Autologous Mesenchymal Stromal Cells Combined with Gelatin Sponge for Repair Intervertebral Disc Defect after Discectomy: A Preclinical Study in a Goat Model

Background: The defect of intervertebral disc (IVD) after discectomy may impair tissue healing and predispose patients to subsequent IVD degeneration, which is thought to be an important cause of recurrence. Cell-based approaches for the treatment of IVD degeneration have shown promise in preclinical studies. However, most of these therapies have not been approved for clinical use due to the risks of abnormal differentiation and microorganism contamination of the culture-expanded cells. Selective cell retention (SCR) technology is non-cultivation technique, which can avoid those preambles in cell expansion. In this study, we used a commercially available BONE GROWTH PROMOTER device (BGP, FUWOSI, Chongqing, China) to concentrate mesenchymal stromal cells (MSCs) from bone marrow aspirate (BMA) through SCR technology. Methods: A small incision was made on the L2/3, L3/4 and L4/5 discs of goats and part of nucleus pulposus (NP) was removed to construct IVD defect model. The L2/3 disc was subjected to discectomy only (DO group), the L3/4 disc was implanted with enriched BMA-matrix (CE group), and the L4/5 disc was implanted cultured autologous bone marrow MSCs matrix (CC group). And the intact L1/2 disc served as a non-injured control (NC group). The animals were followed up for 24 weeks after operation. Spine imaging was analysis performed at 4 and 24 weeks. Histology, immunohistochemistry, gene expression and biomechanical analysis were performed to investigate the IVD morphology, content and mechanical properties at 24 weeks. Results: The CE and CC groups showed a significantly smaller reduction in the disc height and T2-weighted signal intensity, and a better spinal segmental stability than DO group. Histological analysis demonstrated that CE and CC groups maintained a relatively well-preserved structure compared to the DO group. Furthermore, real-time PCR and immunohistochemistry demonstrated that aggrecan and type II collagen were up-regulated in CE and CC groups compared to DO group. Conclusions: The strategy of MSCs enrichment combined with gelatin sponge by SCR technology provides a rapid, simple, and effective method for cell concentration and cell-carrier combination. This reparative strategy can be used in clinical treatment of IVD defect after discectomy. Clinical Trial Registration: NCT03002207.