Image of cells aligned to spell “Toronto”. Courtesy Lian Leng |
Imagine
a machine that makes layered, substantial patches of engineered
tissue—tissue that could be used as grafts for burn victims or vascular
patches. Sounds like science fiction? According to researchers at the
University of Toronto, it’s a growing possibility.
Along
with graduate students from their labs—Lian Leng, Boyang Zhang, and
Arianna McAllister— Associate Professor Axel Guenther of the Department
of Mechanical and Industrial Engineering, cross-appointed to the
Institute of Biomaterials and Biomedical Engineering (IBBME), and
Associate Professor Milica Radisic, core professor at IBBME and the
Department of Chemical Engineering and Applied Chemistry, have invented a
new device that may allow for the uniform, large-scale engineering of
tissue.
“There’s
a lot of interest in soft materials, particularly biomaterials,”
explains Guenther of the materials that help create functional tissue
cultures, “but until now no one has demonstrated a simple and scalable
one-step process to go from microns to centimeters.”
The
invention, presented in a cover article for the journal Advanced
Materials this month (“Mosaic Hydrogels: One-Step Formation of
Multiscale Soft Materials”), is currently being commercialized by MaRS
Innovations in collaboration with the Innovations and Partnerships
Office (IPO) of the University of Toronto, where Radisic and Guenther’s
labs have filed two patents on the device.
But how exactly does a machine grow a large patch of living tissue?
Scientists
manipulate biomaterials into the micro-device through several channels.
The biomaterials are then mixed, causing a chemical reaction that forms
a “mosaic hydrogel”—a sheet-like substance compatible with the growth
of cells into living tissues, into which different types of cells can be
seeded in very precise and controlled placements.
Unique
to this new approach to tissue engineering, however, and unlike more
typical methods for tissue engineering (for instance, scaffolding, the
seeding of cells onto an artificial structure capable of supporting
three-dimensional tissue formation) cells planted onto the mosaic
hydrogel sheets are precisely incorporated into the mosaic hydrogel
sheet just at the time it’s being created—generating the perfect
conditions for cells to grow.
The
placement of the cells is so precise, in fact, that scientists can
spell words (such as “Toronto,” shown here) and can precisely mimic the
natural placement of cells in living tissues. And by collecting these
sheets around a drum, the machine is able to collect layers of cells in
thicknesses made to measure: in essence, three dimensional, functional
tissues.
And
in tissue engineering, cell placement is everything: something that the
new invention delivers. “The cells are able to stretch and connect with
each other, which is very important for ultimately obtaining functional
tissues,” Guenther states.
The
resulting tissues, cites Lian Leng, lead author on the project and a
3rd year PhD Candidate in the Department of Mechanical and Industrial
Engineering, are remarkably stable. “In this case, when we put the cells
in the right places we create cellular organization quite naturally.”
So what’s the next step?
“My
laboratory is currently pursuing different applications of the
technology—different tissues,” says Guenther. The device may provide the
means to create three-dimensional cell cultures for the development of
therapeutic drugs, for instance. “But one of my dreams is to one day
engineer a vascularized leaf—perhaps a maple leaf,” he jokes.
Source: University of Toronto
