[Truncated abstract] Spinal fusion is a commonly used surgical procedure for the treatment of various spinal disorders, such as trauma, degeneration and tumor. The use of autologous bone graft in spinal fusion has been the 'gold standard' for decades. However, the use of the autograft is associated with limitations and complications. Consequently, significant research now focuses on developing substitutes for the autograft for bone tissue applications. An osteoconductive scaffold is an essential element of bone tissue engineering to provide an optimal environment for new bone formation. Natural bone collagen scaffold (NBCS), also known as insoluble bone gelatin (ISBG), is a newly developed osteoconductive scaffold for bone tissue engineering. This thesis focuses on the osteoconductive property of NBCS, and the efficacy of NBCS combined with osteogenic protein-1 (OP-1) or bone marrow cells (BMCs), to induce new bone formation in rabbit and sheep spinal fusion models. To investigate the efficacy of NBCS as a scaffold/carrier for OP-1 to induce new bone formation, a rabbit postero-lateral lumbar fusion model was used. Spinal fusion masses were evaluated by manual palpation, biomechanical testing, radiographic assessment, micro-computer tomography (CT) scanning and histological examination 6 weeks postoperatively. Animals treated with a combination of NBCS and OP-1 achieved 100% solid fusion, which was higher than the control groups (autograft, NBCS only and OP-1 only). Enhanced fusion outcomes were also evidenced in the NBCS + OP-1 group by radiographic examination, micro-CT analysis (bone volume), and biomechanical testing. Histological assessment also demonstrated that treatment of NBCS + OP-1 induced new continuous bone formation in the interval between the transverse processes which was not observed in the other groups. ..... To evaluate the efficacy of NBCS as a scaffold for cell therapy, the osteogenesis of ovine enriched BMCs within NBCS was investigated in vitro, and the new bone formation induced by a combination of NBCS and enriched BMCs was evaluated in an ovine interbody fusion model. In vitro results showed that NBCS supported the population expansion, and osteogenic differentiation of ovine BMCs in vitro, and promoted the new bone matrix generation and mineralization. In vivo outcomes demonstrated that NBCS combined with autologous enriched BMCs enhanced spinal fusion with higher fusion rate, biomechanical stiffness and bone volume than in all control groups. Histological assessment also revealed that the combination of NBCS and enriched BMCs induced new bone formation that integrated well with host bone tissue. These findings indicate that NBCS is an effective scaffold of BMCs, and potentially the combination of NBCS and enriched BMCs may be used as a substitute for the autograft used in achieving spinal fusion. Viewed together, the studies presented in this thesis suggest that NBCS is an effective osteoconductive scaffold for bone tissue engineering, and that combined with growth factors such as OP-1, or enriched BMCs, is able to induce effective new bone formation. Thus, the combination of NBCS and OP-1 or BMCs might be a potential substitute for autologous bone graft in cases of spinal fusion.Thus, the combination of NBCS and OP-1 or BMCs might be a potential substitute for autologous bone graft in cases of spinal fusion.