The aim of the present study was to investigate and compare the capacity of fresh-frozen allogeneic bone, nano-hydroxyapatite/collagen/PLA (nHAC/PLA) scaffold, and nHAC/PLA scaffold loaded with bone marrow mesenchymal stem cells (BMSCs) in inducing bone formation. A 10mm segmental rabbit radial defect was surgically created. The animals were divided into four groups in which the defect was either left untreated, or filled with the abovementioned three grafts. The animals were euthanized at 2, 4, 6, 8, 12, and 18 weeks. Radiographic and histologic analyses were performed on the harvested tissue. We show that nHAC/PLA composite combined with mesenchymal stem cells could enhance and accelerate bone formation in segmental defects of rabbits. nHAC/PLA composite is an ideal bone graft; implanting nHAC/PLA composite combined with mesenchymal stem cells is a potential method for surgical treatment of bone defects.

The prismatic layer is obviously different from the parallel layer in seawater-cultured pearls. X-ray diffraction (XRD), optical microscopy (OM) and micro-infrared (IR) spectroscopy have been applied to characterize the crystallized layers of high-and low-quality seawater-cultured pearls produced in South China. The result shows that the prismatic layer is not only composed of calcite as reported in previous researches. Three types of prisms were found in seawatercultured pearls: calcite prism, aragonite prism and calcite and aragonite prism. Therefore, we have a new understanding of the biomineralization of the prismatic layer in seawatercultured pearls. The result makes us review the traditional viewpoint that the increased content of aragonite improves the quality of pearls. We discovered that some seawater prismatic pearls almost completely composed of aragonite have the worst quality. We thought that the thickness and the spatial distribution of prisms are the main factors that can affect the quality of seawater-cultured pearls.