70 - Reorganization of the nuclear lamina and cytoskeleton of human mesenchymal stem cells on a dendrimer-immobilized surface

Abstract

Human mesenchymal stem cells (hMSCs) have great potential as a cell source for tissue engineering and regenerative therapy due to its capacity to differentiate into many cell types. Differentiation of mesenchymal stem cells is regulated by microenvironmental cues which play an important role in directing stem cell behavior. In this study, we investigated the cytoskeleton-nucleus reorganization of hMSCs cultured on the dendrimer-immobilized surface. Time-lapse observation of hMSCs on a fifth generation (G5) of dendrimer-immobilized surface exhibits active migration behavior and repetitive morphological changes through stretching and contracting, resulting cell aggregates formation. However, hMSCs cultured on polystyrene (PS) surface shows high attachment to the substrate with spreading, flattened and elongated shape of cells also performed passive migration behavior. Fluorescent staining of F-actin and nucleoskeletal protein, lamin A/C, found significant presence of immature stress fibers in the aggregated cells on the G5 surface. In addition, the nuclear envelopes of cells on the G5 surface were wrinkled and relaxed, whereas, on PS surface, the nuclei were flattened by stress fibers and appear stiff and smooth. The observation indicated that the G5 surface permits the regulation of nuclear skeleton structure reorganization associated with alteration in cellular morphology and migratory behaviors. It was also found that cardiomyocyte-specific marker, cardiac Troponin T expression, was, in particular, promoted on the G5 surface, thus supporting the hypothesis that cytoskeleton-nucleus reorganization during active migration induces cardiomyogenic lineage commitment in hMSCs. These results suggest that active migration driven by dendrimer surface could regulate cytoskeleton-nucleus reorganization which possibly initiate mechanotransduction inside cells and directed hMSCs towards cardiomyogenic lineage commitment.