“In Body” Muscle Regeneration


Researchers at Wake Forest Baptist Medical Center’s Institute for Regenerative Medicine have hit upon a new strategy for tissue healing: mobilizing the body’s stem cells to the site of injury. Thus harnessing the body’s natural healing powers might make “in body” regeneration of muscle tissue is a possibility.

Sang Jin Lee, assistant professor of Medicine at Wake Forest, and his colleagues implanted small bits of biomaterial scaffolds into the legs of rats and mice. When they embedded these scaffolds with proteins that mobilize muscle stem cells (like insulin-like growth factor-1 or IGF-1), the stem cells migrated from the muscles to the bioscaffolds and formed muscle tissue.

“Working to leverage the body’s own regenerative properties, we designed a muscle-specific scaffolding system that can actively participate in functional tissue regeneration,” said Lee. “This is a proof-of-concept study that we hope can one day be applied to human patients.”

If patients have large sections of muscle removed because of infections, tumors or accidents, muscle grafts from other parts of the body are typically used to restore at least some of the missing muscle. Several laboratories are trying the grow muscle in the laboratory from muscle biopsies that can be then transplanted back into the patient. Growing muscle on scaffolds fashioned from biomaterials have also proven successful.

Lee’s technique overcomes some of the short-comings of these aforementioned procedures. As Lee put it, “Our aim was to bypass the challenges of both of these techniques and to demonstrate the mobilization of muscle cells to a target-specific site for muscle regeneration.”

Most tissues in our bodies contain a resident stem cell population that serves to regenerate the tissue as needed. Lee and his colleagues wanted to determine if these resident stem cells could be coaxed to move from the tissue or origin, muscle in this case, and embeds themselves in an implanted scaffold.

In their first experiments, Lee and his team implanted scaffolds into the leg muscles of rats. After retrieving them several weeks later, it was clear that the muscle stem cell population (muscle satellite cells) not only migrated into the scaffold, but other stem cell populations had also taken up residence in the scaffolds. These scaffolds were also contained an interspersed network of blood vessels only 4 weeks aster transplantation.

In their next experiments, Lee and others laced the scaffolds with different cocktails of proteins to boost the stem cell recruitment properties of the implanted scaffolds. The protein that showed the most robust stem cell recruitment ability was IGF-1. In fact, IGF-1-laced scaffolds had four times the number of cells as plain scaffolds and increased formation of muscle fibers.

“The protein [IGF-1] effectively promoted cell recruitment and accelerated muscle regeneration,” said Lee.

For their next project, Lee would like to test the ability of his scaffolds to promote muscle regeneration in larger laboratory animals.

Duke University Tissue Engineering Team Grows Self-Healing Muscle in Laboratory


Scientists have grown living muscle in the lab. While this is nothing new, this new advance has succeeded in making muscle that not only looks and works like genuine skeletal muscle, but also heals by itself, which is a significant advance in the field of tissue engineering.

This ultimate goal of this research is to use lab-grown muscle repair muscle damage in human patients. To date, preclinical trials have shown that lab-grown muscle properly regenerated damaged muscle in laboratory mice.

This research comes from Duke University, and the research team responsible for this work thinks that their success was due to the culture environment that they have created to grow muscle in the laboratory. Their well-developed contractile muscle fibers also contained a pool of satellite cells, which are an immature stem cell population in skeletal muscle that are activated when the muscle is damaged. Satellite cells can divide and differentiate into normal muscle tissue in order to heal muscle damage.

Cultured Muscle

Laboratory tests showed that the lab-grown muscle was as strong and good at contracting as muscle isolated from living organism. Also, the laboratory-grown muscle was able to use its satellite cell population to repair itself when the muscle was damaged with toxic chemicals.

Muscle satellite cells

When it was grafted into laboratory mice, the muscle properly integrate into the rest of the surrounding tissue and functioned beautifully when called upon to do so.

The Duke team, however, stresses that more tests must be conducted before this work can be translated into human patients.

The lead researcher for this work, Nenad Bursac, Associate Professor of Biomedical Engineering at Duke University, said: “The muscle we have made represents an important advance for the field. It’s the first time engineered muscle has been created that contracts as strongly as native neonatal [newborn] skeletal muscle.”

UK expert in skeletal muscle tissue engineering Prof Mark Lewis, from Loughborough University, said: “A number of researchers have ‘grown’ muscles in the laboratory and shown that they can behave in similar ways to that seen in the human body. However, transplantation of these grown muscles into a living creature, which continue to function as if they were native muscle has been taken to the next level by the current work.”

Tissue engineering seeks to use stem cells to fashion new organs and tissues from cultured stem cells. Tissue engineering and stem cell biology will certainly transform regenerative medicine, and in many ways it is already doing so. Scientists have already made mini-livers and kidneys in the lab using stem cells, and others are using stem cells to heal damaged heart muscles. Even though some cures and treatments are still some years away, advances continue to pile up. The future of medicine is upon us.