Introduction

Combining a scaffold and living cells to form a tissue-engineering construct is an important concept for promoting the repair and regeneration of bone tissues. Mesenchymal stem cells are often used in such constructs due to their abilities to proliferate and differentiate toward bone-forming cells. The design and fabrication of scaffolds, stem cell isolation and characterization, and the manipulation of stem cell differentiation and function are essential steps toward the development of a biologically viable and clinically useful construct for bone tissue regeneration and function.

Autografts, allografts, xenografts, and alloplastic grafts have been used for bone repair and regeneration. Autograft is derived from the individual for whom the graft is intended. Though it is considered the "gold standard" of bone grafting to induce bone formation and regeneration through osteogenesis, osteoinduction, and osteoconduction, the application of autografts is limited due to insufficient donor bone supply and additional surgical wounds. Allograft is the tissue taken from another individual of the same species as the host. It possesses osteoinductive property due to the presence of the natural components and growth factors. Xenografts are derived from species other than human and provide a natural architectural matrix and an excellent source of calcium and phosphate for new bone generation. Allografts and xenografts have the potential risks of disease transmission and are shunned by some patients. Alloplasts are synthetic materials that can be designed with various chemical compositions, physical forms, and different surface configurations for the repair of bone defects and enhancement of osseous in-growth. They only have osteoconductive property, thus limiting their ability in the repair of challenging defects. In the case of bone regeneration, the grafts are eventually remodeled and replaced by new bone in the host tissue. Due to the limitations of these bone grafts materials, tissue engineering approaches involving scaffolds and living cells have been in the forefront of biomedical research with the advent of biotechnology and stem cell sciences.

Alveolar bone deficiency due to tooth loss, infection, and trauma is the primary limiting factor for dental implant-supported prosthetic therapies. Though numerous bone grafting materials are commercially available, these products invariably fall into the categories of allografts, xenografts, and alloplastic grafts and have significant limitations in clinical applications. An ideal bone tissue-engineering construct is still lacking. A properly constructed scaffold-cell complex may encourage the formation and apposition of new bone by osteoconduction, osteoinduction, and osteogenesis.

The purpose of the present study was to synthesize and develop a collagen-hydroxyapatite (Col-HA) composite through controlled in situ mineralization on type I collagen fibrils with nanometer-sized apatite crystals, and evaluate their biologic properties by culturing with mouse and human mesenchymal stem cells (MSCs) for cell attachment and proliferation assays and biocompatibility assays in vitro.