Computational Modeling of Tissue Engineering Scaffolds as Delivery Devices for Mechanical and Mechanically Modulated Signals - Computational Modeling in Tissue Engineering - page 131

Fig. 8 CFD predictions and l-PIV for flow regimes of interest. a CFD predictions of axial flow
velocity (upper) and shear stress (lower) in the flow chamber at 10 lm from the bottom of the
flow chamber. Flow moves from right (inlet) to left (outlet). b 3D images of flow fields (red
arrows indicate microsphere displacements) around cells (green). Three dimensional confocal
image stacks are analyzed to quantify the flow fields with respect to distance from the substrate
and cell density. d- l Confocal images closest to the basal surface, approximately 2 lm from the
substrate on which cells are seeded (d, g, j), 5 lm from the substrate (e, h, k), and 10 lm from
the substrate (f, i, l). Cells are labeled with calcein green, microspheres exhibit red fluorescence,
and white arrows indicated microsphere displacements in 990 ms. Green, red, and white indicate
cells, microspheres, and displacements, respectively. Adapted from [ 40 ]
5 CFD Modeling for Precise Delivery of Mechanical Signals
to MSCs to Direct Cell Fate
Based on CFD predictions, studies of parallel plate perfusion systems have
underscored how important it is to translate signals delivered in two dimensions to
three dimensions (3D), and at the subcellular length scale [ 1 ]. CFD can be used to
predict flow regimes around cells (in 3D) in known flow chamber geometries and
flow fields, to deliver controlled mechanical signals to cells seeded within. In situ
microscopy allows for concomitant imaging of live cell mechano-adaptation while
tracking the cell's dynamic mechanical environment [ 39 , 41 , 43 ]. Specifically,
microscale particle image velocimetry (l-PIV) allows not only for the validation
of CFD predictions at the length scale of the coverslip (2D) and scaffolds (3D)
onto which cells are seeded for mechanotransduction studies, but also for
observing cell seeding effects on three dimensional flow field in the vicinity of
cells. (Fig. 8 , 9 ) Combined with rtPCR [ 34 , 39 , 41 ] and/or genetically modified
stem cells that express green fluorescent protein upon differentiation.