Podocalyxin expression in renal tissues and correlation with the number of urinary podocytes in children with Henoch-Schonlein purpura nephritis

Abstract

Objective: To analyze the podocalyxin (PCX) expression in the kidney and the number of urinary podocytes in different pathological grades of Henoch-Schonlein purpura nephritis (HSPN), and to determine whether the number of urinary podocytes reflects the renal damage in HSPN.

Methods: Fifty-six children diagnosed with HSPN in our hospital were enrolled in the study and classified into 4 groups by renal pathology: grade II (IIa+IIb) (n=10), grade III (IIIa+IIIb) (n=21), grade IV (n=16), and grade V (n=9). Four kidney autopsy specimens without histomorphologic lesions and 8 urine samples from healthy children served as controls. With immunofluorescence assay, the PCX expression in 4 normal renal tissues and in the renal tissues of the 56 HSPN children was detected and quantitatively analyzed. Positive rate and the number of urinary podocytes were detected in the 8 healthy children and 56 HSPN children.

Results: In the renal tissues of the normal control group and grade II (IIa+IIb) HSPN group, the PCX expression was complete. The percentage of the PCX positive area out of the total glomerular area in the renal tissues of 2 groups had no significant difference (P>0.05). In the renal tissues of grade III (IIIa+IIIb), IV, and V HSPN groups, the PCX expression showed various degrees of loss, decreasing in turn from grade II (IIa+IIb), III (IIIa+IIIb), IV to V, with significant differences between each group (P<0.01). For HSPN with grade III (IIIa+IIIb) or higher, positive PCX expression was found in the urine, suggesting the presence of enough podocytes in the urine. The percentage of fluorescence positive area out of the total glomerular area of PCX in the renal tissues was negatively correlated with the total number of urinary podocytes (r=-0.637, P<0.01).

Conclusion: Podocyte injury plays a certain role in the pathological progression of HSPN. The urinary detection of podocytes can reflect the degrees of pathological damage in HSPN.