Study design:

Rat posterolateral lumbar fusion model.

Objective:

To compare the efficacy of freshly isolated adipose tissue-derived stromal vascular fraction (A-SVF) and bone marrow cells (BMC) cells in achieving spinal fusion in a rat model.

Summary of background data:

Adipose tissue-derived stromal cells (ASCs) offer advantages as a clinical cell source compared to bone marrow-derived stromal cells (BMSCs), including larger available tissue volumes and reduced donor site morbidity. While pre-clinical studies have shown that ex vivo expanded ASCs can be successfully used in spinal fusion, the use of A-SVF cells better allows for clinical translation.

Methods:

A-SVF cells were isolated from the inguinal fat pads, while BMC were isolated from the long bones of syngeneic 6-8-week-old Lewis rats and combined with Vitoss (Stryker) bone graft substitute for subsequent transplantation. Posterolateral spinal fusion surgery at L4-L5 was performed on 36 female Lewis rats divided into 3 experimental groups: [1] Vitoss bone graft substitute only (VO group); [2] Vitoss + 2.5×10 A-SVF cells/side; and, [3] Vitoss + 2.5×10 BMC/side. Fusion was assessed eight weeks post-surgery via manual palpation, micro-computed tomography (μCT) imaging, and histology.

Results:

μCT imaging analyses revealed that fusion volumes and μCT fusion scores in the A-SVF group were significantly higher than in the VO group; however, they were not significantly different between the A-SVF group and the BMC group. The average manual palpation score was highest in the A-SVF group compared with the BMC and VO groups. Fusion masses arising from cell-seeded implants yielded better bone quality than non-seeded bone graft substitute.

Conclusions:

In a rat model, A-SVF cells yielded a comparable fusion mass volume and radiographic rate of fusion to BMC when combined with a clinical-grade bone graft substitute. These results suggest the feasibility of using freshly isolated A-SVF cells in spinal fusion procedures.

Level of evidence:

N/A.