Thesis defence by Mirasbek KUTERBEKOV

Keywords :
microcarriers, human adipose stromal cells, polyelectrolyte coatings, bone morphogenetic proteins, osteogenic differentiation

click here to see the jury members


Abstract :
The regeneration of critical-sized bone defects remains a major healthcare challenge. The limitations of common tissue grafts prompted us to develop a synthetic alternative based on a biomaterial construct, osteoinductive factors and stem cells. For biomaterial construct, we focused on porous polymeric microcarriers as they support large-scale cell expansion and modular tissue assembly, circumventing two important bottlenecks for clinical translation. To insure industrial supply and regulatory approval, we designed an organic-solvent-free method for their fabrication based on the spherulitic crystallization of poly(L-lactide) (PLLA) in its blends with polyethylene glycol (PEG). The PLLA spherulites were easily recovered as microcarriers by rinsing away the water-soluble PEG. Their size and porosity could be independently controlled by tuning the PLLA/PEG ratio and crystallization temperature. The biocompatibility and osteoconductivity of PLLA microcarriers were confirmed through the expansion and osteogenic differentiation of human adipose stem cells (hASCs). Because the latter hASC function is sensitive to different culture parameters, we then used the Design of Experiments approach for their rapid screening. In combination with high-throughput analysis, we identified several parameters that had a pronounced influence on their osteogenic differentiation. Finally, for the delivery of osteoinductive factors, we elaborated polyelectrolyte multilayers (PEM) based on biocompatible poly(L-ornithine) and hyaluronic acid. These PEMs were characterized in terms of their growth, morphology, the ability to incorporate bone morphogenetic proteins (BMP) and to function as coatings on PLLA microcarriers. Our preliminary results showed that the incorporation of BMPs inside PEMs had a strong effect on hASC adhesion. While further studies are needed, hASC-seeded PLLA microcarriers coated with BMP-loaded PEMs could be a promising synthetic implant for improved bone regeneration.

jury members :
 

Prof.	Alain Jonas	IMCN, Université catholique de Louvain, Belgium	President
Directeur de Recherche	Philippe Lavalle	UMR 1121, INSERM, Université de Strasbourg, France	Rapporteur
Directeur de Recherche	Danièle Noël	IRMB, INSERM, Centre Hospitalier Régional Universitaire de Montpellier, France	Rapporteur
Prof.	Susanna Miettinen	BioMediTech, University of Tampere, Finland
Prof.	Karine Glinel	IMCN, Université catholique de Louvain, Belgium	Thesis Director
Prof.	Catherine Picart	LMGP, CNRS, Grenoble INP, France	Thesis Director