Background/Purpose:

Lupus nephritis (LN) is a most important predictor of morbidity and mortality in patients with systemic lupus erythematosus (SLE).Histopathology samples from patients with LN can demonstrate injury to nearly any cell type, including the mesangial, endothelial, podocyte, tubulointerstitial and vascular involvement associated with different pathogeneses, clinical presentations, therapeutic responses, and outcomes in LN patients. Podocytes are epithelial cells that provide the glomerular filtration barrier with foot processes and slit diaphragms. The morphological change with diffuse effacement of the foot processes is correlated with proteinuria in patients with LN. It has also been shown that in patients with nephrotic LN, foot process effacement estimated by the foot process width (FPW) was more extensive than in patients with non-nephrotic LN.We evaluated the possible association between podocyte injury and clinical features in LN.

Methods:

We studied 73 patients with LN who underwent a renal biopsy at our hospital or a community hospital in 1993–2016. We collected the data of clinico-pathological parameters and assessed the FPW for evaluating podocyte effacement. We retrospectively analyzed the complete renal remission (CR) rate at 6 and 12 months after induction therapy and determined the predictive factors for CR. Univariate and multivariable competing risks regression analyses were used to determine the predictive factors of CR. Decision tree models predicting CR were built with the Classification and Regression Trees (CART) algorithm.

Results:

At 6 and 12 months after induction therapy, 34 patients (46.6%) and 47 patients (64.3%) achieved CR, respectively. The multivariate analysis revealed that female gender (OR 5.288, 95%CI: 1.197–37.29, p=0.0267) and FPW (OR 0.999, 95%CI: 0.997–0.999, p=0.0150) for predicting CR at 6 months and lymphocyte counts (OR 1.002, 95%CI: 1.001–1.003, p=0.0028) and FPW (OR 0.998, 95%CI: 0.996–0.999, p=0.0027) for predicting CR at 12 months were significant.The median FPW was 1088 nm (IQR 895–1465 nm) in the total group of 73 patients. The degree of foot process effacement was significantly different among the various types of LN (p=0.0007): 701 nm (IQR 546–902 nm) in class I, 817 nm (IQR 685–1056 nm) in class II, 921 nm (IQR 711–1145 nm) in pure class III, 1294 nm (IQR 1086–1804 nm) in pure class IV, 1283 nm (IQR 899–1484 nm) in pure class V, and 1421 nm (IQR 887–1976 nm) in the combined group (class III + V and IV + V). We found that there was a moderate correlation between the individual FPW value and the amount of proteinuria (r=0.3554, p=0.00022). There was also a significant correlation between the individual FPW and serum albumin (r= −0.4757, p<0.0001) and between the individual FPW and the index of activity (0–24) (r=0.4908, p<0.0001).The cut-off point determined by the CART algorithm showed that FPW <908.3 nm provide the best performance to predict patients who achieve CR at 12 months.

Conclusion:

We found that the lymphocyte count and/or the foot process width are prognostic markers for the achievement of a CR at 6 and 12 months after induction therapy for lupus nephritis. The pathological role of the FPW is still unknown, but it may reflect the degree of podocyte function.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/podocyte-foot-process-width-is-a-prediction-marker-for-complete-renal-remission-at-6-and-12-months-after-induction-therapy-in-lupus-nephritis/