With the recent push towards tissue engineering and related research, it is surprising that no significant breakthroughs have been made despite the amount of attention the field is getting. This was the state of affairs until a revolutionary surgery was successfully completed last month that showcased the power of regenerative medicine.
Swedish surgeon Paolo Macchiarini from Karolinska University Hospital in Stockholm successfully transplanted an artificial, tissue-engineered trachea into a man suffering from the later stages of tracheal cancer. The trachea was constructed entirely in the lab using a scaffold made with a porous polymer. The tracheal tissue was grown from the patient’s own stem cells that were kept inside a bioreactor. This controlled the surroundings of the cells and promoted cell growth. The patient receiving the new trachea has made a full recovery and has been discharged from hospital as of July 8th.
The scaffold used to house the cells that eventually became the new trachea was built by a research team led by Alexander Seifalian, a professor at the University College London. The “InBreath” bioreactor used to house the cells was provided by Harvard Bioscience. The cells taken from the patient’s bone marrow were placed on the polymer scaffold and kept at an optimal temperature and environment within the bioreactor. The scaffold was rotated for a period of two weeks within the bioreactor so that the cells would grow into the fully-functioning organ.
For the first time, stem cells have been used to grow replacement organs for use in the body, which has been the aim of regenerative medicine since research in this field began. While an organ has been engineered from essentially scratch, the organ’s function was only structural since the trachea is essentially used as a channel for air. Therefore, building more complicated organs would be far more demanding in comparison to this successful endeavour.
Some advantages to regenerative medicine are as follow. For one, regenerated organs could be grown at a much faster rate than the time it takes to find a suitable organ from a donor. Also, since the engineered organs are usually made with the target patient’s own cells, rejection should not be a major issue, meaning the need for immunosuppressant drugs would be greatly reduced.
To create the scaffold, the team at the University College London used a polymer structure with millions of tiny pores to allow the patient’s stem cells to hold on to the structure. First, CT scans were taken of the patient’s trachea. Using these scans, a glass mould was made. Strips of polymer were then wrapped around the glass structure to resemble the structural cartilage rings of the trachea. Next, the model was dipped into a liquid mixture of the polymer mixed with salt. To set the liquid polymer on the mould, the contraption was washed in a solution that dissolved the salts, thereby causing the polymer to congeal into a spongy mass that resembles the shape of the trachea.
Once the scaffold was built and the cells were seeded onto it, the tissue was kept in the shoebox-sized bioreactor in much the same way one keeps chicken on a rotisserie. To seed the cells, a solution of stem cells and nutrients from the patient would be poured onto the trachea scaffold, after which the scaffold was rotated to keep the cells sterile and warm. Along with the nutrients included with the stem cell solution, it was imperative that hormones and other biological chemicals were included to help the cells differentiate into tracheal cells. The entire effort would take two weeks with only just two days required to actually grow the cells into the full tracheal tissue.
Needless to say, this surgery is a breakthrough in the field of regenerative medicine, which has been suffering from a number of general setbacks in terms of general research goals. After this massive breakthrough in tissue engineering research, all we need now is to wait for someone to grow more complicated organs and progress towards being able to grow needed appendages at a moment’s notice.