Combination of cell immortalization and apoptosis induction to engineer decellularized matrices as bone graft materials

Infection, trauma or tumors can generate critical bone defects in which the regeneration is compromised, thus necessitating the development of suitable repair strategies. Conventional tissue-engineered approaches proposed the use of a three-dimensional (3D) scaffold that supports cell growth and differentiation, in which the seeded progenitor cells can secrete an extra-cellular matrix (ECM) coating the material. The resulting bone graft can then be implanted in the patient in an autologous set-up. However, a more attractive paradigm consists in the removal of the cellular fraction from the graft prior to its implantation in order to avoid immuno-matching requirements, toward a universal exploitation of the graft. This conceptual strategy relies on the capacity of osteoinductive signals embedded in the ECM to instruct endogenous cells toward bone repair.
The success of this approach requires a standard cell source capable of secreting an osteo-inductive ECM, but also the development of a suitable decellularization protocol that can lead to both an efficient cell removal from the graft and the preservation of ECM properties.
In this thesis, I report the combined development of a standardized cell source and an apoptotic-based decellularization strategy, through the generation of a death-inducible human Mesenchymal Stromal Cell (hMSC) line. This cell line was shown to retain typical hMSC properties while continuously proliferating without signs of tumorigenicity, and being efficiently inducible toward apoptosis. Using this unlimited and well-characterized cellular tool, we successfully generated acellular ECM-coated graft within a 3D perfusion bioreactor. In particular, the induction of cell apoptosis was used as a decellularization procedure leading to the better preservation of key ECM components, as compared to the conventional approach.
Overall, by relying on both a novel cell source and a new decellularization approach, the developed protocol may lead to the development of a bone repair treatment with superior standardization and possibly cost-effectiveness as compared to current strategies.