Periodic acid–Schiff (PAS) staining of renal tissue

Paraffin sections (4 μm) were deparaffinized. They were oxidized with 1% periodic acid aqueous solution for 10 min, then stained with Schiff reagent for 15 min. Nuclei were counterstained with hematoxylin solution. The renal tubular injury was observed under light microscope. The acute injury was characterized by renal tubular epithelial cells swelling and granular degeneration, absence of the brush border and tubulitis [27]. The chronic lesion was characterized by thickening of renal tubular basement membrane and tubular atrophy. The severity of renal tubular injury was divided into (i) no obvious pathological change; (ii) mild pathological changes (lesions involving <25% of the area); (iii) moderate pathological changes (lesions involving ≥25% and <50% of the area); and (iv) severe pathological changes (lesions involving ≥50%) [28].