SPP1 and hyperphosphatemia: Recent studies suggest that two key factors are responsible for vascular calcification in hyperphosphatemia: 1) up regulation of osteogenic factors such as Osterix, Cbfa1, and several bone-associated proteins (Osteopontin, Bone Sialoprotein, Alkaline Phosphatase, and Type I Collagen) [44], [45] and 2) phosphate-induced apoptosis [24], [25].