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Human blood vessels grown in the lab have successfully been added to circulatory systems in people. The blood vessels are grown from the recipient’s own tissue and could be used to replace arteries damaged by heart disease.

Heather Prichard and colleagues at Humacyte, a technology firm in Durham, North Carolina, grew the blood vessels 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 produced an extracellular matrix, a 3D network of proteins including collagen, to make blood vessels. As the vessels formed, fluids were pushed through them to simulate the pressure of blood being pumped in the body.

The researchers separated the cells from the vessels, removing proteins that may be recognised as foreign by a recipient’s immune system. 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 was undergoing dialysis – the filtration of waste products from the blood by a machine outside the body. 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 these people over a four-year period showed that the blood vessels developed into multi-layered tissues that self-healed after injury, effectively becoming like the person’s own vessels.

The blood vessels had no cells when implanted, says Prichard. Over time they became populated with different types of the recipient’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 to use a person’s own arteries or veins. But sometimes this isn’t possible, 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.