Distribution of osteopontin and calprotectin as matrix protein in calcium-containing stone

We recently reported that osteopontin (OPN) and calprotectin (CPT) are pres ent in the matrix of urinary calcium stones, and that OPN mRNA is expressed in the renal distal tubular cells. In the present study, we examined the i mmunohistochemical distributions of OPN and CPT in urinary stones. The ston es used in this study were passed spontaneously from the upper urinary trac t. One half of each of the stones was analyzed with an infrared spectrophot ometer, and were shown to be comprised of calcium oxalate, calcium phosphat e, uric acid and cystine. The other half of each stone was immersed in tetr asodium ethylenediaminetetraacetate (EDTA) solution. The half-stones were e mbedded in paraffin and cut into 5-mu m sections. The avidin-biotin-peroxid ase complex technique was employed. A monoclonal antibody to human milk-der ived OPN and a monoclonal antibody to human granulocyte-derived CPT were us ed as primary antibodies. The immunochemical study using the OPN and CPT an tibodies showed positive staining of the matrix of the urinary calcium ston es. The stones showed staining in two distinct zones: a core area was stain ed with randomly aggregated OPN and CPT, and peripheral layers were stained in concentric circles. On the basis of our observations, it is reasonable to presume that OPN and CPT play roles as the matrix in the structure of ur inary calcium stones.