The effect of osteopontin immobilized collagen granules in the seed crystal method

Osteopontin (OPN) is a urinary protein which inhibits calcium oxalate (CaOx ) crystal growth in the seed crystal system. The aim of this study was to e valuate the effects of OPN immobilized on collagen granules (CG) for CaOx c rystal growth and aggregation in this system. OPN-immobilized CG showed a 3 0% decrease in inhibitory activity compared with non-OPN-immobilized CG. Sc anning electron microscopy revealed that 1) OPN-immobilized CG showed more marked aggregation and adhesion of seed crystals (smaller than 0.5 mum in d iameter) than non-OPN-immobilized CG, 2) the amount of adherent large type crystals (2-3 mum in diameter) did not differ between OPN immobilized and n on-OPN-immobilized CG. In conclusion, immobilized OPN promotes aggregation and adhesion of CaOx crystals smaller than 0.5 mum on CG. These observation s suggest that crystal adhesion to immobilized OPN plays a role in the rete ntion of crystals in the kidney.