Podocyte Injury Predicts Prognosis in Patients with IgA Nephropathy Using a Small Amount of Renal Biopsy Tissue

To predict the progression in patients with IgA nephropathy, we analyzed glomerular lesions except for sclerosis, adhesion and/or crescents in 34 patients with this disease by morphometric analysis. Levels of urinary protein excretion (UP), creatinine clearance (Ccr), serum creatinine (sCr) and mean blood pressure (MBP) at the time of renal biopsy were used as the clinical parameters. The slope of 1/sCr was also used as a prognostic parameter. Renal specimens were obtained by echo-guided biopsy. In PAS-stained light microscopic renal sections, three midsections of open glomeruli were selected and photographed. Stereologic estimation was performed as follows: absolute values of glomerular volume (V_G), glomerular surface area (S_G), podocyte and nonpodocyte cell number per glomerulus (N_G(pod) and N_G(Non-pod)), glomerular surface area covered by one podocyte S_G/N_G(pod)) and glomerular volume occupied by one nonpodocyte cell (V_G/N_G(Non-pod)). There was a significant correlation between the levels of UP and the change of podocyte injury parameters (N_G(pod) and S_G/N_G(pod)) or N_G(Non-pod). N_G(pod) was negatively but S_G/N_G(pod) and N_G(Non-pod) were positively correlated with UP. S_G/N_G(pod) or N_G(Non-pod) was correlated with MBP. N_G(pod), S_G/N_G(pod), N_G(Non-pod), UP or MBP was significantly correlated with the slope of 1/sCr. High specificity was observed for N_G(pod), S_G/N_G(pod) and MBP. High sensitivity was also observed for N_G(Non-pod) and UP. It appears that podocyte injury might provide additional prognostic information in patients with IgA nephropathy.