Tissue engineering to grow bone, ligaments and cartilage

A future in which laboratory-grown organs and stimulated growth of muscle, bones and nerves could play a major role in treating medical conditions was revealed at a recent Tissue Engineering Symposium at Wake Forest University Baptist Medical Center.

The symposium, sponsored by Wake Forest Baptist and the International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine, was part of the society's annual conference. Tissue engineering experts from Wake Forest Baptist, Children's Hospital of Pittsburgh, Carnegie Mellon University, the University of Texas at Austin, as well as Italy and Japan, discussed their latest work.

Tissue engineering, a term that was coined in 1986, describes the science of replacing, repairing or regenerating organs or tissue. The term is often used interchangeably with regenerative medicine.

In the field of orthopaedics, researchers described using growth factors to regenerate bone, using new technologies to enhance the healing of ligaments, efforts to produce tissue-engineered cartilage, and the possibility of use stem cells derived from muscle to improve bone healing. These advances could provide better treatments for sports injuries, cleft palate and osteoporosis, the researchers said.

"The potential in orthopaedics is not only to manage devastating congenital or traumatic problems but also to prevent or slow degenerative processes in order to maintain the activity and function of our aging population," said Gary G. Poehling, M.D., professor and chairman of othopaedics at Wake Forest Baptist.

Anthony Atala M.D., director of the Wake Forest Institute of Regenerative Medicine, said that laboratory-grown organs may one day help alleviate the shortage of donated organs for transplantation. Atala has developed bioengineered urethras, the tube through which urine is excreted from the bladder, that have been successfully implanted in humans. He has also created blood vessels, muscle, bladders, wombs, and vaginas that have been successfully tested in large animals and are close to being ready to test in humans.

Atala's team is working to use patients' own cells to grow more than 20 different tissue types. They harvest cells from humans and apply growth factors, to cause the cells to multiply outside the body. It can take years to develop and perfect these growth factors, which cause a group of cells about one centimeter in size to multiply to fill a football field in about 60 days. The cells are "seeded" on a model, or scaffold, where they continue to grow. The next step is implanting the model in the body, where the scaffold eventually degrades as the new organ or tissue integrates with the body.

In addition to engineering tissues and organs, Atala and his team are also working to identify new sources of stem cells. Because these cells are unspecialized, they can acquire the structure and features of other cell types, and some researchers believe they could be used to replace defective insulin-producing cells in the pancreas, as well as to treat Alzheimer's, liver, heart, muscular and vascular diseases.

Robert Nerem, Ph.D., director of the Parker H. Petit Institute for Bioengineering and Bioscience at the Georgia Institute of Technology predicted that one day tissue engineering and regenerative medicine will result in a revolution in the medical implant industry.

But Nerem and others who work in this emerging field said that while the area is full of promise, there are still many challenges to face before new therapies will be widely available.

"These technologies are expensive and for some of them, distribution is a challenge," said Atala.