(789f) Controlling Localized Xenopus Embryonic Tissue Migration in 3D Microenvironments

Controlling Localized Xenopus Embryonic Tissue Migration in 3D Microenvironments

Jiho Song¹, YongTae Kim², Melis Hazar¹, Metin Sitti¹, Philip R.
LeDuc¹, Lance A.
Davidson³

1 Departments of
Mechanical Engineering, Biomedical Engineering, and Biological Sciences,
Carnegie Mellon University, Pittsburgh, Pennsylvania, United States of America,
2 Koch Institute for Integrative Cancer Research Massachusetts
Institute of Technology, Cambridge, Massachusetts, United States of America, 3 Departments of Bioengineering and Developmental
Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States of
America.

            Cell migration and
growth in multicellular tissues play important roles
in morphogenesis, wound healing, and tumor metastasis. Many studies have
focused on single cell mechanics and the response of motile cells to
topological cues but little is known about the responses of migratory multicellular tissues to complex topological cues.
Understanding cell and tissue migratory responses to well defined 3D substrates
and the factors that regulate those dynamic responses are key to understanding
the basic principles of cell sheet migration during embryonic development,
which can contribute to fields from development to regenerative medicine. Presenting micropost
arrays fabricated via MicroElectroMechanical Systems (MEMS) techniques can
potentially provide advantages for studying the multicellular system response
to substrate-based biophysical stimuli. Using micropost arrays with different diameters
(e.g., different spacing gaps) and Xenopus laevis tissues
cultured in a well-controlled microenvironment are studied for fundamental
multicellular system responses to environmental cues. Our topographical
controlled approach for cellular application enables us to achieve a high degree of control over micropost
positioning and geometry via simple, accurate, and repeatable microfabrication
processes.

            Here
we introduce the methodology of constructing micropost
array gradients to determine the multicellular
system response to topology differences and showed that controlling 3D
microenvironments could impact the shape, formation, and the rate of tissue
cells migration. We have found a preferential
direction of tissue migration over planar substrates yet there was a
correlation between the rate of spreading when compared to micropost
geometry. Cells in ectodermal Xenopus tissues migrated outward as cohesive sheets from their
initial morphology. Post arrays slowed the cell movements over 20 hours. Sequential
images from a representative time-lapse sequence showed that ectodermal tissues
increased their surface area on flat substrates at a relatively rapid rate, but
this movement was slower when the cells moved over the micropost arrays. As a
control, ectodermal tissues migrated faster on entirely flat substrates.
Tissues placed on flat-substrates at the margin of the post array, over the
interface between flat-substrate and posts, and completely over the post array
suggest topological cues may be used to shape tissue form. From these
observations we hypothesized that tissue spreading might be limited by lateral
forces from the posts which would oppose tissue movement. However, when we
decreased the size of the posts the tissues spread more slowly suggesting that
the surface area of the post array was one of the major limiting factors. Therefore, these approaches have lighted an
important connection between cell mechanics and cell phenotype, particularly,
the 2D nature of such techniques that inherently limit the extent to which 3D
morphogenetic phenomena can be investigated although most tissue development is
highly 3D.