Influence of pre-freezing conditions of octacalcium phosphate and collagen composite for reproducible appositional bone formation.

Even though conventionally prepared octacalcium phosphate and collagen composite (OCP/Col) has exhibited excellent bone regeneration and has recently been commercialized for treating bone defects, reproducible appositional bone formation with OCP/Col has never been achieved. The present study investigated whether appositional bone formation could be achieved by altering the density of OCP/Col and applying liquid nitrogen during the preparation of OCP/Col. The prepared OCP/Col disks had eight variations and were divided into categories according to four different type of densities (1.0, 1.3, 1.7, and 2.0) of OCP/Col and two different pre-freezing conditions of gas phase (G group: -80°C) and liquid phase (L group: -196°C). These disks were implanted into subperiosteal pockets in rodent calvaria, five samples per each eight variations. Radiomorphometric analysis was conducted at 4 and 12 weeks after implantation, and histological analysis was conducted at 12 weeks after implantation. OCP/Col samples in the L group tended to retain their height and shape and had enhanced appositional bone formation, whereas OCP/Col samples in the G group tended to lose their height and shape and had limited appositional bone formation. The appositional bone formation increased along with growing density of OCP/Col, and L2.0 demonstrated higher appositional bone formation than other samples. These results suggest that the pre-freezing conditions and densities of OCP/Col affect the appositional bone formation.

Bone augmentation by octacalcium phosphate and collagen composite coated with poly-lactic acid cage.

OBJECTIVE: Although octacalcium phosphate and collagen composite (OCP/Col) has demonstrated excellent bone regeneration, it has never achieved bone augmentation. The present study investigated whether it could be enabled by OCP/Col disks treated with parathyroid hormone (PTH) and covered with a poly-lactic acid (PLA) cage. MATERIALS AND METHODS: The prepared OCP/Col disks with three different types of PLA cages (no hole, one large hole, several small holes) were implanted into subperiosteal pockets in rodent calvaria. Histological, and histomorphometric analyses were conducted at 12 weeks after implantation. RESULTS: Implants with all PLA cage variants achieved sufficient bone augmentation, and analyses showed that new bone was formed from the original bone and along the PLA cage. While the PLA cage variant with no holes sporadically evoked new bone formation even at the central area of the roof of the PLA cage, the PLA cage variants with holes had no new bone in the area of the hole or beneath the periosteum. CONCLUSIONS: These results suggest that sufficient bone augmentation could be achieved by treating the OCP/Col disks with PTH and covering them with a PLA cage, and periosteum might not have been involved in the bone formation in this experiment.

Octacalcium phosphate collagen composite stimulates the expression and activity of osteogenic factors to promote bone regeneration.

OBJECTIVE: This study investigated the bone regenerative properties of an octacalcium phosphate collagen composite (OCP/Col) in a rat calvarial bone defect model. DESIGN: An OCP/Col or ß-tricalcium phosphate (ß-TCP)/Col disk was implanted into the critical-sized calvarial defects and fixed 2 or 4 weeks later. The radiopacity of defects was examined after disk implantation by the radiographic examination and micro-computed tomography (µ-CT). Immunohistochemical and histochemical analyses were carried out to assess the bone matrix maturation, neovascularization, and osteoclast and osteoblast distribution in the neonatal bone. RESULTS: Radiographic and µ-CT examination of the area of implanted OCP/Col indicated the newly formed bone and no difference from those of the original bone. Osteopontin, osteocalcin, Runt-related transcription factor 2, type 1 collagen, vascular endothelial growth factor, and alkaline phosphatase or tartrate-resistant acid phosphatase in the newly formed calvarial bone and the surrounding connective tissue were detected by immunohistochemistry and histochemistry. Biomarker expression was not significantly elevated at the defect site; the area of which was calculated by dividing the distance from the healthy bone margin or calvarium and dura mater surface. There was no difference in the expression of these biomarkers in the OCP/Col group at 2 and 4 weeks after surgery. In addition, the expression levels of all markers were higher in the OCP/Col group than in the ß-TCP/Col group at 2 and 4 weeks after surgery. CONCLUSIONS: The OCP/Col as a bone regeneration material not only exhibits osteoconductive activity that is dependent on residual healthy bone tissue, but also has osteoinductive capacity, which promotes angiogenesis and osteogenic cell invasion from host tissue into the bone defect.