It’s full steam ahead for the development of induced pluripotent stem cell (iPSC)-derived clinical trials. That’s according to a group at the National Human Genome Research Institute in Bethesda, Maryland who report this week in PNAS that the process of reprogramming a skin cell into the embryonic stem cell-like state of an iPSC does not itself cause an increased number of genetic mutations.

Ever since the technique was first devised ten years ago, there has been a lot of excitement about applying IPSCs to cell therapies for patients with unmet medical needs. Unlike human embryonic stem cells (hESCs) which are generated through the destruction of a fertilized embryo, iPSCs avoid ethical concerns because they’re obtained using adult cells like blood or skin. And the fact they’re patient specific carries the additional advantage of delivering iPSC-derived therapies back to the same patient with less concerns of rejection by the immune system.

Still, the use of iPSC-derived therapies has certainly not been worry-free and their translation into human clinical trials has been slow. One big concern is that the process of reprogramming inherently causes cell stress leading to an increased rate of genetic mutations in the cells. An abnormal number of mutations is bad news for cell therapies because they could carry an increased risk of becoming cancerous after being injected into a patient – an event that would end up causing more harm than good. Previous DNA sequencing studies comparing iPSCs with their cell source (skin, blood, etc.) identified many new sequence mutations in the iPSCs. But other studies suggested that many of those mutations already existed in the source cells and so they were essentially inherited during the iPSC process.

The team in this study sought out a definitive answer by tackling this mutation question using an “apples to apples” approach. To explain their approach, let’s first understand a technical detail about the iPSC method. When the iPSC reprogramming factors are added to the adult skin cells, the process is not efficient and only a few become iPSCs. Single iPSCs are then isolated and allowed to divide and make clones of themselves. This population of cells is called a cell “line” and takes several rounds of cell division to multiply into enough numbers to analyze their DNA sequence.

Credit: Darryl Leja and Ernesto Del Aguila III, NHGRI

So the researchers decided to also go through the process of making cell lines from the original skin cells but in this set they did not add the iPSC reprogramming factors. Now, they could compare the fate of DNA sequences in skin cell lines with and without the iPSC reprogramming method. The sequencing results showed that mutations occurred at the same rate in both the skin cell lines and the iPSC cell lines. This direct comparison suggests that iPSCs aren’t any less stable than non-reprogrammed cells. This finding bodes well for moving ahead with iPS-derived clinical trials. That’s certainly the perspective Erika Mijin Kwon, a co-author on the publication:

“Based on this data, we plan to start using iPSCs to gain a deeper understanding of how diseases start and progress,” said Kwon, in a press release. “We eventually hope to develop new therapies to treat patients with leukemia using their own iPSCs. We encourage other researchers to embrace the use of iPSCs.”