I've previously mentioned that my PhD comes under the heading of tissue engineering and regenerative medicine, but what is tissue engineering and what might it do for us in the future?
The main focus of tissue engineering in many respects is the production of replacement tissues and organs in the lab which can be used to repair the human body. The overarching dream is that one day people will be able to have new organs which are available on demand. Why is this something that we want? Firstly, we might be able to use artificial tissues to treat new illnesses, improving quality of life for people by regenerating their bodies. Additionally, by having organs off the shelf, we could eradicate the transplant list. How brilliant would it be to live in a world where no one dies waiting for a transplant? So, how do we make these new replacement organs and how far off are they from being in use?
It's safe to say fully manufactured organs are decades away from use, but small tissue replacements are closer general usage than you might think. The artificial trachea transplant reported in 2011 is a tissue engineering solution and there are tissue engineered patches for heart reconstruction along with tissue engineered heart valves and skin currently going through clinical trials. So we are beginning to move into the area of artificial, regenerative surgery.
How do we make artificial tissues and organs? Firstly we need to understand what gives an organ its ability function. An organ's properties come from both cells and the structure that supports them, made of proteins and other organic molecules, both of which are extremely important. So we need need a material to support cells and provide biological function along with a source of cells to fill this scaffold. At the moment there isn't a single solution to do this. Some researchers are using artificially made polymer materials to create scaffolds, but you can also make fully biological scaffolds. Some researchers are taking tissues from animal sources, removing the cells in it and using the decellularised tissue to provide a natural cell support with the inherent architecture needed to replace an organ. This may sound like a really weird idea, but this it is proving really successful in clinical trials and in many ways is using materials perfectly evolved for a function in an engineered tissue. Finding a cell source is a huge challenge. In some cases it's possible to implant a scaffold and let the cells of the body move into it over time. For example if you give someone an artificial bone or muscle then the scaffold provides mechanical function and cells are not needed immediately. However, when cells are vital where should they come from? In normal transplants patients have to be on immunosuppressive drugs in order to stop the body attacking the transplant, due to the recognition of foreign cells. Therefore, the ideal cell solution needs cells which come from a patient themselves. However, this is difficult in many ways; you need the right type of cells in huge numbers, that means cells must be harvested from a patient and grown in the lab. The most plausible way to do this is arguably to harvest adult stem cells which keep your tissues repaired in normal day to day life and make them into the right type for the scaffold. However, this is time consuming and expensive and could be considered to be the biggest barrier to tissue engineered organs.
What might tissue engineering do for you in the future? It could be a long time before we get to artificial full organ transplants, but you may receive tissue engineered structural tissue fragments for bone, muscle and blood vessel grafts sooner than you might think. However, direct tissue replacement are not the only thing tissue engineering is good for. Manufactured tissue samples could also be used to revolutionise drug development. At the moment it takes around a decade and a huge amount of money for a new drug to get to actual use in a hospital. In that time it will go through laboratory tests, animal tests and numerous human trials. However, the success rate of new drugs reaching hospitals is extremely low and only around 16% of drugs which start clinical trials succeed. The main problem is that animal tests and current lab methods do not give us the actual human response to a drug. Tissue engineering could help overcome this by creating mini-tissues, which we can connect together to create models to examine exactly how a drug effects every part of the human body. This would be a fantastic development on so many levels and could make life saving drugs cheaper and get them to patients quicker. It could also replace animal testing for medicines.
Tissue engineering has the potential to impact on medicine in a huge way. With a lot of hard work and time, in the future we will receive manufactured organs and drugs developed on tissue engineered models. Fingers crossed this will save lives and improve the quality of life for many people around the world.
