Micropit surfaces designed for accelerating osteogenic differentiation of murine mesenchymal stem cells via enhancing focal adhesion and actin polymerization

Recent reports demonstrate that enhanced focal adhesion (FA) between cells and the extracellular matrix (ECM) and intracellular actin polymerization (AP) upregulates cellular functions such as proliferation, stem-cell fate and differentiation. Purposed to accelerate osteogenic differentiation, enhancement of FAs and AP of cells was induced by adding a tailor-made micropit (tMP, 3 × 3 μm2) with different heights (2 or 4 μm). The tMP surface was examined for its differentiation efficiency using mouse mesenchymal stem cells, C3H10T1/2. Though the cell spreading area was not affected by the surface topography, cells on the tMP substrates had enhanced FAs which were significantly confined inside the micropits, increased actin polymerization and traction forces, and osteogenic differentiation. Further experiments with Y-27632 and Blebbistatin, which specifically regulate FA or AP functions, demonstrated that the tMP-induced acceleration of osteogenic differentiation was caused by the rho-associated, coiled-coil containing protein kinase (ROCK) and nonmuscle myosin II (NM II), which are key molecules of the RhoA/ROCK signaling pathway. The tMP is applicable as an osteo-active substrate for the instructive bone cell differentiation and population.