David J. Mooney experiments with new biomaterials that can be used to regenerate injured body tissue or activate the immune system more efficiently. Mooney is Professor of Bioengineering at Harvard University.
»Can biomaterials replace medical implants?«
Historically, we have tended to intervene in the human body in a very gross way. We typically treat the whole body, even though the problem may only exist in one particular tissue. With bioengineering, we are able to target flawed tissue or organs much more precisely. Right now we are developing procedures that use biomaterials, basically plastics, to transport stem cells to where they are needed to repair defective tissue. In the area of bone regeneration, we are exploring the capacity of biomaterials to “recruit” existing stem cells or, in other words, adhere to the cells and draw them to the regeneration site. We can decide when, where, and for how long we want these interventions to happen. Bioengineering will ultimately give us far better control in terms of time and space.
Our material is designed to be biodegradable; it should only be in the body as long as necessary for regeneration. Because the material orchestrates the behaviour of cells in this process, it has to communicate. This can be achieved chemically with biomaterials that release drugs or molecules which adhere to cells and change their function. Or we can change physical properties – such as stiffness – that affect cell responses in the body.
I absolutely believe that medicine will move away from treating symptoms and using materials as crude replacements. Instead, our approach will be to regenerate tissue in the body. It is going to be a tremendous revolution, but it will take some time.
When I first got involved in this area of research, I was very excited about the possibility of using cells to regenerate and grow tissue and organs. Then, in one of my first animal studies, I discovered that the vast majority of the cells that I had transplanted were dying. This experience eventually led to the idea that instead of pursuing transplants, we might be better off “training” cells that were already in the body. Although it was a disappointment, it actually led me down a very important path. Another disappointment came during our initial trials for therapeutic cancer vaccines when we discovered that we were actually making the tumours grow faster. What we learned, however, was that we could have an impact. In other words, if we can make something worse, we can probably also make it better. The worst outcome is zero change.
Over time I have realized that having some effect, any effect, is good. It means we can start to take control.
“We are developing strategies to promote bone and muscle, using stem cells. In particular, we design biomaterials, often based on plastics, that can make stem cells survive for longer times and function better after they are placed in the body. We have recently demonstrated that the stiffness and flowability of these biomaterials has a strong impact on stem cells, and have been exploring if we can design biomaterials to impact tissue regeneration based on control over these mechanical properties.
In addition, we have found that stem cells can significantly improve regeneration of skeletal muscle tissue, and are working to understand how these cells impact the other cells already in the body to orchestrate this behavior.“
Video: Mirko Lomoth
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