In Part I we looked at the basics of stem cell research and some of the technical and ethical challenges. Let's now ponder a little more on these avenues. As their knowledge expands, scientists continue to develop the variety of techniques required for isolating, culturing, and growing (expanding) stem cell populations in the laboratory for storage and future use. These more readily-available cells can be retrieved for further study, transplantation procedures, tissue production and so on. Further expansion of stem cell populations in vitro (meaning 'within the glass' or in other words, in the laboratory) is important for overcoming the problem of obtaining sufficient cells to work on - in vivo (meaning 'within a living body') stem cells are few and far between!Taking a look at stem cell transplantation, recall that in disease or injury, damaged tissue sends a variety of chemical signals to local stem cells, instructing them to replicate and differentiate into specific cells that will replace old tissue cleared away by the immune system. This process can be greatly speeded up by transplanting stem cells directly into the patient. Alternatively reproduction of such processes in vitro enables medical researchers to ultimately grow complex tissues and even organs in the laboratory for subsequent transplantation. The advantage of transplanting stem cells over tissue however, is that you don't worry about the chemical signals required for differentiation - the body does that bit.
A great example of advances in stem cell transplantation was the recent study by JC Voltarelli and colleagues in Brazil, in which a small number of diabetics were treated with their own stem cells to regenerate pancreatic tissue. These patients had the type I form of diabetes, in which the immune system attacks the specialised cells in the pancreas that produce insulin (beta cells). With few available beta cells, little or no insulin is produced and glucose levels in the blood stream can't be controlled. Type I diabetics must therefore regularly inject themselves with insulin. In the stem cell trial, medics first treated the patients with drugs to stimulate the bone marrow to generate large numbers of a particular stem cell - the so-called CD34+ haematopoietic stem cell. As this cell is subsequently released into the blood stream, doctors only had to collect blood to harvest what is effectively a bone marrow-derived cell. Patients were then treated with drugs to knock out the immune cells that were attacking the pancreas. Shortly after this treatment was commenced, the patients were transplanted with the CD34+ cells, which in turn received the appropriate signals in the pancreas to generate replacement beta cells. This procedure resulted in the majority of treated patients no longer requiring insulin injections. You can see how this approach might pave the way for the treatment of any disease by simply transplanting the right stem cells (that's the tricky bit - checking that the cell you use is able to differentiate into the desired terminal cell). Treatment of neurodegerative diseases is high up on the list because neuronal tissue is notorious for its poor regenerative capacity. Similarly, much research exists in the use of stem cells to treat liver diseases. Success here would greatly reduce the need for liver donors.
In the meantime there have been other achievements. Do you recall the recent treatment of the Spanish lady whose bronchus was damaged by TB? In this case, a donor piece of bronchus was stripped of donor cells and the remaining cartilage used to provide a scaffold for rebuilding tissue from cells taken from the TB patient. Risk of tissue rejection and the need for unpleasant immunosuppressive drugs are again avoided. So now you have it. First remove stem cells from an individual, generate a bank of different stem cell types from the ones you removed, then when disease or injury strikes, select the most appropriate stem cell type and transplant into the patient (this applies to both human and animal patients - yes you can have your pet saved from disease by stem cell transplantation too). Or if more appropriate, use a donor or synthetic scaffold to grow a basic tissue construct and transplant that.
So, how long before limbs are replaced in this way? When might the first heart transplant with a laboratory-grown organ occur? This whole field of repairing damaged or diseased tissue with stem cells or stem cell-derived tissue is known as regenerative medicine. This area is in hot pursuit by the pharmaceutical industry - much money is to be made. Indeed, I would suspect that the military would also be actively involved or at least monitoring events in regenerative medicine. Rapid repair of injured soldiers, particularly so that they are able to resume combat duties, would offer a substantive military advantage. Mind you, physical repair is one thing and mental recovery another....
Now here are some further thoughts. Eventually it will be possible to repair damaged areas of brain - so does this mean that you would be able to increase intelligence by stimulating further growth of a particular area of brain in a normal person? Tissue growth is also controlled by chemical factors that inhibit further growth once the appropriate volume is achieved. For example, myostatin prevents excessive growth of skeletal muscle. This ensures that mescle growth doesn't continue after the young adult has reached their full size. Without growth inhibition, you would end up with muscle-bound and distorted figures, as seen in a rare genetic disorder in which myostatin production is reduced or absent. A desire for bodybuilders perhaps, but not for the average person. What of applying this principle to the brain? Physicians could simply transplant stem cells, then treat with inhibitors of the biochemicals that control the level of tissue growth. And there you have a potential genius. Don't believe this principle? Then take a look at the discussions over the studies of Einstein's brain. Evidence suggests that if a specific area of the brain is larger than normal then the function attributable to that area is significantly enhanced. Mind you, the skull will limit growth so you may need surgery to provide more growth space.
Staying with future perspectives, I also believe that we shall see the advent of the true bionic man in around 50 to 100 years. The reason is simple. Man's scientific advances are often based on a specific principle: he wonders how nature works, unravels it's secrets, then exploits and refines them. Look at metals: he learns to extract metals such as iron and copper from different ores. Then he learns to mix them to produce alloys that offer new physical qualities. He continues to discover and extract other metals and produce more sophisticated alloys for even more refined applications. This evolutionary trend is repeated everywhere. Indeed we now understand the structure and physical properties of many of Nature's natural and biological materials. We refine them to taylor the physicochemical properties or we produce completely new materials such as the various polymers (polyethylene, polyvinyl chloride etc). And each time we realise that we have a new advancement in specific physicochemical properties, we exploit it.
Well, this all paves the way for bionic man. The Terminator technology. Astrobionics (which for me sounds more like that branch of science that deals with the advancement of Man’s physico-psycho constitution for deep space travel rather than how NASA describes it). The era of medical and materials technology in which tissue is grown on advanced materials and embedded with electronic devices that can be wired to the central nervous system. Engineered super-muscle. Engineered super-brain. Engineered super-bone. This is where today's science fiction becomes tomorrow's reality. But this is also where we must learn to draw the line and continue to challenge our ethical status. Just as the splitting of the atom gave way to the nuclear weapon, so regenerative medicine could herald new biological weapons in the form of the characters we see in science fiction films. Perhaps it will be the unscrupulous regimes of the future on whom we must keep our eyes focussed.
Signing off on Man's regenerative future,
The Senile Scientist
PS I'll revisit this area because there is still much more to discuss
No comments:
Post a Comment