Introduction: Current therapies for degenerative disc disease (DDD) are aimed at treating the pathologic and disabling conditions arising from DDD rather than directly treating the underlying problem of disc degeneration. Our group are exploring the potential of Cell Therapy to repopulate the disc and stopping the progressive loss of proteoglycans. Stem cells appear to be excellent candidates for this purpose, based on their ability to differentiate along multiple connective tissue lineages. The purpose of this study is to investigate the in-vitro interaction between muscle-deroved stem cells (MdSC) and nucleus polposus cells (NPCs) and to determine in-vivo viability of mesenchymal stem cell (MSC) in the harsh environment of the IVD
Materials and Methods: (1) Human NPCs were isolated from patients undergoing disc surgery and were co-cultured for 2 weeks with MdSCs from 3-wk-old mdx mice and in monolayer culture system at different ratios of 0:100, 25:75, 50:50, 75:25, 100:0. Proteoglycan synthesis and DNA content were measured. (2) Rabbit mesenchymal stem cells were isolated from bone marrow and tagged with a retrovirus delivered LacZ reporter gene for tracking. MSCs were then injected into a healthy rabbit IVD via 30G needle. Rabbits were sacrificed at postoperatively at 3, 6, 12 and 24 weeks. Histological analysis for MSC viability was performed.
Results: (1) Co-culturing of NPCs with MdSCs in the monolayer culture system resulted in vigorous increases in proteoglycans synthesis as compared with NPCs alone. The increases were on the 200% for an NPC-to-MDSC ratio of 75:25. DNA content also increased with co-culture. (2) Histological examination revealed presence of MSCs expressing LacZ without apparent decrease in numbers or diminishment of protein production.
Conclusion: The data from this study show that there is a synergistic effect between stem cells and nucleus pulposus cells resulting in upregulated proteoglycan synthesis in-vitro. Mesenchymal stem cells remain viable and continue to express an ex vivo transduced protein without appreciable cell loss for up to 24 weeks post transplantation into the rabbit IVD. These results suggest that MSCs can survive in the harsh environment of the IVD and may favourably modify ECM production. These studies support the feasibility of developing a stem cell therapy approach for DDD.
Theses abstracts were prepared by Professor Roger Lemaire. Correspondence should be addressed to EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.