Surpassing a major roadblock in lab-development of transplantable tissue, scientists have now found a way to grow the blood vessels and capillaries needed to keep tissues alive.
As its base material, a team of researchers led by co-author Jennifer West and Baylor College of Medicine 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-the network of proteins and polysaccharides that make up a substantial portion of most tissues.
The researchers then 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.
Previously, West and graduate student Joseph Hoffmann published the advancement that 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 findings appeared in the January issue of the journal Acta Biomaterialia.