In what could be an amazing breakthrough for treating children with congenital heart defects, researchers have created artificial blood vessels that can grow with age. The astonishing development has so far been shown to work in lambs, and it is hoped that after seeking approval from the Food and Drug Administration (FDA) clinical trials could begin in humans within a couple of years.

This latest research, published in the journal Nature Communications, could revolutionize surgery for children who need parts of their heart and blood vessels replaced. Currently, children who suffer from these problems require up to five bouts of invasive surgery to replace the grafts as they grow. These new synthetic vessels could, in theory, mean that the child would only need to be operated on once.

The procedure works by first creating a gel that is seeded with fibroblast cells, the part of connective tissue that produces collagen. This is then shaped into a tube and placed into a novel bioreactor that provides the perfect conditions needed for cell growth, by rhythmically pumping nutrients through and around the tube, giving the cells both the food they need, and the “exercise” to strengthen and stiffen the vessel.  

After five weeks in the bioreactor, the new vessels are then removed and stripped of all the living cells. The resulting scaffold can then be placed in storage and used as and when needed “off the shelf”. This means that once placed in the patient, which in these initial trials were lambs, there is no threat of rejection by the host’s immune system. Once the cell-free vessel is then implanted, the patient’s own cells were found to populate the matrix, causing the graft to grow in sync with the recipient.

When the researchers checked back on the lambs after 50 weeks, they found that the synthetic vessel had increased by 56 percent in diameter, was pumping 216 percent more blood through it, and that the level of collagen had increased by 465 percent, proving that the graft was actually growing, and not just stretching.

“What’s important is that when the graft was implanted in the sheep, the cells repopulated the blood vessel tube matrix,” explained Professor Robert Tranquillo, who led the research. “If the cells don’t repopulate the graft, the vessel can’t grow. This is the perfect marriage between tissue engineering and regenerative medicine where tissue is grown in the lab and then, after implanting the decellularized tissue, the natural processes of the recipient’s body makes it a living tissue again.”

The researchers are now talking to doctors to figure out the feasibility of requesting approval from the FDA to start human clinical trials.