The concept of ‘Regeneration and Rejuvenation’ is not new. It has existed for as long as the human kind can trace back their existence. By far immortality has been our biggest and unachievable fascination for ages. There are many stories that exemplify the extent to which people have gone to, to gain immortality. For example, elixir (amrit), a mythical potion believed to cure all ills, when drunk, grants eternal life and youth. Elixir has been widely described in Hindu, Buddhist and Chinese scriptures but in the modern day there is no evidence of its existence.
Regeneration means the process of regrowth and repair of the disease parts of the body. Scientifically, it relates to everyday wear and tear and maintenance of normal working of our body organs and systems. Human bodies are very complex and there are more than one repair systems in action that ensure our bodies can withstand everyday damage and repair them without making us consciously realise it. This is where the Stem Cells come into play.
Adult Stem Cells are one of the repair systems in action in our bodies. A stem cell is a cell that has not yet differentiated, i.e, it is not yet a mature cell with a function but these cells have the potential to grow and become a differentiated or a mature cell that can perform one specific function. Stem cells are present in all organs. For example, a stem cell in skin has the potential to form the skin cells that produces melanin and a pancreatic stem cell can form the pancreatic cell that can form insulin under the right circumstances. Not only that, every organ has one or more different stem cell types present. This means you can have more than one back up systems of stem cells in the same organ. For instance, skin has atleast three, brain has atleast two and bone marrow has atleast three different stem cell types in them, all involved in the regeneration process.
These stem cells are normally in a dormant state, present deep inside the organ, hidden from possible sources of damage such as sunlight. Thus, they need specific triggers to awaken them from dormancy. That trigger can be in the form of a cut or a wound, which stimulates the stem cell and causes it to divide and give rise to new cells, which finally repair and replace the damaged organ. This is how the usual repair system works in our body. An interesting thing to note is that where some organs repair easily like the skin, bone and liver, others seem to heal very slowly, like the brain and the heart. It is not because the brain and the heart do not have stem cells but because the stem cells in these organs have lower ability or potency to give rise to new cells. Thus, in other words, though every organ has stem cells, they all have different regenerative abilities and only give rise to organs they are present in.
There is another most commonly talked about source of stem cells called the embryonic stem cells. These stem cells are highly lucrative source of regeneration as they have the capacity to form all types of entire new organs that can be transplanted and used to replace the old worn out organs in our body, bringing us one step closer to immortality and ditching aging. Human embryos are grown in laboratories and stem cells are taken from these embryos to put them inside the patients. Some may say that the embryonic human stem cells are sourced from unborn persons that are sacrificed for other patients cure. Hence, there is a lot of controversy that surrounds embryonic stem cells and often the morality of using human embryos for scientific research and therapy is under scrutiny, not to mention, the safety issues and side effects that these embryonic stem cells might have and are not fully understood even by the scientific community. This means, more and more scientific research is being done on the stem cells from the adult human bodies and not human embryos.
Some of the most common sources of adult stem cells are bone marrow, skin, liver, intestine, teeth, eyes, etc. One of the major problems in harnessing these stem cells are that they are found in very few numbers in our bodies. For example, only one in 10,000 or 15,000 cells in the bone marrow is a stem cell. Stem cells could also be sourced from a donor (another person) but that would lead to immune rejection by the body of the patient. Second problem is that a stem cell from skin may not be useful for repair in the brain, even though getting a stem cell from skin is easier than getting a stem cell from deep inside the brain.
Thanks to the recent advances in the stem cell biology in the last ten years, scientists have managed to generate another source of stem cells. These are called the human induced pluripotent stem cells (iPSC). These stem cells are created in a laboratory when a mature body cell is taken and its DNA is changed in a way that it starts behaving like a stem cell. For example, a liver cell is taken from patient’s body, its DNA is reprogrammed and then under the right conditions, it converts into a stem cell which can give rise to all the organs of the body like a the pancreas that can be transplanted back inside the patient. These stem cells behave similar to embryonic stem cells and have the capacity to form different organs with only difference that they are sourced from adult humans and not human embryos. Currently, iPSC is one of the most advanced fields of research in human biology.
Finally, the beauty of stem cell therapy lies in the idea that, the stem cells taken from a patient’s body may be controlled to form entire new organs based on that patient’s customised needs; making the patient his/her own organ donor. As a Scientist, I believe it is the holy grail of immortality.
(The author is a final year PhD Student in Division of Cancer and Stem cells, University of Nottingham, UK.)