Scientists in the United Kingdom have reached a milestone decades in the making: human patients have received transfusions of red blood cells grown from stem cells in a laboratory. The RESTORE clinical trial, run by NHS Blood and Transplant in partnership with the University of Bristol and University of Cambridge, marks the first time manufactured blood cells have ever entered human veins — and could one day ease a global shortage that costs lives every year.
At a glance
- Lab-grown blood cells: Stem cells isolated from donated blood are placed in a nutrient solution for 18 to 21 days, where they multiply and mature into fully formed red blood cells ready for transfusion.
- RESTORE trial: The clinical study involves at least 10 participants each receiving two small “mini” transfusions — one of lab-grown cells and one of standard donated blood — to compare safety and longevity.
- Blood transfusion shortage: Demand for donated blood consistently outstrips supply worldwide, and matching blood types between donors and recipients means some patients go without even when blood is available.
How blood gets grown in a lab
The process still begins with a human donor — but scientists are not after the red blood cells themselves. Instead, they isolate blood stem cells, the precursor cells that the body normally uses to generate new blood throughout a person’s life.
Those stem cells are placed into a carefully designed nutrient solution and left to develop over 18 to 21 days. During that window they multiply and mature, eventually becoming functional red blood cells. The resulting cells are then purified and prepared for transfusion — a process that happens entirely outside the human body.
Professor Ash Toye of the University of Bristol has been central to advancing this technique, which has been a scientific goal for several decades. Reaching the stage of human trials represents a significant jump from laboratory bench to clinical reality.
Why longer-lasting cells matter
A red blood cell normally lives for about 120 days. But when you receive a conventional blood transfusion, the donated blood contains cells of all different ages — some near the end of their lifespan, some relatively fresh. The effective benefit is shorter than 120 days, which is why many patients with conditions like sickle cell anemia or other blood disorders need transfusions repeatedly and frequently.
Lab-grown blood is different. Because every cell is made fresh at the same time, they should all reliably last close to the full 120 days. For patients who depend on regular transfusions, that could mean longer gaps between procedures — a meaningful improvement in quality of life.
The RESTORE trial is specifically designed to test this hypothesis alongside basic safety. Each of the at least 10 participants receives two small transfusions — containing just 5 to 10 milliliters, roughly one to two teaspoons, of red blood cells — spaced four months apart. One transfusion contains lab-grown cells; the other contains standard donated blood. Researchers then monitor participants for side effects and track how long each type of cell survives in the body.
So far, two participants have completed transfusions of lab-grown blood cells, with no adverse side effects reported by the research team.
A potential answer to a persistent shortage
Blood donation shortages are a chronic problem in health systems around the world. Supply rarely keeps up with demand, and the added complexity of blood type matching means that compatible donations are sometimes wasted while patients with rare blood types wait. The American Red Cross estimates that someone in the U.S. needs blood every two seconds.
Lab-grown blood could eventually be tuned to any required blood type, which would reduce mismatches and alleviate some of that pressure. NHS Blood and Transplant, which is running the RESTORE trial, sees the technology as a potential long-term complement to conventional donation — not a replacement.
There is also particular promise for people with rare blood types or conditions that complicate transfusion matching, where finding compatible donors is genuinely difficult and the consequences of a mismatch are severe.
Still early days
This trial is a first step, not a finish line. The RESTORE study uses intentionally tiny transfusion volumes — enough to test safety and cell longevity, not enough to treat a patient’s condition. Scaling the manufacturing process from teaspoons to clinically meaningful quantities remains a major engineering and cost challenge. Researchers at the University of Bristol and their partners are frank that large-scale production is still years away, and conventional blood donation remains critical in the meantime.
The World Health Organization estimates that low- and middle-income countries bear the greatest burden of blood shortages, so the long-term equity implications of this technology — including whether manufactured blood will eventually be affordable and accessible globally — are questions the field will need to answer.
For now, though, the fact that lab-grown red blood cells have safely entered a human body for the first time is a moment researchers have worked toward for a generation. The science has crossed a threshold it cannot uncross.
Read more
For more on this story, see: New Atlas — First human patients receive transfusions of lab-grown blood cells
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