Published June 26, 2012
In just a few years, you might be able to grow your own replacement bones from stem cells.
Using pieces of human or animal bone as scaffolds, a Columbia University team has grown more than 50 healthy bones from stem cells -- the largest approximately 2.5 inches long. Among other specimens, the researchers produced a cheek bone, a small part of a femur bone, and a complex temporomandibular joint (TMJ), which is located in front of each ear and allows for chewing, speaking and smiling.
Using custom-built bioreactors housed at Columbia's Biomedical Engineering Lab, the process currently takes three to five weeks, and the team is working on a faster turnaround.
“If we could grow this bone, we could do anything else,” professor Gordana Vunjak-Novakovic, who heads up the team, told FoxNews.com. “Stem cells are very smart. They can make anything as long as you place them in the right conditions and send them the right signals.”
While building the new bone matrix, the cells also break down and decompose the old scaffold. The end result is a fully regenerated bone.
“It looks like bone, feels like bone and responds like bone,” said Sidney Eisig, a mouth, jaw and neck surgeon who collaborates with the lab to provide data necessary for growing anatomically shaped bones.
“Cells that we use are the cells that make bones in our body normally,” Vunjak-Novakovic said of the mesenchymal stem cells which reside in the bone marrow. “They’re constantly making and breaking bone.” Similar to human skin, bone tissue is very metabolically active and regenerates quickly, which is why broken bones are able to heal. Bone tissue is actually easier to make than certain types of muscle, Vunjak-Novakovic explained. For example, the heart muscle is not designed to regenerate and is much harder to grow.
To prepare the scaffolds, Vunjak-Novakovic’s team thoroughly washed the animal bone pieces: first with water, which removed 99 percent of cellular material, then with special detergents to clean water resistant surfaces, and finally with enzymes to remove residual DNA from the cells’ nuclei. The result was a porous “non-identifiable bone” that could serve as a scaffold for any bone graft, including human.
They are also experimenting with synthetic silk scaffolds supplied by Tufts University.
“You want something porous so you can put cells in it, so they would start making their own bone,” Sarindr Bhumiratana, who built the bioreactor together with the lab’s mechanical engineer, told FoxNews.com.
Depending on the size of the graft, bioreactors can be surprisingly small. The TMJ bioreactor can easily fit in a human palm. The hermetically closed chamber holds a silicon insert to keep the scaffold tightly in place. The bioreactor connects to a pump that delivers the cell’s food supply and removes solid waste.
The mesenchymal cells consume the nutrients and the oxygen, generate bone cells and release carbon dioxide, mimicking the process that happens in a human body -- with the pump acting as both the heart and the lungs.
While demonstrating the bioreactor, Bhumiratana emphasized the importance of delivering the nutrients to every cell inside the developing graft, not just the surface cells. To achieve this, the culture medium must be pushed through the new bone and not just around it, similarly to how blood flows through human bones.
“If you don’t do it, you end up with a piece that looks like an M&M candy,” Vunjak-Novakovic said. A small layer of bone tissue would grow on the surface, but inside the piece would be “dead and empty.”
Currently, implants are carved out from the patients’ hip bones. “That requires two surgical sites and we don’t always get the anatomical shape that we desire,” Dr. Eisig told FoxNews.com. With engineered grafts, he can grow a perfect implant. Mesenchymal stem cells are also present in fat tissues so in the future patients won’t have to undergo a painful bone marrow extraction -- just liposuction the necessary cells from the body.
Bhumiratana estimated the cost of the bioreactor as $200 to $400 plus expenses for stem cells isolation and culture media.
Regulatory approval is the real hurdle, however. The implants are currently being tested on mice, but Vunjak-Novakovic believes the commercial technology is only a few years away.
“I am very excited about it,” Dr. Eisig said. “We're very close. We just need to get the technology into the hospital room.”