January 18, 2011
Time-lapse image shows how two types of cells tagged with fluorescent dyes organize themselves into a functioning capillary network within 72 hours. |
Recently, Medtech Pulse reported on research conducted by the National Institute of Standards and Technology and the National Institutes of Health on the use of hydrogels for developing 3-D tissue scaffolds. Hot on the heels of this news, researchers from Rice University (Houston) and Baylor College of Medicine (BCM; Houston) claim to have found a way to employ hydrogels to grow blood vessels and capillaries.
As detailed in the journal Acta Biomaterialia, a team of researchers led by Rice University bioengineering professor Jennifer West and BCM molecular physiologist Mary Dickinson modified polyethylene glycol (PEG), a nontoxic plastic widely used in medical devices and food, to mimic the body's extracellular matrix-- the network of proteins and polysaccharides that make up a substantial portion of most tissues. The scientists 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 containing living cells and growth factors. Then, 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. (See video below.)
"The inability to grow blood-vessel networks--or vasculature--in lab-grown tissues is the leading problem in regenerative medicine today," West remarks. "If you don't have blood supply, you cannot make a tissue structure that is thicker than a couple hundred microns."
To test the 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 that there was normal blood flow in the newly grown capillaries.
Associated with this breakthrough, West and colleagues have developed a new technique called 'two-photon lithography, an ultrasensitive method for using light to create intricate 3-D patterns within soft PEG hydrogels. This patterning technique, West says, allows the engineers to exert a fine level of control over where cells move and grow. In follow-up experiments in collaboration with the Dickinson lab at BCM, West and her team plan to use the technique to grow blood vessels in predetermined patterns.
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