Secreted protein acidic and rich in cysteine (SPARC), also known as osteonectin or BM-40, binds Collagen type I, hydroxyapatite and Ca2+, suggesting a role in the mineralization of bone and cartilage (Termine et al. 1981). It is expressed by osteoblasts, odontoblasts, and many other cell types (Romanowski et al. 1990, Mundlos et al. 1992, Papagerakis et al. 2002). SPARC expression has been used to follow the progression of osteoblast cytodifferentiation.