Ultrastructural osteopontin localization in papillary stones induced in rats

Objectives: To detect in situ the precise osteopontin (OPN) localization in papillary stones, Methods: Immunocytochemical labelling procedures are applied to detect OPN localizations in crystalline material of renal papillary stones, The tissue-processing procedure for electron microscopy, which includes OsO4 postfixation, preserves both immunocytochemical OPN reactivity and cellular membrane contrast up to the ultrathin section, Reflection-contrast light microscopical images are correlated with high resolution transmission-electron microscopical observations from consecutive ultrathin epon sections, Results: Preserved crystalline material in interstitial and peripheral papillary stones is recognized as calcium oxalate monohydrate. After section incubation with markers conjugated to an antibody against OPN (alpha OPN) the crystals are converted into ghosts. In the ghosts, alpha OPN markers are present around microcrystals, The size of these microcrystals ranges from several nanometers to micrometers. It is observed (due to the OsO4-preserved membranes) that interstitial cells are separated from the stone surfaces by unidentified extracellular material, also present in the center as a stone matrix, Conclusion: The microcrystal-growth inhibitor OPN is detected in situ in interstitial stones induced in the rat's papilla and at the surface of the papilla.