Enhancing Lumbar Spinal Fusion Using Hypoxia Preconditioned Culture-Expanded Adipose-Derived Mesenchymal Stem Cells: Evidence From a Rat Posterolateral Lumbar Spinal Fusion Model

BACKGROUND AND OBJECTIVES: Adipose-derived stem cells (ADSCs) offer a practical alternative to bone marrow-derived stem cells. They are often limited by poor cell survival following implantation into the hypoxic environment surrounding the fusion site. Dimethyloxalylglycine (DMOG), a stabilizer of hypoxia-inducible factor-1α, has been shown to boost both osteogenic and angiogenic functions of mesenchymal stem cells under low oxygen conditions. In this study, we investigated whether preconditioning ADSCs with DMOG and hypoxia could improve their bone-forming capacity and stimulate vascularization. METHODS: ADSCs were harvested from the inguinal fat pads of Lewis rats aged 6-8 weeks. After culture expansion, cells at passage 1 (P1) (80% confluency) were preconditioned with DMOG (1 ng) for 24 hours. Cells at passage 2 (P2) were then seeded onto Vitoss scaffolds at a dose of 2 × 106 cells per scaffold for implantation. Rats underwent L4-L5 posterolateral spinal fusion and were randomly assigned to 1 of 2 groups: (1) Vitoss containing DMOG-preconditioned P2 ADSCs or (2) Vitoss containing nonpreconditioned P2 ADSCs. Fusion outcomes were evaluated 8 weeks postoperatively using manual palpation (graded as 0 = nonfused, 1 = partial fusion, and, 2 = fused), micro-computed tomography (micro-CT) imaging (0 = nonfused; 1 = unilateral fusion; 2 = bilateral fusion), and histology. RESULTS: Micro-CT demonstrated that rats receiving DMOG-preconditioned P2 ADSCs developed significantly larger fusion masses compared with counterparts (23.49 mm3 vs 15.39 mm3, P = .001). The DMOG treated group also exhibited a trend toward improved fusion outcomes (1.16 vs 0.50, P = .06) and manual palpation (1.25 vs 0.66, P > .05). Histological evaluation further revealed enhanced bone formation and tissue maturation in the preconditioned group, including increased osteoid matrix, a similarly extensive trabecular structure, larger osteoblast size, and similar vascularization within the fusion site. CONCLUSION: In this spinal fusion model, hypoxia preconditioned ADSCs created larger fusion masses than untreated ADSCs. The DMOG-preconditioned group also demonstrated improved fusion performance, indicated by higher micro-CT, manual palpation scores, enhanced bone formation, and maturation observed on histological analysis.