Growing human tissue is a huge challenge for researchers, even on a small scale. But some ultra-creative scientists hit on a potential solution last week when they flushed out a plant's cells and injected human cells in their place. That was how they got heart cells to beat on a spinach leaf.
A major issue in tissue regeneration is creating a vascular system that ensures blood can flow to the tissue and deliver all-important oxygen and nutrients to keep the tissue alive and growing. Current techniques, including 3D printing, as innovative as it is, can't yet create the blood vessels and tinier capillaries needed in a circulatory system. But guess what's abundant and already has lots of veins? Plants, that's what.
Researchers from Worcester Polytechnical Institute in Massachusetts, Arkansas State University-Jonesboro, and the University of Wisconsin-Madison hope to use plants as "scaffolds" to grow human tissue. For a proof-of-concept experiment, which will be published in the May issue of Biomaterials, WPI biomedical engineering graduate student Joshua Gerslak cleared out spinach leaves' plant cells by flushing a detergent solution through the stem.
What remained after a few days was the vascular framework which kept the cells in place: that is, veins. They're mostly made of cellulose, a material that's safe to use in people and has been used in other regenerative efforts, including cartilage and bone-tissue engineering. Here's what a decellularized spinach leaf looks like. It's just a spinach-shaped shell.
The team put cells that line the inside of human blood vessels into the newly-cleared spinach veins before seeding human heart cells to the outside of the spinach shell. Amazingly enough, the heart cells began to beat on their own. The scientists were able to pump fluids and microbeads comparable in size to human blood cells through the plant veins to confirm that the leaves could transport blood (that's red dye in the video, not actual blood).
Down the line, researchers may be able to use this technique on multiple spinach leaves to create heart tissue, which could be grafted on to the hearts of people who've had heart attacks. (Parts of survivors' hearts have died from a lack of blood flow and no longer contract properly; other researchers are looking into using stem cells to repair this tissue.) While this is all super cool and exciting, we're many years away from any salad-based heart patches.
The team was able to flush the cells out of other plants including parsley, peanut hairy roots, and sweet wormwood, and they think the technique could be adapted to work with other plants that would be a good match to grow certain types of human cells. They wrote:
"The spinach leaf might be better suited for a highly-vascularized tissue, like cardiac tissue, whereas the cylindrical hollow structure of the stem of Impatiens capensis (jewelweed) might better suit an arterial graft. Conversely, the vascular columns of wood might be useful in bone engineering due to their relative strength and geometries."
This is far from the only lab looking to the plant world for body parts: One Canadian researcher is working on making ears out of apples. The phrase "you are what you eat" suddenly takes on a whole new meaning, doesn't it?
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