Will liver transplants be grown from stem cells in our future?
A team of Japanese scientists have transplanted a portion of liver grown from stem cells into mice; the stem-cell-grown liver has successfully performed regular liver functions such as removing toxins from the blood.
The team, from Yokohama City University Graduate School of Medicine, along with other research partners, managed to reprogram skin cells into earlier stages of development before inducing them to grow as particular liver cells.
Growing Liver Tissues From Skin Cells
The liver tissues included two types of stem cells as well as cells from umbilical cords to provide a blood supply. What was astonishing was that the cells rearranged into the optimum pattern, growing into small ‘liver buds’, which resemble those that naturally occur during normal human development.
The buds were grown for two months until they were around 5mm in length before being transplanted under the skin of mice. Within two days, the buds had joined to the blood supply and eventually developed into cells that resembled those in a mature adult liver.
After this, the team gave the mice two drugs, an anti-inflammatory and an anti-hypertensive. They found that the drugs were broken down in a way that human livers normally manage.
The researchers also investigated the cells to see if they could help treat mice with liver failure. One group were given the new liver buds whilst another group acted as a control. Diptheria toxin was given to both groups, and whilst the all of the control mice died within 10 days, the mice with transplanted liver cells lived for over 40 days.
This therefore indicates future liver therapies, including transplants, could be produced from this method. The scientists hope that trials will now move to the human stage.
What Are Stem Cells? How Did Researchers Use Them?
Stem cells can be described as unspecialized cells that are pluripotent, meaning that they have the ability to differentiate into numerous types of cells. The cells that they develop into depend on specific signals.
Because of the ability of these pluripotent cells to differentiate into any kind of cell, science is extensively researching stem cells for their uses in medicine, though there are several boundaries to this type of research, including ethical concerns.
To produce the liver buds, the team used induced pluripotent stem cells. These are reprogrammed adult cells that revert to a state that is similar to embryonic stem cells. These particular cells came from the skin, an area known to have adult stem cells.
Embryonic vs. Adult Stem Cells
These two types of stem cells differ in their origins, as well as the number of cells that they can turn into.
As the name suggests, embryonic stem cells come from embryos. Researchers fertilize and grow egg cells within cell cultures in laboratories. If correctly handled, scientists can control what cells will eventually be grown. Human embryonic stem cell research is very controversial due to the origins of the cells, with several countries restricting the work that can be carried out on the fertilized eggs.
Adult stem cells, despite the name, are found in humans of all ages – in areas of the body such as the skin, bone marrow and blood vessels. These cells tend to be only able to differentiate into a limited number of cells, therefore having a lower level of potency when compared to embryonic stem cells, but as the scientists in Japan have shown, it is possible to reprogram adult stem cells.