Human blood vessels grown in the lab have successfully been added to people’s own circulatory systems. The blood vessels are grown from the recipient’s own tissue and could be used in the future to replace arteries damaged by heart disease.
Heather Prichard and colleagues at Humacyte, a technology firm in Durham, USA, grew blood vessels in the lab using human smooth muscle cells, which are found in arteries and veins.
These cells were spread out on a scaffold and provided with nutrients. They built blood vessels around themselves by producing extracellular matrix, a 3D network of proteins including collagen.
The team separated the cells from the vessels, removing proteins that may be recognised as foreign by a recipient’s immune system. As the vessels formed, pulsations were added to simulate the pressure of blood being pumped through them.
They then implanted the vessels, which were 42 centimetres long and 6 millimetres in diameter, in the upper arms of 60 people with kidney failure.
Each of the recipients were undergoing dialysis – the filtration of waste products from the blood. Normally surgeons have to connect an artery to a vein to create a wider and higher-pressure vessel for transferring blood to the dialysis machine. Everyone in the study was unable to have this procedure – some people’s blood vessels are too narrow for it to work – so they received a lab-grown vessel instead.
Grow your own
Samples taken from 13 of the participants over a 4-year period showed that the blood vessels developed into multi-layered tissues that self-healed after injury, effectively becoming like the patient’s own blood vessels.
The blood vessel had no cells when implanted, says Prichard. Over time it became populated with different types of the patient’s own cells, and became similar to regular living tissue, she says.
Blood vessel replacements are needed in many situations, such as when arteries are damaged by trauma or cardiovascular disease. Coronary artery bypass surgery, for example, involves grafting vessels to restore normal blood flow to the heart. Currently the gold standard is using a patient’s own arteries or veins, which are sometimes unavailable, in which case a synthetic tube is implanted.
The advantage of the bioengineered vessels over implants made from synthetic polymers is that they showed no signs of scarring or inflammatory reactions.
Growing a batch of blood vessels in the lab took around two months. The team is currently scaling up the process, with the hope of producing tens of thousands of vessels per year.
Journal reference: Science Translational Medicine, DOI: 10.1126/scitranslmed.aau6934
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