Microenvironmental control of adult stem cell differentiation: Influence of biochemical ECM composition, ECM stiffness and electric fields
Final Report Abstract
Within the project, stable hybrid polyacrylamide (PAM) sandwich gels with tunable stiffness and defined biochemical matrix composition could be prepared. The integrated amount of sulfated hyaluronan (sHA) derivatives during in vitro fibrillogenesis of collagen (coll) was low, but still showed a significant influence on multipotent differentiation behavior of human mesenchymal progenitor cells (MPCs). Osteogenic differentiation was enhanced in the presence of sulfated HA derivatives independent of the degree of the sulfation while adipogenic and partially chondrogenic differentiation was dependent on the degree of sulfation of used sHA derivatives. Highly sulfated sHA not only increased osteogenic (and chondrogenic) differentiation, but at the same time inhibited adipogenic differentiation. Consequently, the choice of ECM components selectively triggered cellular behavior and thus, using defined coatings in biomaterial development could provide a useful tool for guiding regeneration processes. The additional embedding of cells into the respective matrix did not lead to any further influence on differentiation behavior. Apparently, differentiation behavior is here dominated by the other biochemical and physical factors which makes the effect of 3D integrin engagement negligible. Despite biochemical composition also stiffness of the matrix was essential for cellular commitment showing enhanced osteogenic differentiation on stiffer gels with a stiffness of about 42 kPa (which is in the range of pre-calcified bone) and enhanced adipogenic differentiation on soft gels with a stiffness of 2 kPa (which is in the range of fat tissue). Furthermore, studies showed that not only the biochemical or physical environment alone plays a crucial role in guiding cellular commitment, but in particular the interaction of the various factors is decisive. Cells responded completely differently to biochemical matrix composition or external electric fields when cultured on soft gels compared to cells cultured on their stiffer counterparts. All in all, the data emphasize how important it is not only to investigate the influence of the signals alone, but also to consider the interaction of various signals to finally allow an adequate control of stem cell commitment which would be highly significant to further improve current stem-cell based tissue engineering strategies.
