People in need of a blood transfusion might soon get some not from a donor’s vein, but blood produced in a lab.

Lab-brewed blood is being put to the test in a world-first clinical trial in the UK. The trial will involve living subjects receiving tiny transfusions — around a few spoonfuls each — of the liquid, to see how it interacts with their bodies. Although human donors will likely remain the main source of blood for transfusions, lab-produced blood might be invaluable for people with particular disorders or ultra-rare blood groups, which can find it exceedingly difficult to secure appropriate blood when needed.

Preliminary data, obtained from transfusions with two participants, is encouraging but not sufficient to determine whether the lab-blood is safe for use. The team is aiming at performing transfusions for a total of 10 participants in this early-stage trial and, should it be successful, to expand the tests to include many more participants.

Tailor-made

Blood transfusions are an essential part of modern medicine. Without blood donated by countless people around the world, even routine surgeries could lead to deadly blood loss, as would many accidents or wounds.

That being said, it is much harder to find appropriate blood for some groups of people than others. For starters, each individual falls into one of four blood groups — A, B, AB, and O — and any transfused blood needs to be of one of the appropriate types for each group. Other tissue-matching factors exist beyond the blood groups alone and, if transfused blood is not properly selected, it could lead to the patient rejecting the transfusion with potentially-severe effects.

All these factors are hard enough to juggle for regular patients needing fresh blood. For patients with more exotic blood types, blood conditions (such as sickle cell anemia), or those who depend on regular blood transfusions, having the right type of blood on hand can be a matter of life and death. This is not always easy to pull off, as some of the blood groups and other compatibility markers are very rare in the wider population.

It is exactly these rarer patients that the lab-made blood is meant to help, the team explains. Even if the current trials are a success, it’s overwhelmingly likely that the vast majority of blood used for transfusions will still be obtained the traditional way, from donors.

The current trial is the result of a collaboration between researchers from Bristol, Cambridge, London, and the National Health Service Blood and Transplant. It focuses on replicating red blood cells, the ones that are responsible for ferrying oxygen, nutrients, and waste around the body.

In order to produce their lab-blood, the team starts with a small initial sample (around 470 ml) of donated blood. Magnetic beads are then used to isolate stem cells, which are able to mature into red blood cells, from this sample. The cells are then multiplied in the lab and fostered to develop into red blood cells.

The whole process takes around three weeks. An initial quantity of half a million stem cells can yield up to around 50 billion red blood cells, around 15 billion of which are mature enough to be transplanted, the team explains. This process can easily be automated and run around the clock, they add, allowing for significant quantities of red blood cells to be synthesized and stockpiled.

So far, two people have received test transfusions with the blood as part of the RESTORE trial; eight more are planned as part of the trial. Every volunteer will receive two transfusions of 5-10 ml at least four months apart. One will be of normal blood (control) and the other will be lab-grown blood. Both samples have been tagged with a medical-grade radioactive marker often used in medical procedures, to allow the team to track how long the two types of blood last in the body.

Red blood cells typically survive for around 120 days before being replaced. As typical blood donations contain a mix of red blood cells of all ages, the average lifespan of cells in that blood is less than 120 days. The team hopes that their trial will also prove that the lab-produced blood cells last longer than that in typical transfusions, as they are freshly made and shifted for age before donation.

If this is true, it would mean that smaller and less frequent donations of lab-made blood would be needed, compared to traditional blood.

But if this blood is so good, why not use it for all donations? Well, chief among the reasons is cost. The NHS estimates that an average blood transfusion costs it around £140. Lab-grown blood will be much more expensive per donation, although no definite price figure has yet been set.

Supply is also an issue. There is only a limited quantity of blood that can be produced from the harvested stem cells until these exhaust themselves. The process will need to be significantly improved to allow for more blood to be produced from each seed sample. Lastly, while harvesting blood from donors is simple and can be performed easily on massive scales, the production of lab-grown blood requires specialized equipment and we would only be able to produce limited amounts with our current infrastructure.