Wonders of Biology: Stem cells

Stem cells are unspecialized cells that have the capacity to self replicate and to give rise to specialized cells. They are the building blocks of our body and are present at fetal development and also later on in some adult tissues. Stem cells give rise to every other cell in our body. The ability of stem cells to self renewal and to differentiate holds the key for their use. However there are certain obstacles in their use i.e the amount of stem cells that is needed, their feasibility, to produce the right kind and type of stem cells ,to ensure they reach their target and also their availability in short period of time and also ethical issues. It is due to number of these and many other reasons that progress in this field is very cautious and step by step.

Stem cell technology holds much more potential for the treatment of diseases than any other single treatment and that is one of the reason it has caught the eye of every other biologist.
Stem cell treatment is not a very new idea. It is already in use at limited scale such as blood-forming stem cells in bone marrow (called hematopoietic stem cells, or HSCs), are currently the only type of stem cell commonly used to treat leukemia, lymphoma and several inherited blood disorders. The clinical potential of adult stem cells has also been demonstrated in the treatment of other human diseases that include diabetes and advanced kidney cancer and also recently in case of HIV. However, these newer uses have involved studies with a very limited number of patients.

First main focus of biologists is to find the cure for neurodegenerative diseases using stem cell technique. Treating neuron disease is not an easy task. It is much more difficult to treat neurons than any other single body part. Main reason is due to the diverse types of neurons, their connectivity and their accurate circuit which is the biggest challenge to achieve. Scientists have started to treat neuron diseases that are easy to treat like those which involve replacement or transplant of few cell types. Examples include Parkinson, sensory disorders, glial diseases but diseases like motor system disorders, spinal cord injuries are complex and difficult to treat. Same is the case with the type of diseases that are not an easy target like Alzheimer’s disease because neuron damage is widespread and diffuse but still improvements can be made by using stem cell technique to studying them invitro and eventually the treatment of every type of disease can benefit from stem cell technology. Details can be seen here.

Another focus of stem cell research is to create enough blood cells to boost blood supply for blood transfusion. Researchers at Advanced Cell Technology in Worcester, Massachusetts, announced the breakthrough in stem cell technology by devising a method for making potentially unlimited supplies of synthetic blood from embryonic stem cells. Their findings are published in Blood, a scientific journal. Their research is in preliminary stages. They were able to create hematopoetic embryonic stem cells in lab but these cells were not quite the same as natural blood cells i.e the proteins in them are characteristic of fetal and embryonic cells rather than of mature erythrocytes and are known as erythroid rather than true erythrocytes. They have different globin molecule that carries oxygen and also they are larger, membrane differences from natural ones and also their half life and immunogenicity is another question mark. Another challenge is also to ensure to produce them on vast scale so as to meet the demands of blood transfusion since one pint of blood contains more than one trillion cells and scientists at Advanced dell tech have so far achieved to produce 10 billion to 100 billion red cells starting from a plate of human embryonic stem cells, much less even for one transfusion.

Still these new cells have no nucleus, which is a distinguishing feature of mature red blood cells and has the potential to carry the same amount of oxygen as natural blood cells have. These are the main two aspects that are encouraging to pursue this research further. Another positive aspect of this research on hESCs is that since RBCs are enucleated and short-lived, then in any case of mishap ( like tumor development) or failure, it will not harm the patient since RBCs will disappear after a while without causing any lasting harm. Scientist now are concentrating to convert these hESCs into adult stem cells and their main focus is to create O negative blood group cells (universal blood group).

Another arena for stem cell biologists is to cure heart diseases. So far the success in this field is in different directions but is encouraging. According to some reports, a team of scientists at Harefield heart Science centre, UK has succeeded in creating heart valves from embryonic stem cells that were extracted from bone marrow and have grown them on scaffolds of collagen (connective tissue material). The team will test these valves in animals first and is hopeful that similar valves could be fitted in humans within 5 years and estimated that whole human heart rebuild will require 10 years. Another team of Dutch scientists have created heart muscles from adult stem cells that they have retrieved during surgery. They cultured these cells and allow them to develop into mature heart muscle cells that were in perfect order and contract rhythmically and respond to both electrical activity and adrenalin. Scientists are hopeful that these cultured cells will enable scientists to study heart defects and test new medicines, and could one day be used to repair heart tissue which has been damaged during a heart attack. Another breakthrough in heart stem cell tech is done by the team of scientists at University of Minnesota who have created a beating heart in the laboratory for the first time which is hoped to increase the chances of successful transplantation. This research has so far been done only with rats and pigs and is highly experimental. It is unlikely to be applied to humans for years but will ultimately lead to humans. The principle involved is simple “decellularisation” in which powerful chemicals strip down the cells from the dead heart so that only the protein “skeleton” was left intact. Then the skeleton was seeded with live “progenitor” cells, which multiplied and grew back over it, eventually linking together into a new organ. Such cells are involved in the formative stages of specialized types of tissue such as those found in the heart. Similar procedure was performed by Professor Doris Taylor, director of the university’s centre for cardiovascular repair Taylor and her colleagues, in which they strip the cells from a dead animal heart and then reseeded the remaining protein skeleton with progenitor cells taken from the hearts of newborn animals and let them grow. Four days after seeding that observed that the cells started contracting, and after eight days the hearts started contracting. She is positive that same principle can be applied to humans to rebuild organs by using the skeleton of dead relative. She is hopeful that this will increase organ transplantation by 50% in the next 5 years.

Similar technique is used by British doctor Professor Paolo Macchiarini of Barcelona University, in case of a female patient whose trachea or windpipe was damaged and had a respiratory blockage. They extracted adult cells from that woman and grown them into six million cartilage cells invitro. Then they took windpipe of a deceased woman and removed the dead cells leaving only the collagen scaffold. Then those cartilage cells were grown on to the trachea skeleton, effectively making a windpipe in the lab. The windpipe was then cut into the right length and bent into shape and then was grafted in the patient. Now that patient is able to lead a normal healthy life. According to doctors this is just a start and they are hoping too use the similar technique to transplant other major organs. Details of the transplant were described in an early online edition of The Lancet medical journal.

So concluding my discussion, stem cell technique has started from treating some tissues replacement or transplant and eventually it will be able to create and transplant whole organs or organ systems, and will finally overcome the problem of tissue rejection for the times to come. So all in all we can say that stem cell tech has given us the right to expect miracles from Biology and a hope to end misery of humankind.