A team of tissue engineers has produced the first three-dimensional bone marrow in culture, leading to hopes of transplanting into patients bone marrow that will function immediately, writes Caroline Davis.

Transplants often leave patients extremely vulnerable to infection and bleeding for up to three weeks as the new material grafts to the cavities inside the bone. But an international race is on to produce bone marrow in culture containing immune cells and already producing red blood cells.

Athanasios Mantalaris, of Imperial College London's department of chemical engineering and chemical technology, has grown bone marrow with similar architectural and functional properties to those in living bone. But at present, the cultures die after three months because they have not been able to build the scaffold to keep the cells in place.

He explained that the complexity of bone marrow was the main hurdle. Bone marrow is a spongy tissue that produces hundreds of billions of red blood cells daily. A network of capillaries drains them into a central vein while nutrient arteries run along the bone.

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To simplify the problem, the team is developing a detailed three-dimensional virtual model of the tissue. The starting material would be cord blood cells, taken from the umbilical cord and frozen. Using these immature cells from the patient, which are not embryonic stem cells, would eliminate post-operative rejection issues.

The next step is to use a biodegradable polymer - details of which Dr Mantalaris would not disclose - to create the scaffold for the culture to grow on. Next, they need a bioreactor in which the scaffold is placed to enable the various parts of the tissue to grow in the right place.

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The research will also inform gene therapy, chemotherapy and provide a model for examining drug efficacy.

The Imperial team has applied for six patents in the US.