Papers by Author: H.B. Fan

Abstract: The limited source of autograft has prompted extensive research on bone substitute and biological enhancement of the fusion mass in spinal fusion. Biomaterials impregnated with bone marrow aspirate has been applied to spinal fusion surgery. In this study, the effect of stem cell therapy in enhancing posterior spinal fusion was compared with the bone marrow aspirate method in a standard rabbit model. Bone marrow was aspirated from rabbit proximal femur (BMA group, n=6) and loaded on β-tricalcium phosphate ceramics (β-TCP) in excess. The composite was then implanted onto L5 and L6 transverse processes of the same animal in posterior spinal fusion operation with decortication on the same day. For stem cell therapy group, mesenchymal stem cells (MSCs) were isolated from bone marrow aspirate by adherence on plastic culture-ware. The MSCs were treated with osteogenic supplements (OS) during ex vivo cell expansion (MSC group, n=6). The osteogenic cells were seeded on β-TCP ceramics and cultured for one day. The cell-ceramics composite was implanted into the same rabbit as BMA group. The ceramics acted as control (n=6). Three fluorochromes, tetracycline, xyelonol orange and caclein were injected at week 2, 4 and 6 sequentially. The spinal segments were harvested at week 7 post-operation. The manual palpation of vertebral joint was assesses for solid fusion. The gap distance of inter-transverse process was measured by microCT and the bone mineral content (BMC) and volume of transverse processes by peripheral quantitative computed tomography. The specimens were undergone undecalcified histological analysis. The mineralization process was examined by fluorescent microscopy. By manual palpation, 50% of MSC group samples were found to have solid fusion in comparison with the incomplete fusion observed in the BMA and control group. The gap distance of inter-transverse processes in MSC group was the shortest. The volume of the transverse processes in MSC group was significantly greater than BMA and control group by 16% and 26% respectively. The BMC of transverse processes in MSC group was 40% greater than control (p<0.05) and 8% greater than BMA group. In fluorescent microscopy, both green fluorescent signal (labeled at week 6) and orange fluorescent signal (labeled at week 4) were observed in MSC group compare with the predominantly green fluorescent signal in the BMA group. In conclusion, the augmentation of MSC derived osteogenic cells is superior to bone marrow aspirate in rabbit posterior spinal fusion.

Abstract: Basic fibroblast growth factor (bFGF) has been shown to maintain the osteogenicity of bone marrow derived mesenchymal stem cell (MSCs) in vitro. This study was to investigate whether bFGF with osteogenic supplements could enhance bone formation of posterior spinal fusion. Rabbit bone marrow derived mesenchymal stem cells were selected by adherence on plastic culture-ware. The MSCs were exposed to dexamethasone with (bFGF group, n=6) or without bFGF (OS group, n=6). Treated cells of two groups were seeded on β-tricalcium phosphate ceramics for one day and then implanted onto L5 and L6 transverse processes of the same animal in posterior spinal fusion without decortication. The ceramics acted as control (n=6). Three fluorochromes were injected sequentially as tetracycline at week 2, xylenol orange at week 4 and calcein at week 6. The spinal segments were harvested at week 7. The bone mineral content (BMC) and volume of transverse processes was measured by peripheral quantitative computed tomography. The specimens were underwent undecalcified histology. The mineralization process was examined by fluorescent microscopy. The BMC of transverse processes in OS group was 16% greater than bFGF and control group significantly. The volume of transverse process in OS and bFGF group was significantly greater than control group by 54% and 46% respectively. The volume of transverse processes in OS group was 6% greater than bFGF group though not statistically significant. In histology, newly formed bone grew from two processes towards each other resulting in a relatively short gap distance in OS and bFGF group while less regenerated bone was observed in the control group. At the mineralization front, calcein which was injected into animal at week 6, was predominately labeled in bFGF group. In OS group, both xylenol orange (at week 4) and calcein labeled were found. In conclusion, mesenchymal stem cells pre-exposed to bFGF were not found to give additional enhancement effect on bone formation in the posterior spinal fusion model.