title: Hydrodynamic loading in concomitance with exogenous cytokine stimulation modulates differentiation of bovine mesenchymal stem cells towards osteochondral lineages.
abstract: BACKGROUND
  Mesenchymal stem cells (MSCs) are viewed as a having significant potential for tissue engineering and regenerative medicine therapies. Clinical implementation of MSCs, however, demands that their preparation be stable and reproducible. Given that environmental and bioprocessing parameters such as substrate stiffness, seeding densities, culture medium composition, and mechanical loading can result in undirected differentiation of the MSC population, the objective of this study was to systematically investigate how hydrodynamic loading influences the differentiation of bone marrow-derived mesenchymal stem cells (MSCs) towards the osteochondral lineages both in the presence and absence of exogenous, inductive factors.
  
  
  METHODS
  Expanded bovine MSCs were suspended in 2.5 % agarose, cast in a custom mold, and placed into either static or one of two dynamic culture environments consisting of "high" and "low" magnitude shear conditions. Constructs were supplemented with varying concentrations (0, 1, 10, 100 ng/mL) of either TGF-β3 or BMP-2 throughout cultivation with tissue samples being collected following each week of culture.
  
  
  RESULTS
  In the absence of exogenous supplementation, hydrodynamic loading had little effect on cell phenotype at either magnitude of stimulation. When cultures were supplemented with BMP-2 and TGF-β3, MSCs gene expression progressed towards the osteogenic and chondrogenic pathways, respectively. This progression was enhanced by the presence of hydrodynamic loading, particularly under high shear conditions, but may point the chondrogenic cultures down a hypertrophic path toward osteogenesis reminiscent of endochondral ossification if TGF-β3 supplementation is insufficient.
  
  
  CONCLUSIONS
  Moving forward, these results suggest bioprocessing conditions which minimize exposure of chondrogenic cultures to fluid shear stress to avoid undesirable differentiation of the MSC population.
authors.affiliation: Interdisciplinary Bioengineering Graduate Program, Georgia Institute of Technology, Atlanta, GA,, 30332, USA. stephen.goldman@gatech.edu.|G.W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA,, 30332, USA. stephen.goldman@gatech.edu.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Goldman
authors.affiliation: Interdisciplinary Bioengineering Graduate Program, Georgia Institute of Technology, Atlanta, GA,, 30332, USA. barabino@ccny.cuny.edu.|Department of Biomedical Engineering, City College of New York, 160 Convent Avenue, New York, NY,, 10031, USA. barabino@ccny.cuny.edu.
authors.forename: Gilda A
authors.initials: GA
authors.lastname: Barabino
mesh_terms: D000818:Animals; D001709:Biotechnology; D002417:Cattle; D018929:Cell Culture Techniques / Q000379:methods*; D002454:Cell Differentiation / Q000187:drug effects*; D002478:Cells, Cultured; D020219:Chondrogenesis / Q000187:drug effects*; D016207:Cytokines / Q000494:pharmacology*; D004867:Equipment Design; D057446:Hydrodynamics; D059630:Mesenchymal Stem Cells / Q000166:cytology*; D010012:Osteogenesis / Q000187:drug effects
chemical_list: D016207:Cytokines
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