Injecting stem cells to treat patients with heart attack is showing insignificant progress. The heart does apparently not regenerate its tissues that easily. Recently, it was discovered that the way the heart regenerates new tissues is different and is independent of stem cells.
Recent research is shedding light on the clinical failure involved in stem cell therapies and giving other alternatives.
For humans, it is already possible to regenerate the liver, yet other organs and operations such as the replacements of limbs are unfeasible. Amphibians and fish might contribute deeply in order to resolve some of the weaknesses of our actual system. For instance, an amphibian and fish can grow new limbs and fines. The fish called “zebra fish” has unique ability to regenerate its heart if one-fifth of its lower part has been chopped off. The regeneration process is slow in the beginning but boost up and is able to re-grow the heart within a month.
For us, humans the heart has a restricted potential to produce new heart muscle cells. During a lifetime an individual, has almost all his cells replaced. Conversely, the regenerative capacity of the heart cells is inactive during heart attacks. The speed of regeneration is not increased. The cells are simply replaced by scar tissue, which is a particular tissue that does not contract.
According to a report in 2006 undertaken by Kenneth D.Poss and colleagues at the Duke University, it was recognized that the repair process of organs required stem cell treatments as a basic source. Stem cells are cells that can become functional (somatic cell) and mature cell in our body.
Recently, contradiction to the potential of stem cells was reported in the Journal Nature. It was said that the mature heart muscle cells were responsible for the regeneration of the heart for the Zebra Fish. This research showed that regeneration of cells could be done without stem cells recourse.
A second study was led by Chris Jopling and Juan Carlos Izpisúa Belmonte of the Center for Regenerative Medicine in Barcelona, Spain. This team took a Zebra fish’s heart muscle cells and thereafter did genetically modify to synthesize a fluorescent green protein into it.
They did thereafter cut the bottom part of the heart to allow it to regenerate. It was found that the cells in the new section of the heart shined greenly. This showed that the heart muscles actually present were the sources of regeneration of new tissues.
The recipe for regeneration of cells according to nature might be to revert mature cells back into a form of stem alike cells. Then these cells are set to divide and grow again to generate tissues. This is another perspective relatively different from the proposed differentiation recipe. The previous recipe said that stem cells could differentiate into other tissues.
In nature, muscle cells do not really change back to an embryonic state. Cells do simply de-differentiate a bit. Understanding how some animals can regenerate, and then try to imitate their mechanisms can be a viable solution to solve our problems according to Dr. Izpisúa Belmonte.
It is certainly true that the evolutionary history of a Zebra Fish and mammals are two worlds apart. However, remarkable mammals do also have the capacity to regenerate cells and the ability to dedifferentiate typical heart muscle cells. The structure of a Zebra Fish performs cells dedifferentiation by disintegrating muscle fibers. This process is present for mice, rats and dogs when their heart is injured. However, the second phase of proliferation into new forms of tissues doesn’t occur for them, according to Dr. Izpisúa Belmonte.
If we would be able to promote the proliferation of cells in mammals, similarly to that of the zebra fish than the regeneration process could become possible for mammals.
From at the University of Washington in Seattle, Charles Murray an expert in heart cell biology says that these findings are intriguing. The question why human’s hearts are unable to accomplish such a regeneration process as well is raised. The human heart does the first step; muscle cells dedifferentiate just after an injury and thereafter the DNA increases which is necessary for cell division. Questionably, the process ends uncompleted.
According to Dr. Murray’s view, it might be hard to unravel the clue for regeneration. People oversimplify the matter by saying let us do it as nature does it, but in reality, we do not know how nature succeeds in the process. Brilliant molecular biologists around the world have been trying to solve the puzzle for decades, but it remains a cipher.
There have been heart patient who has been injected with their own bone marrow (stem cells) but the effects are often unseen. Nevertheless, other cell-based treatments have been modestly effective. Some might say that stem cell treatments are not paying-off. According to Dr. Murray, results haven’t been amazing. However, according to him, it would be appropriate to pursue research in a parallel manner. This implies focusing on the how nature assures regeneration and secondly how stem cell treatment might enable regeneration.
It will be interesting to see whether human will be able to develop an artificial regeneration process via stem cell therapy or if nature’s regeneration process can be unlocked before that. This is a challenge, which holds its answers in the future.
Source: New York Times
Mon, Mar 29, 2010
Bioscience, Nanotechnology, Stem cells