Histone Modification of Osteogenesis Related Genes Triggered by Substrate Topography Promotes Human Mesenchymal Stem Cell Differentiation

The clinical success of orthopedic implants is closelyrelatedto their integration in the bone tissue promoted by rough device surfaces.The biological response of precursor cells to their artificial microenvironmentsplays a critical role in this process. In this study, we elucidatedthe relation between cell instructivity and surface microstructureof polycarbonate (PC)-based model substrates. The rough surface structure(hPC) with an average peak spacing (Sm) similar to the trabecularspacing of trabecular bone improved osteogenic differentiation ofhuman bone marrow mesenchymal stem cells (hBMSCs), as compared tothe smooth surface (sPC) and the surface with a moderate Sm value(mPC). The hPC substrate promoted the cell adhesion and assemblingof F-actin and enhanced cell contractile force by upregulating phosphorylatedmyosin light chain (pMLC) expression. The increased cell contractileforce led to YAP nuclear translocation and the elongation of cellnuclei, presenting higher levels of active form of Lamin A/C. Thenuclear deformation alternated the histone modification profile, particularlythe decrease of H3K27me3 and increase of H3K9ac on the promoter regionof osteogenesis related genes (ALPL, RUNX2, and OCN). Mechanism study using inhibitors andsiRNAs elucidated the role of YAP, integrin, F-actin, myosin, andnuclear membrane proteins in such a regulatory process of surfacetopography on stem cell fate. These mechanistical insights on theepigenetic level give a new perspective in understanding of the interactionof substrate and stem cells as well as provide valuable criteria fordesigning bioinstructive orthopedic implants.