Matrix stiffness regulation of integrin‐mediated mechanotransduction during osteogenic differentiation of human mesenchymal stem cells

• Published in: Journal of bone and mineral research Vol. 26; no. 4; pp. 730 - 738
• Main Authors: Shih, Yu‐Ru V, Tseng, Kuo‐Fung, Lai, Hsiu‐Yu, Lin, Chi‐Hung, Lee, Oscar K
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.04.2011; Wiley; Wiley Subscription Services, Inc
• Subjects: Acrylic Resins - chemical synthesis; Acrylic Resins - chemistry; beta Catenin - metabolism; Biological and medical sciences; Biomechanical Phenomena; Calcification, Physiologic - drug effects; Calcification, Physiologic - physiology; Cell Differentiation - drug effects; Cell Differentiation - physiology; Collagen Type I - chemistry; Collagen Type I - genetics; Core Binding Factor Alpha 1 Subunit - genetics; Elasticity - physiology; Extracellular Matrix - physiology; Focal Adhesion Kinase 1 - antagonists & inhibitors; Focal Adhesion Kinase 1 - metabolism; Fundamental and applied biological sciences. Psychology; Gene Expression - drug effects; Gene Expression - genetics; Humans; integrin; Integrin alpha2 - genetics; Integrin alpha2 - metabolism; matrix stiffness; mechanotransduction; Mechanotransduction, Cellular - physiology; mesenchymal stem cell; Mesenchymal Stromal Cells - cytology; Mesenchymal Stromal Cells - drug effects; Mesenchymal Stromal Cells - metabolism; Mitogen-Activated Protein Kinase 1 - antagonists & inhibitors; Mitogen-Activated Protein Kinase 1 - metabolism; Mitogen-Activated Protein Kinase 3 - antagonists & inhibitors; Mitogen-Activated Protein Kinase 3 - metabolism; Myosin-Light-Chain Phosphatase - metabolism; Osteoblasts - cytology; Osteoblasts - drug effects; Osteoblasts - metabolism; Osteocalcin - genetics; Osteogenesis - physiology; osteogenic differentiation; Phosphorylation - drug effects; Protein Kinase Inhibitors - pharmacology; rho-Associated Kinases - antagonists & inhibitors; rho-Associated Kinases - metabolism; RNA, Small Interfering - genetics; Skeleton and joints; Vertebrates: osteoarticular system, musculoskeletal system; Human; Stem cell; Mesenchyma; Mechanical properties; OSTEOGENIC DIFFERENTIATION; Cell differentiation; MESENCHYMAL STEM CELL; Osteoarticular system; Signal transduction; Integrin; MATRIX STIFFNESS; Extracellular matrix; Mechanotransduction; Stiffness
• ISSN: 0884-0431; 1523-4681
• DOI: 10.1002/jbmr.278

Mesenchymal stem cells (MSCs) cultured on extracellular matrices with different stiffness have been shown to possess diverse lineage commitment owing to the extracellular mechanical stimuli sensed by the cells. The aim of this study was to further delineate how matrix stiffness affects intracellular signaling through the mechanotransducers Rho kinase (ROCK) and focal adhesion kinase (FAK) and subsequently regulates the osteogenic phenotype of MSCs. MSCs were cultured in osteogenic medium on tunable polyacrylamide hydrogels coated with type I collagen with elasticities corresponding to Young's modulus of 7.0 ± 1.2 and 42.1 ± 3.2 kPa. Osteogenic differentiation was increased on stiffer matrices, as evident by type I collagen, osteocalcin, and Runx2 gene expressions and alizarin red S staining for mineralization. Western blot analysis demonstrated an increase in kinase activities of ROCK, FAK, and ERK1/2 on stiffer matrices. Inhibition of FAK, an important mediator of osteogenic differentiation, and inhibition of ROCK, a known mechanotransducer of matrix stiffness during osteogenesis, resulted in decreased expression of osteogenic markers during osteogenic induction. In addition, FAK affects osteogenic differentiation through ERK1/2, whereas ROCK regulates both FAK and ERK1/2. Furthermore, α2‐integrin was upregulated on stiffer matrices during osteogenic induction, and its knockdown by siRNA downregulated the osteogenic phenotype through ROCK, FAK, and ERK1/2. Taken together, our results provide evidence that the matrix rigidity affects the osteogenic outcome of MSCs through mechanotransduction events that are mediated by α2‐integrin. © 2011 American Society for Bone and Mineral Research.