Imagine being able to repair muscle that had been damaged in an injury, not by transplanting new muscle or even by transplanting cells, but rather simply by laying the necessary groundwork—and letting the body do the rest.
The ability for the human body to regenerate tissues lost to injury or disease may still be closer to science fiction than reality, but scientists at the Wake Forest Baptist Medical Center in Winston-Salem, North Carolina, have gotten us one big step closer.
Reporting in the latest issue of the journal Acta Biomaterialia, Dr. Sang Jin Lee and his research team describe their ingenious new method for regrowing damaged muscle tissue in laboratory rodents—by supercharging the body’s own natural restorative abilities. As Lee explained in a news release:
“Working to leverage the body’s own regenerative properties, we designed a muscle-specific scaffolding system that can actively participate in functional tissue regeneration. This is a proof-of-concept study that we hope can one day be applied to human patients.”
Normally, the body’s muscles—as well as the majority of organs—sit atop a biological ‘scaffold’ created by a matrix of molecules secreted by surrounding cells. This scaffold gives the organs and muscle their three-dimensional structure.
As of right now, if doctors want to replace damaged muscle they have one of two options: either surgically transfer a muscle segment from one part of the body to the other, or engineer replacement muscle tissue in the lab from a biopsy. Both methods, while doable, are not ideal. In the first, you are reducing the strength of the donor muscle; in the second, you have the added challenge of standardizing the engineered cells so that they will graft successfully.
So, Lee and his team focused on a third way: coaxing the body’s own supply of adult stem cells—which are tissue specific and normally used for general small-scale maintenance—to rebuild the damaged muscle from within. Said Lee:
“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.”
In this study, the researchers developed a method to do just that in the laboratory animals. First, they implanted a new cellular scaffold into the rodents’ legs. After several weeks, they removed the scaffold to see whether any cells had latched on of their own accord.
Interestingly, the team found that without any additional manipulation, the scaffold had developed a network of blood vessels within just four weeks after implanting. They also observed the presence of some early-stage muscle cells. What the researchers wanted to do next was find a way to boost what they already observed naturally.
To do so, they tested whether proteins—previously known to be involved in muscle development—could boost the speed and amount of recruitment of muscle stem cells to the scaffold.
After a series of experiments, they found a leading candidate: a protein called insulin-like growth factor 1, or IGF-1. And when they injected IGF-1 into the newly-implanted scaffolds the difference was remarkable. These scaffolds had about four times as many cells when compared to the plain scaffolds. As Lee explained:
“The protein effectively promoted cell recruitment and accelerated muscle regeneration.”
The real work now begins, added Lee, whose team will now take their research to larger animal models, such as pigs, to see whether their technique can work on a far grander scale.