August 18, 2005
In Vivo Bioreactor Grows Replacement Bone In Rabbits

Needed replacement bone pieces can be grown in a special layer on the surface of other bones.

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.

New Zealand White rabbits were used to test this procedure. The researchers successfully transferred the bone to another location in the rabbits to repair a bone injury at the other location.

The periosteum layer on the outside of bones has stem cells which can be coaxed into growing replacement bone.

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.

Here is the really cool part: This approach might work for growing replacement tissue for organs such as the liver and pancreas.

"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.

While some organ fail too quickly to allow patients to grow new organs to replace them for some types of organ failure the decline of organ function takes months or years and the problem is diagnosed long before the organ reaches an advanced stage of failure. Plus, advances in embedded nanosensors will lead to much earlier identification of failing organs to provide even more time to grow replacements. Therefore the ability to grow replacement organs within one's own body using one's own cells (which will not suffer from immune rejection) would have great value.

An essential component in Strategies for Engineered Negligible Senescence (SENS) is the replenishment of adult stem cell reservoirs in the body with youthful adult stem cells. Imagine then a two stage process for rejuvenation of organs. First, add youthful stem cells to an existing old organ. Then induce the growth of a new replacement organ in a layer created on the surface of the existing organ. Then once the replacement organ develops to full size remove the old organ.

We still need the ability to grow organs outside of a human body. However, for those cases where replacement organs can grow inside one's body we might gain the ability to grow organs much sooner by use of this "in vivo bioreactor" approach.

Share |      Randall Parker, 2005 August 18 10:48 AM  Biotech Organ Replacement


Comments
Sureshan Sivananthan said at December 7, 2005 9:32 AM:

Bone growth in animals is very simple. Especially in the rabbit model, anything seems to grow bone. It seems this group is copy ing the work done by Warnke et al published in the Lancet last year. where a human bone bioreactor was demonstrated. So it is not a world first.

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