Just weeks after the white smoke from the Vatican signalled the election of a new pope, a grimmer pall hangs over the Eternal City — a fog of confusion and misrepresentation about stem-cell therapy. Those who have lit the fire beneath the debate say that they are promoting the translation of stem-cell research into the clinic so that currently incurable diseases can be treated. Nothing could be further from the truth.

The Second International Vatican Adult Stem Cell meeting, held on 11–13 April in Vatican City, was a shamelessly choreographed performance. Sick children were paraded for television, sharing the stage with stem-cell companies and scientists desperate to hawk a message that their therapies must be speeded to clinical use.

A kilometre away at the Italian senate, meanwhile, parliamentarians further eroded protection for vulnerable patients targeted by stem-cell companies. On 10 April, they amended an already controversial ministerial decree (see Nature 495, 418–419; 2013) with a clause that would redefine stem-cell therapy as tissue transplantation, thereby releasing it from any regulatory oversight. If the second parliamentary chamber endorses this amendment, Italy will be out of step with the rules of the European Union and the US Food and Drug Administration, both of which define stem cells modified outside the body as medicines.

Many scientists around the world were appalled by the events in Rome, and rightly so. It is wrong to exploit the desperation of the disabled and the terminally ill and to raise false hopes of quick fixes, as some at the Vatican meeting tried to do. It is also wrong to try to use such patients as experimental animals by bypassing regulatory agencies, as the Italian parliament seems to want to do.

Reputable stem-cell companies insist that stringent regulatory control is necessary, and that patients should be exposed to experimental treatments only when safety and efficacy is assured. Failures in the clinic will hold back the field. But not all of the cell-therapy industry is so tolerant.

With their ability to differentiate into various cell types, stem cells hold enormous potential to repair damaged tissues. Human embryonic stem cells can turn into any cell type, but many groups, including the Catholic Church, find their derivation from embryos unethical.

A lot more research into the deep biology of stem cells is needed.

The current controversy concerns adult stem cells. These exist in several tissues, but can replace only those particular tissues. Big claims are being made for them, with many trials of therapies under way worldwide for conditions as diverse as Alzheimer’s and heart disease. Some stem-cell therapies are approved by regulatory agencies; others sneak under the radar by exploiting rules allowing compassionate therapy, for example, or by operating in countries such as China or Mexico — and perhaps now Italy — where regulation is less strict.

The scientifically naive Vatican finds the concept of adult stem cells attractive simply because embryos are not involved — yet it ignores the ethical implications of false hope.

The main organizer of last week’s conference was the non-profit Stem for Life Foundation, launched by the stem-cell company NeoStem, both based in New York. The foundation says that it is in favour of strict regulation of stem-cell therapies. But its conference programme, which left no room for questions, included many speakers who clearly were not. It was framed as a fight for reason and fairness against an uncaring and intransigent scientific community.

Adult stem cells have already had clinical success, such as in bone-marrow transplantation for leukaemia treatment, growing new skin layers to treat burns and regenerating corneas. More ambitious hopes need to be tempered, however. Many trials involve infusing patients with mesenchymal stem cells from bone marrow, which are relatively easy to extract and grow. These can make only bone, cartilage and fat cells, but trials targeting other tissues use the rationale that other, non-stem properties of mesenchymal stem cells apply. It remains to be seen how effective these properties will be outside the normal biological home of the stem cells.

Given the burden of incurable disease, rapid bench-to-bedside translation is unquestionably crucial. But a lot more research into the deep biology of stem cells is needed. Some trials approved by regulatory agencies may yield useful results, but that is a long shot without strong research data. At least they are safer under regulatory eyes. Unregulated treatment — such as that issued on a compassionate basis by the Stamina Foundation in Brescia, Italy, which led to the current ministerial decree — is more worrying. The second parliamentary chamber needs to heed independent expert advice before voting to deregulate stem-cell therapies.

Stem cells will help to develop treatments for currently incurable diseases. But we are not there yet, whatever the smoke signals may say.