Repairing Damaged Heart Tissue With Embryonic Stem Cells

Heart disease is now considered the most common cause of death in the UK, according to the BBC. This pressing issue has initiated research projects to find the best treatments, long-lasting treatments that involve the regeneration of heart tissue. Experiments back in 2005 involved deliberately inducing heart attacks in 18 sheep in order to test the potential of embryonic stem cells from mice. Research prior to this revealed that attempting to use stem cells from the patient would prove futile as adult stem cells do not have the capacity to differentiate into heart (cardiac) tissue. If this was possible, this would undoubtedly be a desirable solution as the patient's own cells are being used, reducing the risk of rejection.

Therefore embryonic stem cells have been labelled the next hope in the regeneration of damaged heart tissue. The experiment back in 2005 involved separating the sheep into two groups, one the control, the other being given 'multiple injections' of the embryonic stem cells [from mice] after a rest period of two weeks. These cells had been given growth factors to trigger them into developing into cardiac cells. Five sheep from this group were also given immunosuppressants in case there is an issue of rejection. Tagging the stem cells with 'fluorescent proteins' helped scientists to track their progress of colonisation, which was successful after one month. As anticipated, the cells were effective in regenerating the heart tissue in the non-control group, replacing the scarred tissue. In fact, the scientists were able to measure the heart's effectiveness to pump blood from the left ventricle. In the control group, blood ejection rate decreased by an average of 6.6%, whilst it was raised by 10% in the group given stem cell treatment.

By this data, the treatment seems very effective, however only 18 sheep were used in this set of experiments and embryonic stem cells of mice were used. Nevertheless the fact that this technique works in principle gives hope of new treatments involving stem cells. What was more encouraging for the scientists, is that there was no evidence of an attempt of rejection by the immune systems of sheep that were administered immunosuppressant drugs. However geneticist Robin Lovell-Badge, researcher at the National Institute for Medical Research, London, says that there is a "need to be cautious. Other tissues might reject the stem cells". He also pointed out that the sheep were only monitored for one month after the investigation. Side effects to the treatment or rejection could well occur further down the line - this is another implication for human trials.

Since these experiments, another study at the University of Washington Institute for Stem Cell and Regenerative Medicine also found success in the use of embryonic stem cells to regenerate tissue, this time in monkeys. The study summary stated that the stem cells "assembled muscle fibres and began to beat in synchrony with macaque (monkey) heart cells". What was interesting is that this time, human embryonic stem cells were used. The findings were published 30th April 2014 in Nature. 

Above: Green areas depict newly transplanted stem cells forming a graft with the primates original cardiac muscle cells (red). Full credit to the University of Washington

Credit is given to Anna Gosline, writer for New Scientist. Article can be found here. Original study findings can be found in The Lancet (Volume 336, pg 1005). 

University of Washington findings report can be found at ScieneDaily here.