Tissue-engineered bone used in a rabbit model of lumbar intertransverse process fusion: A comparison of osteogenic capacity between two different stem cells

Spinal fusion serves an important role in the reconstruction of spinal stability via restoration of the normal spinal sequence and relief of pain. Studies have demonstrated that the fusion rate is mainly associated with the osteogenic capacity of the implanted graft. Mesenchymal stem cells (MSCs) have been successfully isolated from human degenerated cartilage endplate (CEP) and designated as CEP-derived stem cells (CESCs). Previous studies have suggested that CESCs possesses in vitro and in vivo chondrogenic potential superior to that of bone marrow (BM)-MSCs. In addition, CESCs have shown a stronger in vitro osteogenic ability. The present study aimed to further determine the in vivo three-dimensional osteogenesis efficacy of CESCs for spinal fusion. Tissue-engineered bone grafts were transplanted into a rabbit model of posterolateral lumbar intertransverse process fusion using CESCs and BM-MSCs as seed cells composited with porous hydroxyapatite (PHA). The results of manual palpation and computed tomography (CT) scan reconstruction indicated that the CESCs/PHA group had a higher fusion rate than the BM-MSCs/PHA group, although the difference was not observed to be statistically significant. In addition, RT-qPCR results revealed that the in vitro CESCs/PHA composite expressed significantly higher levels of osteogenic-specific mRNA compared with the BM-MSCs/PHA composite. Finally, micro-CT and semi-quantitative histological analysis further demonstrated that the newly formed bone quality of the CESCs/PHA group was significantly higher than that of the BM-MSCs/PHA group in the intertransverse process fusion model. Therefore, the study indicated that CESCs possess superior in vivo osteogenesis capacity compared with BM-MSCs, and might serve as an important alternative seed cell source for bone tissue engineering. These results may provide the foundation for a biological solution to spinal fusion or other bone defect issues.