Rapid assessment of the osteogenic capacity of hydroxyapatite/aragonite using a murine tibial periosteal ossification model

This is the authors' abstract. We don't add key points for this paper.

Biomaterials are widely used as orthopaedic implants and bone graft substitutes. We aimed to develop a rapid osteogenic assessment method using a murine tibial periosteal ossification model to evaluate the bone formation/remodelling potential of a biomaterial within 2–4 weeks. A novel hydroxyapatite/aragonite (HAA) biomaterial was implanted into C57BL/6 mice juxtaskeletally between the tibia and tibialis anterior muscle. Rapid intramembranous bone formation was observed at 14 days, with 4- to 8-fold increases in bone thickness and callus volume in comparison with sham-operated animals ( p < 0.0001), followed by bone remodelling and a new layer of cortical bone formation by 28 days after implantation. The addition of zoledronate, a clinically-utilised bisphosphonate, to HAA, promoted significantly more new bone formation than HAA alone over 28 days ( p < 0.01). The osteogenic potential of HAA was further confirmed by implanting into a 3.5 mm diameter femoral cancellous bone defect in rats and a 5 mm diameter femoral cortical bone defect in minipigs. To understand the biodegradation and the cellular activity at the cell/biomaterial interfaces, non-decalcified specimens were resin embedded and sections subjected to combined scanning electron microscopy (SEM)/electron backscatter diffraction (EBSD)/energy dispersive X-ray spectrometry (EDS) analysis. We conclude that murine tibial periosteal ossification is a novel method for rapid assessment of the interaction of bioactive materials with osteogenic tissues. This study also highlights that combining calcium carbonate with hydroxyapatite enhances biodegradation and osteogenesis. A murine animal model for rapid assessment of osteogenesis. • A novel murine in vivo model enables rapid assessment of the bone formation capacity of a biomaterial within 14 days. • No bone defects or fractures are involved, ensuring minimal animal suffering. • Significant trabecular callus bone formation from tibial periosteal osteogenic cells is observed within 14 days, which remodels into a new cortical bone layer by 28 days. • New bone formation is quantifiable using μCT and histology, showing a four-to eight-fold increase in tibial thickness and callus formation. • The bone formation and remodelling capacity of HAA biomaterials are reproducible in bone defects in both rats and larger animals.