Induced pluripotent stem cells (iPS cells) have been used to repair damaged heart tissue in mice by a team from the Mayo Clinic in Rochester, Minnesota, US. iPS cells are adult cells that are reprogrammed to act like embryonic stem cells - in this case the iPS cells were derived from ordinary fibroblasts (cells that contribute to scars such as those resulting from a heart attack). When the cells were injected into mice whose hearts had been damaged by a heart attack they improved both the structure and function of the heart. This proof-of-concept study, published in the online issue of the journal Circulation, is the first attempt to use iPS cells to treat heart disease and shows a potential practical use for these experimental cells.
Stem cells offer a vast range of possibilities for regenerative medicine because they can be coaxed into forming 'lab-dish' replacements for cells from the heart, liver, skin, eye, nerve or brain. Since iPS stem cells come from adult tissue their use is considered less controversial than embryonic stem cells that come from embryos only a few days old. Another advantage is that iPS cells are derived from a patient's own cells, so their use effectively eliminates the risk of organ rejection and the dangers associated with anti-rejection drugs. The eventual goal is to one day be able to use a patient's own cells to repair their heart instead of replacing it with a donated heart which are in short supply.
'This study establishes the real potential for using iPS cells in cardiac treatment,' says Dr Timothy Nelson, the study's principal author, adding: 'Bioengineered fibroblasts acquired the capacity to repair and regenerate infarcted hearts (hearts with an area of tissue death due to a local lack of oxygen).'
There are several ways to make iPS cells but in this study Nelson and his team used a virus to transplant genes that 'turned back the clock' on the fibroblast cells. Then, instead of coaxing the iPS cells into a specific type of heart tissue, they transplanted the iPS cells in their most embryonic state. It was found that only two weeks after transplantation the iPS cells had begun making different types of tissue such as heart muscle and blood vessels. Within four weeks the team discovered the cells had actually managed to stop progression of structural damage, restore heart muscle performance lost after the heart attack, and regenerate tissue at the site of the damage.
'We're taking advantage of a diseased tissue environment that is sending out a distress signal that is asking the tissue to repair itself... when we put these iPS cells in, they are able to respond,' Nelson said. ‘They were able to respond to this damaged environment and spontaneously give rise to the appropriate tissues and create new tissues within that diseased heart,' he continued, adding 'that is a key wow factor of this paper.'