In a major research of its kind, the Harvard University stem cell researcher have found an alternative to embryonic stem cells. Thus it is likely to bring an end to the political and ethical tempest that has embroiled hopes for a new generation of medical treatments.

The researchers said they found a safe way to coax adult cells to regress into an embryonic state, alleviating what had been the most worrisome uncertainty about developing the cells into potential cures.The development is the latest in the rapidly advancing and politically charged field of stem cell research.

Scientists last year shook up the scientific and political landscape by discovering how to manipulate the genes of adult cells to convert them into the equivalent of embryonic cells — entities dubbed “induced pluripotent stem cells,” or iPS cells — which could then be transformed into any type of cell in the body. Subsequent work has found that the cells can alleviate symptoms of Parkinson’s disease and sickle cell anemia in mice.

Konrad Hochedlinger, the lead researcher of the study said that his team is working to streamline the conversion, perhaps by supplementing the introduced genes with chemicals that flip biological switches. Many researchers suspect they will eventually find ways to transform cells much more cleanly without transferring genes at all.Although additional work will be necessary to prove that the new approach will work with human cells, Hochedlinger said he is confident it will.

Critics of embryonic stem cell research said the work offered yet more evidence that research on embryonic cells is unnecessary. Last month, another Harvard team announced that it had converted adult cells directly into another type of adult cell, possibly offering another less contentious alternative.