Introduction: Bone marrow-derived stem cells have been broadly used in spinal fusion research.Adipose-derived stem cells offer remarkable benefits, including more significant available tissue volume,higher stem cell concentrations, and reduced donor site morbidity.In a rat model,we compared the efficacy of ADSCs and BMSCs in achieving successful spinal fusion when combined with a clinical-grade bone graft substitute.
Methods: ADSCs were isolated from the inguinal fat pads,while BMSCs were isolated from the long bones of syngeneic 6-8 week old Lewis rats and cultured in vitro until passage-2 for subsequent transplantation. Posterolateral spinal fusion surgery at L4-5 was performed on 36 Lewis rats (6-10 wk old) divided into 3 experimental groups: [1]Vitoss (Stryker) bone graft substitute only (VO group, n=12); [2]Vitoss + 2.5x10^6 ADSCs/side (n=12); and [3]Vitoss + 2.5x10^6 BMSCs/side (n=12). Fusion was assessed eight weeks post-surgery via MicroCT analysis, manual palpation, and histology.Manual palpation scoring was as follows: 0=non-fused; 1=partial fusion, some motion across operative joint; 2=fused, no motion across the operated joint.We evaluated the characteristics and quality of new bone formation by histology.
Results: MicroCT imaging analyses showed that the average fusion volume in the ADSC group was significantly higher than in the BMSC and VO groups (44.3 mm^3 vs. 27.6 mm^3 and 30.0 mm^3, respectively, p<0.01). Average manual palpation score was the highest in the ADSC group compared with the BMSC and VO groups (1.5 versus 0.7 versus 0.8, p=0.03). ADSCs exhibited a faster proliferative rate and a higher CFU-F frequency than BMSCs in vitro. Histologically, ADSC and BMSC groups showed a higher concentration of osteogenic matrix and osteoblasts in the fusion mass compared to VO.
Conclusions: When combined with a clinical grade bone graft substitute in a rat model, ADSCs yielded increased fusion mass volume and rates of fusion than BMSCs. Ongoing studies will explore whether freshly isolated ADSCs will yield similar results.
Patient Care: Our research will change the way spinal fusion surgery is performed for many patients. For example, by establishing the advantages of using adipose stem cells in spinal fusion, our work will be of particular benefit in the treatment of patients requiring large amounts of bone graft and those with compromised donor bone and/or bone marrow, such as the elderly, those suffering with degenerative conditions including osteoporosis, and cancer patients who have undergone spinal radiation therapy.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the potential role of BMSC and ADSC in spinal fusion, 2) Discuss the translational importance of these treatments, 3) Identify advantages offered by these alternatives therapies.