Aim of the thesis was the development of a strategy for the regeneration of cartilaginous tissues considering cell biological and application-oriented aspects; using the example of intervertebral disc (IVD). To facilitate translation of pre-clinical results into a therapeutic procedure, the regulatoriy situation has been accounted for in all steps of the developmental process.
We presented injectable, in situ polymerizing hydrogel with potential as an anchoring hydrogel for chondrogenic cells. Rheological and biological properties of the hydrogel were analyzed in in vitro and in vivo models using rheology, biomechanical testing, and various histological, molecular biological and biochemical methods. Data on growth and differentiation of different human chondrogenic cells in this hydrogel were shown. For adult IVD cells there was evidence for cellular differentiation and matrix deposition, even for donor cells that have been expanded, stored in liquid nitrogen and then re-activated in secondary culture. We demonstrated in nucleotomized sheep that the therapeutic approach is feasible. Injection of autologous of allogenic disc cells into the damaged disc was possible without complications, and the animals showed no signs of pain of inflammatory reactions. Unexpectedly the generated data sets suggest that spontaneous biological repair occurs in sheep IVDs. The cell therapy did not compromise endogenous repair and may even be beneficial.
Finally, we analyzed the relevance of MSC-selective surface antigen markers for the characterization of chondrogenic cells. Our results demonstrated that expression of MSC markers, in particular expression of W5C5 and W8B2 antigens, did not necessarily predict extended stemness of such cells. Under established in vitro differentiation conditions a chondroid but not multi-potent precursor cell type was obtained. Even after an enforced enrichment of putative MSC-like cell populations using MACS technology and enforced osteogenic or adipogenic induction, in vitro expanded chondrocyte cultures did not expose a risk of adverse differentiation. These results are vital regarding regulatory aspects for the approval of cell-based therapies, where the risk of adverse reactions must be estimated.
The development process described in this work led to the successful implementation of an advanced therapies medicinal product. It ist currently tested in clinical trials sponsored by TETEC AG (trademark NOVOCART® Disc).