Researchers from Rice
Univ. and Baylor College
of Medicine (BCM) have broken one of the major roadblocks on the path to
growing transplantable tissue in the lab: They’ve found a way to grow the blood
vessels and capillaries needed to keep tissues alive.
The new research is available online and due to appear in Acta Biomaterialia.
“The inability to grow blood-vessel networks—or vasculature—in
lab-grown tissues is the leading problem in regenerative medicine today,”
said lead co-author Jennifer West, department chair and the Isabel C. Cameron
Professor of Bioengineering at Rice. “If you don’t have blood supply, you
cannot make a tissue structure that is thicker than a couple hundred
microns.”
As its base material, a team of researchers led by West and BCM molecular
physiologist Mary Dickinson chose polyethylene glycol (PEG), a nontoxic plastic
that’s widely used in medical devices and food. Building on 10 years of
research in West’s lab, the scientists modified the PEG to mimic the body’s
extracellular matrix.
West, Dickinson, Rice graduate student Jennifer Saik, Rice undergraduate
Emily Watkins, and Rice-BCM graduate student Daniel Gould combined the modified
PEG with two kinds of cells—both of which are needed for blood-vessel
formation. Using light that locks the PEG polymer strands into a solid gel,
they created soft hydrogels that contained living cells and growth factors.
After that, they filmed the hydrogels for 72 hours. By tagging each type of
cell with a different colored fluorescent marker, the team was able to watch as
the cells gradually formed capillaries throughout the soft, plastic gel.
To test these new vascular networks, the team implanted the hydrogels into
the corneas of mice, where no natural vasculature exists. After injecting a dye
into the mice’s bloodstream, the researchers confirmed normal blood flow in the
newly grown capillaries.
Another key advance, published by West and graduate student Joseph Hoffmann,
involved the creation of a new technique called “two-photon
lithography,” an ultrasensitive way of using light to create intricate
three-dimensional patterns within the soft PEG hydrogels. West said the
patterning technique allows the engineers to exert a fine level of control over
where cells move and grow. In follow-up experiments, also in collaboration with
the Dickinson
lab at BCM, West and her team plan to use the technique to grow blood vessels
in predetermined patterns.
The research was supported by the National Science Foundation and the
National Institutes of Health. West’s work was conducted in her lab at Rice’s BioScience
Research Collaborative (BRC). The BRC is an innovative space where scientists
and educators from Rice University and other Texas Medical
Center institutions work
together to perform leading research that benefits human medicine and health.
