Octacalcium Phosphate: A Potential Scaffold Material for Controlling Activity of Bone-Related Cells <i>In Vitro</i>

Abstract

We have previously established a wet synthesis method of octacalcium phosphate (OCP) in a relatively large scale and found that OCP enhances bone formation more than synthetic hydroxyapatite (HA) if implanted onto bone surface and various bone defects. The present paper reviews, based on our studies, as to how OCP controls in vitro cellular activities of bone-related cells, such as bone marrow stromal cells, and how OCP enhances bone repair in critical sized bone defect experimentally created in animal models. OCP tends to progressively convert to HA in culture media and in rat calvaria defects. OCP is capable of enhancing in vitro osteoblast differentiation and osteoclast formation in the presence of osteoblasts. Recent our studies also indicated that OCP enhances odontoblast differentiation while suppresses chondrogenic differentiation. The physicochemical properties, such as chemical composition and adsorption affinity of serum proteins, vary depending on the advancement of conversion from OCP to HA, which suggests that the change on the surface property during the conversion of OCP may affect the cellular responses in vitro and tissue reaction in vivo. OCP could be used as a scaffold material that can control the activity of bone-related cells.

Exploring the Formation Kinetics of Octacalcium Phosphate from Alpha-Tricalcium Phosphate: Synthesis Scale-Up, Determination of Transient Phases, Their Morphology and Biocompatibility

“…In addition, OCP can explain the existence of non-stoichiometry in apatites [ 3 ] through its ability to interlay with apatite domains [ 3 ]. Moreover, OCP has a plethora of other benefits such as solubility in close equilibrium with blood serum [ 11 , 12 ], substantial affinity towards organic molecules (helpful in biological mineralization, drug delivery platforms) [ 13 ], the tendency to convert to the thermodynamically more stable apatite [ 14 ], and the potential to promote osteoblastic cell differentiation [ 15 ].…”