Effect of Mechanical Loading on Osteogenesis of Human Embryonic Stem Cell-Derived Mesenchymal Progenitors within Collagen Microspheres

Author(s): Shariatzadeh M, Baldit A, Perrault CM, Lacroix D

Mechanical forces and 3D topological environment can be used to control differentiation of mesenchymal stem cells. However, mesenchymal stem cell fate determined by the effect of physical and mechanical cues is not yet fully understood. Understanding how mechanical cues in the microenvironment orchestrate stem cell differentiation provides valuable insight that can be used to improve current techniques in cell therapy. This study investigates the osteogenic effect of mechanical stimulations on soft cellular microspheres loaded with human embryonic stem cell-derived mesenchymal progenitors (hES-MPs) when subjected to dynamic loading and in the absence of chemical stimulation. Microspheres were produced by gelation of bovine collagen type I with 1000 to 2000 hES-MP cells seeded per droplet. Four loading conditions were studied: (1) 10% constant strain was applied by a Bose biodynamic bioreactor for 15 min/day or 40 min/day for 5 or 10 days respectively; (2) 10% adjusted strain was applied (subtraction of polydimethylsiloxane (PDMS) plastic elongation from global strain) using Bose biodynamic bioreactor for the same 4 duration/conditions as in the constant strain protocol. The results indicate that applying mechanical stimulation to hES-MPs/collagen microspheres induced osteogenic differentiation of cells when the loading protocol was adjusted. Alkaline phosphatase activity of samples in the adjusted loading protocol increased significantly on day 14 whilst, the deposited minerals, matrix reorganisation and alignment of collagen fibres enhanced from day 21 post encapsulation onward. Application of cyclic loading to 3D culture of hES-MP cells can be used as a model to regulate mechano-stimulation and linage differentiation in vitro.