SPP1 and nephrolithiasis: Osteopontin (OPN) is another important component of calcium oxalate stone matrix [29], plays an important role in preventing the formation of calcium oxalate monohydrate (COM) kidney stones, which controls switching of calcium oxalate monohydrate morphologies in urine [36] to promote the formation of stones by promoting crystal adhesion and mediating oxidative stress and apoptosis [17, 37].