Last year, in a lab at Loyola University in New Orleans, something happened that has never been seen before — a chicken embryo regenerated a joint. We know lizards regrow their tails and salamanders are capable of growing a new leg, but never has this been seen before in a chicken.
In the case of this event, Rosalie Anderson, a professor in the department of biological sciences at Loyola University, was with her undergraduate lab when removing the elbow joint of the chick embryo’s wing.
“The project was originally initiated to develop a model to study joint-regeneration,” Anderson said. “Because of the accessibility of the chick embryo to manipulation and the many years I had worked on the chick embryo to understand the mechanisms of anterior-posterior patterning during development, I chose to work on the chick.”
Eighteen hours after Anderson removed the joint, it had regrown. In this phenomenon the embryonic cells actually migrated to the location of the missing joint and replaced it.
“While the chicken is not the most obvious choice since it had never been shown to be regenerative, we were asking it to regenerate in a context that had never been tested before,” Anderson said. “Excising the prospective joint tissue and thereby creating a “window” in the limb proved to provide the right environment for regeneration to occur.”
Surprisingly, human genes for development are the same as a chicken’s. This means it is possible to apply this research to humans one day, and our own bodies will be capable of regenerating our joints. There will no longer be problems with our bodies rejecting the new joint and the limited movement of the replacements we have today.
“Our study can only be one of the stepping stones for developing therapeutic methods of restoring joint function,” said Duygu Özpolat, a researcher from the University of Maryland. “The basic idea here is to induce a form of regeneration response in an otherwise non-regenerating structure. In this sense, a chicken embryo is similar to a human’s: We cannot regenerate easily.”
A large interest for this research project is for veteran amputees. The possibility of being able to replace a joint, or even a limb, with their own tissue would be a major discovery.
“We are focused on the joint at present, but we will definitely need to interface our work at some point with the issue of re-growing a limb,” Anderson said. “Currently, our collaborator, Dr. Ken Muneoka, and his laboratory at Tulane University, are making great strides at addressing limb regeneration using their mouse-digit-tip model.”
The model Anderson mentioned was another research project Özpolat worked on.
“One of the reasons why we wanted to understand joint regeneration specifically was due to the mouse-digit-tip regeneration model we have been working on at the Muneoka lab,” Özpolat said. “In this model, when a fingertip of an adult mouse is amputated the structure regenerates. The regenerating structure has both bone and connective tissues, as well as a part of the nail. If you make the amputation a larger one, by including the first joint from the finger tip, there is no regeneration.”
Humans regenerating joints seems like a daunting task for researchers to accomplish.
“It is important to remember that while aiming for the complete limb regeneration can be an intimidating task, even the mildest, smallest tissue regeneration response can make a big difference for somebody who is losing the integrity of their joints through degenerative joint diseases, or another patient who lost a part of their finger,” Özpolat said.
Currently, Anderson and her students are continuing research to find the cells and genes that lead to the embryo’s recovery. One of those students is Jeffrey Coote, a fourth-year undergraduate biological sciences major at Loyola University.
“I do plan on using what I have and will continue to learn about joint regeneration throughout my medical career,” he said. “[I] will definitely keep up with this study and similar studies with the hopes of using what I learn to help my patients.”
KELLY MITCHELL can be reached at firstname.lastname@example.org.