Bio-Engineered Mesenchymal Stem Cell-Tricalcium Phosphate Ceramics Composite Augmented Bone Regeneration in Posterior Spinal Fusion

Abstract

Grafting of autologous iliac crest and decortication approach in posterior spinal fusion surgery has been the “gold standard”. However, the limited source of autograft has prompted extensive research into bone substitute and biological enhancement of the fusion mass. In this study, the application of stem cell therapy by tissue engineering method was investigated to enhance posterior spinal fusion with -tricalcium phosphate ceramics in rabbit model. Rabbit bone marrow derived mesenchymal stem cells were aspirated from trochanter region of proximal femur. The mesenchymal stem cells were grown and directed to differentiate into osteogenic cells by osteogenic supplement (ascorbic acid, -glycerophosphate and dexamethasone) in basal medium (10% FBS in DMEM). The osteogenic cells were seeded on tricalcium phosphate ceramics for one day (MSC group, n=6). The cell-ceramics composite was implanted onto autologous L5 and L6 transverse processes with decortication approach in posterior spinal fusion. The cell free ceramics acts as control (Control group, n=6) and iliac crest autograft as positive control (Autograft group). The spinal segments were harvested at week 7 post-operation. Manual palpation was performed with spinal segments to assess any movement of L5-L6 vertebral joint. The stiffness of the joint was considered as solid fusion. The specimens then were fixed by formalin and transferred to 70% ethanol. The BMC and volume of fusion transverse processes of L5 and L6 was measured by peripheral quantitative computed tomography. In manual palpation, 50% solid fusion was found in MSC group, 60% in autograft group but none in control group. Moreover, the BMC of L5 and L6 transverse processes in MSC group was greater than autograft and control group (45%, 40% respectively, p<0.01). The volume of transverse processes in MSC group was greater than autograft by 45% (p<0.01) and control group by 26% (p<0.05). In conclusion, the mesenchymal stem cells derived osteogenic cells augmented spinal fusion and bone mineralization.