Lab-Grown Blood Vessels Function Like the Real Thing
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The engineered microvessels can form bends and T-junctions. The blue dots are the nuclei of the endothelial cells in the vessel walls, and the cell junctions are red. When smooth muscle cells (green) are introduced, they wrap and tighten around the vessels like they do in the human body.
CREDIT: Ying Zheng, University of Washington |
Skin, bone, hearts, kidneys and lungs someday will be grown in labs and implanted into bodies when needed, making organ-donor lists and immunosuppressant drugs obsolete.
This vision is still decades away, but lab researchers at the University of Washington have taken a step toward its realization by growing the first 3D structure of tiny blood vessels.
The blood vessels were grown inside a network of small channels made out of the protein collagen. These lab-made vessels were put through a series of tests, confirming that they behave like their natural counterparts.
“The significance of our finding is it’s a big step toward building implantable tissue,” bioengineering professor Ying Zheng, the lead study researcher, told InnovationNewsDaily. “There are a lot of challenges toward building these tissues, and we are targeting one of the biggest challenges — the vascularization.”
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Blood vessels have been grown in labs in the past, but these were larger vessels that transported blood to and from the organs. The blood vessels created by Zheng and her team are the smaller vessels that are embedded in the organs and distribute blood within the tissue.
Zheng and her colleagues first constructed a mold for the collagen micro-channels. They used soft lithography — a technology used to etch circuits into computer chips — to form two stamps (the top and the bottom of the mold). Next, they injected the molded network of collagen channels with endothelial cells, which line the walls of human blood vessels.
The engineered vessels took root in the lab-made structure, growing through the channels and forming a vascular network of sorts.
The lab-grown vessels exhibited other similarities to their natural counterparts found in the body. They were able to transport blood smoothly through the curvy channels without clotting. And when treated with an inflammatory compound, the vessels developed clots, similar to what vessels in the body do when they become inflamed.
One key to the team’s development is the type and concentration of the collagen used to form the micro-channel scaffolding. It needed to be soft enough to enable the endothelial cells to modify the shape of the channels and hard enough to support the tubular structure, Zheng said.
The researchers also show that their blood vessels grow sprouts when exposed to tumor-mimicking chemicals, which is how the body’s blood vessels respond to cancer cells. These results suggest that the lab-made vascular system could serve as a model to study cancer.
“This work indeed represents a huge step toward the development of implantable scaffolds for tissue repair and regeneration,” said Sujata Bhatia, assistant director of undergraduate studies in biomedical engineering at Harvard University.
“Currently one of the major challenges in tissue engineering is that the size of the implantable scaffold is limited, as growing tissue requires delivery of oxygen and nutrients. An implantable scaffold that incorporates a microvascular network can overcome this challenge, by ensuring a reliable blood supply to the growing tissue,” she added.
The next step for Zheng’s team is to build heart tissue with this 3D network of blood vessels.
Zheng and her colleagues detail their findings in the May 28 issue of the journal Proceedings of the National Academy of Sciences.
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