Mechanical Strain Enhances Extracellular Matrix-Induced Gene Focusing and Promotes Osteogenic Differentiation of Human Mesenchymal Stem Cells Through an Extracellular-Related Kinase-Dependent Pathway

Abstract

Human mesenchymal stem cells (hMSCs) are a population of multipotent bone marrow cells capable of differentiating along multiple lineages, including bone. Our recently published proteomics studies suggest that focusing of gene expression is the basis of hMSC osteogenic transdifferentiation, and that extracellular matrix proteins play an important role in controlling this focusing. Here, we show that application of a 3-5% tensile strain to a collagen I substrate stimulates osteogenesis in the attached hMSCs through gene focusing via a MAP kinase signaling pathway. Mechanical strain increases expression levels of well-established osteogenic marker genes while simultaneously reducing expression levels of marker genes from three alternate lineages (chondrogenic, adipogenic, and neurogenic). Mechanical strain also increases matrix mineralization (a hallmark of osteogenic differentiation) and activation of extracellular signal-related kinase 1/2 (ERK). Addition of the MEK inhibitor PD98059 to reduce ERK activation decreases osteogenic gene expression and matrix mineralization while also blocking strain-induced down-regulation of nonosteogenic lineage marker genes. These results demonstrate that mechanical strain enhances collagen I-induced gene focusing and osteogenic differentiation in hMSCs through the ERK MAP kinase signal transduction pathway.

Multiway modeling and analysis in stem cell systems biology

“…Furthermore, at each time point tested (days 2, 4, and 5), the strained population always lies closer to the osteoblasts than the unstrained population. This is consistent with our previous finding that application of tensile strain accelerates the osteogenic differentiation of hMSC [31]. …”

The extracellular microscape governs mesenchymal stem cell fate

“…Early studies with MSCs showed that uniaxial strain will induce transient increases in collagen I expression and alignment along that axis [58]. Further, a 3-5% tensile strain on a collagen I substrate can induce osteogenesis in MSCs [59], and biaxial stretching systems can influence alignment of MSCs via mechanosensing [60]. Following from this, the imposition of cyclical tensile strain to mimic the loading and unloading of the skeletal system was shown to promote osteogenesis and angiogenesis on three-dimensional collagen I scaffolds [61].…”

Osteogenic Effects of Rest Inserted and Continuous Cyclic Tensile Strain on hASC Lines with Disparate Osteodifferentiation Capabilities

“…7,23,39 These cells have been shown to readily differentiate down an osteogenic pathway in response to both chemical 8,33,42 and mechanical 30,49,54,66 stimulation. However, in order to produce a tissue engineered bone construct with similar mechanical properties to native tissue, the proper combination of mechanical and chemical stimuli for functional bone tissue engineering needs to be determined.…”

“…However, although MSCs readily undergo osteogenic differentiation. 21,30,37,49,66 isolating bone marrow is a non-trivial procedure for patients and the number of cells recovered is limited. 6,37,41 Adipose-derived adult stem cells (ASCs) are abundant and more easily obtained.…”