Moreover, medical research also reveals that almost all cells in our body contain an entire genome or book of life: enough information to make an entire copy of an individual, which is the basis of cloning technology. So in theory, just about every cell can make any tissue one needs.
Sumera B. Reshi
No doubt we humans are on the edge of a major stem cell breakthrough. It is believed that stem cells will one day provide effective low-cost treatment for diabetes, some forms of blindness, heart attack, stroke, spinal cord damage and many other health problems. Animal stem cell studies are already very promising and some clinical trials using stem cells have started.
So what actually are stem cells? Stem cells are relatively primitive cells that have the ability to divide rapidly to produce more specialized cells. Stem cells in the embryo are capable of huge variation in the kinds of tissues they make, reproduce rapidly and have attracted interest of researchers for decades. However embryonic stem cells are hard to get hold of in humans – you need a supply of human embryos, which requires either breaking the law in some countries or applying for complex licenses in others.
Embryonic stem cells are also hard to control, and hard to grow in a reliable way. They have “minds” of their own, and embryonic stem cells are often unstable, producing unexpected results as they divide, or even cancerous growths. Human embryonic stem cells usually cause an immune reaction when transplanted into people, which means cells used in treatment may be rapidly destroyed unless they are protected, perhaps by giving medication to suppress the immune system (which carries risks).
One reason for intense interest in human cloning technology is so-called therapeutic cloning. This involves combining an adult human cell with a human egg from which the nucleus has been removed. The result is a human embryo which is dividing rapidly to try and become an identical twin of the cloned adult. If implanted in the womb, such cloned embryos have the potential to be born normally as cloned babies, although there are many problems to overcome, including catastrophic malformations and premature ageing as seen in animals such as Dolly the sheep.
Stem cell technology is developing so fast. They are unable to keep up. The most interesting work is often unpublished, or waiting to be published. A Japanese researcher, Nobel laureate Shinya Yamanaka, collected genes from mature adult skin tissue and reprogrammed them to become “‘pluripotent,” which is a stem cell characteristic that means a cell is able to differentiate into multiple types of cells (www.eurostemcell.org)
Previously it was believed that cells in the embryo were multi potent, able to give rise to every tissue, but by birth, this capacity was permanently lost. That has been the reason why almost all research effort focused on embryonic stem cells until just a few years ago.
Today the research reveals that many cells in children and adults have extraordinary capacity to generate or stimulate growth of a wide variety of tissues, if encouraged in the right way.
Professor Jonathan Slack at Bath University has demonstrated how adult human liver cells can be transformed relatively easily into insulin producing cells such as those found in the pancreas, or by using bone marrow cells to repair brain and spinal cord injuries in mice and rats, and now doing the same to repair heart muscle in humans.
Moreover, medical research also reveals that almost all cells in our body contain an entire genome or book of life: enough information to make an entire copy of an individual, which is the basis of cloning technology. So in theory, just about every cell can make any tissue one needs. However, the reality is that in most cells almost every gene you have is turned off – but as it turns out, not as permanently as we thought.
If we take one of your skin cells and fuse it with an unfertilized human egg, the chemical bath inside a human egg activates all the silenced genes, and the combined cell becomes so important that it starts to make a new human being.
What then if we could find a way to reactivate just a few silenced genes, and perhaps at the same time silence some of the others? According to Jonathan Slack, we can find a chemical that would mimic what happens in the embryo, with the power to transform cells from one type into another. Now the impossible has become possible.
The future of stem cells
Embryonic stem cell technology is already in the offing, along with therapeutic cloning. Medical scientists think by 2020, we will be able to produce a wide range of tissues using adult stem cells, with spectacular progress in tissue building and repair. In some cases, these stem cells will be actually incorporated into the new repairs as differentiated cells, in other cases, they will be temporary assistants in local repair processes.
Also some exciting pharmaceutical products are in the pipeline, which promise to do some of the same tricks without having to remove a single stem cell from the body. These drugs may, for example, activate bone marrow cells and encourage them to migrate to parts of the body where repairs are needed.
Using embryos as a source of spare-part cells will always be far more controversial than using adult tissue, or perhaps cells from umbilical cord after birth, and investors will wish to reduce unnecessary risk, both to the projects they fund, and to their own organizations by association.
Despite this, we can expect embryonic stem cell research to continue in some countries, with the hope of scientific breakthroughs of various kinds.