Mechanical Fluid Shear Stress Research Articles

Modulation of the Cellular Microenvironment by Mechanical Fluid Shear Stress and Hypoxia Alters the Differentiation Capacity of Skeletal Muscle-Derived Stem Cells

Skeletal muscle-derived stem cells (MDSCs) are the key modulators of muscle regeneration. An inappropriate cellular microenvironment can reduce the regenerative capacity of MDSCs. This study evaluates the effect of microenvironmental alterations on the cell differentiation capacity using either mechanical fluid shear stress (FSS) or hypoxic conditions. C2C12 mouse myoblasts were differentiated under cyclic FSS (CFSS), periodic FSS (PFSS) for one hour, and hypoxia (3% O2) for up to seven days. Cell proliferation and myogenic differentiation capacities were evaluated using cell viability assays, immunohistochemical staining, and morphometric analysis. The expression of MyoD, myogenin, myosin heavy chain, nitric oxide, hypoxia-inducible factor 1 alpha (HIF1α), vascular endothelial growth factor (VEGF) and mammalian target of rapamycin (mTOR) was quantified by means of RT-qPCR. The data showed that FSS conditions altered cell morphology and increased cell viability and cell distribution compared to static conditions. MyoD and myogenin expression was upregulated under both FSS conditions. CFSS induction improved myogenic differentiation parameters including myotube number, size and fusion capacity. Although hypoxia enhanced cell viability compared to normoxia, it reduced differentiation capacity, as indicated by the downregulation of myogenin and mTOR expression, as well as reducing myotube formation. Under hypoxic conditions, increased nitric oxide production and upregulation of VEGF expression were detected for up to 72 h. The data suggest an improved myogenic differentiation capacity under mechanical FSS; in contrast, the cell differentiation capacity was impaired under hypoxic conditions. The data point out that optimizing the biomechanical and oxidative stressors in the cellular microenvironment could improve stem cell transplantation and enhance their regenerative potential in the context of cell-based therapies.

Bacteria in tumors “hit the road” together

Tumors contain bacteria, but the functional significance of this tumor microbiota is not appreciated. Fu etal. show that bacteria within breast tumor cells contribute to metastasis, in part, by enhancing tumor cell survival to mechanical fluid shear stress as would be found in the circulation.

Combined macromolecule biomaterials together with fluid shear stress promote the osteogenic differentiation capacity of equine adipose-derived mesenchymal stem cells

BackgroundCombination of mesenchymal stem cells (MSCs) and biomaterials is a rapidly growing approach in regenerative medicine particularly for chronic degenerative disorders including osteoarthritis and osteoporosis. The present study examined the effect of biomaterial scaffolds on equine adipose-derived MSC morphology, viability, adherence, migration, and osteogenic differentiation.MethodsMSCs were cultivated in conjunction with collagen CultiSpher-S Microcarrier (MC), nanocomposite xerogels B30 and combined B30 with strontium (B30Str) biomaterials in osteogenic differentiation medium either under static or mechanical fluid shear stress (FSS) culture conditions. The data were generated by histological means, live cell imaging, cell viability, adherence and migration assays, semi-quantification of alkaline phosphatase (ALP) activity, and quantification of the osteogenic markers runt-related transcription factor 2 (Runx2) and alkaline phosphatase (ALP) expression.ResultsThe data revealed that combined mechanical FSS with MC but not B30 enhanced MSC viability and promoted their migration. Combined osteogenic medium with MC, B30, and B30Str increased ALP activity compared to cultivation in basal medium. Osteogenic induction with MC, B30, and B30Str resulted in diffused matrix mineralization. The combined osteogenic induction with biomaterials under mechanical FSS increased Runx2 protein expression either in comparison to those cells cultivated in BM or those cells induced under static culture. Runx2 and ALP expression was upregulated following combined osteogenic differentiation together with B30 and B30Str regardless of static or FSS culture.ConclusionsTaken together, the data revealed that FSS in conjunction with biomaterials promoted osteogenic differentiation of MSCs. This combination may be considered as a marked improvement for clinical applications to cure bone defects.

Fluid shear stress induces Runx-2 expression via upregulation of PIEZO1 in MC3T3-E1 cells.

Mechanically induced biological responses in bone cells involve a complex biophysical process. Although various mechanosensors have been identified, the precise mechanotransduction pathway remains poorly understood. PIEZO1 is a newly discovered mechanically activated ion channel in bone cells. This study aimed to explore the involvement of PIEZO1 in mechanical loading (fluid shear stress)-induced signaling cascades that control osteogenesis. The results showed that fluid shear stress increased PIEZO1 expression in MC3T3-E1 cells. The fluid shear stress elicited the key osteoblastic gene Runx-2 expression; however, PIEZO1 silencing using small interference RNA blocked these effects. The AKT/GSK-3β/β-catenin pathway was activated in this process. PIEZO1 silencing impaired mechanically induced activation of the AKT/GSK-3β/β-catenin pathway. Therefore, the results demonstrated that MC3T3-E1 osteoblasts required PIEZO1 to adapt to the external mechanical fluid shear stress, thereby inducing osteoblastic Runx-2 gene expression, partly through the AKT/GSK-3β/β-catenin pathway.

Influence of mechanical fluid shear stress on the osteogenic differentiation protocols for Equine adipose tissue-derived mesenchymal stem cells

Cell-based therapies have become a promising approach to promote tissue regeneration and the treatment of musculoskeletal disorders. Bone regeneration maintains bone homeostasis, mechanical stability and physical performance. Mechanical stimulation showed to induce stem cell differentiation into the osteogenic fate. However, the effect of various osteogenic protocols on the osteogenic commitment of equine adipose-derived stem cells is not fully elucidated. Here we examined the influence of fluid-based shear stress (FSS) via mechanical rocking to assess whether mechanical stimulation promotes osteogenic differentiation of equine adipose-derived stem cells (ASCs). ASCs were induced into osteogenic fate using osteogenic differentiation medium (ODM) protocol or additional supplementation of 5 mM CaCl2 and 7.5 mM CaCl2 protocol compared to cells cultivated in basal medium (BM) up to 21 day. The ASCs proliferation pattern was evaluated using the sulforhodamine B (SRB) protein assay. Osteogenic differentiation examined via semi-quantification of alizarin red staining (ARS) and alkaline phosphatase activity (ALP) as well as, via quantification of osteocalcin (OC), alkaline phosphatase (ALP), osteopontin (OP), and collagen type-1 (COL1) gene expression using RT-qPCR. We show that mechanical FSS increased the proliferation pattern of ASCs compared to the static conditions. Mechanical FSS together with 5 mM CaCl2 and 7.5 mM CaCl2 promoted osteogenic nodule formation and increased ARS intensity compared to the standard osteogenic protocols. We observed that combined mechanical FSS with ODM protocol increase ALP activity compared to static culture conditions. We report that ALP and OC osteogenic markers expression were upregulated under mechanical FSS culture condition particularly with the ODM protocol. Taken together, it can be assumed that mechanical stress using FSS promotes the efficiency of the osteogenic differentiation protocols of ASCs through independent mechanisms.