If we cut off the tail of a lizard, it grows back. If we cut off the hand of a human being, it does not grow back. Why not? This question has perplexed scientists for a long time. Recently scientists at the Translational Genomics Research Institute (TGen) and Arizona State University (ASU) in the US identified three tiny RNA switches (known as microRNAs) which turn genes on and off and are responsible for the regeneration of tails in the green lizard. Now researchers are hoping that using the next generation genomic DNA and computer analysis will lead to discoveries of new therapeutic approaches to switch on similar regenerative genes in human beings.
Micro RNAs are able to control many genes at the same time. They have been compared to an orchestra conductor controlling and directing many musicians. Hundreds of genes (‘musicians’ playing the orchestra of life), controlled by a few micro RNA switches, have been identified that are responsible in the regenerative process. This may well mark the beginning of a new era in which it may be possible to regenerate cartilage in knees, repair spinal cords and amputated limbs.
Tissue regeneration has become an attractive field of science, triggered by exciting advances in stem cell technologies. Stem cells are undifferentiated biological cells that are then converted into various types of cells such as heart, kidney or skin through a process known as ‘differentiation’. They can divide into more stem cells and provide a very effective mechanism for repair of damaged tissues in the body. The developing embryo contains stem cells which are then transformed into specialised cells as the embryo develops. They can be obtained by extraction from the bone marrow, adipose tissue or blood, particularly the blood from the umblical cord after birth.
Stem cells are now finding use in a growing number of therapies. For instance leukaemia is a cancer of the white blood cells. To treat leukaemia, one approach is to get rid of the diseased white blood cells and replace them with healthy cells. This may be done by a bone marrow transplant through which the patient’s bone marrow stem cells are replaced with those from a healthy, matching donor. If the transplant is successful, the stem cells migrate into the patient’s bone marrow resulting in the production of new, healthy white blood cells that replace the abnormal cells. Stem cells can now be artificially grown and then transformed (‘differentiated’) into the heart, kidney, nerve or other typed of cells.
The field of ‘regenerative medicine’ is developing at a fast pace. It involves the replacement, engineering or regeneration of human tissues and organs so that their normal function can be restored. Tissues and organs can also be grown in the laboratory if the body cannot heal itself. If the cells of the organ being grown are derived from the patient’s own cells, the possibility of rejection of the transplanted organ is minimised. Stem cells may also be used to regenerate organs.
Each year about 130,000 organs, mostly kidneys, are transplanted from one human being to another. The process of growing organs artificially has been greatly accelerated by the advent of 3D bioprinting. This involves the use of 3D printing technologies through which a human organ, liver or kidney, is produced by printing it with cells, layer-by-layer. This became possible when it was discovered that human cells can be sprayed through the nozzles of an inkjet printer without destroying or damaging them. Tissues and organs can thus be produced and transplanted into humans. Joints, jaw bones and ligaments can also be produced in this manner.
Initially, the work was confined to animals when ears, bones and muscle tissues were produced by bioprinting and then successfully transplanted into animals. Even prosthetic ovaries of mice were produced and transplanted so that the recipient mice could conceive and give birth later. While gonads have not been produced by bioprinting in humans, blood vessels have already been produced by the printing process and successfully transplanted into monkeys. Considerable work is also going on in the production of human knee cartilage pads through the bioprinting process. Wear and tear of the cartilage results in difficulties in walking, particular in older age groups, and often requires knee replacement through surgeries. The development of technologies to replace the damaged cartilages with new cartilages made by bioprinting could prove to be invaluable.
Another area of active research in this field is the production of human skin by bioprinting which may be used for treating burns and ulcers. Technologies have been developed to spray stem cells derived from the patient directly on the areas of the body where the skin is needed. In this way, stem cells help skin cells regrow under suitable conditions. Similar progress is being made in generating liver, kidney and heart tissues so that the long waiting time for donors can be circumvented.
When will we be able to print entire human organs? It has been estimated that complete human kidneys and livers should become commercially available through the bioprinting process within five to seven years. Hearts will probably take longer because of their more complex internal structure. However, one thing is clear: a huge revolution is now taking place in the field of regenerative medicine, triggered by spectacular advances in stem cell research. This presents a wonderful opportunity for learning and developing expertise in this field for us in our country.
In Pakistan a number of important steps have been taken in this fast evolving field. One of them is the establishment of a first rate facility for stem cell research in the Dr Panjwani Centre for Molecular Medicine and Drug Research (PCMD) in the University of Karachi. This institution has already earned an international reputation because of its outstanding publications in this field.
A second important development is that plans to set up an Institute for Translational Regenerative Medicine at PCMD so that Pakistan remains at the cutting edge in this fast emerging field are now under way.
Such initiatives can however only contribute to the process of socio-economic development if they operate under an ecosystem that is designed to promote the establishment of a strong knowledge economy.
Pakistan spends only about 0.3 percent of its GDP on science and about two percent of its GDP on education, bringing the nation’s ranking to the lowest 10 countries in the world. This is largely due to the stranglehold of the feudal system over our democracy. It is only by tapping into our real wealth – our children – that Pakistan can emerge from the quagmire of illiteracy and poverty and stand with dignity in the comity of nations.
The writer is chairman of UN ESCAP Committee on Science Technology &
Innovation and former chairman of the HEC. Email: ibne_sina@hotmail.com
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