Hydroxyapatite (HAP) is the major biomineral of bone. Despite the large number of studies addressing HAP formation, a fundamental understanding of the critical roles of HAP-forming proteins in vitro is needed. Effects of two HAP-interacting proteins, osteocalcin (OCN) and osteopontin (OPN) on HAP formation investigated via in vitro biomineralization experiments revealing their outcomes on the crystal structure of calcium phosphate (CaP) crystals. Our data suggests that OCN concentration is negatively correlated with crystal formation rate and crystal size, yet presence of OCN leads to more ordered HAP formation. On the other hand, the OPN protein promotes the faster formation of CaP crystals, and it decreases t... More
Hydroxyapatite (HAP) is the major biomineral of bone. Despite the large number of studies addressing HAP formation, a fundamental understanding of the critical roles of HAP-forming proteins in vitro is needed. Effects of two HAP-interacting proteins, osteocalcin (OCN) and osteopontin (OPN) on HAP formation investigated via in vitro biomineralization experiments revealing their outcomes on the crystal structure of calcium phosphate (CaP) crystals. Our data suggests that OCN concentration is negatively correlated with crystal formation rate and crystal size, yet presence of OCN leads to more ordered HAP formation. On the other hand, the OPN protein promotes the faster formation of CaP crystals, and it decreases the Ca:P ratio and potentially works as a growth site for mineral formation. This effect resulted in a shift from hydroxyapatite-type minerals to less ordered crystals. The crystal size, shape, and Ca:P ratio can be tuned to design improved mammalian hard tissue environment-mimicking matrices by taking the advantage of OCN and OPN proteins on crystal formation. We believe our current findings will lead to innovative approaches for bone biomineralization in regenerative medicine.
