The topography of extracellular matrix regulates the differentiation of mesenchymal stem cells (MSCs). In particular, the effect of spreading shape or area on cellular differentiation and viability of individual MSCs cultured in the confined adhesive regions is an interesting fundamental issue. In this study, the adhesive patterns with the circularity of 0.1 or 1 and the areas of 314; 628; 1,256; or 2,512 μm2 were constructed using micropatterning technology. The expression of osteogenesis marker alkaline phosphatase and the apoptosis level of individual MSCs were measured using double fluorescent staining. Results indicated that individual MSCs confined in the small area showed an apoptotic tendency, and those in the large area might enter into osteogenesis. The branched shape with small circularity increased MSC viability but reduced their pluripotency compared with the circular shape. The expression of other osteogenesis markers, such as osteocalcin and Collagen I, confirmed that large and branched pattern promoted MSC osteogenesis. In addition, the transcriptional coactivator yes‐associated protein (YAP) was transferred higher in the nuclei of the large and branched cells than other micropatterned groups. This study suggested that the spreading area and shape of individual MSCs regulate their viability and osteogenesis through the YAP pathway.

Mechanical microenvironments, such as characteristics defining mechanical environments and fluid flow play an important role in steering the fate of mesenchymal stem cells (MSCs). However, the synergistic effect of adhesion morphology and fluid flow on the biological behavior of MSCs is seldom investigated. In this article, 0.5 or 0.8 Pa fluid shear stress (FSS) was applied to the MSCs on micropatterned substrates, and the apoptosis and osteogenic differentiation of MSCs were measured by double fluorescent staining. Results showed that the cellular adhesion patterns with low circularity and large area are beneficial to the osteogenic differentiation of individual MSCs. Meanwhile, FSS facilitated osteogenic differentiation of MSCs, as shown by the expression of alkaline phosphatase, osteocalcin, and collagen I. In addition, nuclear transfer of Yes‐associated protein, a transcriptional regulator in MSCs, was enhanced after being exposed to FSS. These results demonstrated the synergistic effects of FSS and adhesion morphology in directing the fate of MSCs, and these effects may be adopted to design bio‐functional substrates for cell transplantation in tissue engineering.

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Mechanical cues, including fluid shear stress (FSS) of interstitial flow within bone cavities, induce osteogenic differentiation of mesenchymal stem cells (MSCs). However, whether FSS leads to the apoptosis of MSCs and its relation with osteogenic differentiation are still unclear. In this study, the effect of FSS on apoptosis and osteogenesis of MSCs is investigated. FSS is applied intermittently to MSCs through a cone-plate flow chamber system for 3 d. And results show that FSS inhibits the apoptosis of MSCs. Compared with static culture group, FSS promotes osteogenesis, as shown by the expression of three osteogenic differentiation markers, namely, alkaline phosphatase (ALP), osteocalcin (OCN), and collagen I (COL I). Double staining of individual cells shows that the relationship of apoptosis and osteogenic differentiation of MSCs is mutually exclusive. YAP may mediate the FSS-inhibiting apoptosis of MSCs. The results will further elucidate the mechanism of mechanical stimulation-induced bone remodeling.