Successful Tissue Regeneration in Laboratory Mice. Potential Applications for heart patients and longevity.

Scientists in the United Kingdom who were working with experimental mice found that the miracle mouse could grow back lost limbs, lost tail and a damaged heart muscle. This was reported in TIMESONLINE on August 28, 2005. The report does not say how the first super mouse was created but it does say that it was “created”.

Until now it is known that skin and liver are the only two tissues which can regenerate. Injury to all other tissues is permanent and once they are damaged the are replaced by fibrous tissues which are devoid of nerves, blood vessels and sensation. The only function that these cells can perform is one of holding the damaged ends together.

Picture 1. This mouse’s sacrifices could save your life.

This group of researchers was obviously very inquisitive. Once they had created the super mouse they wanted to know if they could breed the mouse with the same traits. Breeding takes time and to some extent it depends on the moods of the mating creatures and some “genetic chances”. These scientists did not have the luxury of time. They simply extracted some genetic material and injected it into another mouse. To their amazement, they found that they had created another super mouse.

To this date, there is no documented evidence to show that mammals could regenerate myocardial, limb or joint tissue. This finding is significant in that it opens the door to regeneration of tissues in human beings. This discovery will have many applications for human patients. As already discussed in earlier issues, heart diseases are the major killers of human beings. It will make intensive care and coronary care units like the TB and Leprosy Hospitals of days gone by. I would love the see that day come because it will also alleviate a great deal of human pain and suffering.

This ability in a mouse to regenerate tissues is significant because a mouse is a mammal and finding that 'Miracle mouse' can grow back lost limbs, heart and tail are all applicable to the human situation. The fact that the “supermouse traits” were transferable simply by taking cells and transplanting them into an ordinary is significant because it imples that the “super genetic material” is in the cells and is transferable by a relatively simple technique. According to Professor Ellen Heber-Katz, who specializes in immunology at the Wistar Institute, this finding is significant because humans have comparable genes.

The details of this research were presented at a scientific conference on aging, strategies for engineered Negligibles Senescence at Cambridge University in the UK.

According to previous knowledge, 12 to 14 genes were responsible for regeneration of tissues and these were not yet identified.

The following parts of this article describes experimental details which some readers may find offensive. If you are sensitive to such literature, please do not read beyond this point.

The scientists have experimented with amputating and damaging several different parts of the body of the mouse. Some organs, such as the heart (Myocardium), toes, tail and ears were deliberately damaged. The scientists ware surprised to see them regrow, to their amazement. There was one anomaly though, the nervous tissue of the brain did not grow back. This implies that the biochemical pathways or genetic material mediating brain cell regenration is different or that the injected material did not reach the brain because of the existence of the blood brain barrier.

When the scientists injected the super foetal liver cells taken from those animals into ordinary mice, they too gained the “super” power of regeneration. The scientists found the super power of regeneration lasted for upto six months after the injection. It seems to imply that something changes with time, ?aging.

Just like Sir Alexander Fleming, this discovery was made by critical observation. Dr. Heber-Katz observed that the identification holes that scientists punch in the ears of experimental mice healed without any signs of scarring. These mice came to be called self healing and came from a strain labelled as MRL. Once these self healing characteristics were discovered, scientists were keen to capitalise on it so they experimentally subjected these mice to a number of procedures. In one experiment, the mice were anaesthetized and then had their toes amputated. The researchers were surprised to find that the toes and digits grew back, including the joints. This finding has many potential applications for human beings.

Another battery of tests was performed on these mice. After administering an anaesthetic, the tail was cut off from the super mouse and it also regenerated. Then the researchers used a cryoprobe to damage the myocardium of the animals’ hearts. They were surprised to see it grow back. Another similar phenomenon was noticed when the optic nerve of the super mouse was severed and the liver partially destroyed.

Scientists, including Heber-Katz are of the view that the super mouse (MRL) has a higher rate of cell division. She articulated, “Its cells live and die faster and get replaced faster. That seems to be linked to the ability to regenerate.” She presented her findings at the Cambridge conference and planned to publish her results in a research paper. Her concluding remarks were, “We have found that the MRL mouse seems to have a higher rate of cell division”.

This research has many applications. I suspect that the same genes (that increase rate of cell division) could confer greater longevity to mice and to humans. These scientists are now busy measuring the animals’ life span. At the time of the experiment the mice were only 18 months old, the lifespan of this group of mice is about two years.

Human and animal biologists have known that less complex creatures have an impressive ability to regenerate. One amoeba can become two spontaneously. Many fish and amphibians can regrow internal organs or even whole limbs. Lizards are able to regenerate their tails.

Humans are highly specialized mammals. They cannot regenerate anything except their liver provided at least a quarter remains intact, as well as their blood and outer skin, but no other organs regrow at any age.

Picture 2. Scientists working with Tissue cultures under strict sterile technique. The temperature, humidity, and air circulation are monitored closely.

Biologists think this is because most mammalian cells start off with the potential to develop into any cell type, they soon become extremely specialised. This allows the specialised mammals to develop more complex brains and bodies but deprives them of the power of regeneration.

In conclusion, this finding has at least two applications. One, it could be used as therapy for patients with damaged tissues with many far reaching applications. Secondly, it has the potential to increase longevity because it increases the rate at which new cells regenerate.

At the time of publication of this article the chemical or gene which brought about the “super mice” characteristics had not been identified.