Synthetic self-assembling peptides as scalable matrices for human stem cell expansion

Stem cell based therapies currently constitute attractive therapeutic approaches able to address some particular disorders. Nevertheless, given that a limited amount of stem cells can be isolated from donors, the in vitro expansion is often required to achieve sufficient amounts of cells for therapeutic treatments. Due to the complexity of stem cells, the lack of defined culture conditions and the poor scalability of existing culture systems, the industrial production of large batches of clinical grade stem cells is currently challenging. As concerns the development of defined and scalable culture systems, the peptide-based biomaterials currently draw a particular attention as potential culture supports. In this context, the aim of this work was to assess new self-assembling peptides presenting bioactive motifs (derived from RGD sequence, collagen type I, fibronectin and laminin) within their structure as candidates for in vitro cultivation of human stem cells for therapeutic applications. The use of such peptides as thin layers coated at the surface of classical culture supports was thus investigated. This allowed us to establish that the peptides were able to stably adsorb at polystyrene culture supports and enabled the adhesion and growth of human mesenchymal stem/stromal cells. However, their effect varied depending on their structure, the considered culture support and the culture medium. Then the physicochemical characterisation of coated supports was undertaken to analyse the interaction between the peptides and the polystyrene culture supports. We determined that depending on the bioactive sequence the self-assembling peptides presented a distinct behaviour at the surface of culture supports, with different adsorbed amounts, wettability and chemical surface composition. Finally, with the aim to assess the effect of peptide coatings on long-term expansion of human stem cells, static and dynamic cultures on classical T-flasks and microcarriers, respectively, were conducted over up to one month. The peptide coatings enabled efficient cell adhesion, growth, harvest and reattachment on fresh supports, with retention of characteristic spindle-shaped morphology. Moreover, the peptides did not induce any spontaneous differentiation but allowed the cell differentiation towards adipogenic, chondrogenic and osteogenic lineages in inductive media. Importantly, in static conditions, some of the coated supports presented a consistent cell growth and differentiation independently of the donor, while variability was observed on uncoated equivalents. Moreover, the peptide containing a collagen type I-derived motif enabled high levels of mineralisation upon osteogenic differentiation, independently of the donor. Taken together, these results indicate that the experimental peptides, and particularly those containing a collagen type I-derived motif, could constitute interesting starting point for the development of defined, biomimetic and scalable matrices for in vitro cultivation of human stem cells, enabling consistent cell culture and differentiation, independently of the cell donor. However, given their variable behaviour, the peptides should be used with “compatible” culture polymers and media, enabling optimal efficiency of the obtained coatings for stem cell cultivation. Moreover, additional research is required to assess the coating effect in entire expansion processes, starting from the isolation step and using different types of stem cells from several donors.(SC - Sciences) -- UCL, 201