with their antibodies identified the presence of calreticulin on the G0/G1 RMC cell surface. Previous studies have shown that calreticulin can be on the cell surface and can interact with the LDL receptor-related protein, which has been implicated in glucose transport by interaction with glucose transporter 4. Thus, cell surface calreticulin can act as a heparin receptor through a mechanism involving LRP1, which prevents the intracellular responses in high glucose and reprograms the cells to synthesize an extracellular hyaluronan matrix after division.

Approach to Kidney Biopsy: Core Curriculum 2022

The kidney biopsy is an essential tool for diagnosis of many kidney diseases. Obtaining an adequate biopsy sample with appropriate allocation for various studies is essential. Nephrologists should understand key lesions and their interpretation because these are essential elements underlying optimal approaches for interventions. This installment in the AJKD Core Curriculum in Nephrology will review these topics. We will first briefly discuss considerations for allocation and processing of kidney biopsies. We will then present in outline form the differential diagnoses of a spectrum of patterns of injury and consideration for interpretation of specific lesions. Lesions are presented according to anatomic site as glomerular, vascular, or tubulointerstitial. Native and transplant kidney biopsy lesions are included. These lesions and differential diagnoses and specific diseases are then linked to detailed clinicopathologic discussion of specific diseases presented in the AJKD Atlas of Kidney Pathology II. Correlation with immunofluorescence, electron microscopy, and clinical findings are emphasized to reach a differential diagnosis and the final diagnosis.

Heparin affects cytosolic glucose responses of hyperglycemic dividing mesangial cells

Mesangial expansion underlies diabetic nephropathy, leading to sclerosis and renal failure. The glycosaminoglycan heparin inhibits mesangial cell growth, but the molecular mechanism is unclear. Here, rat mesangial cells (RMCs) were growth-arrested in the G₀/G₁ phase of cell division, stimulated to divide in normal glucose (5.6 mm) or high glucose (25.6 mm) with or without heparin, and analyzed for glucose uptake. We observed that RMCs entering the G₁ phase in normal glucose with or without heparin rapidly cease glucose uptake. RMCs entering G₁ in high glucose sustained glucose uptake for the first 3 h, and high-glucose exposure of RMCs only in the first 8 h of G₁ induced the formation of an extracellular monocyte-adhesive hyaluronan matrix after cell division was completed. Moreover, a low heparin concentration under high-glucose conditions blocked glucose uptake by 1 h into G₁ Of note, glucose transporter 4 (glut4) localized on the RMC surface at G₀/G₁ and was internalized into G₁ cells under normal glucose conditions with or without heparin within 30 min. We also noted that, under high-glucose conditions, glut4 remained on the RMC surface for at least 2 h into G₁ and was internalized by 4 h without heparin and within 1 h with heparin. These results provide evidence that the influx of glucose in hyperglycemic dividing RMCs initiates intermediate glucose metabolism, leading to increased cytosolic UDP sugars, and induces abnormal intracellular hyaluronan synthesis during the S phase of cell division.