ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

involved taking into account the concentration of morphogens, their decay rate, the
density of receptors as well as the association-dissociation rate.
Recently, mechanical factors generated through 2D flow chamber, were also proposed
to be involved in the MSC differentiation process [4, 5, 6, 7, 8, 9]. In particular, it has
been shown that direct mechanical loading of MSC through shear stress-induced fluid
flow stimulates late osteogenic markers [9]. Nevertheless, whether MSCs response to
flow occurs as a result of flow-induced shear stresses, chemotransport, or both, remains
unknown. The effect of direct mechanical stimulations on MSC differentiation cannot
be easily decoupled from chemotransport.
We propose to test the hypothesis that MSCs differentiation can be regulated by fluid
flow through changing the fraction of bound receptors on the cell surface.The aim of
this paper is to study the effect of the frequency of an oscillatory flow on the fraction of
bound receptors.
3. METHODS
In the context of experimental flow chamber setup, we modeled the ligands released by
the cells, which have a constant decay rate and bind to receptors on the cell surface
when submitted to flow (Fig. 1). We considered that cells can sense a change in the
fraction of bound morphogens, which induces what we generally call here a “cell
response”[10, 11].
Fig. 1. Illustration of the model
We used the following dimensionless variables:
, , , , , , (1)
where and are the longitudinal and transverse directions, L is the length of cell
colony, h is the height of flow chamber, is the time, D is the ligand diffusivity, is the
half-life of the ligand in solution, is the ligand concentration, is the concentration
used for scaling, Pe is the Péclet number, and V is 4 times the maximum flow velocity
in the chamber.
We analyzed the effect of the frequency of an oscillatory fluid flow on the fraction of
bound receptors. The fluid flow had a sinusoidal profile characterized by a