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New method shows it is possible to grow bone for grafts within a patient's body


See also...
-Dr Molly Stevens
External Sites:
-Vanderbilt University
-MIT
(Imperial College is not responsible for the content of these external internet sites)

For immediate use
Tuesday 26 July 2005

An international team of biomedical engineers has demonstrated for the first time that it is possible to grow healthy new bone reliably in one part of the body and use it to repair damaged bone at a different location.

The research is described in a paper titled 'In Vivo Engineering of Organs: The Bone Bioreactor' published online by the Proceedings of the National Academy of Sciences.

Researchers from Imperial College London, the Massachusetts Institute of Technology and Vanderbilt University hope their discovery, which takes advantage of the body's natural wound-healing response, will transform treatments for serious bone breaks and diseases.

Skeleton

Working with mature rabbits, a species with bones that are very similar to those of humans, they created a space, dubbed the 'in vivo bioreactor', on the surface of a healthy bone. This space re-filled with healthy bone that was easily detached before it fused with the old, leaving the old bone scarred but intact.

"The new bone actually has comparable strength and mechanical properties to native bone," said lead researcher Molly Stevens, a reader in Imperial's Department of Materials. "And since the harvested bone is fresh, it integrates really well at a recipient site."

"We have shown that we can grow predictable volumes of bone on demand," added V. Prasad Shastri, assistant professor of biomedical engineering at Vanderbilt University. "And we did so by persuading the body to do what it already knows how to do."

The approach currently used by orthopedic surgeons to repair serious bone breaks is to remove small pieces of bone from a patient's rib or hip and fuse them to the broken bone. They use the same method to fuse spinal vertebrae to treat serious spinal injuries and back pain.

Although this works well at the repair site, the removal operation is extremely painful and can produce serious complications. If the new method is confirmed in clinical studies, it will become possible to grow new bone for all types of repairs instead of removing it from existing bones. For people with serious bone disease, it may even be possible to grow replacement bone at an early stage and freeze it so it can be used when it is needed, according to Dr Stevens.

Despite the fact that living bone is continually growing and reshaping, the numerous attempts to coax bone to grow outside of the body - in vitro - have all failed. Recent attempts to stimulate bone growth within the body - in vivo - have had limited success but have proven to be extremely complex, expensive and unreliable.

This new research, however, takes a new approach that has proven to be surprisingly simple. Long bones in the body are covered by a thin outer layer called the periosteum. The layer is a little like scotch tape: the outside is tough and fibrous but the inside is covered with a layer of special pluripotent cells which, like marrow cells, are capable of transforming into the different types of skeletal tissue. Because of this, Dr Stevens and her colleagues decided to create the bioreactor space just under this outer layer.

They created the space by making a tiny hole in the periosteum and injecting saline water underneath. This loosened the layer from the underlying bone and inflated it slightly. When they had created a cavity the size and shape that they wanted, next the researchers removed the water and replaced it with a gel that is commercially available and approved by the FDA for delivery of cells within the human body. They chose the material because it contained calcium, a known trigger for bone growth. Their major concern was that the bioreactor would fill with scar tissue instead of bone, but that didn't happen. Instead, it filled with bone that is indistinguishable from the original bone.

"This research has important implications not only for engineering bone, but for engineering tissues of any kind," said researcher Robert S. Langer, Institute Professor at the Massachusetts Institute of Technology and a pioneer in the field of tissue engineering. "It has the potential for changing the way that tissue engineering is done in the future."

The scientists intend to proceed with the large animal studies and clinical trials necessary to determine if the procedure will work in humans and, if it does, to get it approved for human treatment. At the same time, they hope to test the approach with the liver and pancreas, which have outer layers similar to the periosteum.

Other contributors to the study include the late Dirk Schaefer, who was an orthopedic surgeon at Kantonsspital-Basel in Switzerland; Robert P. Marini, chief of clinical surgical facilities of MIT's Division of Comparative Medicine; and Joshua Aronson, an undergraduate student at MIT.

The research was funded by a grant from Smith and Nephew, Endoscopy.

For further information contact:

Abigail Smith
Imperial College London Press Office
Tel: 020 7594 6701
Email: abigail.smith@imperial.ac.uk

Notes to editors

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