USING MESENDODERM PROGENITOR CELLS SEEDED IN HYDROGEL BIOMATERIAL AS A STRATEGY TO REGENERATE THE INTERVERTEBRAL DISC

Conflicts of Interest: CLM and CS are inventors on the patent for NPgel which has been licensed. Sources of Funding: European Union's Horizon 2020 research and innovation program under grant agreement No 825925. Introduction We have shown that an injectable biomaterial ‘NPgel’ can induce regeneration within organ culture systems of goat and human cadaveric IVDs. Here, the ability of NPgel to drive differentiation of mesendoderm progenitor cells (MEPCs) generated from human induced pluripotent stem cells (hiPSC) into matrix producing cells under conditions which mimic the IVD together with an in vivo ovine model of disc degeneration to investigate safety and short-term efficacy. Methods HiPSC were differentiated into MEPCs and seeded into NPgel and viability, phenotype, and matrix production investigated under conditions which mimic the degenerate disc. An ovine nucleotomy model of disc degeneration was used to investigate the safety and short term efficacy (3 months) of NPgel injection alone or in combination with iPSC-MEPCs. MRI grading and disc height, peripheral blood analysis (haematological, biochemical, metabolic and immunological) determined. Following sacrifice spines processed for: macroscopic and microscopic grade of degeneration immunohistochemical assessment, and Alu-sequence-PCR. Results MEPCs cultured within NPgel survived and were immunopositive for NP markers and matrix proteins following 4-weeks in culture. Ovine in vivo treatment with NPgel+MEPCs showed a slight increase in disc height index. No adverse reactions were seen. iPSC-MEPCs were visible within discs 3 months following injection. Matrix protein expression in discs injected with NPgel or NPgel+iPSC-MEPC were similar across all groups, whilst catabolic factors significantly decreased following NPgel+MEPC injection compared to nucleotomy alone. Discussion The injectable gel system described here shows promise to deliver induced pluripotent stem cells in a safe manner to the disc to induce regeneration.