Abstract 426: Biocompatible nanofilms Drive Differentiation of Stem Cells Toward a Cardiogenic Fate
Cell therapy has emerged as a promising therapeutic option for heart failure. To such an aim, optimisation of cell engraftment is mandatory. Both cell survival and secure differentiation are likely to require an extracellular scaffold.
Methods and results: Using nanotechnology, we engineered biocompatible polypeptide and polysacharide multilayer films (PEMS). These included Poly (L-lysine) hydrobromide (PLL) and Hyaluronane (HA). Crosslinking of films using dimethylaminopropyl carbodiimide (EDC) define their rigidity. We found that the most plastic cells (i.e, embryonic stem cells) respond to the force exerted by their attachment to the film. This force is translated into induction of a mesodermal cardiogenic genetic program likely mediated by remodeling of actin cytoskeleton. Indeed, stem cells cultured on PEMS (PLL/HA) with increasing stiffness turned on expression of mesodermal genes. This was associated with changes in cell shape. Real time RT-PCR revealed that the most rigid films (EDC:100), mimicking the infarction scar, induced a 4, 7, 6, 4.5 fold increase in expression of Brachyury, Myocardin, Tbx6 and Mesp1,2, respectively, in comparison with the non cross-linked ones. In fact, more the films were cross-linked, more the cells adhered, changed their shape and expressed mesodermal cardiogenic genes. Furthermore, stem cells were grown on PEMS and specified towards a cardiac lineage using bone morphogenetic protein (BMP2). RT-Q-PCR showed that BMP2 did not further increase expression of mesodermal and cardiac genes. Thus, mechanical signals triggered by the films overcome the chemical ones. In parallel, stem cells respond dramatically in morphology to the stiffness of these films. Cell reshaping was due to changes of the actin cytoskeleton as observed in phalloidin-stained cells in confocal microscopy.
Conclusion: Our work shows that the elasticity of films is crucial for the differentiation of stem cells towards mesodermal cardiac lineage. By exerting traction forces on a substrate, stem cells sense the stiffness and show dissimilar morphology and adhesive properties translated in gene transcription. Biocompatible nanofilms might represent in the future a mean to secure a cell product in therapy of heart failure.